Liquidrage

You would have to read the book to get a good description of the theory with Relativity. I can try but outside of posting the book itself as a reply I can only do so much.

You're right that Eintein's Relativity promoted time to a dimension. But then what is a dimension? It is surely an abstract and not something that exists on its own.
The promotion of time to a dimension was to show that there is no absolute time. Not that there sits the "thing" called time.

Having a minimum time and distance does not hurt Relativity at all. Relativity does not hold in the micro world where these units of space and *time* would occur.
Relativity cannot currently be reconciled with quantum mechanics. The Planck time and length (these are the real names, I wouldn't say it's for "lack of a better term") are at distances were relativity simply cannot be used.

To note, this theory of no-time does not need a Many Worlds interpretation in which all possible events occur. I prefer the idea that while "many worlds" might occur, they all agree.

Kharakov

Possibly,

You started out your post refering to physicists use of the concept of time. When a physicist uses the concept of time (spacetime), they use it to compare the rate of change between 2 objects- velocity, acceleration, etc. If there were not 2 objects to compare, there would be no need for spacetime.

Your additional idea about abandaning the "arrow of time" is valid. In quantum mechanics, scientists have found that time reversal occurs (apparently) randomly- the particles disobey the 2nd law of thermodynamics! However, because we are dealing with quantum mechanics, we can know the probability of time reversal happening, but we cannot say that certain conditions will definately produce it. Even with the definition that the arrow of time is the most probable direction that an action will take (entropy) you are not eliminating the basic need to make a comparison between 2 objects in respect to the rate of change.

In your response to scumble, you said that you were refering to the subjective qualia of time as opposed to a physicists objective interpretation of time.

One of the reasons that looking at a hot girl, or doing anything exciting, will make time seem to pass by faster is that you are paying less attention to other aspects of change, you are focusing upon the boobies rate of change. When sitting in a boring lecture, you pay attention to many different things, the droning of the teachers voice, the clock ticking on the wall, etc. The very comparison between being extremely focused on one thing (a hottie) instead of many things (at the boring lecture) should show you that even your subjective experience of time is related to you comparing different rates of change.

I don't have time to formulate the idea any better now, have to go meet my girlfriend .

-k

Soul Invictus

I've tried to involve myself to a study of time, but I lack the scientific background to give a qualified opinion regarding the law of physics. In my opinion, time is an abstract concept that is attempted to be quantified by a series of benchmarks like seconds, years, months.etc regarding changes from one one state to another. Obsolescence of materials and the fact that human age, or decay is a sign of our change from our earlier stages as we near closer to death. In your example of the tree, I think time would lapse, because (under my reasoning) the change in the tree would be evident in the fact that it's earlier state (erect) is significantly different from it's present state (prostrate) Tell me what you think about that idea...

illoe

Black Moses,

[note: I am a practicing physicist, and although I do not specialize in relativity or cosmology, I know their limits and can solve Schroedinger's equation from here to Sunday]

Your initial post is a little confused, so let me try to parse it. First, let's leave out the canards of subjective time; trees falling in the forest and your flip "sitting on a cute girl" vs "boring lecture" comparisons. These situations are too complex to be fruitful in a serious discussion on the fundamentals of what time *is*. If you wanted to discuss the subjective experience of duration, you should have said so clearly.

According to your initial post, Barbour asserts the following things:

1. "if nothing changed then time would stop"
2. (therefore) time = change
3. (therefore ??) "time does not exist"

Let's look at (1) and try to determine whether it is true.

Imagine a very simple universe that contains only a single neutron, which pops into existence at t=0 (or t=-348 if you prefer, but I'm not going to carry out the conversions for you.) Since there is nothing else, the proton cannot be thought to have any motion and "proper time" is measured in the neutron's frame of reference.

Now, in this free state, the neutron can undergo beta decay:
neutron -> proton + electron + anitneutrino
The half-life of that decay process is around 12 minutes. It is safe to say that in our simple universe the neutron will decay, eventually. And if we took a statistically significant sample of identical universes, about half the neutrons would decay within 12 minutes. This is so even if no one was there to see them and measure the time. This is so even if God gets a cup of tea and stops watching them for a few minutes. This is so even if you and I had never existed. After the decay, the three particles would have relative motion and time would have meaning as a measure of that.

