Timeline of the far future • Hacker News Board

Re: Timeline of the far future

#61

Post by Symmetry » Mon, May 07, 2012, 3:23 PM UTC

majmun wrote: post #33

aneth wrote: post #21

Earlier quoted context omitted.

What's more likely: nearly infinite sentient universes complete with false memories of human experiences emerging from entropic chaos, or that we don't quite understand the nature of entropy? The Boltzmann theory is one of those thought experiments that should draw into question it's assumptions out of the pure absurdity of its logical conclusions rather than be taken seriously itself.

Error in Boltzman brains theory is that he assumes that universe with brains randomly fluctuated into existance into its current form , and concludes that this form is more complex than just brain and therefore brains without environments are more common (maybe iPhones or Bible are even more common then), and assumes that brain can exist without environment. also second law of thermodynamics states that resulting ent…

iPhones or Bibles probably are more common. And an isolated brain without an environment really is much more likely than a brain and body and environment, at least if we're talking about random fluctuations rather than structures created as a consequence of the the availability of useful energy in the environment.

If you think about it in terms of the Canonical Ensemble the regions of states that correspond to "a brain and body" are obviously a small subset of the regions that correspond to "a brain". The incompressability of phase space means that this translates directly to the world being less likely to wander into those smaller regions via random fluctuations in direct proportion to their size.

In the end, the second law of thermodynamics is only a (very strong) statistical likelihood. If you mix some salt water and fresh water, then wait long enough you'll eventually find all the salt in one side of the glass (in time proportional to 2^N where N is the number of salt ions). Its not something written into the fabric of the universe directly, but a consequence of more fundamental laws and if you take Statistical Mechanics in college you'll get to re-derive it and see why it works that way. In fact, I'd really recommend taking a Stat Mech class to anyone considering it, it was probably the most interesting class I took in college.

Re: Timeline of the far future

#62

Post by possibilistic » Mon, May 07, 2012, 3:29 PM UTC

eliben wrote: post #22

aneth wrote: post #21

Earlier quoted context omitted.

What's more likely: nearly infinite sentient universes complete with false memories of human experiences emerging from entropic chaos, or that we don't quite understand the nature of entropy? The Boltzmann theory is one of those thought experiments that should draw into question it's assumptions out of the pure absurdity of its logical conclusions rather than be taken seriously itself.

Isn't this just a simple matter of probability? Given an event, however unprobable it is, it can happen given infinite time? From a purely mathematical standpoint, this is correct.

Just because something has a nonzero probability doesn't mean it will ever occur.

Entropy is just dS = dQ/T. It's simply a thermodynamic property that measures where system energy is. All of these grand notions extrapolated from thermodynamics are crazy.

Thermodynamics is/was just a first approach at studying macroscale systems because we didn't yet grasp the underlying quantum behavior. It's incredibly useful when applied to chemical and physical problems, but you can't use it to make wild claims like this.

Re: Timeline of the far future

#63

Post by jberryman » Mon, May 07, 2012, 3:32 PM UTC

diminish wrote: post #28

"At 15:30:08 UTC on Sun, 04 December 292,277,026,596 AD, the Unix time stamp will exceed the largest value that can be held in a signed 64-bit integer.[84]"

We better start preparing for Y2KKK92.

Re: Timeline of the far future

#64

Post by aneth » Mon, May 07, 2012, 3:41 PM UTC

othermaciej wrote: post #42

aneth wrote: post #23

Earlier quoted context omitted.

If your assumption is infinite time and complete entropy, yes it's correct. It's also why some level of common sense (e.g. Occam's razor) should be applied before such silliness is seriously proposed. I don't think Boltzmann assumes infinite time and entropy, just enough for the completely random emergence of sentient life that thinks (perhaps falsely) that it lives in a universe populated by similar beings who creat…

The absurdity heuristic is not a good way to decide what is true. People once thought that the idea of humans being descended from monkeys was absurd. Or that the earth going round the sun, rather than vice versa, was absurd. Occam's razor is more sensible than the absurdity heuristic, but it applies to the fundamental building blocks of a theory, not to the outputs it predicts. So it would cut against a hypothetical…

If a theory implies an absurd outcome, I think it is a reasonable heuristic to question the theory and it's assumptions. I am not saying absurd implications indicate the theory is flawed, only that they should cause one to suspect so and perhaps find a theory that explains reality with less broadly absurd implications.

Re: Timeline of the far future

#65

Post by Symmetry » Mon, May 07, 2012, 4:02 PM UTC

possibilistic wrote: post #62

eliben wrote: post #22

Earlier quoted context omitted.

Isn't this just a simple matter of probability? Given an event, however unprobable it is, it can happen given infinite time? From a purely mathematical standpoint, this is correct.

Just because something has a nonzero probability doesn't mean it will ever occur. Entropy is just dS = dQ/T. It's simply a thermodynamic property that measures where system energy is. All of these grand notions extrapolated from thermodynamics are crazy. Thermodynamics is/was just a first approach at studying macroscale systems because we didn't yet grasp the underlying quantum behavior. It's incredibly useful when a…

Its certainly possible that the universe will end in a crunch or a rip, and all this speculation will be for naught. But thermodynaics is still a perfectly valid way of looking at these things, and hasn't been changed much by the addition of quantum mechanics except that we now talk about probability distributions within phase space instead of points. Its basically the same stuff, with the same consequences.

