1. I was thinking, if you drop a brick, it will break in a certain way. This piece will fly this way, that piece will go that way.

But, if you somehow get a brick that is exactly the same as the first, and you drop it the exact same way, with the exact same conditions, it should break in exactly the same way, right?

So what if the big bang theory is true, and the universe comes all back together, and the big bang happens again, and it happens in the exact same way, should the universe be exactly the same? all the way down to what the next word you say will be?

each spec of dust will land in the exact same place, the temperature will be the exact same on one date as it was in the last universe? every single conversation will be exactly the same?

what does anyone think of this?

maybe we don't have choice of what we do, maybe it was all determined at the big bang.

2.

3. Originally Posted by Weterman
But, if you somehow get a brick that is exactly the same as the first, and you drop it the exact same way, with the exact same conditions, it should break in exactly the same way, right?
No.
For given values of "exact".

So what if the big bang theory is true, and the universe comes all back together
That's TWO "ifs".

and the big bang happens again, and it happens in the exact same way, should the universe be exactly the same? all the way down to what the next word you say will be?
No. See the link given above.

4. Originally Posted by Dywyddyr
For given values of "exact".
Not quite. Here's the original context for Lorenz's discovery from James Gleik's book 'Chaos'.

Suddenly he realized the truth. There had been no malfunction. The problems lay in the numbers he had typed. In the computer's memory, six decimal places were stored: .506127. On the print out, to save space, just three appeared: .506. Lorenz had entered the shorter, rounded-off numbers, assuming that the difference - one part in a thousand - was inconsequential.
If Lorenz ran either calculation, six decimal places or three, thousands of times he would have received the exact same answers for 3 decimal places and for 6 decimal places each time. If computers did not do this for the "given values of 'exact'" they would be of no use to science.

5. Originally Posted by Laurieag
Originally Posted by Dywyddyr
For given values of "exact".
Not quite. Here's the original context for Lorenz's discovery from James Gleik's book 'Chaos'.

Suddenly he realized the truth. There had been no malfunction. The problems lay in the numbers he had typed. In the computer's memory, six decimal places were stored: .506127. On the print out, to save space, just three appeared: .506. Lorenz had entered the shorter, rounded-off numbers, assuming that the difference - one part in a thousand - was inconsequential.
If Lorenz ran either calculation, six decimal places or three, thousands of times he would have received the exact same answers for 3 decimal places and for 6 decimal places each time. If computers did not do this for the "given values of 'exact'" they would be of no use to science.
Which was my point: how "exact" will the second brick be as a replica? How "exact" will the conditions be?
A computer simulation is one thing - limited number of variables for example, and direct reproducibility of those variables.
The real world tends not to function like that.

6. I think he's asking a hypothetical question about determinism, and the fact that you cant technically make two bricks that are perfectly identical in the real world is inconsequential for the conclusion you can draw from a thought experiment involving them.

The point is, the same set of initial conditions will lead to the same outcome. The universe in state x at time t will invariably evolve to state delta x after time delta t.

7. Originally Posted by Weterman
I was thinking, if you drop a brick, it will break in a certain way. This piece will fly this way, that piece will go that way.

But, if you somehow get a brick that is exactly the same as the first, and you drop it the exact same way, with the exact same conditions, it should break in exactly the same way, right?

So what if the big bang theory is true, and the universe comes all back together, and the big bang happens again, and it happens in the exact same way, should the universe be exactly the same? all the way down to what the next word you say will be?

each spec of dust will land in the exact same place, the temperature will be the exact same on one date as it was in the last universe? every single conversation will be exactly the same?

what does anyone think of this?

maybe we don't have choice of what we do, maybe it was all determined at the big bang.
I believe what you are asking here is if nature is fundamentally deterministic or stochastic. Well, we don't really know. There are two fundamental models we use to describe nature. One is General Relativity, which is a purely deterministic model. There is not any part of General Relativity that deals in probabilities. The other fundamental model of nature is Quantum Mechanics. Quantum Mechanics is heavily dependent on probabilities. And these probabilities don't arise from potential measurement error, but are fundamental to the model. SEE; Quantum indeterminacy - Wikipedia, the free encyclopedia

So let's say that we can drop a brick, then rewind the universe to a point where we drop the brick again under precisely identical conditions. Would the exact same result occur in both trials? According to GR the brick will always fall the same way. According to QM the precise arrangement of the bricks atomic particles might be different.
Beyond these, I'm personally uncertain as to the exact implications.

8. Radioactive decay is one of those quantum processes. It can have macroscopic effects, like when a cell undergoes a mutation and the organism dies, or a new species is evolved. Then things take a different course.

