UKC

In the wake of that rocket launch on Saturday I was pondering a few things and, among others, I googled "furthest known object from Earth".

It turns out to be a galaxy known as MACS0647-JD and it's 13.26 billion light years away. Then, when you think that a light years is 671000000 miles that's a bloody long way. It begs the question: what is there BEYOND that distance? I suppose it's also feasible that the said galaxy no longer exists .

Given such unthinkable enormity I really cannot convince myself that we are alone!

when you compare the time that the signal had to travel to us and compare it with the current estimates of the age of the universe ...  (13.8 billion years)

The scale is mind blowing. We are "seeing" something that "happened" just after the Big Bang

Most or pretty much all of the universe is unstable be because the rate of expansion of the universe means that light can never reach us.

To be honest, I don't think our monkey brains are well adapted to deal with this sort of concept. 

That, to my simple brain, suggests that universe is expanding faster than the speed of light.

Of course, there's always the possibility that our universe and all it's planets, suns and galaxies are just molecules in another, larger universe that contains them all...

Or,  as the,  in many ways annoying,  Devs tv series portrayed,  you can't tell the difference between reality and a simulation.

Precisely. Nothing stops space itself expanding faster than light, but nothing can travel through that space faster than light.

CB

"Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space."

Well. Someone had to quote it. Might as well be me.

Ah yes, Devs.  I thought it had some very good stuff in it , along with few irritating glitches - in particular, the discussion where Katie is challenging Lily to think of an event that isn't contingent on a measurable causal event.  I find it hard to believe that two such super-smart people working at a quantum computing company, (and Katie is shown attending a lecture on quantum uncertainty) would not have heard of Schrodinger's Cat and the randomness of radioactive decay.  Even if an argument could be made that this too is deterministic, it's a miles better example that anything Lily came up with.

Also, the business on the dam.  Who would (literally) fall for such a spurious argument (including a reference to quantum uncertainty) given the insight they had had just had that enabled to the breakthough to be made?

However, as I say, lots of very thoughtful touches too, especially the ignorance of some very smart but narrowly educated people.    

An ex-colleague didn't sleep for two days after he started thinking about this once.

"so we know the universe is expanding, but what's it expanding into? There can't be nothing, there must be something"

That's not really a possibility because the nature of atoms is totally different to the nature of solar systems and galaxies. 

The most mainstream idea as I understand it is that our observable universe is one of infinitely many "bubbles" that has condensed in an inflationary multiverse. Have a look on YouTube if these words sound like complete nonsense. 

Are you Greta Garbo?

Existence sprawling out infinitely in all directions, The Universe being part eyelash and part planet, part parrot's arse, part everything, depending how much you zoom in and out like a 3D mandelbrot?

Ad infinitum.

Intriguing.

Ah, you say that, - that's what they want you to think!

Not the one,  that from a molecule picked out the air,  you could derive all the information to see Jesus on the cross, as well as a complete simulation of the entire universe ?

I've asked  on a number of occasions and I still don't know how we can be sure the universe isn't contracting. After all from where we are any objects closer to the centre than us will be going faster so will be going away, and ditto we will be going faster than any objects further away from the centre so they will appear to be getting further away as well. Until - KABOOM! (I'd really like to see that, wouldn't that give Cummings something to really look miserable about!)

'see Jesus on the cross.' Curious thing to highlight. When I was 8 I was taught by a spinster - Miss Taylor - who was a devout Christian.  On several occasions she referred to the idea that science might 'one day' be able to reproduce speech from history - and she was genuinely longing to be able to hear Jesus's voice. I think she may have died disappointed.

I don't think that's right is it?

Its just that the two bodies are moving away from each other at a high velocity. Neither body breaching the speed of light but relative to each other it is faster than the SOL?

I take it you didn't watch Devs  ?

Infinite not just in the sense of an unfathomable number but in the sense that alternate universes are continually create at the junction of each 'choice' at the sub atomic level. Each sub-atomic particle being 'either, or ' (think quantum bits) is a 'choice' and at this point a new universe is created with both options existing.  Obviously this is an infinite number of 'choices' but the majority of these universe collapse because they are inherently unstable due to the 'wrong choice' (hence the fundamental laws of physics).  This model of universe bubbles is therefore continually frothing as more universes are created and destroyed.

A good argument for free will I think, even within a designed universe.

This make the fact we are happily plodding along in our own universe all the more amazing.

I'm pretty sure that isn't right either!  Isn't that specifically what Special Relativity says doesn't happen?

There is no centre. The distance between any two galaxies you pick is getting bigger (the usual 2D analogy used is drawing dots on a balloon and blowing it up).

I'm not sure!

now you mention it neither seem right.

You're right. Nothing goes faster than the speed of light, whatever way you cut it. 

I guess you have to accept the premise that they have some next-level-but-one quantum foam computing technology (they seem to have cracked anti-gravity in some way) and have got round infinite storage capacity problem.  They very sensibly don't go into that but I think they did manage to capture the queasiness of the logical consequences of the physics we already have, if we were to find some way of building the technology to go there.  It all seems impossible, but that's how the technology and knowledge we have now would have seemed only 50 years ago.  Maybe something truly amazing is just around the corner.

As for choosing to go back to the crucifixion, I wondered whether Katie was a bit of a high-tech god-botherer (and there is the joke about the name of the system).  I realised that if they had access to such a system, perhaps quite a lot of people would go to this this pretty much as their first destination.  I'm not sure how long it would have taken me to think of it but it wouldn't have been in my top ten. 

In any inertial frame (ie one that's not accelerating) then special relativity will govern how things work. Two spaceships moving apart, each traveling at 0.8c, will not see the other moving at 1.6c. 

But cosmology isn't set in an inertial frame because of the expansion of the universe. Special relativity can't help here - you need general relativity, which is much harder. Special relativity (the special case where a =0) is comparatively straightforward!

We can see things moving with redshifts that correspond to much greater speed than c. It doesn't mean they are breaking the speed of light because what we are measuring is the expansion of the space between us.

That's exactly what it implies.  Whilst light itself is still restricted to light speed, space itself can expand faster.

The fact that we see redshifts (and not blueshifts) tells us that space is expanding, not contracting. It's analogous to the way you can tell from the siren that the ambulance is moving away from you and not towards you.

There is no centre. The balloon analogy is good here - no point of the surface is or was the centre#. Also it's not really the dots moving at all - it's the balloon surface expanding.

# or, perhaps better, it was all centre at the very beginning!

With apologies for my pedantry - I normally succeed in not being niggled, but this one really gets to me - that's not what enormity means!

SR won't apply when the space itself between distant bodies is expanding.

