This topic has been archived, and won't accept reply postings.
As we have so many experts here on UKC, this thread is for questions and answers on things you think you ought to know but don't! no cheating on Google please, only answer if you actually KNOW the answer.
I'll start.
Why doesn't the earth on Twin & Earth cable have any separate insulation? Or, another way, why DOES the earth in round cable have insulation?
Over to you
I'll start.
Why doesn't the earth on Twin & Earth cable have any separate insulation? Or, another way, why DOES the earth in round cable have insulation?
Over to you
In reply to Oceanrower:
Are all calories equal. Specifically, does my body extract the energy from food (a bite of apple or toast, say) to the same extent whenever it is consumed?
Are all calories equal. Specifically, does my body extract the energy from food (a bite of apple or toast, say) to the same extent whenever it is consumed?
In reply to Oceanrower:
Ooh good question. I was 99% sure I knew the answer but did have a cheeky google to confirm my suspicions. So I won't spoil it
Ooh good question. I was 99% sure I knew the answer but did have a cheeky google to confirm my suspicions. So I won't spoil it
In reply to Oceanrower:
Does light get "used up" lighting a space.
For example a room with one window will be lit by a certain amount of light at midday on a clear day. Now, all things being equal, if you made a window on the otherside of the room that looked into a windowless room(i.e completely dark until window was made to room with window), then would the light in the original room be diminished? (as some light floods into dark room annexed)
probably doesn't make any sense but It was something I pondered whilst watching Sarah Beeney's "double your house for half the cash" where a couple had built an extension without considering enough windows.
Does light get "used up" lighting a space.
For example a room with one window will be lit by a certain amount of light at midday on a clear day. Now, all things being equal, if you made a window on the otherside of the room that looked into a windowless room(i.e completely dark until window was made to room with window), then would the light in the original room be diminished? (as some light floods into dark room annexed)
probably doesn't make any sense but It was something I pondered whilst watching Sarah Beeney's "double your house for half the cash" where a couple had built an extension without considering enough windows.
In reply to lowersharpnose:
I don't think so. We'd have to feed you on just apples for a while, and then try burning your apple poo in a calorimeter to see how many calories remained. Repeat with toast poo.
I am not a dietician. I'm not Gillian McKeith either.
I don't think so. We'd have to feed you on just apples for a while, and then try burning your apple poo in a calorimeter to see how many calories remained. Repeat with toast poo.
I am not a dietician. I'm not Gillian McKeith either.
In reply to Oceanrower: in twin and earth it an extra expence. In normal cable it need to be insulated because if it was bare it might touch the other connections in the plug.
Why don't polar bears eat penguins?
Why don't polar bears eat penguins?
In reply to Oceanrower:
Two possible answers that I am aware of:
1. Cost saving, 'cos it doesn't need to be insulated.
2. This is the one I hold with - as the circuit protective conductor, its job is to carry fault current safely away in the event of an earth fault. Insulating it would effectively provide a an additional protective layer against any such fault and impede its ability to do this. Put very simply: If you put a nail through a cable, you really want the earth to touch the live before you do.
> Why doesn't the earth on Twin & Earth cable have any separate insulation?
Two possible answers that I am aware of:
1. Cost saving, 'cos it doesn't need to be insulated.
2. This is the one I hold with - as the circuit protective conductor, its job is to carry fault current safely away in the event of an earth fault. Insulating it would effectively provide a an additional protective layer against any such fault and impede its ability to do this. Put very simply: If you put a nail through a cable, you really want the earth to touch the live before you do.
In reply to lowersharpnose:
No- all calories are not made equal. Simply chewing your food more will release more calories and nutrients. Also, what you eat can have an effect, for e.g. finishing a meal with a pudding will move the food further along the digestive tract reducing how well you will digest it. Drinking a cold drink too will affect the action of breaking down food by diluting gastric juices and also by reducing enzyme action as they all have an optimal temperature.
BW
> (In reply to Oceanrower)
>
> Are all calories equal. Specifically, does my body extract the energy from food (a bite of apple or toast, say) to the same extent whenever it is consumed?
>
> Are all calories equal. Specifically, does my body extract the energy from food (a bite of apple or toast, say) to the same extent whenever it is consumed?
No- all calories are not made equal. Simply chewing your food more will release more calories and nutrients. Also, what you eat can have an effect, for e.g. finishing a meal with a pudding will move the food further along the digestive tract reducing how well you will digest it. Drinking a cold drink too will affect the action of breaking down food by diluting gastric juices and also by reducing enzyme action as they all have an optimal temperature.
BW
In reply to Game of Conkers:
Slightly. Each surface light "bounces" off will make it lose some energy (the surface absorbs a photon, and emits a new one with slightly lower energy, keeping some for it's self as a vibration) the new room will mean that some of the light that would have been bouncing off that wall will now be bouncing round in the other room a number of times before coming back to you. You'd never notice it tho if for instance you were facing the opposite wall from where this new window appeared.
There was a cool TED talk about seeing round corners by collecting the light bounced back...
Slightly. Each surface light "bounces" off will make it lose some energy (the surface absorbs a photon, and emits a new one with slightly lower energy, keeping some for it's self as a vibration) the new room will mean that some of the light that would have been bouncing off that wall will now be bouncing round in the other room a number of times before coming back to you. You'd never notice it tho if for instance you were facing the opposite wall from where this new window appeared.
There was a cool TED talk about seeing round corners by collecting the light bounced back...
In reply to krikoman:
Because the commute to the other end of the earth is really inconvenient.
> Why don't polar bears eat penguins?
Because the commute to the other end of the earth is really inconvenient.
In reply to Oceanrower:
The earth in T&E doesn't need it because it's at earth potential.
Round earth(and I assume you mean seperate earth such as earth straps) carries unsulation in case it has to do the job it's there for. Then the insulation provides protection.
> As we have so many experts here on UKC, this thread is for questions and answers on things you think you ought to know but don't! no cheating on Google please, only answer if you actually KNOW the answer.
>
> I'll start.
>
> Why doesn't the earth on Twin & Earth cable have any separate insulation? Or, another way, why DOES the earth in round cable have insulation?
>
> Over to you
>
> I'll start.
>
> Why doesn't the earth on Twin & Earth cable have any separate insulation? Or, another way, why DOES the earth in round cable have insulation?
>
> Over to you
The earth in T&E doesn't need it because it's at earth potential.
Round earth(and I assume you mean seperate earth such as earth straps) carries unsulation in case it has to do the job it's there for. Then the insulation provides protection.
In reply to Wulfrunian:
Two possible answers that I am aware of:
1. Cost saving, 'cos it doesn't need to be insulated.
2. This is the one I hold with - as the circuit protective conductor, its job is to carry fault current safely away in the event of an earth fault. Insulating it would effectively provide a an additional protective layer against any such fault and impede its ability to do this. Put very simply: If you put a nail through a cable, you really want the earth to touch the live before you do.
Pretty much, the opposite arguement "Why does 3-core flex have an insulated earth?" is down to the name "flex". As a flexible cable it is imporant for it to be physically balanced to avoid excessive wear. Twin and Earth is designed to be static and so doesn't need to be symetrical.
Two possible answers that I am aware of:
1. Cost saving, 'cos it doesn't need to be insulated.
2. This is the one I hold with - as the circuit protective conductor, its job is to carry fault current safely away in the event of an earth fault. Insulating it would effectively provide a an additional protective layer against any such fault and impede its ability to do this. Put very simply: If you put a nail through a cable, you really want the earth to touch the live before you do.
Pretty much, the opposite arguement "Why does 3-core flex have an insulated earth?" is down to the name "flex". As a flexible cable it is imporant for it to be physically balanced to avoid excessive wear. Twin and Earth is designed to be static and so doesn't need to be symetrical.
In reply to Game of Conkers: Yes, it does get used up. Light is simply radiation. It can be transfered to heat (which is why there are some losses passing through glass etc)
Women.
In reply to Wonko The Sane: Ok, I think I get it, but it has resulted in me coming up with another scenario to try to explain my point..
Two identical candles burn in two windowless rooms (room A and room B). Room A is 1m cubed, room B is 1km cubed. Both rooms have non reflective wall surfaces. If you sat reading a book half a metre away from the candle in room B, would you have less light than sitting in the same spot in room A?
Two identical candles burn in two windowless rooms (room A and room B). Room A is 1m cubed, room B is 1km cubed. Both rooms have non reflective wall surfaces. If you sat reading a book half a metre away from the candle in room B, would you have less light than sitting in the same spot in room A?
In reply to Oceanrower: at the risk of sounding thick.... light is reflected by white/shiny surfaces, but 'absorbed' by matt/dark ones - what the hell happens to it when it's absorbed?
In reply to Baron Weasel:
Thanks.
That seems reasonable. I already knew that calories in food were no ,longer the same as the bomb-calorimeter-calorie, that they were adjusted to take account of how the body fealt with the food. But these are averages and take no account of the circumstances when you ate the food. I felt sure that a square of chocolate eaten after a few hours in the hills will be much more efficiently used than a square eaten after a meal.
How can I find out more?
Thanks.
That seems reasonable. I already knew that calories in food were no ,longer the same as the bomb-calorimeter-calorie, that they were adjusted to take account of how the body fealt with the food. But these are averages and take no account of the circumstances when you ate the food. I felt sure that a square of chocolate eaten after a few hours in the hills will be much more efficiently used than a square eaten after a meal.
How can I find out more?
In reply to lowersharpnose:
Also, cooking food greatly increases the energy that you can access from it.
It is one theory that the transition to cooked food marked a bit of an evolutionary and developmental jump in humans, as it enabled us to fuel bigger brains and free up some time previously spent time gathering food and chewing.
> (In reply to Oceanrower)
>
> Are all calories equal. Specifically, does my body extract the energy from food (a bite of apple or toast, say) to the same extent whenever it is consumed?
>
> Are all calories equal. Specifically, does my body extract the energy from food (a bite of apple or toast, say) to the same extent whenever it is consumed?
Also, cooking food greatly increases the energy that you can access from it.
It is one theory that the transition to cooked food marked a bit of an evolutionary and developmental jump in humans, as it enabled us to fuel bigger brains and free up some time previously spent time gathering food and chewing.
In reply to riddle: full box weighs about 10gms. As the property houses are plastic I guess about 2gms?
In reply to riddle:
What is the total weight of the property featured on a Monopoly Board?
You need more information to answer that one. Are we talking the cumulative weight of all the properties on all the 'real life' roads. The total weight of the real life roads based on mean hotel weight for the area? Are we counting the mass of the water and electricity infrastructures? Or are you just talking about 20g of plastic?
What is the total weight of the property featured on a Monopoly Board?
You need more information to answer that one. Are we talking the cumulative weight of all the properties on all the 'real life' roads. The total weight of the real life roads based on mean hotel weight for the area? Are we counting the mass of the water and electricity infrastructures? Or are you just talking about 20g of plastic?