You may argue that a proton is not a fundamental particle, so it is by no means the simplest possible universe. That's correct. Let's take, instead, an electron. Electrons do not decay, and in a universe that contained only an electron, I would say that Barbour's initial assertion is correct. "If nothing changed then time would stop." Time would indeed be meaningless in such a universe. However, a lone electron violates certain symmetry principles, this hypothetical universe has an imbalance of charge, spin, and lepton number. I'm not certain whether such an imbalance makes it an impossible universe. If you add any other particle to correct the imbalance, then you've got relative motion and there is no problem with measuring time.

(We could consider a photon universe and all sorts of other nice things would come up but I don't want you all to stop reading.)

We have with our neutron and electron examples established:
a) It is the case that no observer must be present for time to have meaning,
b) perhaps it is the case that without change, time would stop.
b) any universe in which no change is possible is a boring (and possibly an impossible) universe.

Now, with that in mind, and aknowledging our universe is more complex than even the natty neutron universe, let's examine Barbour's other assertions:

2. time = change
3. "time does not exist"

Substitution (from (2)) of "change" for "time" in (3) gives the assertion "change does not exist," which is clearly false even in the neutron universe. So (3) is false, therefore time exists.

SO what is the point of this thread? You seem to just want to argue. But you don't seem very clear as to what you are arguing or why. Go back and read IntenSity's responses to you. His points are clear and well-made. Your responses to him only obfuscate the issues.

tronvillain

If time was analagous to a spatial dimension, then "nothing changes" would not necessarily imply "time stops." There could be no change over huge amounts of time, but time could still be said to have passed. Say you have a stack of photographs, the first ten of which show continous change, followed by a hundred identical pictures - while change has ceased, there is still a distance between the first identical picture and the last identical picture.

illoe

Tron,

That is just what I meant with the proton example. The proton is like your stack of identical photographs; it might look absolutely static until the moment it decays. Your example is probably more illuminating.

Liquidrage

I think the last batch of rebuttles have unfortunately trivialized Barbour's theories by pointing to flaws in this presentation.
Though I understand this may be the only exposure to these theories for many of you the actual theories do not fall to these recent examples.

Let me put forth this.
What separates the past from present?
Barbour puts forth that the present accounts for the past. One could look at this as very similar if not identical to using entropy as definition to the flow of time. Which might not be a common view but is certainly not rare.

Barbour does not claim that all your pictures are not different. In fact he uses similar analogies to point out that each of these are different.
Where he feels he removes time is that what puts these pictures in order (or "time") is simply that one picute accounts for the past.

I would also add that as a layman my opinion matter little. However, it appears to me that his research has been met with mostly positive reviews. And again, this book is not an easy read. It makes something like The Elegant Universe or Three Roads to Quantum Gravity look like Green Eggs and Ham.

[ July 27, 2002: Message edited by: Liquidrage ]</p>

tronvillain

Well, my post was not intended to rebut Barbour's theories, so I don't see that as a problem.

Still, I fail to see what the problem with the question "What seperates the past from the present?" is supposed to be (other than its assumption that there is a unique present). If you are simply asking "What seperates 10:00 PM from 10:25 PM?" the obvious answer would seem to be "twenty-five minutes" or "time", just as the answer to "What seperates my parents house from town" would seem to be "twenty-five kilometres" or "distance."

Answerer

Well, theorically, we can think of human's awareness of time as solely caused by the presence of our memories. Apparently, if humans don't have memory function in our brains, there will be no way that we can experience or appreciate the awareness of time. Things and concept like rates of change or historical events will meaningless as we will be almost behaving like ants which only see and focus on the present rather than the past or future.
Neverthless, our awareness of time doesn't show time truly exists as a dimension, it could be said to be something no more than an indirect product of our own memories and awareness.

tronvillain

Still, having a look at his <a href="http://www.platonia.com/" target="_blank">website</a> I am not sure that his view is that different from mine. I do not think that time is something that "passes" or that there is any unique present either.

[ July 27, 2002: Message edited by: tronvillain ]</p>