For an accessible discussion on the radius of the observable universe look up the Hubble Radius. It's also a "proof" of the expansion of the universe and solution to Olber's Paradox (Why is the sky dark at night?).

Briefly, if the universe is expanding the velocity of increasing separation between any two points is proportional to the distance between them. So when the distance is such that the recession velocity from the observer =light speed, nothing beyond that point can be observed.This defines the Hubble Radius for that observer. Whatever size the universe is, nothing beyond the HR can be observed.

There are some additional complications, needless to say. Currently the HR is thought to be approx 4.2 billion parsecs (13.7 billion l.y. ).

There so much both fascinating and mind boggling out there.

Neutron stars are the collapsed core of a giant and have a very strong gravitational field in the order of hundred of billions of times stronger than that on Earth.

If an object was dropped from 1 metre above the surface of a typical neutron star(diameter 12 km) it would, in theory, hit the surface at about 1400km/second(that's around 5 million km/hour), though tidal forces caused by the huge gravitational field would broken the object before impact.

Dave

It's already happened, kinda...  youtube.com/watch?v=94KBXL4D3p4&

The multiverse implied by inflation isn't the same as the multiverse implied by the many worlds theory of quantum mechanics. Some people think both are true - we inhabit a multimultiverse. 

A bad argument for free will I think

No. All velocity is relative. A relative velocity cannot be greater than the speed of light.

While not disputing your pedantic accuracy, I think referring to the enormity of the universe is a very graphic description of the situation! Thanks for your clarifications though.

I've just finished getting halfway through a book pointing out that reality as we perceive it is a misnomer, and in fact what we see is an illusion, some kind of model which provides us with a localised benefit.

I say halfway because the author, one Donald Hoffman, manages to reduce an interesting idea to a series of banal psychological theories.

Where you are going wrong is to think that there is a centre. An analogy would be a deflating spherical balloon (the universe is the surface of the balloon). No point on the surface is "special" - there is no "centre". As the balloon deflates, every point on the surface gets closer to every other point. If it were inflating, every point would be receding from every other point.

Nesyamun sounded like he'd had too many beans for breakfast?

They aren't moving away from each other in the normal sense.  The space between them is expanding.

Thanks all.... still cant get my head around it. I have some youtube homework for this evening.

😁

It's in a shoebox. On top of a wardrobe. At least that's what I decided when I pondered the matter as an eleven-year-old...

ps. If only there were someone on UKC who could explain it. You know, like a professor of astrophysics...

A centre of gravity still exists.

I have a few related questions:

Is it meaningful to talk about the 'point' at which the centre of gravity exists?

Would such a point still be part of the current universe?

Presumably that will be the original location of the big bang?

Is there or could there be anything still there?

Do you mean centre of mass? 

I don't think it does. Using the balloon analogy, there is no centre of mass on the surface of the balloon  (every point is equivalent) and the surface of the balloon is analogous to the whole universe (there is nothing outside it), so where could this centre of mass be?

I think it is meaningless to talk about the location of the big bang (unless, maybe, the location in a mutiverse where an inflationary bubble gave rise to our universe). The big bang was everywhere and everything in our own universe.

As far as I was aware, the centre of gravity entirely depends on where you are.  Anything outside our observable universe isn't part of the gravity of our observable universe.  The observable universe is, as I understand it, a sphere centred on the observer wherever that observer is.

The problem with the balloon analogy is that it's much too simple to describe what's really going on.  One might say it gets... stretched too far (ba-dum tish).  For a start it's describing a 3D system with a 2D plane.

Trying to locate the big bang in our universe doesn't really make sense.  It was everywhere (or, perhaps more precisely, everywhere was at the big bang).  This is why the CMB seems to come from everywhere (it wasn't emitted at the moment of Big Bang, but it was pretty early on, around 370,000 years old, at the point of recombination of electrons and protons into atoms).

It's very tempting to imagine the universe as a simple sphere that is expanding, but as I understand it the topology may well not be that simple.  Sadly this is again general relativity... there's a reason SR was a mandatory first year topic in my degree and GR was a 4th year option that only the really good students went for!

It'd be a great place to train though.

Maybe the Big Bang was a bit like a fart with a follow through

As a newcomer backyard astronomer one of my ambitions is to find the furthest visible object with my modest setup. At  the moment I am at around 12 million light years, hoping that my upgraded refractor and a couple of good nights' seeing will get me into the twenties. The distances I'm talking about are enormously smaller than the one you quote but the thrill lies in the actual vision: a lot of hobby astronomers use the camera as their eyes and  count an image as seen if the camera produced it where the eye/ eyepiece couldn't discern it  .It definitely gives you a hollow feeling when you study some of these objects in live vision , if you can use that word for such an activity.                      

Even my current best (M81 and M82) means that I'm seeing light which began its journey in the late Miocene era.

Explains much.

The observer. Since the universe extends 1 Hubble Radius in every direction and anything beyond that has no gravitational influence ) or influence at all.

Corollary...

You are literally at the centre of the observable universe!

The Whirlpool galaxy should be easy enough if you've managed to see M82.

Thanks for that. I can envisage how everywhere might have been simultaneously at the location of the big bang, which also neatly explains why it doesn't make sense to refer to 'outside' of the universe. But I struggle with the limits of the observable universe, not in theory but presumably it's a fair bet that plenty of matter exists beyond our observable reach and presumably also it's theoretically impossible not only to prove the existence of anything beyond that but also to have even the slightest inkling how much of it there is? To the point of which our observable universe may well be an absurdly tiny part of the actual universe as a whole.

My understanding is that the shape of the Universe is such that there is no centre

there was a kind of centre when the Universe was at a minute scale but all parts of it then started to expand away from each other - that does not allow a centre but it certainly gives me a headache trying to imagine a shape/topography for something behaving like that.  with the space between now expanding it really is rather hard to imagine what it would "look" like - perhaps impossible for the mathematically challenged ...

the great green Arkleseizure sneezed it out

I do, sometimes, but only when the speed of light has been brought down to a few cm per second which I understand has been done

Space doesn't exist. 

Is it turtles, all the way down?

If space exists then how come no matter where you are you are always here? 🙂

I don't think anyone has corrected the large error in your post.

A light year is 6 million million miles. Not 600 million, you're out by a factor of 10 thousand.

As for the rest, yes, it's huge.

If space exists, why are my cupboards always full?

T.

And my rucksack.

Big bone of contention, that, Jamie!!!

I work by starhopping  as opposed to Go To technology but it is so easy to find the location of M51 that it should be a cert. But I know exactly where to look and can't get it. ( on my Messier ticklist  the Whirlpool is 4 places down from M82 but categorised with the same brightness)

Anyway, small Aldi tent on lawn tonight and ugraded scope  might give me a new tick or two.

