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Would you get the exact same universe from a common starting point?


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If we could say turn back time for the entire universe, by which I mean every single atom, every single photon, every energy state, every particle position and it's vector etc etc etc became what it was at any chosen point in the past, and then let it then run forward in time as per normal, would then everything be as it is now, or would things diverge to a slightly different future state/position etc ?

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In a chaotic system there is no place for random events. Only in a non-deterministic system do we have true randomness. The big problem is that we cannot distinguish between randomness from chaos if t

If we could say turn back time for the entire universe, by which I mean every single atom, every single photon, every energy state, every particle position and it's vector etc etc etc became what it w

No Stephen, the fact that we cannot rewind time makes it moot... Doesn't mean we can't ponder though

Short answer: We do not know.

Longer answer: If the apparent non-deterministic behaviour at the quantum level is really a matter of a deterministic system with hidden variables (like Bohm's theory), then the universe could best be seen as a chaotic, but deterministic system. In chaotic systems, an infinitessimally small change in initial conditions can lead to profound changes in the outcome. However, identical conditions lead to identical outcomes, so starting at the same initial conditions would lead to the same outcome. By contrast, if the universe really is non-deterministic (as many theoreticians suggest), then the outcome would not be the same.

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The Heisenberg Uncertainty principle would indicate that you can never know that level of detail:

If we could say turn back time for the entire universe, by which I mean every single atom, every single photon, every energy state, every particle position and it's vector etc etc etc became what it was at any chosen point in the past, and then let it then run forward in time as per normal, would then everything be as it is now, or would things diverge to a slightly different future state/position etc ?

Given that, the question becomes moot?

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So, in a non-chaotic universe, the entire future of universe would basically be set in stone as it were from the it's starting point? .. start from exactly the same state, you get exactly the same future.

But yes, I did expect we don't yet know (probably never will), but it's good to see various answers to some of the bigger questions.

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The Heisenberg Uncertainty principle would indicate that you can never know that level of detail:

Given that, the question becomes moot?

No Stephen, the fact that we cannot rewind time makes it moot... Doesn't mean we can't ponder though :)

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So, in a non-chaotic universe, the entire future of universe would basically be set in stone as it were from the it's starting point? .. start from exactly the same state, you get exactly the same future.

I would say no to that. You would have to remove random chance from the equation for that to happen. Even with the exact same starting position changes to the outcome would be affected by random events.

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The Heisenberg Uncertainty principle would indicate that you can never know that level of detail:

Given that, the question becomes moot?

I myself would say all questions are valid, no matter what the answer maybe ;)

Could the uncertainty be the effect of what we have yet to comprehend? .. and so causing what we see/class as uncertainty simply be the result of what lies 'beneath' as it were?

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I would say no to that. You would have to remove random chance from the equation for that to happen. Even with the exact same starting position changes to the outcome would be affected by random events.

Random events as in?

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So, in a non-chaotic universe, the entire future of universe would basically be set in stone as it were from the it's starting point? .. start from exactly the same state, you get exactly the same future.

But yes, I did expect we don't yet know (probably never will), but it's good to see various answers to some of the bigger questions.

No, not really. In the physical meaning of the word, chaos is deterministic (very confusing to most). So in a chaotic universe paths of particles are set in stone, if the initial conditions (including variables we fundamentally cannot measure) are identical. Only if the universe is really non-deterministic (as suggested by quantummechanics), are paths fundamentally unpredictable.

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So, in a non-chaotic universe, the entire future of universe would basically be set in stone as it were from the it's starting point? .. start from exactly the same state, you get exactly the same future.

But yes, I did expect we don't yet know (probably never will), but it's good to see various answers to some of the bigger questions.

I get that the "non-chaotic" model would produce the same results right up until "free" thinking entities are established. otherwise, I have no valid reason to try to preserve our resourses or for that matter care about anything other than my own existance (and perhaps not even that) as the outcome is already determined. I'm not prepared to believe that I'm not making choices but merely playing ot my role in a universal play.

Just my musings of coarse :D

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Random events as in?

The movement of particles (for example) is, according to quantum mechanics, completely at random once you get down to the atomic level.

Schrodinger's Cat is a thought experiment that demonstrates this. Even though the initial starting conditions are known, due to the randomness in atomic decay you cannot know if the cat is dead or alive at any point until you check.

