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[Il Palazzo]

The more interesting thing about entropy is that it cannot be defined for universe as a whole. Entropy only makes sense about an object in relative equilibrium, and universe is not in equilibrium with itself. It never was.

Can you elaborate? I don't get your meaning.

http://en.wikipedia.org/wiki/Heat_death_of_the_universe#Current_status

"There is much doubt about the definition of the entropy of the Universe. In a view more recent than Kelvin's, it has been recognized by a respected authority on thermodynamics, Max Planck, that the phrase 'entropy of the Universe' has no meaning because it admits of no accurate definition"

That's not a very good wiki entry, to say the least.

For a view on cosmology more recent than Kelvin's they bring up Max Planck and his 1897 book? From before GR and before anyone knew anything about the universe, including whether or not it was static, infinite and eternal, or that the Milky Way was not the totality of it all?
Not to mention that in the rest of the very paragraph from which the statement is quoted Planck explains how to correctly attribute the meaning given extended systems.

I find no support for the statement in the quoted source.


The bit I was curious about the most was the 'equilibrium'. Whether or not entropy can be defined in non-equilibrium systems is something I wouldn't touch with a ten foot pole, but even the author of the book quoted in the wiki for the support of this bit (W.Grandy) wrote an article on treatment of entropy in non-equilibrium systems.

But why would you say the universe was never in thermal equilibrium? The primordial nucleosynthesis and the homogeneity of CMBR depends on it being so, and one of the purposes of inflation is to explain how it could have happened on such a scale (see: horizon problem).


In any case, cosmologists appear to have been using entropy to analyse the universe without much issue, so I wouldn't take such proclamations very seriously.

[Arx]

And more unrelated stuff...

Article on anti-vaxxers and why they are.

It all seems a bit meta.

[alway]

The more interesting thing about entropy is that it cannot be defined for universe as a whole. Entropy only makes sense about an object in relative equilibrium, and universe is not in equilibrium with itself. It never was.

Can you elaborate? I don't get your meaning.

http://en.wikipedia.org/wiki/Heat_death_of_the_universe#Current_status

"There is much doubt about the definition of the entropy of the Universe. In a view more recent than Kelvin's, it has been recognized by a respected authority on thermodynamics, Max Planck, that the phrase 'entropy of the Universe' has no meaning because it admits of no accurate definition"

That's not a very good wiki entry, to say the least.

For a view on cosmology more recent than Kelvin's they bring up Max Planck and his 1897 book? From before GR and before anyone knew anything about the universe, including whether or not it was static, infinite and eternal, or that the Milky Way was not the totality of it all?
Not to mention that in the rest of the very paragraph from which the statement is quoted Planck explains how to correctly attribute the meaning given extended systems.

I find no support for the statement in the quoted source.


The bit I was curious about the most was the 'equilibrium'. Whether or not entropy can be defined in non-equilibrium systems is something I wouldn't touch with a ten foot pole, but even the author of the book quoted in the wiki for the support of this bit (W.Grandy) wrote an article on treatment of entropy in non-equilibrium systems.

But why would you say the universe was never in thermal equilibrium? The primordial nucleosynthesis and the homogeneity of CMBR depends on it being so, and one of the purposes of inflation is to explain how it could have happened on such a scale (see: horizon problem).


In any case, cosmologists appear to have been using entropy to analyse the universe without much issue, so I wouldn't take such proclamations very seriously.

Judging by the talk page on the wiki article that was linked, it's pretty much been edit-warred into nonexistence by a pervasive editor who doesn't like the idea of a heat death.

[Il Palazzo]

Judging by the talk page on the wiki article that was linked, it's pretty much been edit-warred into nonexistence by a pervasive editor who doesn't like the idea of a heat death.

Yeah, I figured as much. Usually technical stuff on wiki is of much higher quality than that.

(reading the talk page: jesus, what's his problem?)

[alway]

Judging by the talk page on the wiki article that was linked, it's pretty much been edit-warred into nonexistence by a pervasive editor who doesn't like the idea of a heat death.

Yeah, I figured as much. Usually technical stuff on wiki is of much higher quality than that.

(reading the talk page: jesus, what's his problem?)

Unfortunately, this sort of thing is becoming increasingly pervasive on wikipedia; largely because such editors stick around for years (since at least 2013 in the case of that article), and so there's nothing any individual can do about it without becoming an equally ridiculous stalker of the page for years on end. Wikipedia doesn't really seem to do anything about that sort of thing, since they also tend to be good at rule lawyering, and so in the end will likely be the downfall of the site.

[Il Palazzo]

That makes me sad

To give some closure to the discussion amidst the misinformation:

Heat death appears to be the most likely end scenario for the universe, since the cosmological constant does appear to be constant (gravitationally bound systems will remain bound).

A big rip scenario has been given way too much press since it was proposed circa 2003. It is currently not taken seriously anymore for the reason stated above (thanks to the recent WMAP and the ongoing PLANCK missions providing ever-improving measurements).

For those interested, here's a lightweight analysis of the heat death scenario by John Baez - a respected mathematician and cosmologist (also known for the crackpot index):
http://www.math.ucr.edu/home/baez/end.html

[Putnam]

Isn't another theory that the universe wil continue to expland forever? And it will just die because everything is so far apart

I'm sure that in 100 years our view of universe's future will completely change and people from that age will consider us stupid for even believing this.

