time flows differently forward and backwards:

Originally posted by apathist
That seems to me to imply that, for example, your birth and your reading this post and your death all happened in a single instant.

No, I am saying I never was born. That I was born is merely a 'memory' of the past recorded in the current state of the universe. One could think of it as a 'prediction' of what the past was based on the current state and it is no more real than a prediction about the future. So my birth is no more real than the suns eventual demise. Both are clearly necessary outcomes from the present state of the universe but in different directions of time.

Under one interpretation of quantum mechanics there are many possible pasts. But they tend to converge. So although I may not know exactly where any given atom was in the past, on the larger scale I can be fairly sure about some things. Whereas the future diverges and only some things can be certain (such as the suns eventual death).

I understand the concept, twite. Essentially, the physics maths don't give an arrow to time.

Do you realize that your expression of that concept keeps contradicting itself? For example, you say you were never born, and then say that you were. For another example, you say the present never changes, and then you identify changes that occur as the present changes (the sun's eventual demise is not 'real' but is 'clearly necessary'😉.

The whole issue is resolved by realizing that time is not a substance or a force of any kind - it is merely an arbitrary measurement of change. Take a close look at any time-measurement device. Something must move; something must change. Time is not what makes those changes happen!

Originally posted by apathist
Do you realize that your expression of that concept keeps contradicting itself?

Not so much contradicting myself as simply not having the language to express it correctly as well as looking at it from different perspectives at different times.

The whole issue is resolved by realizing that time is not a substance or a force of any kind - it is merely an arbitrary measurement of change.
No, that doesn't resolve anything. I am not currently seeing nor proposing time as some sort of force.

Take a close look at [b]any time-measurement device. Something must move; something must change. Time is not what makes those changes happen![/b]
Time is a dimention. Those changes happen along the time axis.

I am proposing a radically different view of the universe. I am proposing that we look at only the present and not at a moving present as we traditionally do. I am saying that if we take a snapshot of the universe then look at it in detail, we can, using the laws of physics, determine the 'past' and 'future'. For any given particle, we know its possition and momentum (within limits) and can predict where it came from and where it is going. However, for some reason we can tell much more precisely where it came from than where it is going. I want to better understand why that is.
In my radical view, the past is determined by the present, not the other way around. The current state of the universe tells us what the past was like. When we cannot tell what the past was like, then we say 'all possible pasts existed'. Interestingly this is similar to one interpretation of quantum mechanics.
Imagine the two slit experiment with a twist. The screen has just absorbed one photon which we have recorded. It has also just emitted one photon. We can determine that the absorbed photon came through one of two slits. We may even know what light source the photo came from. So although there are several possible pasts for the photon, they converge over time (to the light source).
However, we know next to nothing about the emitted photons future. We have very little information about what direction it was emmited in and where it will end up. We know only that it is moving away from the screen.
Clearly there is a dramatic difference between the two time directions. I am sure it is intimately entwined with entropy and the 2nd law, but I want to understand it better.

Originally posted by twhitehead...
I am proposing a radically different view of the universe. ... For any given particle, we know its possition and momentum (within limits) and can predict where it came from and where it is going.

I'm not a determinist, so I don't accept that proposal. I guess you're aware of the Uncertainty Principle and that it is fundamentally impossible to know both the position and the momentum of a particle at the same time.

However, for some reason we can tell much more precisely where it came from than where it is going. I want to better understand why that is.

The past leaves traces, records, scars, trails, fossils etc for us to study. The future hasn't happened yet so has left nothing for us to study.

I partially agree with you: the closer to now we look (past or future) the clearer things seem; while the farther from now we look (past or future) the fuzzier things tend to get. I know that's not really what you're trying to get at, though.

Originally posted by apathist
I'm not a determinist, so I don't accept that proposal. I guess you're aware of the Uncertainty Principle and that it is fundamentally impossible to know both the position and the momentum of a particle at the same time.

I am not asking you to accept or reject it. I am suggesting it as a different way of looking at things. A different perspective.
Then we discuss the implications and whether or not the past or future can be determined.

If you are not a determinist, then in my model, you have to ask yourself whether the past is determined and if so, why? If we cannot know the exact position and momentum of a particle, then how do we know where it came from?