That's only true under Special Relativity ( which only applies in inertial  reference frames)

, but under General Relativity it can. GR allows separation velocities for objects like galaxies to exceed c. ( Under SR a mass can't even be accelerated to c, but the physics, and the meaning of mass, are different in GR.).

But is that not due to the expansion of space rather than movement through space? Am I not right in thinking that no relative velocity through space can exceed the speed of light?

It seems to me meaningless to talk about the centre of gravity of the universe. The centre of gravity of an object changes as it's position changes with regard to the source of the gravity (the centre of gravity of an object on the surface of the earth will be slightly  different when it 10000 miles above the surface). The centre of gravity of something is always with regard to something external to it, and since, by definition, there is nothing external to the universe, the notion of its centre of gravity is meaningless.

As for centre of mass, as I said earlier, I suspect that does not exist either since no point in the universe is special.

 To say that it is the centre of your own personal observable universe just seems silly to me.

I've hurt my own brain a few times by trying to imagine if "nothing existed"...

Most people ask: What colour would it be?

What they meant (I think) is that light travelling in opposite directions is traveling at the speed of light but the leading edge of each light beam is being distanced from the other at double the speed of light.

And why does a bicycle have no windows?

That is what I meant, but I fear that may be misunderstanding things. 

Robert above has stated that were you positioned at the leading edge of one light beam travelling c, then the other light beam would still only appear to you to be travelling c in the opposite direction. is that right?

Presumably, because time slows as speed approaches c, the other beam would then appear to you to be travelling in relative and proportionate slow motion, i.e. no faster than c

Yes.  This is the fundamental point of special relativity - that any two observers* MUST both measure the speed of light to be c, regardless of any relative motion. 

Because measuring speed is a result of the length of your ruler and the rate of your clock, this means they must disagree about one (or both) of those things.

* in the same inertial frame

Yes, possibly.  It's a tricky concept that the distance between two points separating at c is getting bigger quicker than that because of the expansion of space-time. 

But would you agree that an observer looking down on a candle is seeing lightwaves leaving in opposite directions that are each travelling at c and that c is not being exceeded but the distance they are separating at is growing at a rate that a single beam could only cover at twice the speed of light

Isn't this happening all the time though like the sun is sending out light to objects opposite to us and the light reaching the other object more quickly than a beam we could send from earth that we 'launch' at the same time

Or if two spaceships set off from earth in opposite directions at three quarters the speed of light, would we measure their separation as increasaing at one and a half times the speed of light? I think the answer is yes.

what happens if the spaceshipo travelling at 0.9c shoots a space gun in the same direction of travel. The projectile is going 0.2c- does it exceed light speed or does it ever even exit the barrel of the gun?!

Indeed.

In reply to La benya:

No.

Yes.

The hard question is: what speed does the spaceship captain measure the projectile as travelling with, and what speed do I (a stationary observer) measure?  These will not have the same answer.

Edit: before you ask, the captain measures 0.2c, whereas I measure 0.932c.

Presumably those on board would record the missile leaving at 0.2c, and those back on earth, from which the spacecraft is receding, would not be able to record the missile at all as the light from it would never reach them.

Edit: which raises another curious question. If something is receding from an observer at a speed of precisely c, what does the observer see, and does the image change?

Edit again!: Presuming that reaching a speed of c is in practice impossible, how about a star that's on the horizon of visibility, such that its perceived distance from us is growing at precisely c?

No - because the missile can't break the speed of light, I (stationary/on the earth) can still see it. 

You need to use the Lorentz transformation to figure out how fast I see it going.  That number cannot ever equal or exceed c.

interesting that you gave a specific answer! is that because time and or distance are measured differently by the 3rd party and the captain?

Yes, exactly (and you can figure it out either using time or distance).  If I get a quiet ten minutes this afternoon I can have a go at explaining the idea behind it.

The Lorentz transformation allows you to figure the speeds out.  For a moving frame (the spaceship) at speed u with an object moving within that frame (the missile) at speed v, the speed that the stationary observer will measure the missile will be (u + v) / (1 + uv).  It's a clever equation - whatever values you pick for u and v, the answer can never be greater than 1.

Thanks for putting me right; this stuff always makes my head hurt, no matter how many times I think I get it (and then forget it all again some months or years later!

I can see now why the earth observer would still see the missile. Imagine the spaceship is displaying an image of the receding missile on a screen. this screen image could then be live-transmitted to earth, albeit very slowly, so the cumulative speed of light transmition from the missile to earth must still be less than c

thanks, that would be really interesting.

I think both would appear frozen. (?)

No because its mass would increase as it approached the speed of light and it wouldn't reach 0.2 c in the first place, because the energy that would have propelled it to 0.2 c from resting would now no longer be enough. Equally light shining from the front of the ship would only have a relative velocity of 0.1 c

That's my intuition too. But suppose the colour or shape or some other attribute of the receding star was constantly changing. Would we see all colour/shapes at the same time? And because light from all periods of time would be arriving at precisely the same time, would it be the brightest thing in the sky?

Would not something almost at our horizon be massively redshifted? I think we would see it frozen as it was immediately after the big bang/inflation. After that time, light would not have (or ever be able to) reach us. I think!

Can someone answer this one for me?

The Universe is expanding and everything we see is moving away from us as a consequence (the point on the surface of an inflating balloon analogy).

Does this mean that the atoms in my body are undergoing the same process or the movements of the subatomic particles that makes them up? If yes, wouldn't that lead to a change in fundamental physical constants over time? If no, then at what scale does it cease to operate? 

I think it's bigger.
186000 x 60 x 60 x 24 x 365.25 = 5,869,713,600,600

'Everything' in the universal sense mean celestial bodies, rather than individual atoms. this is governed by Gravity, where as and sub atomic particles are (i think) not subject to gravity in the same way (quantum stuff).

The difficulty is the nature of space. Special Relativity is the simplified special case that retains an idealised Newtonian view of space. Einstein's General Relativity (there are others!) was the paradigm shift that dispenses with gravity as a force, doesn't yet have a concept of mass, and introduces higher dimensional curvatures ('curvature' being an analogy to what a curve would be in 2 or 3 dimensions ) into space itself. What 'space' is, is the subject of live research programmes. Even Einsteinian GR has multiple geometrical formulations for different approaches depending on what is being calculated.

The consequence of the difficulty is that, because of the curvatures involved, there simply is no coherent definition of relative velocity in GR. (It seems like there should be, but that is to drop back into the classical physics that is our "common sense" view of the world based on limited local experience. Common sense isn't any use at all as a guide to theoretical physics as it really is quite counter-intuitive.)