9. Originally Posted by Dywyddyr
A computer simulation is one thing - limited number of variables for example, and direct reproducibility of those variables.
The real world tends not to function like that.
We can probably take the recent CERN/OPERA neutrino speed issue as a case in point. The calibration process of the entire experiment was retested with a smaller packet size after publication and was found to have the same error rates as the original calibration. So does this mean that the results were true (they were published before the issue was resolved) or that the problem was wrapped up in the calibration process/equipment itself or were the theoretical aspects of the experiment wanting?

The deterministic, repeatable experiment is at the core of modern science and physics. By limiting understanding of the use of computers in science to simulations you can grossly underestimate their involvement in the experimental domain and, particularly in probabilistic situations, can totally miss real problems and their resolutions.

The following paper "Cosmology and Inductive Inference: A Bayesian Failure" by John Norton covers the issue http://philsci-archive.pitt.edu/4866..._inductive.pdf

10. Originally Posted by Waveman28
I think he's asking a hypothetical question about determinism, and the fact that you cant technically make two bricks that are perfectly identical in the real world is inconsequential for the conclusion you can draw from a thought experiment involving them.

The point is, the same set of initial conditions will lead to the same outcome. The universe in state x at time t will invariably evolve to state delta x after time delta t.
The QM effect though a tiny variable for macro scale objects would accumulate very quickly resulting in a wide range of end conditions. It would probably be un-meauresureable for a brick, but over astronomical scales very noticeable.

11. Originally Posted by GiantEvil
Originally Posted by Weterman
I was thinking, if you drop a brick, it will break in a certain way. This piece will fly this way, that piece will go that way.

But, if you somehow get a brick that is exactly the same as the first, and you drop it the exact same way, with the exact same conditions, it should break in exactly the same way, right?

So what if the big bang theory is true, and the universe comes all back together, and the big bang happens again, and it happens in the exact same way, should the universe be exactly the same? all the way down to what the next word you say will be?

each spec of dust will land in the exact same place, the temperature will be the exact same on one date as it was in the last universe? every single conversation will be exactly the same?

what does anyone think of this?

maybe we don't have choice of what we do, maybe it was all determined at the big bang.
I believe what you are asking here is if nature is fundamentally deterministic or stochastic. Well, we don't really know. There are two fundamental models we use to describe nature. One is General Relativity, which is a purely deterministic model. There is not any part of General Relativity that deals in probabilities. The other fundamental model of nature is Quantum Mechanics. Quantum Mechanics is heavily dependent on probabilities. And these probabilities don't arise from potential measurement error, but are fundamental to the model. SEE; Quantum indeterminacy - Wikipedia, the free encyclopedia

So let's say that we can drop a brick, then rewind the universe to a point where we drop the brick again under precisely identical conditions. Would the exact same result occur in both trials? According to GR the brick will always fall the same way. According to QM the precise arrangement of the bricks atomic particles might be different.
Beyond these, I'm personally uncertain as to the exact implications.
Yes indeed.

I recall a debate on another thread some time ago, in which I was made aware there are scientists who hold that the apparent indeterminacy embedded in QM is due to "hidden variables" that one day, they hope, will enable us to reinstate a purely deterministic model of physics. While this may be true, I suppose, it struck me as an example of faith-based science, in that the conviction that there must be hidden variables BECAUSE of the apparent indeterminacy of QM is not something one can deduce logically. Personally, as a chemist, I've grown up with quantum indeterminacy and have become comfortable with the idea that it may be fundamental. I think the poster I was debating with was terrified that someone might use QM indeterminacy as some sort of spurious argument for the existence of God. It seemed to be an article of faith for his strand of atheism that the world MUST be fully deterministic.

12. Originally Posted by Weterman
I was thinking, if you drop a brick, it will break in a certain way. This piece will fly this way, that piece will go that way. But, if you somehow get a brick that is exactly the same as the first, and you drop it the exact same way, with the exact same conditions, it should break in exactly the same way, right?So what if the big bang theory is true, and the universe comes all back together, and the big bang happens again, and it happens in the exact same way, should the universe be exactly the same? all the way down to what the next word you say will be? each spec of dust will land in the exact same place, the temperature will be the exact same on one date as it was in the last universe? every single conversation will be exactly the same? what does anyone think of this?maybe we don't have choice of what we do, maybe it was all determined at the big bang.
I can see where you are going with this. Chemically, two atoms will always bond in the same when under normal conditions. So, why can't a brick break into pieces the same way twice? I'm a little confused about the whole Big Bang theory thing and how we're just a duplication of some other time.

