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Physicists Debate Hawking’s Idea That the Universe Had No Beginning

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Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#91

Post by MisterOctober »

quotemstr wrote: post #16
sp332 wrote: post #13

Earlier quoted context omitted.

You can still have causality.

Causality without time makes no sense. Even if you don't have a ticking clock, you can define "time" with a counter and a Lamport clock. Any time you have state, you have time. A timeless universe is hard to grasp.

Julian Barbour has what I consider to be a pretty well-reasoned notion a timeless universe composed of a large number of mathematical configuration spaces he calls "nows" -- i.e., it contains many states, but no objective notion of time -- outlined in his pop-sci book "The End of Time" [1999] and his website http://platonia.com/

p.s. for the record, Barbour is no clown, but a serious cat -- he is also the guy that wrote "Absolute or Relative Motion / the Discovery of Dynamics" which is a bedrock treatise on Machian ideas in physics

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#92

Post by semi-extrinsic »

Balgair wrote: post #88
SketchySeaBeast wrote: post #70

Earlier quoted context omitted.

If you are restricted to the typical 3 dimensions of movement (and 1 through which we are non-optionally traveling) - you should either get to a physical boundary, or you end up in a loop, right? I mean, you won't travel so far you end up in Tuesday.

Sorta. We are in this thing called space-time. It came out of the Big Bang (we think). There is a finite amount of it (about 45 GLY in radius, maybe). You can only ever see about 14GLY of it due to some speed limits. You can't get to an edge or boundary of space-time because it's not 3-D, it's curved in this really weird way. There are a lot of holes in space-time that we're still thinking a lot about. For some reaso…

> You can't get to an edge or boundary of space-time because it's not 3-D, it's curved in this really weird way.

Can you elaborate? I was under the impression that the curvature is essentially zero and that the universe is open.

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#93

Post by semi-extrinsic »

EdwardDiego wrote: post #64
sonnyblarney wrote: post #59

Earlier quoted context omitted.

The word is 'speculation' not 'belief' that that's pretty much what all science is. The evidence usually comes later.

There I was thinking that the scientific method involved falsifiable hypotheses - so how are they going to prove or disprove their respective beliefs? I'm getting string theory flashbacks where half of the physics community is into it, the other half is not, and no-one can prove anything, but they still have a grand old time arguing about it anyway.

The trouble is, unless you have a grand old time arguing vague ideas, you might not find the ideas that can lead to new falsifiable hypotheses.

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#94

Post by AnimalMuppet »

Cyph0n wrote: post #27
pavel_lishin wrote: post #25

Earlier quoted context omitted.

The computer, and the external universe of which it is unaware, still have time.

Total amateur here: how do we know that time did not exist before the beginning of the universe?

Almost-total amateur here: We don't.

We really don't. We don't have any physical evidence of anything from before the big bang (presuming that's what we call the "beginning"). Zero. All we have is people having views on the current situation, trying to apply those views backwards to "before", where they may or may not fit, and saying "I think it's like this".

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#95

Post by AnimalMuppet »

0815test wrote: post #33
pavel_lishin wrote: post #15

Earlier quoted context omitted.

Can you expand on this? How can you have causality - cause and effect - that's divorced from some sort of flow of time?

Both causality and the "flow" of time are ultimately artifacts due to the fact that a "universe", by definition, is something thay starts out in a highly-ordered state and evolves away from it. The basic laws of physics are time-symmetrical, at least in a practical sense - they do not involve any distinction between "cause" and "effect".

> a "universe", by definition, is something thay starts out in a highly-ordered state and evolves away from it.

I don't think that's "by definition". That's by observation of an example of one.

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#96

Post by Balgair »

semi-extrinsic wrote: post #92
Balgair wrote: post #88

Earlier quoted context omitted.

Sorta. We are in this thing called space-time. It came out of the Big Bang (we think). There is a finite amount of it (about 45 GLY in radius, maybe). You can only ever see about 14GLY of it due to some speed limits. You can't get to an edge or boundary of space-time because it's not 3-D, it's curved in this really weird way. There are a lot of holes in space-time that we're still thinking a lot about. For some reaso…

> You can't get to an edge or boundary of space-time because it's not 3-D, it's curved in this really weird way. Can you elaborate? I was under the impression that the curvature is essentially zero and that the universe is open.