On your first point, whether expansion or dynamics is responsible for superluminal speeds, the answer is you can model observed data for distant galaxies in any proportion between 100% due to expansion or 100% due to dynamics. The 'real' situation cannot be determined from the data. Pick (or develop) your theory, and look at the consequences. How to test your theory is the real spadework of science and it can result in the abandonment of prior postulates. [Einstein's Second postulate of Special Relativity  is properly "the speed of light is constant, independent of the (movement of) the source". Bear in mind the speed of light in matter is lower than in vacuo (refractive index and all that) so light speeds can be exceeded).]

Anyhoo, there's more to be had from a history or philosophy of science approach than I can sensibly put in a forum post... the frustration is partly that technical terms don't mean the same thing in different theories. 

Yes - and only really big celestial bodies at that.  Even in the scale of an entire galaxy, local gravity is strong enough to counter the Hubble flow, so the milky way is not expanding. In fact even in the local group of galaxies there is no expansion*.  You only see the Hubble flow when you look on the scale of many galaxies.

* Andromeda is heading towards us, as the two galaxies are attracting each other, and they will collide soon**.

** When a cosmologist says soon, they don't mean soon.

No one mentioned dark matter/energy yet?
Not that I want to make things anymore difficult

Tektronix i think advertised oscilloscopes some years ago where the speed of the trace moving across the screen was faster than light.

Of course nothing physical is moving.

Sweeping a laser beam across the night sky is moving the "target" points of the beam faster than the light from the laser is travelling. 

So you could sweep a beam across the face of the moon faster than light but unfortunately no information could be transmitted along that line across the face of the moon.

but not to the crew - they should measure it as c.

OK - so there's one rule for the big and one rule for the small (We'll call it the 'Cummings' discontinuity). Given they both exist within the same fabric of the Universe and are composed of the same matter, at what scale does the break in the rules occur?

What I can't resolve is the local vs non-local scales. Everything appears to be rushing away from everything else because of the 'balloon inflation' effect (there is no central point). Locally, of course, things might move together but the fabric of space is expanding, so surely these local effects occur against an overall background of expansion. 

yes, I always find it interesting when 'they' say they've discovered the largest known thing in the universe, and that is a collection of an unfathomable number of galaxies, dust and Gas.  Presumably what classes it as a 'thing' on the universal scale, opposed to a collection of smaller things, is the fact that the consituent parts are all expanding together in the same direction away from other stuff (but probably still moving towards each other in the local sense).

I think that's not right.  It's my understanding that, on local scales, gravity completely counters the Hubble expansion - that spacetime itself is not expanding within, say, a galaxy.  But this is, once again, general rel, and I'm not terribly well acquainted with that - I can bluff my way with special rel but never formally studied general!  I have a sneaky sense that Basemetal knows more about this than I do so I'd be interested in what they have to say.

Yes, I realised yesterday that my figuees were out

Good question. It occurs frequently in our patchwork instrumental physics. There's the same problem with the applicability of quantum mechanical models as with cosmological models -not just that there are breaks, but that it can be unclear between applicable theories where the break manifests. General Relativity, for example, is a non-quantum, geometric, gravity theory. SR is basically incompatible with QM. QM is "the most successful physical theory to date" despite being in shreds with competing  candidate theories that have absolute contradictions between them. Niels Bohr didn't confuse his Copenhagen formulation of quantum mechanics (really Heisenberg's) with being an explanation of ontological reality -he maintained it was a useful predictive tool, whatever reality was doing.

What lies beneath all the complicated theories is -to date- "we don't know". And more disturbingly, there's a lot we don't know how to test. Reminiscent of Phaedrus' problem in "Zen and the Art of Motorcycle Maintenance" it's possible to generate any number of theories to account for a given set of observations. And it's possible to model most theories mathematically. But in the end "Data trumps theory". As of 2020, all our theories are still effectively trumped by observed contradictions to their models. Pragmatically, many are useful in certain ranges and domains - for predictions, rules of thumb, engineering etc -but we don't have anything like a an all-encompassing 'complete physics'. 

I was brought up with the idea that science can do anything and will find out everything and is built of concrete epistemological foundations. I was a bit shocked when I first realised how soon the "frontiers of science" are reached. On graduating I worked as a physics teacher for a few years  than re-trained and switched to engineering, then after a career I went back to formal study in foundations of physics. When my supervisor realised my physics degree was pre-1988, he said 'well, forget the quantum mechanics models you were taught - it pretty much all changed in '88. " [Not true of introductory text-books, but they deliberately don't reflect the state of the art]. My field of study became the nature of probability in physics, with particular reference to candidate Quantum Mechanical models. In the course of that I was exposed to a lot of the ragged underbelly of theoretical and experimental physics and I have to say it was life changing for me. I'm by no means anti-scientific, but I'm painfully aware of the limitations of "scientific method". Many of the basics are actually still missing... in fact, the basics are where most current research is directed. Your theory will follow your fundamental ontology (what exists and how does it manifest?) -be it particles, waves, fields, densities, information -but the bugbear is that a theory can accommodate most observed facts and still not be "right", and some are acknowledgedly untestable hence not actually "scientific" in the original sense. If two fundamentally contradictory theories both 'work', what do you know about reality? 

The take away from this is simply that the pronouncements of different physical theories often don't  fit together well at the overlaps and this is an indication we aren't there yet.

Have a read at the intro and conclusion of this 2008 paper by Baryshev, for example, just to see these sorts of concerns expressed at the working level.

http://ppc08.astro.spbu.ru/materials/thesis_pdf/52-baryshev3.pdf

Irrelevent factoid: Angela Merkel has a doctorate in quantum chemistry.

Thank you for the most detailed answer. 

I'll have a read....

If it did it would be a pane? 

It's pretty clear we're not there yet - which is why it's so interesting to watch.  Any time I want my brain fried and a look at competing theories, I try to follow an episode of PBS spacetime.

Nothing to add to the physics, but scanning over that pdf reminded me of the RSE (Russian Scientific English) of my PhD students: Leave out definite articles, remember that they are missing, sprinkle them liberally and randomly over the manuscript....

Read it, and it is actual science, unlike the "theses" in the pseudoscientific subjects fancied by the majority of German polticians!

CB

Indeed.  I was thinking of it from the perspective of an imaginary 'side on' observer.

OK, so here is a terribly rough and ready idea of Special Relativity.  This is how I explain it to curious sixth formers - it's not really on any of the A level syllabi (AQA touches on it if you pick the right option but even then it's hugely simplified) so I don't formally ever teach this material, it's just that I have been asked about it so often that I need a half decent explanation handy.  It is utterly full of shortcuts, misses out some major contributions from other scientists, and glosses over some nasty problems, but it does give you a basic idea of what the hell is going on...

