Whatsa(dark)matta'U

Replies to This Discussion

Permalink Reply by Richard ∑wald on March 8, 2012 at 6:30pm

…simple explanation of dark matter at about 2:14

Dark energy...

Permalink Reply by Tony Carroll on March 8, 2012 at 7:11pm

Okay Richard. Somewhat clearer. The dark energy was a actually easier to understand. Somewhat similiar to virtual particle pairs, right? From the point of causing expansion. Dark matter, a new elementary particle? Matter around us now? Unseen, not interacting with normal matter? Uh is that a neutrino? Boson? Like I said, a lay person. Just trying to understand. Thanks.

Permalink Reply by Loren Miller on March 8, 2012 at 7:32pm

Tony, if you liked the short version of Lawrence Krauss's lecture, here's the full version of it.  A bit long, but I really enjoyed it:

Permalink Reply by Sean Murphy on March 8, 2012 at 8:35pm

Right now, nobody actually knows what Dark Matter is. We know it is out there, by the way galaxies move. Orbital math can be used to calculate  mass from speed or speed from mass, and we know the mass of what we can see of galaxies, and the speed they spin at, but they don'rt add up right. The speeds tell us that the galaxies are on average approximately ten times more massive than what we can see of them (the stars and dust and gas clouds). The missing mass, or invisible mass, is Dark Matter.

The way I have heard Dark Energy explained is that it is a force (again, we don't actually know what it is yet but we can indirectly tell it is there by its effects) that causes the "fabric" of space to stretch and expand.

Permalink Reply by Sean Murphy on March 8, 2012 at 8:43pm

The really interesting thig about Dark Energy is that General Relativity does not say that space can't move faster than light, in contrast to matter. In fact, the most popular/likely model of the early history of the universe requires that the universe did in fact expand faster than light can travel during the Inflationary Period. Space expanded faster than light, and carried the miasma of energy with it, forcing it to rapidly cool as its volume expanded and leading to the evetual formation of matter.

Which means, if Dark Energy is something we can learn to manipulate, it can provide a loophole in General Relativity that could make interstellar travel possible.

Permalink Reply by Tony Carroll on March 8, 2012 at 8:57pm

You're talking superluminal velocities, right?

Permalink Reply by Sean Murphy on March 8, 2012 at 9:10pm

Yeppers. If a spaceworthy craft could reduce the Dark Energy density in front of it, while increasing the Dark Energy density behind it, the section of space it was moving through would effectively move in the same direction, carrying the spacecraft along. Take it to a high enough extreme and you travel at superluminal velocity (and possibly get torn to little pieces if your warp bubble is less than perfectly balanced)...

Permalink Reply by Tony Carroll on March 8, 2012 at 9:25pm

So, you're surfing on a wave of energy?

Permalink Reply by Sean Murphy on March 8, 2012 at 9:27pm

More like on a stretching sheet of space.

Permalink Reply by Tony Carroll on March 8, 2012 at 10:28pm

So like, the sheet is stretching ahead of you, and bunching up behind you? Ow! I just burst an aneurysm. Mye earrrrs are bloooodinn! 4&*uto stu.....

Permalink Reply by Sean Murphy on March 9, 2012 at 4:22am

Technically, the sheet would be stretching behind you and bunching up in front of you, thus pushing and pulling you along...

Permalink Reply by Tony Carroll on March 9, 2012 at 5:26am

Okay. Anuerysm resolved. You know, as much as I love thinking of this stuff, and I truly do, sometimes my brain just melts. And I mean that in a good way. Thanks for trying to answer some of my questions. There will be more (hey! I heard those groans! now cut that out). Seriously all you guys, thanks. It does bring some light into the darkness. Peace. Going to work. Can't wait to get home tonight to see what else is on here. Until then, peace.

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