No.

We don't believe this, for one. The Heat Death is currently considered the most likely fate of the universe, but if you told a scientist to commit they would refuse. It is known that we do not have enough data to come up with a reasonable conclusion. We also know every possible ending of the universe given the data so far, and we have a lot of data. Unless something completely and utterly weird happens within the next 100 years, our ideas of the fate of the universe will be less broad, but not completely different. The argument that "everything we know today will be seen as idiocy in 100 years" works for medicine and psychology, but not physics.

99 years ago, the theory of General Relativity was discovered. It hasn't been overturned since; in fact, all evidence points to its truth. Quantum Mechanics happened just ten years later and it's still going strong. Physics is not medicine. The universe is not nearly so complex as a human body.

What I said relates to this universe and these bodys

Biological immortality is very much a thing. There is no law whatsoever stating that humans must die. In fact, death itself has been redefined repeatedly; it used to be "no breathing", but then we could fix that, so then it was "no heartbeat", but then we could fix that, so now it's "brain has no function", but even that may yet have some further method of resuscitation.

[Il Palazzo]

Eh, I'd disagree about the medicine bit (and stay silent on psychology due to complete ignorance).
It's not like it's possible that further advances will significantly change our understanding of organ functions, or overturn the germ theory (unless you're into this anti-vaccer's woo-woo: Good-bye germ theory).

The same refinements of the body of knowledge that happen in physics happen in medicine, and in any other area of knowledge that follows the scientific method (aka 'being sensible').

[Putnam]

I mean in the treatment sense, not in the knowledge sense. Organic chemistry is a gigantic mofo.

[Descan]

Also, biological immortality is nice and all, but it isn't the only method. It's just the safest in terms of "Will it still be me on the other end?"

Only way to fix that is to have some sort of temporal bridging mechanism, like bolting on a bunch of hard-drives to your face and wait a bunch of years until your brain has expanded into the hard-drive so much that losing the original organic brain doesn't matter, or converting each and every single neuron into a more robust, possibly-mechanical or whatever version of a neuron.

But by the time we're talking on the order of "Trillion years old terran sapients turning back the death of the universe," the idea of us still having cells or anything like cells is like saying "So where's the flint and iron to run that there computer, mate?" on a much larger scale.

[~Neri]

Isn't another theory that the universe wil continue to expland forever? And it will just die because everything is so far apart

I'm sure that in 100 years our view of universe's future will completely change and people from that age will consider us stupid for even believing this.

No.

We don't believe this, for one. The Heat Death is currently considered the most likely fate of the universe, but if you told a scientist to commit they would refuse. It is known that we do not have enough data to come up with a reasonable conclusion. We also know every possible ending of the universe given the data so far, and we have a lot of data. Unless something completely and utterly weird happens within the next 100 years, our ideas of the fate of the universe will be less broad, but not completely different. The argument that "everything we know today will be seen as idiocy in 100 years" works for medicine and psychology, but not physics.

99 years ago, the theory of General Relativity was discovered. It hasn't been overturned since; in fact, all evidence points to its truth. Quantum Mechanics happened just ten years later and it's still going strong. Physics is not medicine. The universe is not nearly so complex as a human body.

What I said relates to this universe and these bodys

Biological immortality is very much a thing. There is no law whatsoever stating that humans must die. In fact, death itself has been redefined repeatedly; it used to be "no breathing", but then we could fix that, so then it was "no heartbeat", but then we could fix that, so now it's "brain has no function", but even that may yet have some further method of resuscitation.

No brain function isn't defined as death currently. A number of braindead people have regained brain activity over time. Current definition is when the body begins to rot.

[Frumple]

... don't we have varying conditions that can cause bits (maybe everything?) to start rotting without actually killing someone? I guess one of the more advanced stages of decomposition is the line?

[i2amroy]

An important part of the current definition of "brain death" is that the condition be "irreversible". That's why situations where people are loosely termed to be "braindead" (such as people in deep comas, on some drug overdoses, and in chronic vegetative states) don't fall under the medical definition, and why it requires two confirming physicians to declare someone to be "brain dead".

[Cryxis, Prince of Doom]

Just watched kingsmen and I have a few questions concerning things that happened including weapons


1- what is the fastest acting deadly neurotoxin known to man?
2- if someone disengages from an unstable, small platform in low earth orbit and begins falling sporadically how difficult would it be for a highly trained person to regain stability in their fall?
3- would it be possible to make a bullet proof business suit?
4- Bullet proof umbrella gun?
5- Shutting down the Brian's decision making bit (not a neuro scientist here) and over stimulating the anger/rage/violence part to turn people into homocidal maniacs using sound or electronic signals?

[~Neri]

An important part of the current definition of "brain death" is that the condition be "irreversible". That's why situations where people are loosely termed to be "braindead" (such as people in deep comas, on some drug overdoses, and in chronic vegetative states) don't fall under the medical definition, and why it requires two confirming physicians to declare someone to be "brain dead".

Currently it's irreversible if you're trying to reverse it. However it can naturally reverse itself.