In reply to ripper: For a start, there are few truly non refelctive surfaces. What we see as black is usually 'almost black'
But what happens to the absorbed radiation is the question............
It a quantum thing. The photon excites the electrons of the atoms they hit to a higher quantum state (which therefore contain more energy)
This additional energy is then re emitted in a different part of the radiation spectrum (light is just a SMALL band in the radiation spectrum)
There are some losses in the state change. Hence being re emitted as a different frequency of radiation.
Otherwise know as 'The object the light hits, heats up'
But what happens to the absorbed radiation is the question............
It a quantum thing. The photon excites the electrons of the atoms they hit to a higher quantum state (which therefore contain more energy)
This additional energy is then re emitted in a different part of the radiation spectrum (light is just a SMALL band in the radiation spectrum)
There are some losses in the state change. Hence being re emitted as a different frequency of radiation.
Otherwise know as 'The object the light hits, heats up'
In reply to Game of Conkers:
No, because light travels in a linear fashion at a set speed (piss off, science pedants, KISS (Keep it simmple, stupid)
So in either room you are getting the same amount of light because in a 1km cubed room, the light hitting the walls is 'what's left over' from hitting your book etc.
I do not recommend trying to read in a 1cubic metre room.
> (In reply to Wonko The Sane) Ok, I think I get it, but it has resulted in me coming up with another scenario to try to explain my point..
>
> Two identical candles burn in two windowless rooms (room A and room B). Room A is 1m cubed, room B is 1km cubed. Both rooms have non reflective wall surfaces. If you sat reading a book half a metre away from the candle in room B, would you have less light than sitting in the same spot in room A?
>
> Two identical candles burn in two windowless rooms (room A and room B). Room A is 1m cubed, room B is 1km cubed. Both rooms have non reflective wall surfaces. If you sat reading a book half a metre away from the candle in room B, would you have less light than sitting in the same spot in room A?
No, because light travels in a linear fashion at a set speed (piss off, science pedants, KISS (Keep it simmple, stupid)
So in either room you are getting the same amount of light because in a 1km cubed room, the light hitting the walls is 'what's left over' from hitting your book etc.
I do not recommend trying to read in a 1cubic metre room.
In reply to ripper:
I think it excites an atom.
Incidentally, the wavelength of visible light is 4-7 * 10^-7 m. This is huge compared to the diameter of an atom ~10^-10m. That's three or four orders of magnitude, like a tall tree disappearing into a matchbox.
I think it excites an atom.
Incidentally, the wavelength of visible light is 4-7 * 10^-7 m. This is huge compared to the diameter of an atom ~10^-10m. That's three or four orders of magnitude, like a tall tree disappearing into a matchbox.
In reply to Wonko The Sane: I appreciate the KISS
Ok so in that case, If I have understood you correctly, my first example of the room with a window would not be affected by exposure to a dark room through another window and would remain as bright as before.
Ok so in that case, If I have understood you correctly, my first example of the room with a window would not be affected by exposure to a dark room through another window and would remain as bright as before.
In reply to Game of Conkers:
Correct.
The dark room would become lighter. How light depends on the size of the window from the bright room.
> (In reply to Wonko The Sane) I appreciate the KISS
>
> Ok so in that case, If I have understood you correctly, my first example of the room with a window would not be affected by exposure to a dark room through another window and would remain as bright as before.
>
> Ok so in that case, If I have understood you correctly, my first example of the room with a window would not be affected by exposure to a dark room through another window and would remain as bright as before.
Correct.
The dark room would become lighter. How light depends on the size of the window from the bright room.
In reply to lowersharpnose:
Erm, no. the wavelenght is just that, the lenght of the wave. Not the size of the photon.
> (In reply to ripper)
>
> I think it excites an atom.
>
> Incidentally, the wavelength of visible light is 4-7 * 10^-7 m. This is huge compared to the diameter of an atom ~10^-10m. That's three or four orders of magnitude, like a tall tree disappearing into a matchbox.
>
> I think it excites an atom.
>
> Incidentally, the wavelength of visible light is 4-7 * 10^-7 m. This is huge compared to the diameter of an atom ~10^-10m. That's three or four orders of magnitude, like a tall tree disappearing into a matchbox.
Erm, no. the wavelenght is just that, the lenght of the wave. Not the size of the photon.
In reply to Wonko The Sane:
yeah ok, I knew I'd sound thick...
>
> Otherwise know as 'The object the light hits, heats up'
> Otherwise know as 'The object the light hits, heats up'
yeah ok, I knew I'd sound thick...
In reply to ripper:
Not at all......... most people don't really think about energy transfer in an engineering way. No reason they should.
For instance, in your mind, when you jump into the air, you think you are moving away from the earth.
An engineer thinks, 'I am moving away from the earth, and the earth is infintisimally moving away from me too.
Every action has an equal and opposite reaction and all that.
> (In reply to Wonko The Sane)
> [...]
>
> yeah ok, I knew I'd sound thick...
> [...]
>
> yeah ok, I knew I'd sound thick...
Not at all......... most people don't really think about energy transfer in an engineering way. No reason they should.
For instance, in your mind, when you jump into the air, you think you are moving away from the earth.
An engineer thinks, 'I am moving away from the earth, and the earth is infintisimally moving away from me too.
Every action has an equal and opposite reaction and all that.
In reply to Game of Conkers:
My schoolboy physics tells me that light is energy and energy can't be destroyed only converted SO the light in the room will be converted in to heat so the room will end up a tiny tiny tiny tiny bit warmer. Errrrr I think!
> (In reply to Oceanrower)
>
> Does light get "used up" lighting a space.
>
> Does light get "used up" lighting a space.
My schoolboy physics tells me that light is energy and energy can't be destroyed only converted SO the light in the room will be converted in to heat so the room will end up a tiny tiny tiny tiny bit warmer. Errrrr I think!
In reply to Wonko The Sane:
But...some of it bounces back of the walls and helps you read. The proportion of this that reaches you is bigger in a 1m^3 room than a 1km^3 room. Therefore 1m^3 is brighter.
> (In reply to Game of Conkers)
> [...]
>
> No, because light travels in a linear fashion at a set speed (piss off, science pedants, KISS (Keep it simmple, stupid)
> So in either room you are getting the same amount of light because in a 1km cubed room, the light hitting the walls is 'what's left over'
> [...]
>
> No, because light travels in a linear fashion at a set speed (piss off, science pedants, KISS (Keep it simmple, stupid)
> So in either room you are getting the same amount of light because in a 1km cubed room, the light hitting the walls is 'what's left over'
But...some of it bounces back of the walls and helps you read. The proportion of this that reaches you is bigger in a 1m^3 room than a 1km^3 room. Therefore 1m^3 is brighter.
> (In reply to Wonko The Sane) Ok, I think I get it, but it has resulted in me coming up with another scenario to try to explain my point..
>
> Two identical candles burn in two windowless rooms (room A and room B). Room A is 1m cubed, room B is 1km cubed. Both rooms have non reflective wall surfaces. If you sat reading a book half a metre away from the candle in room B, would you have less light than sitting in the same spot in room A?
>
> Two identical candles burn in two windowless rooms (room A and room B). Room A is 1m cubed, room B is 1km cubed. Both rooms have non reflective wall surfaces. If you sat reading a book half a metre away from the candle in room B, would you have less light than sitting in the same spot in room A?
Good scenario. There is a skill in coming up with the simplest situation that illustrates your point - I think programmers call it a minimal working example.
If the walls are non-reflective, then they absorb all the light that falls on them. So the only light falling on your book is the light that's coming straight from the candle. Since the light has only travelled 50cm when it arrives at your book, it doesn't 'know' about the walls yet, so the presence of walls can't affect the amount of light falling on your book.
In reply to Oceanrower:
The lack of insulator on the earth of a twin and earth cable is a design feature, without the earth there is more chance, if the cable is damaged, there is more chance of the current going safely to earth tripping a safety device rather than electrocuting someone.
The lack of insulator on the earth of a twin and earth cable is a design feature, without the earth there is more chance, if the cable is damaged, there is more chance of the current going safely to earth tripping a safety device rather than electrocuting someone.
In reply to gethin_allen:
Also, twin and earth cables should be insulated where they enter a fitting by adding a green/yellow sleeve.
Also, twin and earth cables should be insulated where they enter a fitting by adding a green/yellow sleeve.
In reply to MG:
No, because he STATED non reflective walls. I qualified my statement by saying few surfaces are truly non reflective.
> (In reply to Wonko The Sane)
> [...]
>
> But...some of it bounces back of the walls and helps you read. The proportion of this that reaches you is bigger in a 1m^3 room than a 1km^3 room. Therefore 1m^3 is brighter.
> [...]
>
> But...some of it bounces back of the walls and helps you read. The proportion of this that reaches you is bigger in a 1m^3 room than a 1km^3 room. Therefore 1m^3 is brighter.
No, because he STATED non reflective walls. I qualified my statement by saying few surfaces are truly non reflective.
In reply to gethin_allen: That makes sense. Thanks, and to all the others above.
In reply to Wonko The Sane: Missed that, sorry....
But all walls are reflective! I think a small room will appear brighter, partly because you will generally be nearer the window but partly because of reflection. Note windows with shutters normally have them sensibly angled when open to reflect light in to the room. I approve of shutters.
But all walls are reflective! I think a small room will appear brighter, partly because you will generally be nearer the window but partly because of reflection. Note windows with shutters normally have them sensibly angled when open to reflect light in to the room. I approve of shutters.
In reply to Oceanrower: While I'm on a roll, another one.
Does it cost more to play a stereo (showing my age here) or TV loudly or is quieter cheaper?
Does it cost more to play a stereo (showing my age here) or TV loudly or is quieter cheaper?
In reply to Pursued by a bear:
What, when you get right down to it, is the point?
There is no point, but the point is to try and behave as though there is one...
What, when you get right down to it, is the point?
>
There is no point, but the point is to try and behave as though there is one...
In reply to MG: It was a thought experiment, MG.
I clearly said that there are few truly non reflective surfaces.
In a small space such as a room though, your distance from the window is almost meaningless apart from if there are things in the way. Light from the sun is to all intents and purposes, parallel rays. Of course there is also reflected light coming in at different angles of incidence. But unless the light has alread hit a surface, you'll notice little difference in the readings.
I have actually had to DO this when I was on my foundation year for uni............ go out to the mezzanine floor which was black and white tiled and take light readings to show distribution.
I also had to backward engineer a 13amp plug, which was a lot more fun that it sounds.
I clearly said that there are few truly non reflective surfaces.
In a small space such as a room though, your distance from the window is almost meaningless apart from if there are things in the way. Light from the sun is to all intents and purposes, parallel rays. Of course there is also reflected light coming in at different angles of incidence. But unless the light has alread hit a surface, you'll notice little difference in the readings.