In the beginning there was Newtonian (really Galilean) relativity.  This held that there exists an absolute space, within which Newton's laws are correct. You can imagine inertial frames within this universal space - these are frames which might be moving with respect to each other - Galileo's example is of a boat moving perfectly smoothly and steadily.  If you were below decks, no experiment that you could conduct would reveal to you whether the boat was still or moving at constant velocity.  All inertial frames share a universal time - there is an implicit 'master clock' that ticks away in the background. 

In Galilean relativity, if a ball is thrown at 5m/s forwards from the deck of the boat moving at 10m/s, a stationary observer will see the ball move at 15m/s.  All very straightforward.

In the 1860s, James Clerk Maxwell published what became known as Maxwell's equations.  These unified what were then the somewhat disparate ideas of electricity and magnetism, showing that they were intimately connected.  They are wonderfully elegant - they can quite easily be written on a postage stamp.

But there's something really interesting you can do with these four equations.  You can solve them together (those who remember simultaneous equations from school will recognise what I mean by that) and what you end up with is one overall equation.  This equation is what any physicist would immediately recognise as a wave equation; it describes the position of a wave in both time and space.  And you can read from within a wave equation what the speed of a wave will be.  If you do this with the new wave equation that's just been derived, you get 3.00x10^8m/s, which is the speed of light.  So this new wave that Maxwell's equations of electricity and magnetism predict turns out to travel at c.  The obvious conclusion is that light is an 'electro-magnetic' wave. This is later confirmed by Hertz producing radio waves and measuring their speed to be c.

This solves an existing problem (of what light actually is) - up till then we had not been sure.  All good, although it does lead to geeks wearing this t-shirt: https://www.spreadshirt.co.uk/shop/design/and+god+said+maxwell+equation+men...

But then it brings up a new problem, which is that the solution absolutely insists that you measure the speed of light in vacuum to be exactly 3.00x10^8.  You must get that answer, regardless of your own velocity.

So suddenly Galilean relativity no longer holds.  If a spaceship doing 0.5c shines a beam of light forwards, they must measure the speed of the beam to be c.  But so must the stationary observer.

Einstein's answer to the paradox is that, if the two observers in different inertial frames are to agree on the speed of that light beam, they must disagree either on the length of their rulers or the rate at which their clocks run.  As a result of this we can observe time dilation (fast clocks run slow) and length contraction (fast rulers get shorter).  This means that, from the PoV of the observer in the stationary frame, the observer in the moving frame either uses a clock that runs slower than their own or a ruler that has been compressed compare to their own, and thus measures the speed of the beam of light to be the same.

It's vital to impress that this isn't an untested theory.  We know it happens.  If you remove the relativistic correction to the calculations that your phone uses to interpret the signals from the (fast moving) GPS satellites, error would accumulate at around 10km/day due to their clocks being time dilated (1).  And there are high energy particles - muons - created by gamma ray collisions in the upper atmosphere that have very short lifetimes, and should never be able to reach the surface of the earth - but they do all the time.  And they do it because they move very fast and their internal timekeeping is dilated.

You can use the Lorentz transformations to work out the new speed as observed in a moving frame - the maths isn't hard to do, although the derivation uses some upper sixth level calculus.

SR is not the complete answer.  It still doesn't answer what would happen if you travel at c.  The equations suggest time would dilate so far it stops.  However, there's an additional result that also shows that as objects go faster they get heavier, and this mass shoots off to infinity as you approach c - which means it is impossible for anything with mass to reach c.  So in effect the question becomes meaningless because you cannto get there.  And SR also only deals with non-accelerating frames - if you need to deal with accelerating frames, or in other words with allowing gravitational effects, you need the much wider general theory.  So it's correct to think of SR as just a special case of GR, and in fact Galilean relativity is just the special case of SR where the speeds are so low that the effects become unmeasurable.

(1) actually because the GPS satellites are orbitting within the earth's gravitatational field, GR affects the timing more significantly than SR.

Phew.  Any questions..?

I wish I'd had you to teach me physics 50 years ago!

the best bit in the whole of O level was e=Hf.  Sadly my maths meant I changed to arts for A level despite having really enjoyed science up to then.

Yes, thousands of questions.  But you've already spent enough time trying to explain it to us plebs so thank you.  

Yes, but what will they have done on grit?

High friction Andromedan sandstones in low G just don't cut it

Cheers, both.  It's no bother - I don't exactly have much to do right now... and as is so often the case, being forced to write stuff down actually helps me to fine tune some of the explanations, so it's a useful exercise.

E=hf?  Crikey, that leads to quantum mechanics, which is a whole different rabbit hole..!

I did want to try to pick up a few of the existing questions.  So:

Two spaceships set off in opposite directions, each travelling at 0.75c.  The stationary observer sees their separation increase at 1.5c; no problem with that.  Each ship sees the other recede at a speed = (0.75+0.75)/(1+0.75^2) = 0.96c.

Another spaceship travelling at 0.9c fires a projectile at 0.2c.  This is perfectly possible - although it will take MUCH more energy than a simple KE calculation would suggest as the mass will increase.  The spaceship will see the projectile move off at 0.2c; the stationary observer will see it move at 0.93c.

John's questions are harder (both the above are completely standard SR questions).  But his force us into GR.  SR doesn't answer what happens if an object recedes at c, because it is not possible.

In SR we have to abandon the concept of a universal time - everyone has their own clock and they are all correct in that frame.  But it does all still take place on a flat, Euclidean background of space.  In GR we have to abandon that as well.  The expansion that we observe is due to the expansion of the space, NOT due to relative velocities within space.  In fact, these relative velocities within space are called peculiar velocities (the fact that Andromeda is falling towards us, and therefore appears blue-shifted, is a good example) and they make figuring things out even harder.

So under GR it is perfectly possible for another object to be receding from us at c, or even faster.  Hubble's equation, v = Hnought x d, lets us figure out how far away you would need to be.  It's about 4.3 billion parsecs, or about 13.5 billion LY.  But here's the thing - there is nothing particularly meaningful or significant about this speed or this distance.  We can still see it - the light is travelling towards us at c, absolutely regardless of how fast the object might be receding.  It will be quite red-shifted but still visible.   

It's also important to spot that although it's 13.5BLY away, it has not taken 13.5BY for the light to get here.  There is a proper explanation for this involving tensor mathematics and funky curved diagrams, where we have to abandon the concept of three space and one time dimension and instead work in four dimensional spacetime... but that is way above my pay grade. The simple explanation (and this is an analogy rough enough to draw blood) is that for most of the light's travel, the universe was smaller.

