Anti-Matter Concerns

[DaShi]

Originally posted by KrazyHorse
I don't profess to understand the physics of what happened prior to the inflationary epoch well enough to make any statement about its entropy, and anybody who does is a quack. We don't really understand the inflationary epoch very well either. We're working on it as hard as possible, though. I promise you. I went in to work on the weekend just so you could get an answer quicker.

People like KH are the real heros!

[Jaguar]

Originally posted by DaShi
You have to use anti-magnetics. The real hard part is that anti- particles move backward in time. That means they exist before you make them.

[KrazyHorse]

Originally posted by DaShi


People like KH are the real heros!

Thank you. Thank you.

[KrazyHorse]

I have to admit that I sort of slacked off today though.

[Ben Kenobi]

Interesting. I can't imagine how you would induce a dipole moment on a hydrogen ion, those are symmetrical particles.

[Seeker]

"No. There are reasons why high energy densities correspond to unknown physics. Those reasons do not apply for the energy density of today's universe."

I'm not talking about 'today's universe', I'm talking about making predictions about the far-future universe using our present knowledge.

If uniformity* has not be true at any point in the past, why make the bold leap of applying it indefinetly into the future?

*or whatever the word is. laws applying in the same way in all places and times.

[KrazyHorse]

I'm not talking about 'today's universe', I'm talking about making predictions about the far-future universe using our present knowledge.

Err...yeah. And we're heading toward even lower energy densities (probably levelling off at some point in the future)

Whereas if you roll the tape backward there comes a point where we obviously don't understand the physics.

In other words, we can "predict" backwards and say that the physics shouldn't make sense to us at some point in the past. If we predict forwards we don't see the same problem.

[KrazyHorse]

If uniformity* has not be true at any point in the past, why make the bold leap of applying it indefinetly into the future?

Uh...because we already know why our current laws can't hold in the past. We don't understand basic particle physics at those densities and those energy scales. It's not a mystery that at some point in the past the laws stopped applying. They stopped applying when our physical laws, projected backward from the current state of the universe, predict a state of the universe in which the standard model breaks. Like the scale of the Higgs boson, or higher. The theory itself undergoes a catastrophe at those scales.

We knew it didn't work before we even saw evidence of it not working. We recently got evidence that it didn't work (proving inflation). Now you're saying that even though our theory should work at low energy scales and low densities that we should assume it's wrong?

[Seeker]

I'm not saying you should assume it's wrong for the present few trillion years or whatever. I just think it's an unwarranted assumption to extrapolate the end of universe based on present conditions.

I'm basing this on speculation regarding the origin of the universe, which guesses that it was a random event.

Surely, something that happened once has a none-zero chance of happening again given infinite time?

It just doesn't make sense to me that whatever process was responsible for the universe was a 'one-off' event.

Speculation I have read says that it might have been some type of 'quantum fluctuation'...and IF that's the case then why should rule out such an event never happening again, ever?

Given indefinite time? It just doesn't make sense to me to assume that time and space will always be how they are now, given that they have changed so dramatically in the past.

[Ben Kenobi]

It just doesn't make sense to me that whatever process was responsible for the universe was a 'one-off' event.

It does to me. Unless one can reverse entropy, you will see systems deteriorating into less ordered states.

Even presuming that the expansion will not continue forever, you are still left with the puzzle of how do you open the box once everything collapses together? A black hole the mass of the universe isn't going to let anything out.

[KrazyHorse]

I'm basing this on speculation regarding the origin of the universe, which guesses that it was a random event.

Even if it was, which you are in no position to claim, then the event itself is dependent on the conditions it occurs in. Those were far different in the early universe than they are now or will be again.

[Seeker]

"or will be again"

I'm afraid I'm just not as confident as you are to make blanket statements about all eternity.

[Bill3000]

The universe can't go back into a less entropic state, silly.

[KrazyHorse]

Originally posted by Seeker
"or will be again"

I'm afraid I'm just not as confident as you are to make blanket statements about all eternity.

I'm not at all going to make a blanket statement. I'm a logical positivist. The universe could decide tomorrow that it doesn't like gravity and thus abolish it.

That doesn't mean that your logic is any more convincing. The fact that our theory fails where we knew it would fail has no bearing on a region of spacetime in which our theory has no reason to fail. It might fail or it might not. If you don't have a reason it should fail then we must presume that the most likely outcome is that it doesn't fail.

I have no problem with you asserting that we don't know everything. I admit that freely and without reservation. But your postulated "quantum fluctuations" in the early universe don't have anything to do with the late universe, as far as I can see.

Whenever I make a statement, it should be appended with the phrase "to our best current understanding". Always. If I tell you that gravity attracts two bodies together then you should also assume I'm not sure it always does so.

[Seeker]

"Future measurements of supernovae, gravitational lensing and
clusters of galaxies from a Large Synoptic Survey Telescope, LSST, and the Joint Dark Energy Mission,
JDEM, will reveal definitively whether dark energy behaves like Einstein’s cosmological constant or
like some new substance that changes with time as the universe evolves."

Now I'm going to piss you off by quoiting a popular magazine...to me these experiments seem to indicate doubt that the universe will be fundamentally the same forever, especially if 'dark energy' changes (drastically) over time, say reversing. It seems to me that there must be many possible unknown processes which could recreate something like the conditions of the early universe.

Ben:
That seems naive to me...on the time scale I'm talking about I'm assuming the evapouration of all black holes and the decay of all normal particles. To recreate the conditions of the early universe all space/time would have to be reduced to an unknowably small point, not merely some matter stuck in some gravity well.