Low on Gas ..?

[ZeroID]

http://www.smh.com.au/world/science/stars-fade-as-universe-starts-to-run-out-of-gas-20110821-1j4ru.html

No time scale given though.

[CraigS]

Low estimate ~ 10^12;
High estimate ~10^14 years:

.. from 'Timeline of the future' (http://en.wikipedia.org/wiki/Timeline_of_the_far_future) in Wiki (follow the references given, for more info).

Cheers

[Robh]

Fascinating read.
Thanks for that.

Regards, Rob

[Ric]

That timeline is an amazing read.

I'm going to have to read it a few times though just to get a handle on it regarding the future stuff and let it all sink in.

[Ric]

I was reading about the Boltzmann brain out of the future timeline, that I find very confusing.

Suposedly a brain or self aware entity will randomly appear within the universe.

That one is way out of my league.

http://en.wikipedia.org/wiki/Boltzmann_brain

[renormalised]

What it's basically saying is that given enough time, a self aware entity will appear out of the random fluctuations which occur within spacetime. Given that despite the 2nd law of thermodynamics (that entropy of any closed system will always increase), random (stochastic) fluctuations within spacetime (and hence the entropy of that spacetime) will produce an entity that will be self aware.

It's a blending of chaos and the anthropic principle, if you will. Chaos Theory states that you cannot determine the future outcomes within a system because it's impossible to state with any certainty what the initial conditions of such a system were...and the system itself is sensitive to those initial conditions. The Anthropic Principle basically states that the conditions that produced us within this Universe must be here because we are here to observe them. In other words, the Universe is here because we are here to observe it.

Now, we know that the 2nd law of thermodynamics states entropy (disorder) within a closed system will always increase. That being the system will try to move towards a state of equilibrium with itself...the present system of things being ordered and in disequilibrium. So, if you look at any system obeying the 2nd Law, it's more likely you will see small and discrete fluctuations towards equilibrium than one large one, or many large ones. Small fluctuations with little organisation (order) are more common in systems where entropy increases than large fluctuations which produce more highly ordered states. However, our existence would suggest that large, random fluctuations do occur (AP selection bias). Nevertheless, the fact being that small fluctuations are more common than large ones would suggest that if a highly ordered system can produce many self aware entities, then the greater likelihood of the smaller fluctuations in a highly entropic (less complex and disordered) system have a better chance of producing a single sentient entity within such a system, hence the Boltzmann Brain.

[CraigS]

Seems to me to be an attempt at pushing the Laws of Thermodynamics beyond the boundary of their appropriateness.

As per our 'Nuggets' thread, it became clear that no natural 'system' can ever be truly considered as bounded (or isolated .. as all complex processes are irreversible). There's always other things to include in the analysis beyond that which we normally consider to be part of the system we're analysing. When those other things are included, anything can happen in the calculation of entropy within the system then being considered.

In my view, the 2nd Law is a flawed basis for considering what happens in an infinite, unbounded universe. It also says nothing about the actual structures present as a result of 'ordering'.

Complexity theory is the modern approach, which takes us much further.

Cheers

[renormalised]

Maybe Boltzmann thought he was the "brain" that made its appearance:):P

He did make quite a few assumptions in his deliberations.

[CraigS]

Was it actually Boltzmann who came up with it .. or someone else attempting to use the Laws for another purpose ?? (I don't know).

Cheers

[renormalised]

It was Boltzmann.

Tell you what, though. It lends itself well to a HHGTTG scenario:):P

[sjastro]

I've been called a lot of things in my time, a statistical fluctuation isn't one of them.

Steven

[renormalised]

There's always a first for everything:):):P

[renormalised]

Just had a thought.....a Boltzmann Brain is a self aware entity which appears out of a random fluctuation of an equilibrated system at max disorder (max entropy). If you think of the "nothingness" before the BB as a system in perfect disorder (therefore maximum entropy), the appearance of the Universe as a random fluctuation in that disorder could be likened to the birth of a Boltzmann Brain. For all we know, it could be a self aware entity unto itself. We ourselves and all other life in this Universe may just be aspects of that sentience which came into existence in order to observe itself.

Something to ponder over tea and bickies:):)

[Ric]

Thanks Carl for the explanation, it's definitely a bit easier to get my head around it now.

Yes, I'll definitely be pondering this one over several cups of tea and bickies.