This idea leads us to accept that the observable universe is quite a bit bigger than the simple result you could obtain, by saying that it's 13.8BLY in each direction because it's 13.8BY old.  In fact, the observable universe is about 46BLY in each direction.  We can see stuff that is 46BLY away, because although the light has only had 13.8BY to travel in, for much of that time the size of the universe was smaller.  (edit: working out how far this limit is involves knowing about the rate of expansion, whcih we are increasingly sure is not smooth...)

This is a useful thing to chuck in, I think - there is a background of microwave radiation that we see coming from every direction.  This is the CMBR, and we explain it by saying that when the universe was about 380,000 years old, it started emitting gamma rays.  These rays have been travelling ever since then, and have been red-shifted so far that they are now microwave.  Every bit of the universe was 'shining' this light at every other bit.  If we figure out how far away the CMBR that we receive today came from, we get 45.7BLY, so it's coming from near the edge of the observable universe (edit - and coming from stuff that is now receding much quicker than c).

(This, by the way, is the source of much of the black-and-white static that you see on a detuned TV screen.  That's not a random pattern - your aerial is picking up, and trying to decipher, the echoes of creation itself...) 

So how big is the whole universe?  We simply don't know.  It's quite possible that our observable universe is a tiny fragment.  This is why we can't answer the centre-of-mass question - we have no idea of how far it goes, or where we are within it, or even if it is topologically simple or if it does clever wrapping-around at the edges.

That's a great answer. I'll leave it unsullied by questions about planes on treadmills!

I found the article you referenced interesting (with as much understanding as I could muster from ancient A level maths). So it seems we don't know, but we do know things differ at different scales which was the thrust of other answers above. Makes me glad I'm a biologist!

Oh gods no - biology is properly messy! Give me the physics any day! 😉

One more thing I thought worth adding: the OP mentioned a candidate for the furthest imaged object, a dwarf galaxy called MACS0647-JD. It's 13.3BLY away if you measure the time that the light took to get here - in other words as far as the photons are concerned they've been travelling for 13.3BY, so we see it as it was 13.3BY ago. But its comoving distance (ie how far away is it now, if you froze the expansion of the universe) is 32BLY. So it's around 2/3 of the way to the edge of our observable universe.

Good contributions Jamie. Nice of you to take the time and trouble.

I was searching for something worth watching on tv for tomorrow night and noticed this- "Inside Einstein's Mind - The Enigma of Space and Time" on BBC 4 at 10:50 pm (Thursday night). It looks at GR apparently; which is a tough challenge for a regular tv channel.

 It may be a repeat but is not flagged as such in my newspaper and I've certainly not seen it before. Most of these types of programmes are unfortunately often rather superficial, for the benefit of a general audience, but it might be worth a look. It's a very long time (in any reference frame 😊) since I last studied GR so I'll be giving it a try but I suspect it will be rather lightweight.

Thanks Jamie.

Is there a reason we know of why time or instance change or why mass increases as you approach C so that c can never be breached? As in is there a force acting- or is it simply a fundamental law of physics and thats that?

Given that we are only seeing a small part of the universe but we think it started from a single small point. Are we able to determine where that start point is/was and how far we are from it?

I think that is a meaningless question. Before the big bang there was no universe to have a start point in it. 

Go back to the balloon analogy: if everything is moving away from everything else, then it must all have started out at the same place. So the answer to "where is that point" is "here" for every point in the universe.

If you still have some maths from uni time, here is a great youtube lecture on GR.

youtube.com/watch?v=foRPKAKZWx8&

I enjoyed it a lot, and I am a biologist as well!

CB

I'm in marking hell at the moment but will watch later.

I enjoyed A-level maths but found I was losing understanding from Uni level maths courses. Never - I repeat never - let mathematicians teach maths to non-mathematicians! I had a mathematician acquaintance when I was doing my PhD who was doing something on set theory. I asked him to explain it to me but lost the drift when he started talking about 'monsters' in the second sentence.

Still - applies to us all. The in-laws call me Sheldon....  

The balloon analogy is an example of the opposite- Not all parts of the uninflated balloon surface were in the same place to start with.

Another solution is continuous creation, even in an extended homogenously distributed universe. ( The idea of  continuous creation - of matter, energy, or space, or space-time- being no more problematic than their initial creation.)

Why not? the balloon starts as a point and expands outwards (obviously a real balloon doesn't but that is not a problem).

Maybe this is a better analogy.  Imagine a muffin with lots of raisins in it.  As it's cooked, the muffin rises, and all the raisins spread apart from each other.  If you videoed this proces, and then played it backwards, you'd see them all move together.  If this process was carried on far enough you'd see all the raisins in one point.

The raisins are like galaxies; the muffin dough is spacetime.  In the beginning all of the raisins, and all of the dough, were at one point, so it's not meaningful to ask, at our current time, which raisin or which bit of dough is 'the middle'.

You could argue that you could use the oven as a background reference system, to work out which bit of the dough happens to be in the same location as the point where everything expanded from.  But (puts on Keanu glasses) there is no oven.  The dough is all there is - it is all of spacetime.

I guess if you take the analogy very literally so that balloon has an uninflated state with a finite size.

As in Fred Hoyle? Is there a modern version of this?

Simply, that points don't physically exist? They're mathematical abstractions. So given the real balloon case, or real universe, it's not an essential deduction that observation of separation implies an original singularity. Or, given such an original point, what evidence is there for there only being one? Why not a distributed infinity of them? The universe could have started off infinite in dimension and still be expanding. It's not possible to determine relative velocities under current theories ( GR, Quantum Gravity) so even the direction component of any velocity of recession is undefined, so we can't extrapolate back to any 'point'. All I'm countering is the assumption that expansion implies single point of origin. We don't even know if the universe is a closed or open system.

There's a funny thing with observational data that gets in the way sometimes and it's that your theory constrains the data you can recognise. ( 'The theory-dependence of observation'.) Heisenberg's insight on electron trajectories in atoms was a good example. They were part of the then-current pre-quantum atomic theory and his insight was that electrons cannot have trajectories - they get from one position to another without being in all the places in between.

Physics is Fun : o)

If there's a good argument for time dilation and length contraction, I don't know it.  I can draw you clever diagrams of light bouncing between moving mirrors, and show you why the gamma factor needs to be what it it, and that the two phenomena are basically the same thing seen from different angles, but I don't think I can say why it happens, other than it is necessary to make SR work.  This does feel a bit like QM, where there are a lot of things that it's rather hard to justify...

There is a better argument for mass increase, because one of the things that comes out of SR is that mass and energy are the same thing.  As I add energy to an object its mass always goes up.  In most situations this is insignificant, but if we're talking about the amount of KE needed to get to a decent fraction of c then it becomes quite significant indeed!

