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Author | Topic: What is Time and Space | |||||||||||||||||||||||||||
cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
If we take the position that the universe always existed I assume this is the same as saying that time never had a beginning which seems to me to be impossible for the reason that without a beginning how can any point in time ever be arrived at? Ok, first read my post above. You'll see the problem with thinking of time-flow a fundemental property of the universe. If you read through the Penrose stuff that GDR quotes, you'll see the idea that time is intimately wrapped up in conciousness. I have a lot of sympathy for this idea. So there is no time variable that montonically increases... there is just a fixed, possibly infinite, time dimension. Part of the four dimensional mess of matter that makes up the universe are these sub-structures that we call humans, although we are more familiar with dealing with single cross-sections of these humans. These strcutures are sufficiently complex that somehow (don't ask me how) this thing known as conciousness arises, and appears as a dynamic 3-d process within the static 4d structure. How this conciousness makes sense of a temporal order is difficult to determine but certainly the thermodynamic arrow of time is involved. Does this start to answer your question?
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
Yes, I had read through your posts. I must admit that I am a little skeptical about the relevance of our perceived passage of time to the deeper notions of the connections of conciousness and time. I'm fairly sure tests have shown that a perceived minute doesn't change much over our lifetime, once we have a good idea of what a minute is. This is really just a function of processing speed. The larger scale perception of time passing seems more to do with the ratio of information gathered to information stored. I would describe both of these as high-level, cognitive issues, and would be true whether time-flow existed completely independent of conciousness or not. Well, that's my thoughts anyway...
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
Can you tell me what you believe would be left if all consciousness ceased to exist. Presumably time would cease but would matter exist? Is the suggestion then that the existance of the entire universe depends on consciousness? Hmmm, starting to stray into Strong Anthropic territory here. This is a GR-"solution"-inspired view:The universe does not depend upon conciousness. It just is. It has no dynamics, it does not evolve. Every slice that we think of as a moment in time is fixed and exists "always". However, us theoretical physicists tend to revere consistency above all else. And so far our only datapoint is that a consistent universe involves conciousness...
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
Typical, you're picking up on the "other" stuff about conciousness I wasn't really going there...
Penrose is not suggesting a new force, but he starts with the idea that our conciousness can come up with non/un-computable stuff like Godel Incompleteness, P/NP, etc and hence conciousness must be more than computation. He suggests quantum computation through the micro-tubule stuff. Now Roger's difficulties with classical emergence (collapse of the wave-function) have always confused me as he spent a reasonable amount of time with Chris Isham and should be satisfied with de-coherence as an excellent approach to the problem (Isham being a pioneer of this with Jim Hartle). But then Roger is a mathematician pretending to be a physicist unlike the rest of us who are physicists pretending to be mathematicians. To be honest, none of this is what I was discussing. I'm not so much interested in the origins of conciousness (for this particular debate) but rather the role of conciousness in "flow of time" - generating or merely observing. I'm at least 50% with generating... i.e. the "flow of time" is as much an observer dependent quantity as "red" or "Emaj7". That said, I am at least 25% convinced that conciousness is a necessary element of what we call existence (note, nothing of my religious beliefs intrudes here.)
If the universe must, according to some imbalance or difference in potential,move in a given direction as to effect an arrow of time is it necessary that we discover the mechanism as a consequence of the quantum physics or is the problwem of finding a suitable means of testing by experiment to settle the question? The arrow of time does not in itself imply a flow of time, merely an ordering of the fixed four dimensional solution. Statitsical, thermodynamic considerations lead to the arrow but they do not imply "flow".
Ionce read on the paradox about the wave particle duality and in that same book the author was implying that the wave aspect is simply a measure of the probability of a particle and the particle aspect was the actual matter point itself. NO! This is very naive and shows the lack of understanding by many who profess to know and then to teach! Neither description is correct, but both suffice in different situations. The particle is better described as a quite complex (quantum) excitation of a field. Edited by cavediver, : Does there have to be a reason?
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
Is it sufficient to say that these two measurements are similar to a description of a cone... Yes, a good analogy, and closer to the truth that you realise. When I ask, "what is the position of the particle?" I am projecting the wave-function in a particular way that gives me a position-like answer. When I ask about the momentum of the particle, I am projecting the wave-function in a different way, just like your "side" or "end-on" projections of your cone. Notice how the two projected aspects, position and momentum, cannot possibly be observed simulataneously by the same observer...
Is the difficulty in the ability of our brains to concieve of a geometry that allows these two descriptions to co-exist without the seeming paradox? It probably plays a large part, yes. We are so used to "things" sitting in space and "processes" applied to "things" at our length scale. This is so unlike the quantum field picture.