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I would say no to that. You would have to remove random chance from the equation for that to happen. Even with the exact same starting position changes to the outcome would be affected by random events.

In a chaotic system there is no place for random events. Only in a non-deterministic system do we have true randomness. The big problem is that we cannot distinguish between randomness from chaos if there are limits to what we can observe. After all, David Bohm succeeded in drawing up a deterministic Shrödinger equation that makes identical predictions to the non-deterministic original.

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I get that the "non-chaotic" model would produce the same results right up until "free" thinking entities are established. otherwise, I have no valid reason to try to preserve our resourses or for that matter care about anything other than my own existance (and perhaps not even that) as the outcome is already determined. I'm not prepared to believe that I'm not making choices but merely playing ot my role in a universal play.

Just my musings of coarse :D

The universe of course does not care about what us mortals think. You cannot scientifically discount a theory just because you do not like it. This does not stop many scientists from trying, of course. Some people attribute much of the progress of astronomy to people disliking Fred Hoyle's theories enough for them to build new instruments to prove him wrong :D

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Could the apparent random path not be infact random, but instead be due to as yet to be discovered factors of the universe?

Not if they are random :-)

In a chaotic system there is no place for random events. Only in a non-deterministic system do we have true randomness. The big problem is that we cannot distinguish between randomness from chaos if there are limits to what we can observe. After all, David Bohm succeeded in drawing up a deterministic Shrödinger equation that makes identical predictions to the non-deterministic original.

Now I feel like Blackadder. I should put my underpants on my head, pencils up my nose and utter "Wibble, wibble"

:grin: :grin:

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Could the apparent random path not be infact random, but instead be due to as yet to be discovered factors of the universe?

Yes, that is what David Bohm postulates. Some people consider string theory and brane theory to be attempts to model hidden variables. Some criticise these fields for that reason, because they are very hard to verify or falsify.

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I'm not prepared to believe that I'm not making choices but merely playing ot my role in a universal play.

So are you saying our own insecurities should be taken into account ;) ?

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The universe of course does not care about what us mortals think. You cannot scientifically discount a theory just because you do not like it. This does not stop many scientists from trying, of course. Some people attribute much of the progress of astronomy to people disliking Fred Hoyle's theories enough for them to build new instruments to prove him wrong :D

I get that the universe does not care. and that the past cannot be changed, but surely the future is not written in stone. If I send this post or not will change what happens in the future. will you stay in long enough to read it if I post it or if I don't will you leave your house early enough to be hit by the 2pm bus and not make that discovery that changes life as we know it. I can't believe that I have no choice and that my sending this is already decided. I wish I could explain myself better :)

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Just some food for thought on randomness vs hidden variables:  Suppose I have a series of observations of some random process (Brownian motion of some particle). I can always construct a deterministic model that explains that particular path, provided I can stick in sufficient parts. An even more complex model could in principle be built to explain any series of observations. However, we might be able to explain the same observations by a much simpler random (non-deterministic) mechanism (which is where statistical physics and quantummechanics come in). Occam's Razor suggests the simpler is preferable (although it might be wrong, of course). What is striking is that Bohm's theory is not really very complicated (compared to regular quantummechanics, that is), and yet it makes the same predictios as a random model.

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I get that the universe does not care. and that the past cannot be changed, but surely the future is not written in stone

I guess it depends whether our thoughts are purely due to all the atomic states (quantum effects, particle position/vector et all) being in a certain state at any one point in time?

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So are you saying our own insecurities should be taken into account ;) ?

 No, I did not say that. Are you saying you did not ask a question in your origional post but were merely doing what you were predestined to do?

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 Are you saying you did not ask a question in your origional post but were merely doing what you were predestined to do?

I don't know ;)

I guess that's what I'm asking, was my asking the question in the first place a predestined event?

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I get that the universe does not care. and that the past cannot be changed, but surely the future is not written in stone. If I send this post or not will change what happens in the future. will you stay in long enough to read it if I post it or if I don't will you leave your house early enough to be hit by the 2pm bus and not make that discovery that changes life as we know it. I can't believe that I have no choice and that my sending this is already decided. I wish I could explain myself better :)

I have just started reading up on Everrettian physics and he would postulate that the second you decide to post your reply a copy of yourself is made in another universe that chose not to hit the reply button.

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