What really bakes my noodle is what to use as a ruler. An expanding ruler would keep pace, rendering changes in distance undetectable? Or should an odd geometric effect manifest itself? The SI metre being defined as a stated number of light wavelengths, what would be the  effect on 'the metre', or for that matter, the speed of light?

I'm going to stop short of questioning the constancy of the " Universal Constants" that govern the speed of light, but that's another set of assumptions we make.

I think we're wholly relying on the idea that local gravity >> Hubble flow, so our ruler (be it made of perspex or light wavelengths) isn't subject to expansion? 

If mu-nought and epsilon-nought are changing then I've had enough and I'm going home

It's the light wavelength bit that gets me -when light (or any other em wave) is doing the inter-galactic travelling. 

In reply to Jon Stewart:

Yes. That Baryshev paper I linked to above talks about the vacuum creation issue and has some further references.

So assuming the muffin is a good analogy, it has an edge and a point that is the furthest away from the edges and that would be the middle. So I suppose I was asking if we knew where we are relative to the middle?

I very much doubt that we are alone. But even if we're not.. we still very much are. It seems completely implausible that humanity will ever be able to meet occupants of another world, if there are any. Who knows, I'd love to be alive in a few thousand years to see what's going on!

It's all in "there is no oven" I'm afraid. 

I think that's why it's not such a good analogy. It has an arguable advantage over the balloon in being three dimensional, but the big disadvantage of having a boundary and a middle.

I like the argument that if the universe is infinite then it must always have been infinite if there was a big bang because it is not possible to go from a finite size to an infinite size in a finite time, and so the big bang must have happened everywhere at once in an infinite universe. But this does seem weird, so does it suggest that the universe is finite?

I think the problem here is that all analogies are poor ones - at least all analogies that we can get at without some seriously heavy maths, most of which I have either forgotten or was never taught in the first place.  I can hardly remember how to define a four-vector and I never did metric tensors, and trying to imagine the nature of spacetime without them is, I understand, basically impossible.

I like the muffin anaolgy because at least it gets things into the right number of dimensions, and it's relatively easy to get the idea of it all being in one place at the beginning.  It has the pitfall of you being able to imagine where its centre lies, and asking if that was the spot where big bang took place.  That's not the right way to think about it, for two reasons: one is that the dough is all that there is, and without the external coordinate system that the oven would supply, you can't reasonably ask where big bang happened - literally every bit of the dough was exactly there, so where that point is now within the muffin is meaningless.  

And the other is that (as Robert points out) the muffin has a clearly defined edge.  We do not think this is necessarily how the universe works, and in fact we have reason to think it's not.  To show you what that means, the balloon is the better analogy, because it has no edge.  The 2D surface of the balloon 'wraps around' - a 2D creature like an ant could walk forever and never find an edge. 

The problem with that is that we have to extend this picture into 3D.  It is simple to see how the 2D surface wraps around itself because we can visualise the 3D space in which this happens.  I am b*ggered if I can visualise how 3D space could wrap around to join back up.  It's evolution's fault - we are brilliant at doing stuff in 3 dimensions, because all the trees and fruit and sabre-toothed tigers all existed in a 3D space.  The tigers never came at you from a fourth dimension so we never bothered to get good at picturing it!

As far as I know we simply don't know what shape the universe is, if and how it wraps around, or whether it's infinite or not.

We're really not good at handling " infinites", so they almost always invoke paradoxes for us. it might be possible to be infinite and still bounded, although I think maths can do tricks that physics won't cash out. Hence constructivist maths I suppose. I can't answer your question, but I suspect our whole notion of spacetime isn't close to reality yet. We have some physical theories of matter-energy, but not much of a handle on 'space' at all, or time. As in, "Think of nothing at all, not even empty space..." Or even, "Why is there anything at all?". Existence is a very strange phenomenon!

You're hitting the nail on the head I think. The skill for a lot of theoretical physics is comfort with the formalism rather than reliance on visualisation. That's why there's so much maths.

Historically physics was literally "phenomenal", ie based on the human senses and things we could sense. Heat, light,sound, motion etc. At school common shared life experience acts as quite a guide when learning ( and teaching) the classical physics syllabus.. Then you hit magnetism - often the first stumbling block- because we have no common sense about it. Then the physics gets harder the less we can sense it - rotational dynamics, wave mechanics, and so on. When we get into abstract concepts we have to develop new familiarities to get past the strangeness of it all.

Yes, I also get accused of nerding out in record time!

CB

What freaks me out is how stuff is linked to fundamental maths in surprising ways. Why are there even natural numbers, i.e. why do we count things (sets of stuff we deal with, in the most general terms) in discrete steps rather than as a continuum? Why does pi crop up in physics even in contexts that are not obviously linked to geometry (and even in biology)?

CB

Careful! You are getting awfully close to saying that Pefa was right all along.

Out of interest, could you give an example?

The edge of the observable universe, and looking at it as it was 'shortly' after the Big Bang (well half a billion years after). 

So if the universe is expanding and has done so since the big bang (I think evidence suggests expansion is actually speeding up?), where is that galaxy now? Does it still exist? And how big is the 'unobservable' universe?

My head hurts just trying to think about it.

I feel your pain. I know this sort of thing is way beyond matters that somebody as lowly as me is capable of understanding and YET I still keep thing about such things. I was thinking about it in bed this morning.

When you look up at the sky during daylight it seems even harder to understand what is up there and out there. I suppose somewhere out there are other "intelligent" life forms with similar thoughts.

"Hello, is there anybody there?"

I got interested in that when I read EugeneWigner's paper on the Unreasonable effectiveness of maths in the physical sciences.

My own view is that maths isn't special, but useful. It's a pattern game with rules and symbols. What we're good at is pattern recognition and analogy. We simplify and idealise observations into regularities and seek to find narrative explanations for them. The narratives are then expressed as laws, rules, algorithms, whenever we can. Mapping a narrative pattern to a mathematical pattern becomes second nature - but I contend that the narrative is the science, not the maths used to express it efficiently ( but not always perfectly accurately). The biggest current consequence of this is Everett's 'many worlds' formulation of QM where the superposition terms in the quantum wave function are all granted concurrent reality. I'm arguing they can't be real and too much faith is placed in the maths. ( Oxford disagrees ).

One way pi gets in to a lot of physics is through wave mechanics and descriptions of oscillating systems. Any motion that can be expressed with an angular component will pick up a angular rotational (pi) expression. Another related way in is Fourrier analysis, where even a square impulse (for example) is approximated by combinations of sinusoidal waves.