Entropy is much more than just dS = dQ/T. I mean, that equation is mostly valid the same way that Newton's laws are mostly valid, but you won't be able to get any sort of feel for it approaching the subject that way. Imagine a mathmatical space with six dimensions for every particle, three for position and three for momentum. The state of the universe is a single point moving in this space according to pre-defined rules. Now, we don't know which point or microstate corresponds to our universe, because we can only make crude measurements of statistical aggregates of particles like temperature and pressure and so forth. So by making these measurements we can narrow which universe we're in to a set of these microstates, a 6N-k dimensional region of the 6N dimensional space that we'll call a macrostate. The entropy of an observed macrostate is proportional to the log of the number of microstates that a macrostate contains, S = k log W. In a sense, Entropy is a measure of our ignorance of which universe we're in, which is ultimately why Maxwell's demon doesn't work.

Please note, the above does contain simplifying assumptions which don't change the main point. For the full story, go get a physics minor at a good university or start reading Wikipedia[1] and asking your physics major friends questions until you can re-derive the laws of thermodynamics yourself.

[1]http://en.wikipedia.org/wiki/Statistical_thermodynamics

Re: Timeline of the far future

#66

Post by obtu » Mon, May 07, 2012, 4:10 PM UTC

joering2 wrote: post #54

aint that funny how we paint future in such a dark colors (since sun will die in 5 billion years) and assume we all gonna die with it at the end, but yet we don't put humans evolution taken into consideration. "in 600 million years plants will die" -- seriously now? look when we have been 1,000 or even 100 years ago. think when we will be in next 1,000, given nuclear war will not push us back to the stone age. otherw…

We've done things that seem like magic to some hunter-gatherer; that doesn't imply everything that seems like magic to us will come true. (does anyone have a catchy name for this fallacy?)

The boundary between things we know to be possible and impossible is in fact stronger now, because (for most of the events in this timeline) we're now basing this knowledge on the laws of physics.

Sidebar: future events that derive solely from thermodynamics don't really have a get-out-of-jail card; deflecting some of the others would require us to meaningfully harness much larger amounts of energy at the scholar system scale, bootstrapping that sort of thing would require multiple jumps of a few orders of magnitude which might be solvable as an engineering problem, but is economically dicey when we're already squandering the fossil fuel dividend on our current, unsustainable needs. That is to say, please solve politics or economics before dreaming of magitech.

Re: Timeline of the far future

#67

Post by spurgu » Mon, May 07, 2012, 4:14 PM UTC

diminish wrote: post #27

Betelgeuse red giant supernova explosion, can it hurt the life on the earth?

I would really want to be around when it blows up. Stasis pods please!

Re: Timeline of the far future

#68

Post by [deleted] » Mon, May 07, 2012, 4:16 PM UTC

Symmetry wrote: post #61

majmun wrote: post #33

Earlier quoted context omitted.

Error in Boltzman brains theory is that he assumes that universe with brains randomly fluctuated into existance into its current form , and concludes that this form is more complex than just brain and therefore brains without environments are more common (maybe iPhones or Bible are even more common then), and assumes that brain can exist without environment. also second law of thermodynamics states that resulting ent…

iPhones or Bibles probably are more common. And an isolated brain without an environment really is much more likely than a brain and body and environment, at least if we're talking about random fluctuations rather than structures created as a consequence of the the availability of useful energy in the environment. If you think about it in terms of the Canonical Ensemble the regions of states that correspond to "a bra…

[deleted]

Re: Timeline of the far future

#69

Post by krschultz » Mon, May 07, 2012, 4:31 PM UTC

obtu wrote: post #66

joering2 wrote: post #54

aint that funny how we paint future in such a dark colors (since sun will die in 5 billion years) and assume we all gonna die with it at the end, but yet we don't put humans evolution taken into consideration. "in 600 million years plants will die" -- seriously now? look when we have been 1,000 or even 100 years ago. think when we will be in next 1,000, given nuclear war will not push us back to the stone age. otherw…

We've done things that seem like magic to some hunter-gatherer; that doesn't imply everything that seems like magic to us will come true. (does anyone have a catchy name for this fallacy?) The boundary between things we know to be possible and impossible is in fact stronger now, because (for most of the events in this timeline) we're now basing this knowledge on the laws of physics. Sidebar: future events that derive…

Based on what we believe the laws of physics to be, which isn't yet a fully settled question.

Re: Timeline of the far future

#70

Post by majmun » Mon, May 07, 2012, 4:31 PM UTC

Symmetry wrote: post #61

majmun wrote: post #33

Earlier quoted context omitted.

Error in Boltzman brains theory is that he assumes that universe with brains randomly fluctuated into existance into its current form , and concludes that this form is more complex than just brain and therefore brains without environments are more common (maybe iPhones or Bible are even more common then), and assumes that brain can exist without environment. also second law of thermodynamics states that resulting ent…

iPhones or Bibles probably are more common. And an isolated brain without an environment really is much more likely than a brain and body and environment, at least if we're talking about random fluctuations rather than structures created as a consequence of the the availability of useful energy in the environment. If you think about it in terms of the Canonical Ensemble the regions of states that correspond to "a bra…

This is simply not possible (maybe in star trek), because self-aware brain requires certain kind of environment to exist into. so if there is brain there is organized environment. probability that boltzman brain exist is 0%. probability that self-aware brain in an orginized environment exists : 100% probability that Bible exists in a some unimaginable place far far away: unknown.

Anyway what is the point of this (Boltzman brain paradox)? (or point that was supposed to be?)