A question for people smarter than myself 8)

  • Context: Graduate 
  • Thread starter Thread starter PeterReynolds
  • Start date Start date
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
Sign up Log in
15 replies · 3K views
PeterReynolds
Messages
6
Reaction score
0
My question is if information cannot be destroyed and if the universe will eventually implode and then explode again, has anyone considered the possiblity that the universe will do it all over exactly like it did before?
 

Discussion

Astronomy news on Phys.org
People have often considered the idea that the universe will eventually implode and then reexplode in a neverending cycle. The idea is appealing, however that is not what current observations indicate. We measure a cosmological constant or 'dark energy', which is the source of a repulsion that is causing the expansion to accelerate, meaning that the universe will never collapse.
 
PeterReynolds said:
My question is if information cannot be destroyed and if the universe will eventually implode and then explode again, has anyone considered the possiblity that the universe will do it all over exactly like it did before?

As the above notes, we do not live in a universe which will eventually recollapse. Assuming we did, however, I still do not see how you arrive at your conclusion. Yes, people have considered cyclic universes whereby the collapse of one universe produces another, but there is no way to make them "exactly the same". Even if you were able to ensure that the "initial conditions" (whatever that means, in regards to the birth of a universe...) were identical, we do not live in a deterministic universe. Quantum mechanics guarantees that things are inherently probabilistic, so they would turn out differently.
 
Yeah, But if it were to implode and explode and information is not destroyed. Would the same formula that created the universe lead to the same earth, you, and every single photon of light? Like watching a movie twice.
 
Nabeshin said:
Quantum mechanics guarantees that things are inherently probabilistic, so they would turn out differently.

Ok I think you answered my question. I was under the understanding that probability is simply A concept that comes from what cannot be fully formulated.

It will either rain tomorrow or it will not. Probability exists within the context of not having all the information necesary to state it will or will not rain. But it is true that even with all of the information it still comes down to probability?
 
If the universe collapse and recollapse as you thought,it will contradict the time evolution theory of the probability of an event reoccuring twice.
 
It's Heisenberg's uncertainty principle that describes the indeterministic nature of quantum mechanics. Uncertainty is not an inerrant feature of probability in of itself.
 
At the ripe old age of 30(ish) I've been pondering my own mortality and guess that's what lead me to the idea. 8) I couldn't even begin to answer the question on my own so thank you for the responses.
 
Smiles302 said:
It's Heisenberg's uncertainty principle that describes the indeterministic nature of quantum mechanics. Uncertainty is not an inerrant feature of probability in of itself.

So would it be true to say that if the universe was to implode down to the singularty and then explode with the exact same formula as before. It would recreate all of the laws that exist now, and in turn all of the same actions and reactions. leading to the exact same universe. Right down to every single person, planet, and photon of light? My notion is that it would have to if it's the same formula.
 
PeterReynolds said:
So would it be true to say that if the universe was to implode down to the singularty and then explode with the exact same formula as before. It would recreate all of the laws that exist now, and in turn all of the same actions and reactions. leading to the exact same universe. Right down to every single person, planet, and photon of light? My notion is that it would have to if it's the same formula.

No, because the Universe is indeterminate. Even if you started the Universe with exactly the same conditions, you would expect a different outcome.

Classical physics fits your thinking. Modern physics doesn't.
 
I am not smarter than you, so I will not answer this question :cool: .
 
think of it like this...
you drop a ball from a fixed position onto the peak of a two sided ramp (^) you drop the same ball from the same spot over and over and count how many times it goes one direction and how many times it goes the other direction. you can then assign a probability of how often it will fall to one side or the other. now, no matter how much data you collect, and no matter how accurately you can predict the outcome based on probability, there is no way to say with certainty which way the ball will roll.
same thing here, only much much bigger. while some things may have the same outcome, that does not mean you will have the same universe. say the re-made universe had the exact same laws of physics and the same gasses present at it's creation, they wouldn't produce the exact same planets as we have today. the interactions would change the outcome. while it may be similar, it will not be identical.
the fact that information cannot be destroyed also does not dictate that the same information will be dispersed in the same way. the new universe will may have the same number of water molecules as our present one does, but there may not be one drop of liquid water in existence. all the ingredients for life may be present, but again, no guarantee that life will start to exist, or if simple life did start, it would not evolve in the same way, so again, you and i would not exist.
given the fact that the universe is continually expanding faster and faster, this is of course a moot point, but a very fun philosophical question none the less.
thanks for posting, this one was fun to ponder :)
 
btw...
the fact that i replied in no way indicated my level of intelligence in comparison to yours :P
it was a neat question that got me thinking so i waded in. most or all of what i said could be in fact quite off base, but they were generalizations of scenarios to help make the point. don't sell yourself short, most people don't even think deeply enough to ask the questions you are now considering. :)
keep thinking and digging, without questions like that, we would never progress at all
 
PeterReynolds said:
It will either rain tomorrow or it will not. Probability exists within the context of not having all the information necesary to state it will or will not rain. But it is true that even with all of the information it still comes down to probability?

This is a common question people have when they encounter the probabilistic interpretation of quantum mechanics for the first time. The belief that quantum mechanics is incomplete, and there are additional variables in the universe not described by QM, which if known about would allow the theory to become deterministic, is known as "Hidden variable theory." Now, don't feel bad if this makes a lot of sense to you, Einstein himself was one of the biggest proponents of these theories.

The general idea is exactly like you say, there is extra information not described by QM. Presumably, when this information is taken into account by a more complete theory, the probabilities of QM vanish and we get a deterministic theory. The problem is, John Bell showed in the 1960's that assuming particles do not communicate faster than the speed of light, these theories give different observational predictions than those of probabilistic QM (and those of probabilistic QM are the ones we observe!). So a large class of these theories, so-called 'local hidden variable theories' (since particles only communicate at light-speed or below) have been ruled out by experiment. The remaining class, as you can guess 'non-local hidden variable theories' have the peculiar quality that particles communicate faster than the speed of light. The most famous of these theories is the Bohm interpretation of quantum mechanics. You can read more about this here if you're interested: http://en.wikipedia.org/wiki/Hidden_variable_theory

But the moral of the story is, you cannot naively have the situation as you describe. If you want to add extra variables, they have to be sort of weird =)
 
Nabeshin said:
If you want to add extra variables, they have to be sort of weird =)

that might just be my favorite statement i have read today, nice way to put it :)