13. Originally Posted by exchemist
I recall a debate on another thread some time ago, in which I was made aware there are scientists who hold that the apparent indeterminacy embedded in QM is due to "hidden variables" that one day, they hope, will enable us to reinstate a purely deterministic model of physics. While this may be true, I suppose, it struck me as an example of faith-based science, in that the conviction that there must be hidden variables BECAUSE of the apparent indeterminacy of QM is not something one can deduce logically. Personally, as a chemist, I've grown up with quantum indeterminacy and have become comfortable with the idea that it may be fundamental. I think the poster I was debating with was terrified that someone might use QM indeterminacy as some sort of spurious argument for the existence of God. It seemed to be an article of faith for his strand of atheism that the world MUST be fully deterministic.
It is my guess that because of the large number of stochastic inputs on the quantum level and by the law of large numbers that our universe appears ordered and predictable. Otherwise that the universe tends to operate on a bell curve. If the universe were wholly deterministic then chaos theory would rule and without complex mathematical modeling it wouldn't appear that anything necessarily follows anything else. And with a theory of "hidden variables", where do the hidden variables come by their values?

14. Originally Posted by Weterman
... if you somehow get a brick that is exactly the same as the first, and you drop it the exact same way, with the exact same conditions, it should break in exactly the same way, right?
That is an unsupported assumption. Indeed we have contrary data.

A radioactive atom decays in a way that is, as far as we can tell, unpredictable on an individual basis. We can only say that an atom will decay in the next second with a probability thus-and-so. Otherwise identical atoms do not decay at the same instant. So, if we were to rewind the movie of history, you'd get a new movie upon playback.

Nature seems to run on probabilistic rules. Thus far, all attempts to show the existence of "hidden variables" have failed. So, our best theory so far is that nature is not deterministic.

15. As to my understanding in the event that every factor of the second brick's drop is the exact same as the first, the results should be the exact same. However, this is implying that everything is the same to the first, hence all matter (to a molecular level, possibly to the level of electron orbit around every atom's nucleus, or the isotopes and the ionization of individual atoms) being exactly identical to the first instance. I myself also formed a theory similar to yours of the big bang recurring. Most likely, such an event would be caused by all of the matter, as well as all antimatter, in the universe to form into a singularity. The resulting collisions would create energy, and the big bang recurs. If all of the matter and antimatter in the universe is used in this process, and the matter-to-energy-to-matter transfer has a 100% efficiency rate, the resulting universe should be identical to our own.

16. There is still a great degree of conjecture whether QM is deterministic or not dependent on your choice of interpretation (refer to 'Comparison of Interpretations). What is central to this argument is your verdict on whether wave-function collapse or the wave function itself is 'real' or 'not' and the resultant role if any that the observer plays in this relationship. With a greater appreciation of aspects of entanglment and correlated ensembles which appears to be ubiquitous as opposed to special cases in QM and a resulting increasing willingness to disgard notions of conterfactual definiteness and/or locality there appears to be a growing trend in the debate towards a deterministic viewpoint which supports classical physics. :-))

17. See the reply above yours.

And:
Originally Posted by Jigowatt
If all of the matter and antimatter in the universe is used in this process, and the matter-to-energy-to-matter transfer has a 100% efficiency rate, the resulting universe should be identical to our own.
What?

18. I've read and re-read post #14 trying to see what the poster was on about but I'm afraid it is pure gibberish.

19. Originally Posted by Weterman
if the big bang theory is true, and the universe comes all back together, and the big bang happens again, and it happens in the exact same way, should the universe be exactly the same?
If memory serves, the singularity is thought to have a spin to it, that was determined to be (I forget) left or right. This is supposed to explain some arbitrary properties of QM or cosmology(?). And apparently life would be quite different or impossible if not for that.

So when the hypothetical big crunch occurs, and forms the next singularity, which way will it be spinning?

Damn I wish I could remember which way to push when the time comes.

20. The antimatter collides with matter, creating energy. Let's say that this energy transfers back to matter, as in the big bang. Assuming that no energy is lost, the output of matter and antimatter should be in the same quantity as what came in?

21. Originally Posted by Jigowatt
The antimatter collides with matter, creating energy. Let's say that this energy transfers back to matter, as in the big bang. Assuming that no energy is lost, the output of matter and antimatter should be in the same quantity as what came in?
Even ignoring the fact that it can't be 100% efficient there's still the question: so what?

22. Originally Posted by Jigowatt
The antimatter collides with matter, creating energy. Let's say that this energy transfers back to matter, as in the big bang. Assuming that no energy is lost, the output of matter and antimatter should be in the same quantity as what came in?
The same quantity, but not necessarily the same form.

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