I have actually had to DO this when I was on my foundation year for uni............ go out to the mezzanine floor which was black and white tiled and take light readings to show distribution.
I also had to backward engineer a 13amp plug, which was a lot more fun that it sounds.
In reply to Oceanrower:
Why do you bounce?
If you fall on a stretchy rope, and it brings you to a halt, why doesn't it just bring you to a halt? Where does the energy to ping you back up again come from? If there's enough energy to ping you back up, why didn't you stop falling earlier?
Why do you bounce?
If you fall on a stretchy rope, and it brings you to a halt, why doesn't it just bring you to a halt? Where does the energy to ping you back up again come from? If there's enough energy to ping you back up, why didn't you stop falling earlier?
In reply to Oceanrower:
Yes, it costs more. You're using more energy.
I'd hate to be the one trying to measure the difference though.
It takes relatively little energy to vibrate air.
> (In reply to Oceanrower) While I'm on a roll, another one.
>
> Does it cost more to play a stereo (showing my age here) or TV loudly or is quieter cheaper?
>
> Does it cost more to play a stereo (showing my age here) or TV loudly or is quieter cheaper?
Yes, it costs more. You're using more energy.
I'd hate to be the one trying to measure the difference though.
It takes relatively little energy to vibrate air.
In reply to ripper: You have a point, but that's not *the* point. The point about the point is that there has to be a point rather than no point, otherwise speculation would be pointless. The fact that speculation often is pointless is not the point either.
So what, when you get right down to it, *is* the point?
T.
So what, when you get right down to it, *is* the point?
T.
In reply to nniff:
This could go on all day!!
F=MA
Force = mass x acceleration.
the rope is 'storing' energy from your acceleration (or in non engineering speak, deceleration)
As you go higher, you increase your potential energy.
When you fall, that potential energy is tranformed into kinetic energy.
So the rope is not just catching your weight, it is taking up the energy from your acceleration. It is storing this until it reaches a point where it now has all your kinetic energy, you've come to a halt, and the energy in the rope is now above that of your 'weight' so you rebound.
> (In reply to Oceanrower)
>
>
> Why do you bounce?
>
> If you fall on a stretchy rope, and it brings you to a halt, why doesn't it just bring you to a halt? Where does the energy to ping you back up again come from? If there's enough energy to ping you back up, why didn't you stop falling earlier?
>
>
> Why do you bounce?
>
> If you fall on a stretchy rope, and it brings you to a halt, why doesn't it just bring you to a halt? Where does the energy to ping you back up again come from? If there's enough energy to ping you back up, why didn't you stop falling earlier?
This could go on all day!!
F=MA
Force = mass x acceleration.
the rope is 'storing' energy from your acceleration (or in non engineering speak, deceleration)
As you go higher, you increase your potential energy.
When you fall, that potential energy is tranformed into kinetic energy.
So the rope is not just catching your weight, it is taking up the energy from your acceleration. It is storing this until it reaches a point where it now has all your kinetic energy, you've come to a halt, and the energy in the rope is now above that of your 'weight' so you rebound.
In reply to Pursued by a bear: no, i'm sure i'm right, the point is not that there's a point, it's that there's no point, but as I said it's crucial to behave as though there is a point otherwise everything we do would be totally pointless, and what would be the point of that?
while I don't think there's a point, though, there is always a pint
while I don't think there's a point, though, there is always a pint
In reply to Oceanrower: On the subject of light...
If a light source is shining through an infinitely straight tunnel that has completely unreflective sides, will you ever be able to see light apart from at the source?
The photons will be going through but if there is nothing to reflect off are they essentially not there?
If a light source is shining through an infinitely straight tunnel that has completely unreflective sides, will you ever be able to see light apart from at the source?
The photons will be going through but if there is nothing to reflect off are they essentially not there?
In reply to Wonko The Sane:
But the wavelength is a characteristic length scale of the wave, so, while it may not be the "size" of the photon exactly, it still makes physical sense to compare it to other length scales, like the "diameter" of the atom. In fact the wavelength determines how small an object you can probe (or "see") with electromagnetic waves.
As you said, the wavelength of light is about 10^{-7} m. That means that objects smaller than about 10^{-7}m across won't scatter light and you can't see them. But an electron at the sort of energies you'd find in an electron microscope has a much smaller wavelength - about 10^{-11}m I think - and an EM can reconstruct images at least down to the single nanometer scale.
> Erm, no. the wavelenght is just that, the lenght of the wave. Not the size of the photon.
But the wavelength is a characteristic length scale of the wave, so, while it may not be the "size" of the photon exactly, it still makes physical sense to compare it to other length scales, like the "diameter" of the atom. In fact the wavelength determines how small an object you can probe (or "see") with electromagnetic waves.
As you said, the wavelength of light is about 10^{-7} m. That means that objects smaller than about 10^{-7}m across won't scatter light and you can't see them. But an electron at the sort of energies you'd find in an electron microscope has a much smaller wavelength - about 10^{-11}m I think - and an EM can reconstruct images at least down to the single nanometer scale.
In reply to James Malloch:
They are there. Some, by pure chance will be travelling parallel to the tunnel walls. These photons will be visible at the 'other end' of the infinite tube if you had a sensitive enough instrument. How snesitive it needs to be will depend on the light source and how much light happens to be travelling parallel.
however, this is an infinite tube and light IS deflected by gravity. The tunnel walls will have mass and therefore gravity, so any photon which is slightly nearer to one wall than another would be deflected over an infinite lenght and hit the wall of the tunnel and be abosrbed and excite the electron of the atom it hits, which would go to a higher quatum state and emit a different frequency of radiation.
The non parallel rays would sooner or later hit the tunnel wall with the same result.
> (In reply to Oceanrower) On the subject of light...
>
> If a light source is shining through an infinitely straight tunnel that has completely unreflective sides, will you ever be able to see light apart from at the source?
>
> The photons will be going through but if there is nothing to reflect off are they essentially not there?
>
> If a light source is shining through an infinitely straight tunnel that has completely unreflective sides, will you ever be able to see light apart from at the source?
>
> The photons will be going through but if there is nothing to reflect off are they essentially not there?
They are there. Some, by pure chance will be travelling parallel to the tunnel walls. These photons will be visible at the 'other end' of the infinite tube if you had a sensitive enough instrument. How snesitive it needs to be will depend on the light source and how much light happens to be travelling parallel.
however, this is an infinite tube and light IS deflected by gravity. The tunnel walls will have mass and therefore gravity, so any photon which is slightly nearer to one wall than another would be deflected over an infinite lenght and hit the wall of the tunnel and be abosrbed and excite the electron of the atom it hits, which would go to a higher quatum state and emit a different frequency of radiation.
The non parallel rays would sooner or later hit the tunnel wall with the same result.
In reply to crossdressingrodney:
The question is not about whether you can SEE the smaller particles (atoms, electrons or whatever) the question was what happens to the light. The photons do collide with the electrons hence the 'heating up'
SEEING the said electron is a completely different matter.
> (In reply to Wonko The Sane)
> [...]
>
> But the wavelength is a characteristic length scale of the wave, so, while it may not be the "size" of the photon exactly, it still makes physical sense to compare it to other length scales, like the "diameter" of the atom. In fact the wavelength determines how small an object you can probe (or "see") with electromagnetic waves.
>
> [...]
>
> But the wavelength is a characteristic length scale of the wave, so, while it may not be the "size" of the photon exactly, it still makes physical sense to compare it to other length scales, like the "diameter" of the atom. In fact the wavelength determines how small an object you can probe (or "see") with electromagnetic waves.
>
> As you said, the wavelength of light is about 10^{-7} m. That means that objects smaller than about 10^{-7}m across won't scatter light and you can't see them. But an electron at the sort of energies you'd find in an electron microscope has a much smaller wavelength - about 10^{-11}m I think - and an EM can reconstruct images at least down to the single nanometer scale.
The question is not about whether you can SEE the smaller particles (atoms, electrons or whatever) the question was what happens to the light. The photons do collide with the electrons hence the 'heating up'
SEEING the said electron is a completely different matter.
In reply to lowersharpnose:
There is no such thing as a 'blue' photon.
But photons are ickle.
How ickle, I'm not sure without googling or looking at a book, which I can't be arsed to do.
> (In reply to Wonko The Sane)
>
> How big is a photon then (how about a blue one)?
>
> How big is a photon then (how about a blue one)?
There is no such thing as a 'blue' photon.
But photons are ickle.
How ickle, I'm not sure without googling or looking at a book, which I can't be arsed to do.
In reply to Oceanrower: Why are there two tides a day. Note the world spins only once a day. (I know of various answers, not sure one(s) which is correct).
In reply to Oceanrower:
Who put the bomp in the bompalompalomp?
Who put the ram in the ramalamadingdong?
Who put the bomp in the bompalompalomp?
Who put the ram in the ramalamadingdong?
In reply to MG:
Good one. I'll let someone else answer!
> (In reply to Oceanrower) Why are there two tides a day. Note the world spins only once a day. (I know of various answers, not sure one(s) which is correct).
Good one. I'll let someone else answer!
In reply to Blue Straggler: The Edsels.
In reply to ripper: But if there is no point then what's the point in pointing out the absence of a point then behaving as though there is a point after all?
I feel this discussion is suffering from the absence of a pint, mind.
T.
I feel this discussion is suffering from the absence of a pint, mind.
T.
In reply to MG:
though the pedant in me wants to point out that actually, the Earth spins ALL day, not once a day.
It does however complete one rotation per day. Ish. A sidereal day being a teeny bit less than 24 hrs.
But I'm not going to point that out. It would be churlish.
> (In reply to Oceanrower) Why are there two tides a day. Note the world spins only once a day. (I know of various answers, not sure one(s) which is correct).
though the pedant in me wants to point out that actually, the Earth spins ALL day, not once a day.
It does however complete one rotation per day. Ish. A sidereal day being a teeny bit less than 24 hrs.
But I'm not going to point that out. It would be churlish.
In reply to Game of Conkers:
This made me think of something I've previously wondered about; if you had a sealed box with reflective internal surfaces and a light-bulb inside, would turning the light on then off again mean the box would stay lit from the light particles bouncing back and forth?
> (In reply to Oceanrower)
>
> Does light get "used up" lighting a space.
>
>
> Does light get "used up" lighting a space.
>
This made me think of something I've previously wondered about; if you had a sealed box with reflective internal surfaces and a light-bulb inside, would turning the light on then off again mean the box would stay lit from the light particles bouncing back and forth?
In reply to Oceanrower: To transfer signal two wires are needed.
In case of twin cable the earth plays the role of magnetic disturbances protection to the signal conducted by the twin wires.
In case of the round cable the signal is transferred by the wire and the earth so the earth is to be coated to exclude damage and for esthetic purposes .
We do not speak of insulation for round cable is designed for low voltage.
In case of twin cable the earth plays the role of magnetic disturbances protection to the signal conducted by the twin wires.