I have to admit that I am attracted to the extreme opposite view of the place of mathematics in reality having read Max Tegmark's "Our Mathematical Universe", in which he propose that, at the very deepest level, the universe IS mathematics. The idea that pure mathematical objects or structures exist outside physical reality does seem to (sort of!) get around the "why is there something rather than nothing?" question; all possible mathematical objects just "are" and reality can somehow emerge from a suitably complex one - so our universe is just something that emerges from one such object. 

It's comoving distance (which is our term for the distance you would need to travel if you paused the universe and just flew across it with no further expansion taking place) is about 32BLY.  Of course, if you set off today, the space between you and it would expand a hell of a lot further than this during your journey.

I don't think we have any idea.  It's a pretty tiny galaxy, so it may well have been swallowed up by another or pulled aside by other objects. 

We just don't know.  We have a sneaky feeling that it might be much, much bigger than the observable.

In reply to mypyrex:

Have you had a look at the ideas behind the Drake equation?  Might well be interesting.

In reply to basemetal:

Like Robert, I have more faith in the maths, but I also know full well that I haven't studied this even slightly far enough to be confident!

Philosophy of maths is an absolutely fascinating subject. I started off as a mathematical realist but became more intuitionist/instrumentalist along the way. I'm not a materialist ( you can't be either if you hold the real existence of mathematical objects independent of minds and mathematicians...). 

To retreat  from phil.math. and keep things more on track, do you remember in school solving quadratic equations for physics problems and being told to ignore the negative solution because it was meaningless physically? [Square root of 4 is both 2 and -2]. That would be an example of the math pattern not perfectly mapping the physical. That's the kind of thing that happens quite often in physics. To be fair, there have been cases where mathematical patterns have led physics to discoveries too, often involving symmetries in equations ( eg Dirac and the positron). But my contention is that maths has to be deliberately, not blindly, mapped onto physics.

QM may be in the state it is because we mostly have math-led candidate theories for it and they are very hard to test.

Edit: I just remembered a good example of maths doing its thing to physics. It might blow a few gaskets, and there are deeper papers on it, but look up "Norton's Dome.".

Here's his paper.. [sorry can't get the link to pdf to work!] Citation is: Norton , John D ' The Dome, An unexpectedly simple failure of determinism' Philosophy of Science, 75 (December 2008) pp. 786–798. 0031-8248/2008/7505-0025$10.0

I prefer the view that at the fundamental level the universe is information. Part of this we process as noise and part of it as structure. We use math for the latter part and it has some level of predictibility. But it is (in my view) not certain that the total of the information can be described with math.

When you say 'fundamental', what is it that is structured to encode information?  I'm intrigued by the possible non-physical ontology of this worldview. Which definition of information is in play?

I was totally with you on this until you stole the oven. Where’s my muffin gone??

Hi, what do you mean with definitions of information?

With fundamental I mean that you can argue that the information is more important by itself than whatever it is that encodes it.

Long ago I was taught that the fundamentals of physics are that universe consists of space, time, and particles. But I am not so sure anymore about particles . In field theory you consider particles to be well-defined structures in a field. Next to the particles, there is lots of other stuff happening in the fields that does not have nice structure. This is background to my comment that maybe math is not sufficient to describe the universe. Now to ontology. I'd argue that the fields are more fundamental to reality than the particles. But maybe even the fields themselves have no meaning and the only meaning is in the data of the values of the fields in spacetime?

in my blurry way i have come to the conclusion that particles are not more than "observed field interactions".

by the way, is there any strength to the idea that the Universe is still a singularity in "unrolled dimensions" and so distance is just illusory in our 3D space as every point is part of/in contact with the singularity?

The more I read and the more episodes of PBS Spacetime I sit through, the more I realise that monkey brains aren't really evolved for all this.

What I find extraordinary is that monkey brains evolved for hunter gathering in small bands on the African savannah have got so far with all his. How come our brains can come up with something as abstract advanced mathematics and cope with stuff like quantum mechanics and general relativity? Where's the survival advantage in that?

I'd rather look at consciousess as the wonder and think about what's missing in the materialist world view. Evolution is a literal non-starter as a theory of origins- the maths simply won't allow it - but it's an untestable article of faith for many. It's a big idea that doesn't have to be right to serve a function as an interpretive grid, but it isn't "scientific" [unrepeatable; untestable; unfalsifiable; no consensus narrative; unobservable (breeding, adaptation and micro evolution aren't the same); dependent on reproduction and transmission of characteristics from the first; teleologically mystical -e.g. "why survive?" And so on...] . Not intending a thread hi-jack as it's a whole 'nother topic.

Stuff doesn't evolve for survival: natural mutations cause all sorts of harmless dormant mutations which either prove beneficial or not depending on environmental stresses.

Point being the mutations have to have happened largely before the environmental stresses change to select them, not that mutations happen in response to stresses. The ability of our brains was a mutation or series of mutations which almost certainly started millions of years ago.

I don't think there needs to be a reason does there? Some genes just do survive - nothing mysterious about it.

Yes, I think we are making the same point. The ability of our brains to do maths and physics seems to be an evolutionary accident or maybe a sideproduct of something else which has been selected.

I was happily replying then realised I was writing an essay rather than a post So to spare everyone's attention span... I'll agree with you.

There is a drift in many papers on ontology that wander between ontology proper (the stuff) and functional descriptions of what the stuff might be doing. It's a little further confused in the Information Ontology discussions as there's a lot of interference from the information science definiton of ontology of information which is a different subject from a communication discipline. But you can see the wires crossing and its a bit painful.

The current action in physics is somewhere between Quantum Field Theory (QFT) (bit of a mish-mash at present, not compatible with GTR) and various stabs at Ontic Structural Realism (OSR). OSR was my final resting place in physics, but the leading proponents of OSR are controversial, and you could say the front runner isn't actually OSR at all.  I throttled back to Epistemic Structural Realism (ESR), the view that what we can know about the universe should in some way reflect the actual structures involved as far as our theories go, but acknowledging that we are studying what we know, not the universe itself.

The best paper I have ever read on this, and it cost me two years of work that I subsequently had to write off, was

Frigg & Watsis 2011 "Everything you always wanted to know about Structural Realism but were afraid to ask." (60 page pdf file...)

https://core.ac.uk/download/pdf/157866326.pdf

Space is expanding. Every bit of space is expanding so effectively inflation at the time of the Big Bang meant expansion was faster than light. However nothing exceeded light speed.

We can see back almost to the Big Bang 13.5 billion years ago. That is our horizon, the universe extends beyond that horizon but we can never see it.

Every point in space is expanding simultaneously. The " start" point in effect would be every point in space.