Space and time aren't fundamental properties of the universe

[Elderly Sumo Prophecy]

Fish!

[Cold Meat Platter]

Too slow, chicken marengo!

[Johnny Yesno]

Too slow, gazpacho!

[bespoke]

Seems like this will go on for a bit https://www.youtube.com/watch?v=uD4izuDMUQA

[greencalx]

Thanks, that's really intresting.

If it helps at all, here's what Brian Cox says, i just jotted it down as he said it, so there may be some mistakes/typos:

he then goes on to caviet the above by saying not everyone agrees on the full picture, but that they do agree that our picture of time and space is wrong.

Glad my ramblings were halfway useful.

I'm afraid to say that my formal education in GR/Cosmology stopped short of black holes, and in any case, it looks like most of what is being talked about is stuff that's happened since then, and I've not done a good job of keeping up with what's going on in other corners of my discipline.

My best guess is that Cox is talking about the black hole information loss problem and/or the holographic universe. A nice readable article, with links to more technical stuff, is here: https://www.vox.com/2015/6/29/8847863/holographic-principle-universe-theory-physics. Nothing strikes me as being aggressively wrong there, but I'm not an expert and I'm also not the type to fake expertise by bandying around buzzwords from a skimread of a document I've barely understood.

The holographic part is the bit that I have the most intuition for. In purely mathematical terms, it just means that the properties of the interior of some object are completely specified by properties of the surface. It's not so difficult to see how this could be true. Suppose you have a load of building blocks that can only be put together in a certain way, and you use this to construct some object (e.g., a cube). Now you look at the pattern of blocks on the outside of the cube. If the way you can attach blocks to the outer layer to make the first inner layer is sufficiently constrained that there is only one way to construct that inner layer, and the same is true going from the first inner layer to the second inner layer, then before you know it you've completely determined the entirety of the interior. There's a bunch of things in mathematics and physics that work like this, at least partially, so it's not a huge leap to imagine that this is true of the universe as a whole. There are also many other cases where you can construct the same mathematical theory in different numbers of dimensions - even for things like the simple pendulum. I guess it's possible that some processes look mysterious in the interior but more natural (e.g., local rather than nonlocal) on the boundary, but when you have two equivalent representations I think it's risky to propose that one is somehow more real than the other.

I can't quite get my head round the information loss problem, unfortunately, even though entropy is more my stock in trade. It seems to be a manifestation of the same idea, that information inside a black hole is encoded on the event horizon, so doesn't get consumed as the black hole disappears. Such consumption is problematic from the point of view of the second law of thermodynamics (erasure of information = less entropy, and entropy is supposed to go up, not down according to the 2nd law). For reasons I've never quite understood, the second law is considered sacred by most physicists (even though we already know that it isn't a microscopic law, and only strictly applies to macroscopic systems). Anyhow, apparently it's all fine in the end if you don't lose information into the black hole and it gets encoded on a surface instead. I suspect, and it's here where my uncertainty-o-meter is on the verge of exploding, that Cox may be referring to entanglement between what's inside and outside a black hole -- or perhaps even between two black holes. This seems to cover the latter proposal, and sounds close to what Cox seemed to be referring to: https://www.quantamagazine.org/wormholes-reveal-a-way-to-manipulate-black-hole-information-in-the-lab-20200227/

Personally, I think there may be a bit of grandstanding on Cox' part. I don't find it helpful to say that space and time don't meaningfully exist, because clearly they do meaningfully exist in our everyday lives and no theory will invalidate that, even if it turns out that our everyday experience is some weird limiting case of something more general and abstract. Again, there's been plenty of examples of that sort of thing throughout physics (even Newtonian mechanics) and I'm not particularly troubled by it.

[TheBrownBottle]

I'll echo the favourable comments re Jim Al-Khalili docs, his output is excellent - but I would genuinely appreciate it if one of these guys would do more discussion on the chances that string theory and 11 dimensions and all of that stuff is just the theoretical physics version of jazz; talented people in their field basically enjoying themselves and running with something that might be a load of old shite.