In case of the round cable the signal is transferred by the wire and the earth so the earth is to be coated to exclude damage and for esthetic purposes .
We do not speak of insulation for round cable is designed for low voltage.
In reply to nufkin:
As a thought experiment, yes.
However, there is nothing known which is 100% reflective so in reality, no.
> (In reply to Game of Conkers)
> [...]
>
>
> This made me think of something I've previously wondered about; if you had a sealed box with reflective internal surfaces and a light-bulb inside, would turning the light on then off again mean the box would stay lit from the light particles bouncing back and forth?
> [...]
>
>
> This made me think of something I've previously wondered about; if you had a sealed box with reflective internal surfaces and a light-bulb inside, would turning the light on then off again mean the box would stay lit from the light particles bouncing back and forth?
As a thought experiment, yes.
However, there is nothing known which is 100% reflective so in reality, no.
In reply to panz:
Ah. I misunderstood the question.
He meant the difference between T&E and flex.
I took it to mean the difference between T&E and single earth strap.
> (In reply to Oceanrower) To transfer signal two wires are needed.
>
> In case of twin cable the earth plays the role of magnetic disturbances protection to the signal conducted by the twin wires.
>
> In case of the round cable the signal is transferred by the wire and the earth so the earth is to be coated to exclude damage and for esthetic purposes .
>
> We do not speak of insulation for round cable is designed for low voltage.
>
> In case of twin cable the earth plays the role of magnetic disturbances protection to the signal conducted by the twin wires.
>
> In case of the round cable the signal is transferred by the wire and the earth so the earth is to be coated to exclude damage and for esthetic purposes .
>
> We do not speak of insulation for round cable is designed for low voltage.
Ah. I misunderstood the question.
He meant the difference between T&E and flex.
I took it to mean the difference between T&E and single earth strap.
In reply to Oceanrower:
When bubble wrap is shipped from the factory, what do they wrap it in?
When bubble wrap is shipped from the factory, what do they wrap it in?
In reply to krikoman:
They can't get the wrapper off.
Sorry if this has already been answered but I haven't read the whole thread
> (In reply to Oceanrower) in twin and earth it an extra expence. In normal cable it need to be insulated because if it was bare it might touch the other connections in the plug.
>
> Why don't polar bears eat penguins?
>
> Why don't polar bears eat penguins?
They can't get the wrapper off.
Sorry if this has already been answered but I haven't read the whole thread
In reply to 999thAndy:
A sacrificial layer of bubble wrap?
A cardboard box?
> (In reply to Oceanrower)
> When bubble wrap is shipped from the factory, what do they wrap it in?
> When bubble wrap is shipped from the factory, what do they wrap it in?
A sacrificial layer of bubble wrap?
A cardboard box?
In reply to hokkyokusei: Sorry you already answered it.
In reply to Oceanrower:
I have just asked this on another thead on Dogs.
(so no cheating in case someone has answered.)
The question is , how does a blind person know where his guide dogs shit is , so they can pick it up ?
I have a blind friend, but he does not have a guide dog, and he does not know either !
I have just asked this on another thead on Dogs.
(so no cheating in case someone has answered.)
The question is , how does a blind person know where his guide dogs shit is , so they can pick it up ?
I have a blind friend, but he does not have a guide dog, and he does not know either !
In reply to Game of Conkers:
Whenever light hits a surface a certain percentage is absorbed and the rest is scattered. If you have a white paint that reflects 90% of the light that hits it then after 43 bounces you will be down to about 1% of the incoming light left.
Given a room where the average distance between bounces is 10m (big room!), and a speed of light of 299,792,458 m/s then that would take about 1.43 millionths of a second.
Whenever light hits a surface a certain percentage is absorbed and the rest is scattered. If you have a white paint that reflects 90% of the light that hits it then after 43 bounces you will be down to about 1% of the incoming light left.
Given a room where the average distance between bounces is 10m (big room!), and a speed of light of 299,792,458 m/s then that would take about 1.43 millionths of a second.
In reply to Wonko The Sane:
I think I read somewhere that the total sound energy generated during the FA cup final is enough to make one cup of tea.
> It takes relatively little energy to vibrate air.
I think I read somewhere that the total sound energy generated during the FA cup final is enough to make one cup of tea.
In reply to Wonko The Sane:
Whilst I'm thinking about packaging, which moron came up with those plastic boxes welded at the edges that need a machete to open? Why weld the f#####g edges in the 1st place?
Whilst I'm thinking about packaging, which moron came up with those plastic boxes welded at the edges that need a machete to open? Why weld the f#####g edges in the 1st place?
In reply to crossdressingrodney:
It's the closest thing to a 'real day'
i.E. how long it takes the earth to rotate once using a (relatively) fixed object as a reference. Distant stars are used.
In navigation, we do a 'sun sight' every day at noon. I.E. just before the sun reaches it's zenith, we take out the sextant and keep measuring the angle of the sun until instead of seeing it rise, we see it start to fall. This is 'noon'
It's surprisingly accurate.
however......... the earth is moving AROUND the sun. So for purposes of measuring the LENGHT of a day, it's inaccurate.
> (In reply to Wonko The Sane)
>
> Since we're not allowed to google stuff: what is a sidereal day?
>
> Since we're not allowed to google stuff: what is a sidereal day?
It's the closest thing to a 'real day'
i.E. how long it takes the earth to rotate once using a (relatively) fixed object as a reference. Distant stars are used.
In navigation, we do a 'sun sight' every day at noon. I.E. just before the sun reaches it's zenith, we take out the sextant and keep measuring the angle of the sun until instead of seeing it rise, we see it start to fall. This is 'noon'
It's surprisingly accurate.
however......... the earth is moving AROUND the sun. So for purposes of measuring the LENGHT of a day, it's inaccurate.
In reply to 999thAndy: Bubble wrap comes in a big polythene bag, at least mind does and i buy it direct.
In reply to Wonko The Sane:
Blue photons are what make up blue light. So a blue photon is one with a wavelength of about 4 x 10^{-7}m.
Now you're saying that photons have a size? Earlier you said that you are not talking about wavelength. So what do you mean by size?
> There's no such thing as a blue photon.
Blue photons are what make up blue light. So a blue photon is one with a wavelength of about 4 x 10^{-7}m.
> But photons are ickle.
Now you're saying that photons have a size? Earlier you said that you are not talking about wavelength. So what do you mean by size?
In reply to Jim C: How does a guide dig know where it is going? If (I were blind and had a guide dog and) I wanted to go to, say, the bookmakers, how does the dog know where the the bookmakers is?
Ps: I DONT have a gambling problem.
Ps: I DONT have a gambling problem.
In reply to jonathan shepherd: We had a delivery of bubble wrap the other day.
I asked the boss what to do with it and he told me to pop it in the stores.
3 hours later.................
I asked the boss what to do with it and he told me to pop it in the stores.
3 hours later.................
In reply to 999thAndy:
To stop people stealing or tampering with goods at some point between factory and end user.
> Why weld the f#####g edges in the 1st place?
To stop people stealing or tampering with goods at some point between factory and end user.
In reply to 999thAndy:
For the stuff used in factories, it's generally wrapped in cellophane, 4 large rolls to a pallet I found.
> (In reply to Oceanrower)
> When bubble wrap is shipped from the factory, what do they wrap it in?
> When bubble wrap is shipped from the factory, what do they wrap it in?
For the stuff used in factories, it's generally wrapped in cellophane, 4 large rolls to a pallet I found.
In reply to Blue Straggler:
Whats wrong with nice cardboard box and a tamper evident seal? Seems to work for lots of stuff and best of all - no machete required
Whats wrong with nice cardboard box and a tamper evident seal? Seems to work for lots of stuff and best of all - no machete required
In reply to crossdressingrodney:
I deserve that for being pedantic myself. But no, it is not a 'blue photon' it is simply a photon at a specific frequency. It's 'blueness' is just something we perceive.
Lol, again, I deserve this. I was trying to keep it simple.
No, they do not have 'size' as such. And I do not claim to understand it fully. They do have a volume of sorts.It is not certain one way or the other whether they have mass.
I do not pretend to understand WHY light is affected by gravity if they don't have mass. I'm sure I was taught some explanation of it years ago, but it was over 20 years ago!
> (In reply to Wonko The Sane)
>
> [...]
>
> Blue photons are what make up blue light. So a blue photon is one with a wavelength of about 4 x 10^{-7}m.
>
>
> [...]
>
> Blue photons are what make up blue light. So a blue photon is one with a wavelength of about 4 x 10^{-7}m.
>
I deserve that for being pedantic myself. But no, it is not a 'blue photon' it is simply a photon at a specific frequency. It's 'blueness' is just something we perceive.
> [...]
>
> Now you're saying that photons have a size? Earlier you said that you are not talking about wavelength. So what do you mean by size?
>
> Now you're saying that photons have a size? Earlier you said that you are not talking about wavelength. So what do you mean by size?
Lol, again, I deserve this. I was trying to keep it simple.
No, they do not have 'size' as such. And I do not claim to understand it fully. They do have a volume of sorts.It is not certain one way or the other whether they have mass.
I do not pretend to understand WHY light is affected by gravity if they don't have mass. I'm sure I was taught some explanation of it years ago, but it was over 20 years ago!
In reply to toad:
Yes but if you gave a hungry polar bear a penguin, it would eat it.
> (In reply to krikoman)
>
> [...]
>
> Because the commute to the other end of the earth is really inconvenient.
>
> [...]
>
> Because the commute to the other end of the earth is really inconvenient.
Yes but if you gave a hungry polar bear a penguin, it would eat it.
In reply to Oceanrower: Twin and earth has a solid earth conductor, flex has multi stranded, the insulation is there to keep the strands together hence the cross sectional area of the protective conductor constant.
In reply to Wonko The Sane:
Applying what I've learnt (I think) from earlier posts here, the light would be absorbed as heat, would it?
> (In reply to nufkin)
> [...]
>
> As a thought experiment, yes.
> However, there is nothing known which is 100% reflective so in reality, no.
> [...]
>
> As a thought experiment, yes.
> However, there is nothing known which is 100% reflective so in reality, no.
Applying what I've learnt (I think) from earlier posts here, the light would be absorbed as heat, would it?
In reply to Oceanrower: Why on phone key pads is "1" at top left but on calculator keypads at bottom left?
In reply to lowersharpnose:
No. Not if it is indigestible roughage, for example. You probably would find it pretty hard to extract the calories from chewing up a piece of wood, even though it contains plenty of them.
> (In reply to Oceanrower)
>
> Are all calories equal. Specifically, does my body extract the energy from food (a bite of apple or toast, say) to the same extent whenever it is consumed?
>
> Are all calories equal. Specifically, does my body extract the energy from food (a bite of apple or toast, say) to the same extent whenever it is consumed?