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
Do you agree with him that most physicists would agree with his statement? Well I agree with his statement, and I think most physicists in our field would as well. Outside our field, I wouldn't be so sure.
What does he mean by illusion? If time is just a series of nows that are eternal I'm wondering if that would qualify as an illusion. The illusion is the "time-flow", or passing of time. To me, every moment exists, it is just my conciousness only revealing a slice at a time.
Is Penrose's thinking on this consistent with Julian Barbour? In general, yes. But my description depicts a static 4d universe, with all the time layers neatly ordered. Barbour sees a collection of possible states of 3d spaces that are brought together or picked out to form the 4d universe.
How come all you guys that seem to write about this come from the UK? It's the tea Too bad you chucked all of yours into the sea a while back
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
That would be our good friends to the south I was going to excuse myself by saying I thought I was replying to Sidelined, then just checked his location So... what is it that makes the Canucks ask all the awkward questions?
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
Yeah, I know Don a little He was Hawking's sidekick before my time so I only ever met him on his visits. He's done some interesting work in his time.
not only will we eventually find that time is an illusion but so is space This is very much the picture from something as "mundane" as classic string theory, when looked at from the relativist/mathematical viewpoint (as opposed to the particle physicists). In this case, reality is only two dimensional and our 4d universe and everything in it inlcuding us is a projection.
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
So much emphasis has been put on the possible point singularity In an infinite universe, the singularity is not a point but infinite in extent.
If one can fathom the likely probability that time and space are infinite in all directions then one can see how silly it is to think that the same singularity (or event) that started the process of our expanding universe also created the interwoven time that we use to perceive it upon. In physics, we do not use terms like "silly". They have no place. We use terms such as "consistent with" or "implied by". Some of the most sensible sounding ideas are nonsense and some of the most outlandish ideas have been shown to be true.
Time is an absolute and can have no beginning or end. Some may try to argue otherwise but that’s because they base their deductions on a house of cards that can easily blow over with a sneeze. Einstein's theory of General Relativity argues otherwise. So far, it is the only theory of time we have and also stands as the most accurately tested theory in the history of science. It wil be superceded by a deeper, more unified theory at some stage, but it will never be superceded by aimless waffle and random terminology such as I see in this thread.
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
You have to remember that Barbour's stuff is very advanced conceptually. It's a real struggle how to explain this without introducing innumerable other concepts that each need explaining
Ok, let's try a super-brief version: imagine all possible variations of the universe at a fixed time - a sort of universe cross-section(ignore relativistic objections to this concept for now), in an Everrett many-worlds sort of way. Stick them all in one big super-universe - a universe of universe-cross-sections. They will be arranged by "smoothness" - universes very similar will be close together, universes less similar will be further apart. Given the infinite number of degrees of difference you could have, this super-universe is infinite-dimensional. Now, pick a path through these universe-cross-sections. This gives us "our universe". There will be certain rules that restrict the possible directions of this path, and that gives us time. Far from perfect, but a start.
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
when you say "imagine all possible variations of the universe at a fixed time " I can't come up with more than one Sure you can. Look around you. Imagine slight changes that would still seem to be consistent with the laws of phsyics. From my desk, I can imagine my mouse slightly to the right, a bit more to the right, perhaps slighlty to the left. Perhaps the fan in my PC has a slighlty lower voltage, the drawer to my left is shut rather than open. These all give rise to similar universes centered around the one I am experiencing.
Is a universe one precise organization of all matter at one precise time? In my super-simplifed version, yes.
When you say in the last sentence "our universe" are you speaking about a universe that is the one that all of us experience? Could be, or perhaps individualistic... the model's not sufficiently well defined on that point! Take you pick...
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
I assume that each individual picks their own path No, I don't think so. What makes the individual is the path that is taken. That path would probably be determined by some minimisation of some "action"-like quantity... as in the principle of least action.
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
Why assume that what we know as the laws of physics should be relevant to a different universe? In this concept, there are no "different universes", just an infinitude of possible slices that could make up a universe. There will be some over-arching laws that govern this super-space, that give rise to our observed laws. But in terms of the quote, I was merely trying to get GDR to appreciate what I meant by possible universes. Edited by AdminJar, : close quotebox
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
For instance in the path integral approach This is actually more closely related to moduli-space work than to PI formalism. Check out some of Nick Manton's soliton dyanmics, for example.
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
So do you think that MR. Green is saying that time is basically a concept? I guess that must depend on what you mean by 'concept'. Off the top of my head, 'time' refers colloquially to at least three different concepts in General Relativity, and mixing these up is at the heart of most of confusion in this topic. Time is a dimension, it is a coordinate, it is a path through space-time, it is a rate (of affine parameterisation) along that path - ah, that's four...
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