The past leaves traces, records, scars, trails, fossils etc for us to study. The future hasn't happened yet so has left nothing for us to study.
And I am not satisfied with that explanation. I say that the only reason you say the past has 'happened' is because it leaves traces and the only reason you say the future 'hasn't happened' is because it doesn't leave traces. So I say your explanation is circular.
I want to know why one leaves traces and one doesn't, it the laws of physics do not have a built in time direction.

I partially agree with you: the closer to now we look (past or future) the clearer things seem; while the farther from now we look (past or future) the fuzzier things tend to get. I know that's not really what you're trying to get at, though.
What I am trying to get at is that in the past, many things are crystal clear even in the very distant past, even though there is fuzziness in between. We don't know the momentum and position of a particle but we know where it was in the past. When a photon hits the screen in the two slit experiment using a star, the photon may have taken two different paths to get there, but we know which star it left millions of years ago.

Your proposal assumes that determinism is true. Also, it suggests that the present 'doesn't move', an idea I don't grasp (it sounds like it says the present never changes). Your proposal leads you to wonder why the past leaves traces on the present while the future doesn't, given that time has no direction in the laws of physics.

I hope that doesn't misrepresent you too much. Anyway, I think I've had a partial insight into what you are trying to express. The past leaves traces in the present, which could not have occurred any other way - and the future cannot occur any other way than it will occur, given the present. You're expecting a symmetry: if there are now traces of the past, there should also now be traces of the future.

Am I anywhere close?

Originally posted by apathist
Your proposal assumes that determinism is true.

No, I don't think so. Determinism is the claim that the exact past and exact future can be known from the present. I am not making that claim. I am claiming that at least something can be known about both based on the laws of physics. That is not determinism.

Also, it suggests that the present 'doesn't move', an idea I don't grasp (it sounds like it says the present never changes).
Its a difficult idea to get I know. After all, thinking takes time, so the concept of 'studying' the present to work out the past almost requires a moving present. Imagine you are a being independant of time and you are studying one single moment in time. Every human you study appears to think that it had a past and is yet to have a future, yet for you, this is an illusion.

The past leaves traces in the present, which could not have occurred any other way - and the future cannot occur any other way than it will occur, given the present.
I am not claiming the second bit, merely speculating on why the future isn't fixed, or doesn't seem fixed.

You're expecting a symmetry: if there are [b]now traces of the past, there should also now be traces of the future.[/b]
Exactly.

Suppose we have a deterministic computer program. You feed in some numbers, it processes for 2 hours, then spits out some numbers. Because we know how it works, we can take the output, work backwards, and determine what the input was. If you halt the program at 1 hour, and study its state, you can know what the inputs and outputs were, and to you, there is no real difference between the two.
So what would give this program a direction? I am guessing the answer is one way determinism ie if the outputs tell us what the inputs were but not the other way around. Some sort of reverse hash function? Randomness? Is whatever this is the equivalent of entropy?

I suggest you are seeing crystal spheres or castles in the clouds. Pattern recognition. A powerful and useful human trait if you learn to control it.

Time goes one way: from the start, onward. Maybe things are different in sub-atomic reality, but we don't live there.

Originally posted by apathist
I suggest you are seeing crystal spheres or castles in the clouds. Pattern recognition. A powerful and useful human trait if you learn to control it.

I can't really tell what I have said that could be labbeled 'pattern recognition'.

Time goes one way: from the start, onward. Maybe things are different in sub-atomic reality, but we don't live there.
So you just make an assertion without any reasoning to back it up and refuse to look at it in any other way because 'you don't live there'? This is the science forum, looking at sub-atomic reality is what we do here.

I've looked at it in ways you can't imagine yet. You made the proposal, the burden is on you. Show that time in our reality does not always move from the beginning.

Your whole pipe dream is based on the fact that t has no direction in many physics math formulas. That isn't a trivial dream. But confuse math with reality at your peril.

Originally posted by apathist
I've looked at it in ways you can't imagine yet. You made the proposal, the burden is on you. Show that time in our reality does not always move from the beginning.

Your whole pipe dream is based on the fact that t has no direction in many physics math formulas. That isn't a trivial dream. But confuse math with reality at your peril.

I think you have totally misunderstood me. I am merely suggesting a different way of looking at time, then asking what the implications are for reality, and if it doesn't match with reality, then I am asking why, in order to better understand reality.
And as for pipe dreams, your belief that the quantum world does not effect you directly is the real pipe dream. The very fact that light acts like a wave is a quantum effect. Without quantum effects you couldn't even look at yourself in a mirror. No, strike that, you couldn't even look.