No. Not if it is indigestible roughage, for example. You probably would find it pretty hard to extract the calories from chewing up a piece of wood, even though it contains plenty of them.
In reply to nufkin:
Simply put, yes.
> (In reply to Wonko The Sane)
> [...]
>
> Applying what I've learnt (I think) from earlier posts here, the light would be absorbed as heat, would it?
> [...]
>
> Applying what I've learnt (I think) from earlier posts here, the light would be absorbed as heat, would it?
Simply put, yes.
In reply to Wonko The Sane:
Hang on. Let me see if I understand. Are the following statements true?
1) A second is defined so that 'a day' (=24 hours) is the time between consecutive noons. This is constant throughout the year and doesn't matter where you measure it on earth (as long as the sun is visible).
2) A sidereal day is how long it takes for the earth to do one complete rotation, relative to the sun and stars, which can be regarded as pretty much fixed.
3) A day and a sidereal day are not the same. But over a year there should be roughly 1 more of one than the other. So their lengths differ by about 1 part in 365.
I have to admit that I don't know which way the earth orbits around the sun, so I can't tell whether a sidereal day is slightly longer or slightly shorter than 24 hours.
Incidentally, does anyone happen to know the derivation of the word sidereal?
> It's the closest thing to a 'real day'
> i.E. how long it takes the earth to rotate once using a (relatively) fixed object as a reference. Distant stars are used.
> i.E. how long it takes the earth to rotate once using a (relatively) fixed object as a reference. Distant stars are used.
> In navigation, we do a 'sun sight' every day at noon. I.E. just before the sun reaches it's zenith, we take out the sextant and keep measuring the angle of the sun until instead of seeing it rise, we see it start to fall. This is 'noon'
> It's surprisingly accurate.
>
> however......... the earth is moving AROUND the sun. So for purposes of measuring the LENGHT of a day, it's inaccurate.
> It's surprisingly accurate.
>
> however......... the earth is moving AROUND the sun. So for purposes of measuring the LENGHT of a day, it's inaccurate.
Hang on. Let me see if I understand. Are the following statements true?
1) A second is defined so that 'a day' (=24 hours) is the time between consecutive noons. This is constant throughout the year and doesn't matter where you measure it on earth (as long as the sun is visible).
2) A sidereal day is how long it takes for the earth to do one complete rotation, relative to the sun and stars, which can be regarded as pretty much fixed.
3) A day and a sidereal day are not the same. But over a year there should be roughly 1 more of one than the other. So their lengths differ by about 1 part in 365.
I have to admit that I don't know which way the earth orbits around the sun, so I can't tell whether a sidereal day is slightly longer or slightly shorter than 24 hours.
Incidentally, does anyone happen to know the derivation of the word sidereal?
In reply to crossdressingrodney: I like that one, I also read in an inflight magazine recently that one tea bag (hidden down a seat cushion) on a Boeing 747 will use up an extra 1 litre of fuel over a year.
I have to say I was rather underwhelmed by that stat, but it stuck with me for some reason
I have to say I was rather underwhelmed by that stat, but it stuck with me for some reason
If it takes 366 days for dog with a wooden leg to catch a cat with a glass eye, how many lumps of lead does a tramp need to make a padlock?
In reply to crossdressingrodney:
Not me!
> (In reply to Wonko The Sane)
> [...]
>
> [...]
>
> Hang on. Let me see if I understand. Are the following statements true?
>
> 1) A second is defined so that 'a day' (=24 hours) is the time between consecutive noons. This is constant throughout the year and doesn't matter where you measure it on earth (as long as the sun is visible).
>
Not absolutely, no. If you want to get picky about it, our orbit is not perfectly circular, nor is our angle of rotation set. > [...]
>
> [...]
>
> Hang on. Let me see if I understand. Are the following statements true?
>
> 1) A second is defined so that 'a day' (=24 hours) is the time between consecutive noons. This is constant throughout the year and doesn't matter where you measure it on earth (as long as the sun is visible).
>
> 2) A sidereal day is how long it takes for the earth to do one complete rotation, relative to the sun and stars, which can be regarded as pretty much fixed.
>
No. The sidereal day is one rotation measured against a RELATIVELY fixed point. A distant star. Not our own. We travel in a direction around the sun. For practical purposes, this error is removed if measuring against a distant star.>
> 3) A day and a sidereal day are not the same. But over a year there should be roughly 1 more of one than the other. So their lengths differ by about 1 part in 365.
>
I'd have to sit and think about it......... but no, the two do not have to match up any more than the gregorian calender has to match to a 'real' year. Hence leap years to synchronise them.>
> I have to admit that I don't know which way the earth orbits around the sun, so I can't tell whether a sidereal day is slightly longer or slightly shorter than 24 hours.
>
It is shorter, haven't thought about it so also do not know which direction we travel in.>
> Incidentally, does anyone happen to know the derivation of the word sidereal?
Not me!
From the Latin sidereus (astral or of the stars).
Some bloke in Italy wrote a book Sidereus Nuncius, typically they locked him up!
Some bloke in Italy wrote a book Sidereus Nuncius, typically they locked him up!
In reply to Philip:
Although, I should make it clear, it wasn't that book that upset the Papal twit.
> From the Latin sidereus (astral or of the stars).
>
> Some bloke in Italy wrote a book Sidereus Nuncius, typically they locked him up!
>
> Some bloke in Italy wrote a book Sidereus Nuncius, typically they locked him up!
Although, I should make it clear, it wasn't that book that upset the Papal twit.
> I do not pretend to understand WHY light is affected by gravity if they don't have mass. I'm sure I was taught some explanation of it years ago, but it was over 20 years ago!
You are wrong that light doesn't have mass; it doesn't have rest mass.
In reply to Game of Conkers:
A good illustration of what a tiny tiny percentage of a 747's fuel consumption 1 litre is!
> (In reply to crossdressingrodney) I like that one, I also read in an inflight magazine recently that one tea bag (hidden down a seat cushion) on a Boeing 747 will use up an extra 1 litre of fuel over a year.
>
> I have to say I was rather underwhelmed by that stat, but it stuck with me for some reason
>
> I have to say I was rather underwhelmed by that stat, but it stuck with me for some reason
A good illustration of what a tiny tiny percentage of a 747's fuel consumption 1 litre is!
In reply to Wonko The Sane:
It's getting philosophical now. If a gajillion blue-range photons are blue, then what about half that number? And half that? And so on...
Also there are biological entities in nature that can detect single photons. Do they see blue or not?
Anyway, I take your point.
Not sure about volume. I'm not an expert in this, but the only physical length quantity possessed by propogating light that I know of is the wavelength.
>It is not certain one way or the other whether they have mass.
I think the correct statement is that photons have zero rest mass, but they have momentum and hence they have mass-energy: we know from Einstein that energy is a contribution from rest mass plus kinetic energy. Actually you can't see this from E=mc^2, you have to use Einstein's full version that holds for masslass particles, which I think (without Googling) is
E^2=m^2c^4+p^2c^2 (?)
Nowadays, gravity is understood to be the bending of space-time by mass-energy (which includes light!), and light follows the shortest path through this curved space. It therefore appears to be bent by massive bodies, like stars.
But I think we were talking in the context of Newtonian mechanics?
Start with Newton's second law: F=ma, where m is the mass of the object A. Let B be some large gravitating object of mass M and write down the force from Newton's law of gravitation:
F = mMG/r^2
where r is the distance between A and B, G is Newton's constant. Put both sides together
ma = mMG/r^2
cancel the m
a = MG/r^2
and you get an equation for acceleration that is independent of m. so it makes sense also when m=0. So the equation for massless particles is the same as the equation for massive ones.
> I deserve that for being pedantic myself. But no, it is not a 'blue photon' it is simply a photon at a specific frequency. It's 'blueness' is just something we perceive.
It's getting philosophical now. If a gajillion blue-range photons are blue, then what about half that number? And half that? And so on...
Also there are biological entities in nature that can detect single photons. Do they see blue or not?
Anyway, I take your point.
> Lol, again, I deserve this. I was trying to keep it simple.
> No, they do not have 'size' as such. And I do not claim to understand it fully. They do have a volume of sorts.
> No, they do not have 'size' as such. And I do not claim to understand it fully. They do have a volume of sorts.
Not sure about volume. I'm not an expert in this, but the only physical length quantity possessed by propogating light that I know of is the wavelength.
>It is not certain one way or the other whether they have mass.
I think the correct statement is that photons have zero rest mass, but they have momentum and hence they have mass-energy: we know from Einstein that energy is a contribution from rest mass plus kinetic energy. Actually you can't see this from E=mc^2, you have to use Einstein's full version that holds for masslass particles, which I think (without Googling) is
E^2=m^2c^4+p^2c^2 (?)
> I do not pretend to understand WHY light is affected by gravity if they don't have mass. I'm sure I was taught some explanation of it years ago, but it was over 20 years ago!
Nowadays, gravity is understood to be the bending of space-time by mass-energy (which includes light!), and light follows the shortest path through this curved space. It therefore appears to be bent by massive bodies, like stars.
But I think we were talking in the context of Newtonian mechanics?
Start with Newton's second law: F=ma, where m is the mass of the object A. Let B be some large gravitating object of mass M and write down the force from Newton's law of gravitation:
F = mMG/r^2
where r is the distance between A and B, G is Newton's constant. Put both sides together
ma = mMG/r^2
cancel the m
a = MG/r^2
and you get an equation for acceleration that is independent of m. so it makes sense also when m=0. So the equation for massless particles is the same as the equation for massive ones.
In reply to ripper: Scrap paper calc assuming 10 hours a day for 300 days a year, 45 million litres a year!
> Also there are biological entities in nature that can detect single photons. Do they see blue or not?
The answer is yes and no. Yes in the sense that a nothing else distinguishes a photon, so that you can't have two 'blue' photons that are then distinguished by anything else (except plane of polarization). So two blue flowers would be two blue flowers to a bee - albeit they won't be able to comprehend them and their colour range is different than ours.
But it's also no in that we can be tricked into seeing colours - at the moment your screen is using a mixture of red, green and blue. Our eyes have optimum wavelengths for the detection of light - we are best at green. It would be possible to make two objects look the same colour to us but be distinguished by a spectrophotometer, and therefore possibly different to a different creature. But as I said, the photons from these two objects would not be identical.
As an aside, do the slugs that ate my strawberries and my fennel have the same perception of those flavours (and do they like Greg Wallace off Masterchef think they go together )
In reply to Punter S Thompson:
Wondered how long that would take
Wondered how long that would take
In reply to crossdressingrodney:
Did you just describe the behaviour of a quantized unit of energy according to relativity and then drop out a result in classical mechanics?
Did you just describe the behaviour of a quantized unit of energy according to relativity and then drop out a result in classical mechanics?
In reply to crossdressingrodney: Cheers for that. Good explanation.
In reply to Punter S Thompson:
In classical climbing E1.