Best described here: https://www.livescience.com/33646-universe-edge.html

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#97

Post by erikpukinskis »

logicchains wrote: post #46
quotemstr wrote: post #18

Cosmology is deeply disturbing if you think about it too long. Why should the universe exist? What is a causeless cause? How can something come from nothing? Regardless of the precise mechanisms involved, at some scale, some kind of steady-state cyclic model seems unavoidable --- the whole idea of existence not existing is bizarre and puzzling. The only way out of the causeless effect problem is to nop out of the eff…

From a probabilistic point of view, we're observing with extreme selection bias: we only see the universe in which we do exist, not all the ones in which we don't, so no matter how incredibly unlikely existence is, from the perspective of existing consciousness it is guaranteed. This means it's possible for consciousness to arise from pure entropy: https://en.wikipedia.org/wiki/Boltzmann_brain .

Related question: how fast does time go in a “pure entropy” situation?

Or, maybe more useful, what happens to time as you asymptotically approach pure entropy? Does it speed up?

If so, it would make a Boltzmann brain inevitable. Or... not an inevitable brain, but an inevitable random low entropy state, right?

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#98

Post by d0m »

Say we could break any physical rules of our current universe, is there a good theory that would explain how something might have been created out of nothing? i.e. imagine for a second that we're in a simulation and that the current laws of physic are just arbitrary created by a "host". This "host" could have very different physical laws. Could we think of any theory that would explain the creation of something out of nothing in this "host"?

I'm very puzzled as to why the universe even exist.. wouldn't it have been much simpler not to have anything at all? I can only think of one answer: It couldn't have been otherwise. I.e. physically speaking, it had to happen.

Maybe that's how we should approach the problem? Let's try to "create nothing"... maybe we'll realize that it's actually impossible to "have nothing" unless X happens, and maybe we'll figure out that X happening would explain how our universe was created?

Or said in a different way, maybe the universe is actually "nothing", like it always was and will always be. But "nothing" may just be physically impossible so you need "positive" and "negative" things to cancel each other out so that the end result is "0".

I'm not too sure where I'm going with this, but it reminds me of the quote "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." So, whatever the theories about big bang, multi-verse, universe expanding/collapsing indefinitely or even God-based theories, all of it comes back to "how did the first thing come out out of nowhere?" People talk about "Singularity", but this is just "kicking the can down the road". Still, by kicking the can I guess we keep learning new things, and maybe someday we will have the technology to answer these questions. Unfortunately, it seems like answering the next frontier seems to be an order of magnitude harder (time-wise and cost-wise) than answering the previous question.

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#99

Post by winter_blue »

djsumdog wrote: post #10

This seems different than the concept of infinite time, where prior to the big band there was something the collapsed into a ball of energy and maybe someday our universe will collapse back again (which has lost merit since we've seen matter in the universe isn't slowing down in spreading apart, but accelerating .. meaning in a few trillion years, atoms may be so far apart that light can't reach anything .. the event…

> matter in the universe isn't slowing down in spreading apart, but accelerating

How come this does not violate the law of conservation of energy which says there's a fixed amount of energy in the universe? For matter to accelerate would require energy right? Where is the energy fueling this universal acceleration coming from? According to Newton's laws, doesn't there also need to be an external actor causing this acceleration? (Sorry if this sounds like a basic question--I don't know much physics besides some required intro courses I took for my CS major).

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#100

Post by FartyMcFarter »

abtinf wrote: post #17

The explanation I've found most persuasive is to take a purely philosophical approach: the universe had no beginning and will have no end because those concepts do not apply. The universe is everything. If there was something that "caused" the universe, it would just be part of the universe. If there is something after the universe ends, it would just be part of the universe. There is nothing outside the universe, if…

Yep. If you're a programmer, think about a "game of life" simulation (or any other simulation).

The answer to "what was there before the first state in my simulation?" is simply: "nothing, within this universe".

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