It's official. The universe is dying.

[BrianSoddingBoru4]

But where does all the energy go?

It doesn't really 'go' anywhere, in reference to the universe as a whole. The energy contained in and produced by a star is still there when that star goes nova or supernova, it's just spread out across a much bigger area.

Imagine you've got a bucket of sand (don't we all) and you decide to scatter that sand across an area of a thousand square miles (like people do). The sand isn't 'gone' in any meaningful sense. It's still there, just harder to find and no longer contained in a bucket.

Boru

addendum: I call upon the actual science people on this board to tell me how bad that analogy is. Thank you.

[robvalue]

Good. I'm fucking sick of it.

I'm sick of all the suffering that goes on every day that I'm painfully aware of and unable to stop.

I've had enough of helpless people and animals being hurt and tortured at the hands of evil people. Willow had the right idea.

It breaks my heart... I'm sobbing my eyes out thinking about it. Being depressed makes me even more acutely aware. You may say I have to weigh the bad with the good, and I'm focusing in the negative. But honestly, I don't think any amount of good can balance out the suffering. It's not in the same currency. When I think of helpless animals especially, relying on humans who abuse them in ways they can't understand... it's just too much for me.

Sorry, I just had to get that out.

[ignoramus]

There's a very wise saying that goes:

Nothing really good or really bad lasts a long time.
I suppose that goes for most things in life.

Guys, why would we even care what happens to the universe long after we're gone?
It was dead before we sprouted and it'll just go back to how it was. No biggie.

It's this self awareness and consciousness thing, isn't it?
It always gets in the way of a fact and turns it into a operatic tragedy!

[Alex K]

http://www.msn.com/en-au/news/world/the-...spartandhp

Without applause or encore, the lights are going out across the universe, as old stars die faster than new ones are born to replace them.

Astronomers described the slow death of the cosmos in fresh detail on Monday after training some of the world’s most powerful telescopes on a vast region of space.

They analysed starlight from more than 220,000 distant galaxies and found that the universe has lost about half of its twinkle over the past two billion years. It will lose far more in the next two billion.

“The universe is curling up on the sofa and becoming a couch potato,” said Joe Liske, an astronomer at the European Southern Observatory in Garching, Germany, who took part in the study.

But where does all the energy go?

Ok, so, energy conservation is a funny thing ina changing spacetime. Naively, energy is not conserved. Boru's sand analogy is true for matter at rest (i.e. rest energy E=mc2) with respect to the cosmic rest frame, which simply gets more dilute while the amount stays the same. It is not true for kinetic energy, the extreme example being light which has no rest mass. In addition to being diluted, it gets redshifted, thus actually losing energy. A photon that got sent by a star billions of years ago will now carry less energy because it is redder. The CMB photons have lost a factor of 1100 of energy since they started their journey. In general relativity, his violation of energy conservation can be seen immediately from the equations because the usual conservation law gets an additional modification from curved space (somewhat simplified, it is actually the so-called connection which is not the same as curvature). A conserved quantity can nevertheless be constructed when one assigns an energy to the curvature of spacetime itself. In this case, one gets a conserved energy where during the expansion, energy leaks out from the contents of the universe into the geometry.

[ignoramus]

Alex, out of curiosity, is there such a thing as perpetual motion in the universe?
eg: planets spinning around each other, etc

or must THAT also come to an end at some stage by loss of energy somewhere? (any latency issues here)

[Alex K]

Alex, out of curiosity, is there such a thing as perpetual motion in the universe?
eg: planets spinning around the sun, etc

or must THAT also come to an end at some stage by loss of energy somewhere? (any latency issues here)

Even if you ignore tidal friction, a planetary system is basically a gravitational wave emitter and would gradually lose its rotation to gravity waves which then get redshifted away.  We are however talking loooong times here, orders of magnitude longer than the current age of the universe.

[ignoramus]

what will happen? break apart or come together?

[Alex K]

double post

[Alex K]

what will happen? break apart or come together?

I had hoped you wouldn't ask. The moon goes away due to friction but I think that only happend because it gets energy from earths rotation. A bound system with a kepler potential would usually come together and crash if it slowly loses energy. I think... The virial theorem says that smaller ~ less energy. Yes, it should shrink and the planets fall into what is left of the sun.

[brewer]

Good. Those fucking new stars are always a pain in the ass. All that light when I'm trying to sleep. Always, look at me, look at me, I'm so new I got to have a name. Come investigate me, I'm every sooooo interesting. Meh. If I see any around here I'm gonna turn the hose on um. Take that bitches!