Apply relativity (to non Peak routes) HVS.
However, it's really a quantum problem and you can't be accurate about climbing it and grading it. The more accurately you do one the less accurately you do the other.
> (In reply to Oceanrower)
>
> What grade is Three Pebble Slab?
>
> What grade is Three Pebble Slab?
In classical climbing E1.
Apply relativity (to non Peak routes) HVS.
However, it's really a quantum problem and you can't be accurate about climbing it and grading it. The more accurately you do one the less accurately you do the other.
In reply to Philip:
No, he described it in terms of both. Seperately.
After all, you would expect that light behaved in a predictable way and not change depending on how YOU were viewing things.
> (In reply to crossdressingrodney)
>
> Did you just describe the behaviour of a quantized unit of energy according to relativity and then drop out a result in classical mechanics?
>
> Did you just describe the behaviour of a quantized unit of energy according to relativity and then drop out a result in classical mechanics?
No, he described it in terms of both. Seperately.
After all, you would expect that light behaved in a predictable way and not change depending on how YOU were viewing things.
In reply to Wonko The Sane: a senior air traffic controller once told me that a VC10 taking off used about the same amount of fuel as an average family car would get through in 40 years...
In reply to ripper: I bet he's right!
Of course, the other way of looking at it is that a 747 does about 100 miles to the gallon per person. Which ain't too bad!
Of course, the other way of looking at it is that a 747 does about 100 miles to the gallon per person. Which ain't too bad!
In reply to MG:
There aren't exactly two tides per solar day; the tides are influenced mainly by the moon, so follow the lunar day (which is coincidentally very close to the solar one). The gravity of the moon pulls the water in the oceans along with it as it orbits around us. 99.9% sure about this, but in the spirit of the thread haven't googled anything
> (In reply to Oceanrower) Why are there two tides a day. Note the world spins only once a day. (I know of various answers, not sure one(s) which is correct).
There aren't exactly two tides per solar day; the tides are influenced mainly by the moon, so follow the lunar day (which is coincidentally very close to the solar one). The gravity of the moon pulls the water in the oceans along with it as it orbits around us. 99.9% sure about this, but in the spirit of the thread haven't googled anything
In reply to Reach>Talent:
Yes in real life. Just the properties mentioned, at the start of the game and before anyone has built additional houses and hotels.
Train stations, without trains.
As for Utilities... guesstimation!
Yes in real life. Just the properties mentioned, at the start of the game and before anyone has built additional houses and hotels.
Train stations, without trains.
As for Utilities... guesstimation!
In reply to Wonko The Sane:
Yes, I do want to get picky about it! So how is a second defined then? So that the average noon to noon time is 24 hours or what?
What do you mean, a "relatively fixed point"?
I shouldn't have said 'relative to the sun and stars'. Rotations are not relative things, they're absolute. How about just:
(2) A sidereal day is how long it takes for the earth to do one complete rotation.
with no mention of the sun or stars. I think it's useful to separate the concept of what it is you're measuring (the rotation) from the way you happen to measure it (by looking at the stars): after all you could still define and measure the sidereal day even if we didn't know about stars!
If it's shorter than 24 hours then: the earth goes anti-clockwise round the sun, looking down on the orbital plane from 'above' (i.e. with the N pole visible) (I think this is right...). Perhaps an easier way to remember this is that you travel faster at night!
> Not absolutely, no. If you want to get picky about it, our orbit is not perfectly circular, nor is our angle of rotation set.
Yes, I do want to get picky about it! So how is a second defined then? So that the average noon to noon time is 24 hours or what?
> No. The sidereal day is one rotation measured against a RELATIVELY fixed point. A distant star. Not our own. We travel in a direction around the sun. For practical purposes, this error is removed if measuring against a distant star.
What do you mean, a "relatively fixed point"?
I shouldn't have said 'relative to the sun and stars'. Rotations are not relative things, they're absolute. How about just:
(2) A sidereal day is how long it takes for the earth to do one complete rotation.
with no mention of the sun or stars. I think it's useful to separate the concept of what it is you're measuring (the rotation) from the way you happen to measure it (by looking at the stars): after all you could still define and measure the sidereal day even if we didn't know about stars!
> It is shorter, haven't thought about it so also do not know which direction we travel in.
If it's shorter than 24 hours then: the earth goes anti-clockwise round the sun, looking down on the orbital plane from 'above' (i.e. with the N pole visible) (I think this is right...). Perhaps an easier way to remember this is that you travel faster at night!
In reply to crossdressingrodney:
Ok. A sidereal day is one roation of the earth.
We usually measure this using a relatively fixed point such as a distant star. Although there are still errors which can be accounted for to give the time for a single rotation.
A second is 1x60x60x24th of a solar day. A solar day is longer than a sidereal day (I.E. one full absolute rotation of the earth) because we move around the sun, so measuring a day by 'noon' is more than one absolute rotation.
Yes, thnking about it, this would appear correct.
> (In reply to Wonko The Sane)
> [...]
>
Ha! determined to make me actually THINK here, aren't you?> [...]
>
> Yes, I do want to get picky about it! So how is a second defined then? So that the average noon to noon time is 24 hours or what?
>
>
Ok. A sidereal day is one roation of the earth.
We usually measure this using a relatively fixed point such as a distant star. Although there are still errors which can be accounted for to give the time for a single rotation.
A second is 1x60x60x24th of a solar day. A solar day is longer than a sidereal day (I.E. one full absolute rotation of the earth) because we move around the sun, so measuring a day by 'noon' is more than one absolute rotation.
> [...]
>
> What do you mean, a "relatively fixed point"?
>
See above....... The position of us relative to a distant star changes infintisimally over the period of one rotation, meaning we can get a much more accurate idea of a single absolute rotation by sighting off a distant star than we can from doing the same with the sun, where the relative movement is much larger.>
> What do you mean, a "relatively fixed point"?
>
> I shouldn't have said 'relative to the sun and stars'. Rotations are not relative things, they're absolute. How about just:
>
> (2) A sidereal day is how long it takes for the earth to do one complete rotation.
>
Yes.>
> (2) A sidereal day is how long it takes for the earth to do one complete rotation.
>
> with no mention of the sun or stars. I think it's useful to separate the concept of what it is you're measuring (the rotation) from the way you happen to measure it (by looking at the stars): after all you could still define and measure the sidereal day even if we didn't know about stars!
>
Yes, it is, but I did qualify the measurement with the word 'relatively'>
> [...]
>
> If it's shorter than 24 hours then: the earth goes anti-clockwise round the sun, looking down on the orbital plane from 'above' (i.e. with the N pole visible) (I think this is right...). Perhaps an easier way to remember this is that you travel faster at night!
>
> If it's shorter than 24 hours then: the earth goes anti-clockwise round the sun, looking down on the orbital plane from 'above' (i.e. with the N pole visible) (I think this is right...). Perhaps an easier way to remember this is that you travel faster at night!
Yes, thnking about it, this would appear correct.
In reply to Oceanrower: And before you bring it up, I SHOULD have said average solar day.
Any given day will be of a different lenght depending on where we are in our orbit of the sun, plus other longer term cyclic variables.
Phew.
Any given day will be of a different lenght depending on where we are in our orbit of the sun, plus other longer term cyclic variables.
Phew.
In reply to Oceanrower:
It's a constant mystery to me how time can pass at different speeds depending on the activity being undertaken.
It's a constant mystery to me how time can pass at different speeds depending on the activity being undertaken.
In reply to Philip:
No.
The classical mechanics was classical mechanics, trying to explain why people thought the light would be affected by gravity, even before general relativity.
The relativity bit was supposed to explain that the modern explanation for mass bending light is to do with the bending of space-time.
Einstein's formula was supposed to show that particle with zero rest-mass can still have momentum and energy. My understanding is that that equation applies to light. Perhaps you know otherwise?
> Did you just describe the behaviour of a quantized unit of energy according to relativity and then drop out a result in classical mechanics?
No.
The classical mechanics was classical mechanics, trying to explain why people thought the light would be affected by gravity, even before general relativity.
The relativity bit was supposed to explain that the modern explanation for mass bending light is to do with the bending of space-time.
Einstein's formula was supposed to show that particle with zero rest-mass can still have momentum and energy. My understanding is that that equation applies to light. Perhaps you know otherwise?
In reply to Wonko The Sane:
I think we're on the same page now regarding sidereal days, thanks.
I get it now. You were using "relatively fixed" to mean "more-or-less fixed". I thought you meant fixed relative to some other thing.
> Ha! determined to make me actually THINK here, aren't you?
Well, your replies have been very interesting. I think we're on the same page now regarding sidereal days, thanks.
> Yes, it is, but I did qualify the measurement with the word 'relatively'
I get it now. You were using "relatively fixed" to mean "more-or-less fixed". I thought you meant fixed relative to some other thing.
In reply to jalien:
Without googling, I think we get a full tidal cycle every 12.4 hours or so.
> (In reply to MG)
> [...]
>
> There aren't exactly two tides per solar day; the tides are influenced mainly by the moon, so follow the lunar day (which is coincidentally very close to the solar one). The gravity of the moon pulls the water in the oceans along with it as it orbits around us. 99.9% sure about this, but in the spirit of the thread haven't googled anything
> [...]
>
> There aren't exactly two tides per solar day; the tides are influenced mainly by the moon, so follow the lunar day (which is coincidentally very close to the solar one). The gravity of the moon pulls the water in the oceans along with it as it orbits around us. 99.9% sure about this, but in the spirit of the thread haven't googled anything
Without googling, I think we get a full tidal cycle every 12.4 hours or so.
In reply to Wonko The Sane:
Whoops, missed this one!
But you just told me that solar days are not all the same length...
Whoops, missed this one!
> A second is 1x60x60x24th of a solar day.
But you just told me that solar days are not all the same length...
In reply to Ava Adore:
How long a minute is clearly depends on which side of the toilet door you are at.
CB
> (In reply to Oceanrower)
>
> It's a constant mystery to me how time can pass at different speeds depending on the activity being undertaken.
>
> It's a constant mystery to me how time can pass at different speeds depending on the activity being undertaken.
How long a minute is clearly depends on which side of the toilet door you are at.
CB
In reply to crossdressingrodney:
MEAN solar day
> (In reply to Wonko The Sane)
> Whoops, missed this one!
>
> [...]
>
> But you just told me that solar days are not all the same length...
> Whoops, missed this one!
>
> [...]
>
> But you just told me that solar days are not all the same length...
MEAN solar day
In reply to Wonko The Sane:
Just to join in the pedantry...
You are discussing the impact of "...which way the earth orbits around the sun" in relation to the difference this makes in terms of 'day' length.
My contribution:
The concept of 'clockwise' and 'anti-clockwise' is a relative one. You are assuming that there is an 'up', which in relative terms there is not. We think of the North Pole as 'up' and the South Pole as 'down', but this is entirely conceptual.
