Dark, Perhaps Forever

[groovedaddy]

BALTIMORE — Mario Livio tossed his car keys in the air.

They rose ever more slowly, paused, shining, at the top of their arc, and then in accordance with everything our Galilean ape brains have ever learned to expect, crashed back down into his hand.

That was the whole problem, explained Dr. Livio, a theorist at the Space Telescope Science Institute here on the Johns Hopkins campus.

A decade ago, astronomers discovered that what is true for your car keys is not true for the galaxies. Having been impelled apart by the force of the Big Bang, the galaxies, in defiance of cosmic gravity, are picking up speed on a dash toward eternity. If they were keys, they would be shooting for the ceiling.

“That is how shocking this was,” Dr. Livio said.

It is still shocking. Although cosmologists have adopted a cute name, dark energy, for whatever is driving this apparently antigravitational behavior on the part of the universe, nobody claims to understand why it is happening, or its implications for the future of the universe and of the life within it, despite thousands of learned papers, scores of conferences and millions of dollars’ worth of telescope time. It has led some cosmologists to the verge of abandoning their fondest dream: a theory that can account for the universe and everything about it in a single breath.

“The discovery of dark energy has greatly changed how we think about the laws of nature,” said Edward Witten, a theorist at the Institute for Advanced Study in Princeton, N.J.

http://www.nytimes.com/2008/06/03/science/03dark.html?th&emc=th

[klyon]

1. it is simple - all gravity is local

until we get to the end .... we really don't know

[magellan]

2. Maybe there is some force beyond the boundaries of our universe

...that is stronger than all the forces within the universe combined?

[patriotvoice]

5. Move vacuum than vacuum?

Interesting thought: all deep-space objects are being blown outward not because of initial momentum, but because of differential.

[FiveGoodMen]

6. For the differential, though, you still need an outward-pointing force to exist

And the nature of that force is the big mystery, right?

[patriotvoice]

7. We are looking for the wind; perhaps we should look for the pressure areas.

(I just woke up, so I'm speaking sooner than perhaps I should.)

Suppose we are in an area of "high" pressure, and the outside is an area of "low" pressure. The acceleration we see is the "wind", that physical effect resulting from an equalizing differential. Perhaps gravity operates in a similar way: high pressure ("mass") and low pressure ("mass") creates a wind ("acceleration"). So maybe it's just that we have so much mass in the core of our Universe, and that there is so little mass outside the Universe, that Nature is simply equalizing. Thus, we are looking to better understand a force we already know about, rather than inventing a new force to account for it.

(Note: I perfectly understand the experiments implying missing mass and energy, and thus why we think we need dark stuff. I am, however, quite skeptical about dark stuff: it smells a little too much of luminiferous aether, to me.)

[FiveGoodMen]

8. Well, that gives it a different name...

Either way, we know about a force (gravity) that pulls mass together and have been surprised by evidence that some force or other is pushing things apart.

On edit: Are you saying that pressure from interstellar mass (near vacuum but not quite) or cosmic background radiation is enough to push everything apart?

[patriotvoice]

9. No: just that we should consider what lies at the universe boundary more completely.

Perhaps anti-matter galaxies are pushing away our matter galaxies. I understand the CPT arguments against that, but anti-matter anti-gravity would explain away the dark matter. In that case, the differential is our usual relativistic gravity, expect for the nagging fact that gravity has no modeled anti-particle.

Perhaps our matter universe is a bubble inside a larger anti-matter universe, and that the anti-matter universe surrounding us is attracting and consuming us just as we are attracting and consuming it. In that case, the differential is the charge attraction between matter and anti-matter at the boundary and the gravitational spring between the edge and the inside.

Likening it to weather, it's hard to understand the concept of wind until you understand the concept of pressure zones and boundaries -- that is, the middle is made clear by defining the edges.

[HereSince1628]

3. I have to admit I find the idea of an oscillating universe

more comforting than the one way cold slide into darkness. And I know that my fondness for that idea is completely irrational.

[SteppingRazor]

4. Multidimensional string theory has an answer for this.

With its proposal of 10-25 dimensions, string theory explains dark energy as an extension of the strong nuclear force over distance through the GUT (electronuclear force) part of the theory.

I understand what I typed, but I'm not nearly bright enough to explain the math behind it. :dunce:

On edit: There's also the cosmological constant (dark energy is simply the inherent energy of a very large space) and quintessence (dark energy is a fifth force in the universe), but I'm even stupider in regard to those two proposals.