I'm an absolute layman (cleverly disguised in the above comment) on all of this, beyond the standard pop science books / BBC Four docs, so I'd love an answer from one of yer physicist types.  I wonder if it's a 21st Century version of the luminiferous ether

[Johnny Yesno]

Personally, I think there may be a bit of grandstanding on Cox' part. I don't find it helpful to say that space and time don't meaningfully exist, because clearly they do meaningfully exist in our everyday lives and no theory will invalidate that, even if it turns out that our everyday experience is some weird limiting case of something more general and abstract. Again, there's been plenty of examples of that sort of thing throughout physics (even Newtonian mechanics) and I'm not particularly troubled by it.

I've not seen the show but perhaps he's referring to one of the differences in thinking between Newton and Einstein. Newton thought that space was like a container where if you took all the planets and the other matter out, you'd still have an empty container. Einstein proposed that if you did that, the container would cease to exist because the space is solely defined by the distance between the bits of matter.

Have I got that right? I'm no expert on this stuff either and get most of my information from the Veritasium youtube channel these days.

[Mrs Wogans lemon drizzle]

I've not seen the show but perhaps he's referring to one of the differences in thinking between Newton and Einstein. Newton thought that space was like a container where if you took all the planets and the other matter out, you'd still have an empty container. Einstein proposed that if you did that, the container would cease to exist because the space is solely defined by the distance between the bits of matter.

Have I got that right? I'm no expert on this stuff either and get most of my information from the Veritasium youtube channel these days.

I don't think he's referring to the difference between Newton and Einstien, could be wrong though.

[Mrs Wogans lemon drizzle]

double post

[Cuellar]

What if Peter Sissons isn't a fundamental property of the universe?

[Mrs Wogans lemon drizzle]

lol

[Mrs Wogans lemon drizzle]

ugh.

[Sebastian Cobb]

they are because they are alternative names for bofa

[mothman]

I'm basically just waiting until just before the thread is locked so I can take the opportunity to say that you are all the most obnoxious, trumped-up, farty little smegheads it has ever been my misfortune to encounter!

[touchingcloth]

I've come to regard you all as people I met.

[Blumf]

I can't quite get my head round the information loss problem, unfortunately, even though entropy is more my stock in trade. It seems to be a manifestation of the same idea, that information inside a black hole is encoded on the event horizon, so doesn't get consumed as the black hole disappears. Such consumption is problematic from the point of view of the second law of thermodynamics (erasure of information = less entropy, and entropy is supposed to go up, not down according to the 2nd law). For reasons I've never quite understood, the second law is considered sacred by most physicists (even though we already know that it isn't a microscopic law, and only strictly applies to macroscopic systems).

I think that's the part Quantum physics has a stronger say, being a bit more detailed in the way information is handled than classical physics. Not sure on the details.

[Mr Farenheit]

I ate a sandwich once and I had the uncanny feeling it was from the future.
Seven years later and guess what turns up?

Spoiler alert

The same sandwich!

[close]

[GoblinAhFuckScary]

I've come

[Mister Six]

A load of utter wicky wacky woo woo.

[druss]

I like Cox.

[shiftwork2]

He was doing a PhD or post-doc or some other worthless time-filling caper when I was an undergraduate; D-Ream were going but it was (just about) pre-Blair.  No recollection of him getting to meet me.

[mothman]

I ate a sandwich once and I had the uncanny feeling it was from the future.
Seven years later and guess what turns up?

Spoiler alert

The same sandwich!

[close]

Ah, now you've brought up this subject; given that God is infinite, and that the Universe is also infinite... would you like a toasted teacake?

[Bigfella]

I've come

Was it something I said?

[Elderly Sumo Prophecy]

S-E-X you know I want it
S-E-X I'm gonna get it
S-E-X I think I found it

[touchingcloth]

S-E-X you know I want it
S-E-X I'm gonna get it
S-E-X I think I found it

So what is it?

[Johnny Yesno]

We've exited the time loop now, btw. tc just had a very sheltered upbringing.

[touchingcloth]

We've exited the time loop now, btw. tc just had a very sheltered upbringing.

Oh! A magic door!

[Mrs Wogans lemon drizzle]

I've come

Where from?

[GoblinAhFuckScary]

Where from?

Your white hole

[Mrs Wogans lemon drizzle]

Your white hole

Welcome to my toilet galaxy!