So - from one point in space, the earth would seem to be travelling 'clockwise' around the sun, whereas from another point we would be travelling anti-clockwise.
The answer to your question about day length therefore depends not on 'clockwise' versus 'anticlockwise', but instead on whether the rotation of the earth on its axis is the same or opposite to the rotation of the earth 'around' (simplifying things...) the sun.
Just sayin'
B.
Just to join in the pedantry...
You are discussing the impact of "...which way the earth orbits around the sun" in relation to the difference this makes in terms of 'day' length.
My contribution:
The concept of 'clockwise' and 'anti-clockwise' is a relative one. You are assuming that there is an 'up', which in relative terms there is not. We think of the North Pole as 'up' and the South Pole as 'down', but this is entirely conceptual.
So - from one point in space, the earth would seem to be travelling 'clockwise' around the sun, whereas from another point we would be travelling anti-clockwise.
The answer to your question about day length therefore depends not on 'clockwise' versus 'anticlockwise', but instead on whether the rotation of the earth on its axis is the same or opposite to the rotation of the earth 'around' (simplifying things...) the sun.
Just sayin'
B.
In reply to McBendy:
We know this and never said otherwise. Convention uses Earth's north as 'solar system north'
Never said it did. I clearly mentioned our orbit of the sun being eliptical. Kepler and all that.
> (In reply to Wonko The Sane)
>
>
>
> The concept of 'clockwise' and 'anti-clockwise' is a relative one. You are assuming that there is an 'up', which in relative terms there is not. We think of the North Pole as 'up' and the South Pole as 'down', but this is entirely conceptual.
>
> The concept of 'clockwise' and 'anti-clockwise' is a relative one. You are assuming that there is an 'up', which in relative terms there is not. We think of the North Pole as 'up' and the South Pole as 'down', but this is entirely conceptual.
>
We know this and never said otherwise. Convention uses Earth's north as 'solar system north'
> So - from one point in space, the earth would seem to be travelling 'clockwise' around the sun, whereas from another point we would be travelling anti-clockwise.
>
See above.>
> The answer to your question about day length therefore depends not on 'clockwise' versus 'anticlockwise', but instead on whether the rotation of the earth on its axis is the same or opposite to the rotation of the earth 'around' (simplifying things...) the sun.
>
>
Never said it did. I clearly mentioned our orbit of the sun being eliptical. Kepler and all that.
>
> B.
> B.
In reply to crossdressingrodney:
The second is not defined in terms of solar days.
Half the info on here is years out of date. FFS use google, it's better than misinformation.
> (In reply to Wonko The Sane)
> Whoops, missed this one!
>
> [...]
>
> But you just told me that solar days are not all the same length...
> Whoops, missed this one!
>
> [...]
>
> But you just told me that solar days are not all the same length...
The second is not defined in terms of solar days.
Half the info on here is years out of date. FFS use google, it's better than misinformation.
In reply to McBendy:
It is true that "clockwise" and "anti-clockwise" are meaningless descriptions on their own. But "North pole up and anti-clockwise" is meaningful, and is equivalent to "South pole up and clockwise", and also, (hopefully), is correct!
Mathematically, what you're doing is specifying an orientation on the plane that the earth travels in; I thought the above was easier thing to visualise.
But to pre-empt your comment I already said that you can think of this as travelling faster at night.
> Just to join in the pedantry...
The more the merrier...> The concept of 'clockwise' and 'anti-clockwise' is a relative one.
> You are assuming that there is an 'up', which in relative terms there is not.
> We think of the North Pole as 'up' and the South Pole as 'down', but this is entirely conceptual.
> So - from one point in space, the earth would seem to be travelling 'clockwise' around the sun, whereas from another point we would be travelling anti-clockwise.
> You are assuming that there is an 'up', which in relative terms there is not.
> We think of the North Pole as 'up' and the South Pole as 'down', but this is entirely conceptual.
> So - from one point in space, the earth would seem to be travelling 'clockwise' around the sun, whereas from another point we would be travelling anti-clockwise.
It is true that "clockwise" and "anti-clockwise" are meaningless descriptions on their own. But "North pole up and anti-clockwise" is meaningful, and is equivalent to "South pole up and clockwise", and also, (hopefully), is correct!
Mathematically, what you're doing is specifying an orientation on the plane that the earth travels in; I thought the above was easier thing to visualise.
> The answer to your question about day length therefore depends not on 'clockwise' versus 'anticlockwise', but instead on whether the rotation of the earth on its axis is the same or opposite to the rotation of the earth 'around' (simplifying things...) the sun.
But to pre-empt your comment I already said that you can think of this as travelling faster at night.
In reply to Philip:
Wow, thanks for your input Philip. Hardly in the spirit of the thread.
> FFS use google, it's better than misinformation.
Wow, thanks for your input Philip. Hardly in the spirit of the thread.
In reply to Philip:
Sigh. Yes, I know about atomic clocks. Yes, I know this is what we use now. The second is still based on the solar year........
Then what they did was say to themselves, hmmm, how can we measure this accurately?
I know, we can base it on cesium decay (or whatever)
So let me put it differently for you.
Our unit of measurement known as the second came from the solar year, but is now measured and defined by the half life of some material or other.
Didn't need Google.
> (In reply to crossdressingrodney)
> [...]
>
> The second is not defined in terms of solar days.
>
> Half the info on here is years out of date. FFS use google, it's better than misinformation.
> [...]
>
> The second is not defined in terms of solar days.
>
> Half the info on here is years out of date. FFS use google, it's better than misinformation.
Sigh. Yes, I know about atomic clocks. Yes, I know this is what we use now. The second is still based on the solar year........
Then what they did was say to themselves, hmmm, how can we measure this accurately?
I know, we can base it on cesium decay (or whatever)
So let me put it differently for you.
Our unit of measurement known as the second came from the solar year, but is now measured and defined by the half life of some material or other.
Didn't need Google.
In reply to Philip: If you read how we arrived at the discussion........ I.E. the rotation of the earth.......... you'd see where the discussion came from and the context.
In reply to Oceanrower: War Hmm? Good God. What is it good for?
In reply to Oceanrower:
Why does flammable and inflammable mean the same thing?
When the prefix ‘in’ normally means the opposite, as in sane/insane, edible/inedible, evitable/inevitable.
Why does flammable and inflammable mean the same thing?
When the prefix ‘in’ normally means the opposite, as in sane/insane, edible/inedible, evitable/inevitable.
In reply to Oceanrower:
If a tree falls in a forrest but no one is there to hear it... does it make a sound?
If a tree falls in a forrest but no one is there to hear it... does it make a sound?
In reply to crossdressingrodney:
Only if she finds out
> (In reply to RCJ)
>
> If a man says something and there's no woman there to hear it, is he still wrong?
>
> If a man says something and there's no woman there to hear it, is he still wrong?
Only if she finds out
In reply to crossdressingrodney:
yes, because they assume you've said it...
yes, because they assume you've said it...
In reply to RCJ:
Ah, easy one! Yes.
> (In reply to Oceanrower)
> If a tree falls in a forrest but no one is there to hear it... does it make a sound?
> If a tree falls in a forrest but no one is there to hear it... does it make a sound?
Ah, easy one! Yes.
In reply to Mark Edwards:
I like that one. Wondered about it myself in the past.
> (In reply to Oceanrower)
>
> Why does flammable and inflammable mean the same thing?
> When the prefix ‘in’ normally means the opposite, as in sane/insane, edible/inedible, evitable/inevitable.
>
> Why does flammable and inflammable mean the same thing?
> When the prefix ‘in’ normally means the opposite, as in sane/insane, edible/inedible, evitable/inevitable.
I like that one. Wondered about it myself in the past.
In reply to Mark Edwards: INflammable is the original word with Latin origin. Inconsiderate, inordinate, etc are Greek based where "in" means "not". In Latin the "in" means "on, towards" or a tendency to be flammable.
The word flammable is a later usage for the same word. The opposite of which is non-flammable.
I learned something in my degree. Bloody hell..
The word flammable is a later usage for the same word. The opposite of which is non-flammable.
I learned something in my degree. Bloody hell..
In reply to Wonko The Sane:
Clearly you do as that is wrong. You're like the beardy blokes who stand next to quiz machines giving out wrong answers and claiming it used to be right up until a few years ago.
> (In reply to Philip)
> [...]
>
> Sigh. Yes, I know about atomic clocks. Yes, I know this is what we use now. The second is still based on the solar year........
>
> Then what they did was say to themselves, hmmm, how can we measure this accurately?
> I know, we can base it on cesium decay (or whatever)
>
>
> So let me put it differently for you.
>
> Our unit of measurement known as the second came from the solar year, but is now measured and defined by the half life of some material or other.
>
>
>
> Didn't need Google.
> [...]
>
> Sigh. Yes, I know about atomic clocks. Yes, I know this is what we use now. The second is still based on the solar year........
>
> Then what they did was say to themselves, hmmm, how can we measure this accurately?
> I know, we can base it on cesium decay (or whatever)
>
>
> So let me put it differently for you.
>
> Our unit of measurement known as the second came from the solar year, but is now measured and defined by the half life of some material or other.
>
>
>
> Didn't need Google.
Clearly you do as that is wrong. You're like the beardy blokes who stand next to quiz machines giving out wrong answers and claiming it used to be right up until a few years ago.
In reply to Philip:
Oh FFS, tosser.
Here, from Wiki:
The second (symbol: s) is the base unit of time in the International System of Units (SI)[1] and is also a unit of time in other systems of measurement (abbreviated s or sec[2]). Between 1000 (when al-Biruni used seconds) and 1960 the second was defined as 1/86,400 of a mean solar day (that definition still applies in some astronomical and legal contexts).[3][4] Between 1960 and 1967, it was defined in terms of the period of the Earth's orbit around the Sun in 1900,[5] but it is now defined more precisely in atomic terms. Seconds may be measured using mechanical, electric or atomic clocks.
19th- and 20th-century astronomical observations revealed that the mean solar day is slowly but measurably lengthening and the length of a tropical year is not entirely predictable either; thus the sun–earth motion is no longer considered a suitable basis for definition. With the advent of atomic clocks, it became feasible to define the second based on fundamental properties of nature. Since 1967, the second has been defined to be:
the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.[1]
Do you think that because how a second is currently measured they just did away with what it's BASED on??
No.
I like the way you slag stuff off without offering a thing yourself.
> (In reply to Wonko The Sane)
> [...]
>
> Clearly you do as that is wrong. You're like the beardy blokes who stand next to quiz machines giving out wrong answers and claiming it used to be right up until a few years ago.
> [...]
>
> Clearly you do as that is wrong. You're like the beardy blokes who stand next to quiz machines giving out wrong answers and claiming it used to be right up until a few years ago.
Oh FFS, tosser.
Here, from Wiki:
The second (symbol: s) is the base unit of time in the International System of Units (SI)[1] and is also a unit of time in other systems of measurement (abbreviated s or sec[2]). Between 1000 (when al-Biruni used seconds) and 1960 the second was defined as 1/86,400 of a mean solar day (that definition still applies in some astronomical and legal contexts).[3][4] Between 1960 and 1967, it was defined in terms of the period of the Earth's orbit around the Sun in 1900,[5] but it is now defined more precisely in atomic terms. Seconds may be measured using mechanical, electric or atomic clocks.
19th- and 20th-century astronomical observations revealed that the mean solar day is slowly but measurably lengthening and the length of a tropical year is not entirely predictable either; thus the sun–earth motion is no longer considered a suitable basis for definition. With the advent of atomic clocks, it became feasible to define the second based on fundamental properties of nature. Since 1967, the second has been defined to be:
the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.[1]
Do you think that because how a second is currently measured they just did away with what it's BASED on??
No.
I like the way you slag stuff off without offering a thing yourself.
In reply to Wonko The Sane:
Transitions between hyperfine levels are not the same thing as half life.
I don't see the point in you being a pedant about something you vaguely understand. It just makes you look like the knob in the pub.
Transitions between hyperfine levels are not the same thing as half life.
I don't see the point in you being a pedant about something you vaguely understand. It just makes you look like the knob in the pub.
>I like the way you slag stuff off without offering a thing yourself.
Thank you. It's welcoming to be appreciated. I see it as the best way to encourage further learning - look how it took you to wikipedia. No need to thank me, your reaction is satisfaction enough.
Back to spirit of this thread then. Without Google, explain how the Fens or Norfolk formed. I only have vague idea and I don't think I have a book on it to check.
Also, why is gold yellow in colour whereas all other metals around it are silver (Pd, Pt, Ni, Hg, Cd, Zn, Ag - Cu isn't). I know this one but it's explanation is enjoyable - I promise not to be a pedant.
Thank you. It's welcoming to be appreciated. I see it as the best way to encourage further learning - look how it took you to wikipedia. No need to thank me, your reaction is satisfaction enough.
Back to spirit of this thread then. Without Google, explain how the Fens or Norfolk formed. I only have vague idea and I don't think I have a book on it to check.
Also, why is gold yellow in colour whereas all other metals around it are silver (Pd, Pt, Ni, Hg, Cd, Zn, Ag - Cu isn't). I know this one but it's explanation is enjoyable - I promise not to be a pedant.
In reply to Philip:
Secondly, I mentioned before Googling that it was based on caesium decay. I knew this before my initial answers......... I.E. atomic clock. However, the atomic clock is used to give precise, non differing measurements. The duration of a second as measured by that clock isn't just abitrary though, is it? It's based on........ oooh, I wonder what!
The fens formed because the land bridge between us and Europe was flooded when the ice retreated as this current ice age, (because technically, we are in one) started to reverse.
Or do you mean why is it flat? (don't know)
Not a clue.
> Thank you. It's welcoming to be appreciated. I see it as the best way to encourage further learning - look how it took you to wikipedia. No need to thank me, your reaction is satisfaction enough.
>
Couple of things here, the point of the thread was NOT Googling.>
Secondly, I mentioned before Googling that it was based on caesium decay. I knew this before my initial answers......... I.E. atomic clock. However, the atomic clock is used to give precise, non differing measurements. The duration of a second as measured by that clock isn't just abitrary though, is it? It's based on........ oooh, I wonder what!
> Back to spirit of this thread then. Without Google, explain how the Fens or Norfolk formed. I only have vague idea and I don't think I have a book on it to check.
>
Define what you mean here?>
The fens formed because the land bridge between us and Europe was flooded when the ice retreated as this current ice age, (because technically, we are in one) started to reverse.
Or do you mean why is it flat? (don't know)
> Also, why is gold yellow in colour whereas all other metals around it are silver (Pd, Pt, Ni, Hg, Cd, Zn, Ag - Cu isn't). I know this one but it's explanation is enjoyable - I promise not to be a pedant.
Not a clue.
In reply to Philip:
But I'm not. I'm quite happy to learn what I don't know such as why light is bent by gravity.
Considering I'm drawing from maths and physics I stopped reading about 20 years ago....... I'd say my understanding is a little better than 'vague'
> (In reply to Wonko The Sane)
>
> Transitions between hyperfine levels are not the same thing as half life.
>
Fair enough.>
> Transitions between hyperfine levels are not the same thing as half life.
>
> I don't see the point in you being a pedant about something you vaguely understand. It just makes you look like the knob in the pub.
But I'm not. I'm quite happy to learn what I don't know such as why light is bent by gravity.
Considering I'm drawing from maths and physics I stopped reading about 20 years ago....... I'd say my understanding is a little better than 'vague'
In reply to Wonko The Sane:
Okay. Over reaction by me.
The fens are interesting, a book in the new naturalist series was due to be published explaining it as a natural phenomenon. It was halted when new evidence showed them man made. I wondered how well known this was and also don't know how it was achieved without googling.
I thought the gold thing would be up your street. It's only explainable by mixing some relativity into quantum.
Okay. Over reaction by me.
The fens are interesting, a book in the new naturalist series was due to be published explaining it as a natural phenomenon. It was halted when new evidence showed them man made. I wondered how well known this was and also don't know how it was achieved without googling.
I thought the gold thing would be up your street. It's only explainable by mixing some relativity into quantum.
In reply to Philip:
My understanding of quantum mechanics is limited....... coming from engineering rather than pure maths or physics.
Re the fens........ they were artificially drained I heard (or read somewhere) , I don't know when that started though. I wasn't sure what you meant re how they were formed.
> (In reply to Wonko The Sane)
>
> Okay. Over reaction by me.
>
> The fens are interesting, a book in the new naturalist series was due to be published explaining it as a natural phenomenon. It was halted when new evidence showed them man made. I wondered how well known this was and also don't know how it was achieved without googling.
>
> I thought the gold thing would be up your street. It's only explainable by mixing some relativity into quantum.
>
> Okay. Over reaction by me.
>
> The fens are interesting, a book in the new naturalist series was due to be published explaining it as a natural phenomenon. It was halted when new evidence showed them man made. I wondered how well known this was and also don't know how it was achieved without googling.
>
> I thought the gold thing would be up your street. It's only explainable by mixing some relativity into quantum.
My understanding of quantum mechanics is limited....... coming from engineering rather than pure maths or physics.
Re the fens........ they were artificially drained I heard (or read somewhere) , I don't know when that started though. I wasn't sure what you meant re how they were formed.
In reply to Oceanrower: By the way.
Ok, there WAS a beard, but I was trying it out again for a few weeks and it went yesterday :/
Ok, there WAS a beard, but I was trying it out again for a few weeks and it went yesterday :/
In reply to Oceanrower: I don't own sandals or cords.
In reply to Philip:
It's the way light inteacts with the surface, they don't really have a colour, it all to do with the inferearnce of the light with the surface.
Butterfly wings are the same the colour is from interferance pattern from th scales on their wings.
Look at a CD in the light and you'll see arainbow effect, same thing the disk isn't coloured and the colour moves around as you change the angle the light hits.
> Also, why is gold yellow in colour whereas all other metals around it are silver (Pd, Pt, Ni, Hg, Cd, Zn, Ag - Cu isn't). I know this one but it's explanation is enjoyable - I promise not to be a pedant.
It's the way light inteacts with the surface, they don't really have a colour, it all to do with the inferearnce of the light with the surface.
Butterfly wings are the same the colour is from interferance pattern from th scales on their wings.
Look at a CD in the light and you'll see arainbow effect, same thing the disk isn't coloured and the colour moves around as you change the angle the light hits.
In reply to Oceanrower: My question - why does it smell of fish?
In reply to krikoman:
Nice try, but no. It really is interesting (if you enjoy quantum chemistry) and of course all colour is due to interactions, but it isn't an interference effect.
> (In reply to Philip)
>
> [...]
>
> It's the way light inteacts with the surface, they don't really have a colour, it all to do with the inferearnce of the light with the surface.
>
> [...]
>
> It's the way light inteacts with the surface, they don't really have a colour, it all to do with the inferearnce of the light with the surface.
Nice try, but no. It really is interesting (if you enjoy quantum chemistry) and of course all colour is due to interactions, but it isn't an interference effect.
> Butterfly wings are the same the colour is from interferance pattern from th scales on their wings.
>
They are interesting.>
In reply to Oceanrower: Just taken delivery of some MDF. Is there any low or hight density fibreboard? If not, why isn't it just called fibreboard?
In reply to Oceanrower:
Yep.
There is low density fibre board, though it isn't sold as that name. It's often used in expansion joints etc.
There are higher density fibre boards too, though again, not sold under that name.
Moisture resistant MDF is a bit of a misnomer, since it's actually a high density board. Though the density is not made up of more fibres, but of more resin impregnated under higher pressure.
> (In reply to Oceanrower) Just taken delivery of some MDF. Is there any low or hight density fibreboard? If not, why isn't it just called fibreboard?
Yep.
There is low density fibre board, though it isn't sold as that name. It's often used in expansion joints etc.
There are higher density fibre boards too, though again, not sold under that name.
Moisture resistant MDF is a bit of a misnomer, since it's actually a high density board. Though the density is not made up of more fibres, but of more resin impregnated under higher pressure.
In reply to krikoman:
Can't quite remember the exact way it was put, but I think it is the other way around.
Not long after God put Eve on the earth, Adam saw Eve bending over to smell some flowers that he'd also put on this earth. Adam couldn't stop himself and ran up behind her and consumed by a feeling that he'd not experienced before and proceeded to sh*g her silly. When he'd finished God happened along and Adam told him what had just happened. God looked a bit perplexed, and asked where Eve was now. Adam says she's down at the river "washing" herself. To which God let out a moan and muttered "Oh no, I didn't want the fish to smell like that".
Not sure if I got that totally correct, but it was a long time ago when we were told that by the priest at Sunday School. I was only 7 at the time and not a lot of it made sense until I was older, and got a whiff of one. By one I don't mean a fish.
> (In reply to Oceanrower) My question - why does it smell of fish?
Can't quite remember the exact way it was put, but I think it is the other way around.
Not long after God put Eve on the earth, Adam saw Eve bending over to smell some flowers that he'd also put on this earth. Adam couldn't stop himself and ran up behind her and consumed by a feeling that he'd not experienced before and proceeded to sh*g her silly. When he'd finished God happened along and Adam told him what had just happened. God looked a bit perplexed, and asked where Eve was now. Adam says she's down at the river "washing" herself. To which God let out a moan and muttered "Oh no, I didn't want the fish to smell like that".
Not sure if I got that totally correct, but it was a long time ago when we were told that by the priest at Sunday School. I was only 7 at the time and not a lot of it made sense until I was older, and got a whiff of one. By one I don't mean a fish.
This topic has been archived, and won't accept reply postings.
Loading Notifications...