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space-race
2004-Nov-27, 11:13 PM
i am very ignorant of but highly interested in the mechanics of the universe,so will probably ask a lot of "general knowledge" questions,but the people on this site seem very well informed & helpful,so i'll give it a go.i have read that approximately 90% of the universe is made up of non-visible "dark matter",but that our galaxy seems not to contain dark matter?this seems unlikely,as what would prevent dark matter from existing in our galaxy,we are after all just 1 little galaxy in a very large universe/multiverse?
the science-fiction necessity of superlumenal travel by "folding" space as found in the "Dune" series states that instead of travelling faster than light,you could bend space to bring two points close together,cross the relatively short distance that now exists and then restore space to it's original condition.but space is not empty,so instead of moving one small ship you have to move unknown,probably vast, quantities of matter.are there any theories along this line?

antoniseb
2004-Nov-27, 11:23 PM
Originally posted by space-race@Nov 27 2004, 11:13 PM
approximately 90% of the universe is made up of non-visible "dark matter", but that our galaxy seems not to contain dark matter?
The percentages might be off on what you read about dark matter , but the idea is mostly right, except for this: Our galaxy probably has its fair share of dark matter. I don't know where you might have read that it doesn't.

Concerning the folding of space a la Dune, and so many other science fiction tales, there are sometimes things written in real research papers about this sort of thing, but it is not something that can be tested now, nor any time in the forseeable future. There is an excelent chance that it will prove impossible.

bossman20081
2004-Nov-28, 05:31 PM
Thats the thing about dark matter, we cant see it. Dark matter is supposed to be non-luminous and its suppose to have a very low albedo. The only reason we say its there is because all of the visible matter in the universe has insufficient gravity to account for what we're seeing. So we dont really know how much dark matter there is- if any- because its just a hypothesis- a guess.

blueshift
2004-Nov-28, 08:58 PM
bossman,

The reason for proposing DM was because of Kepler's laws that hangs over our observations..While you may see this clearly, someone like OLDGIT might drop in on your post and take in the wrong impression..

Dr. Monica Valluri at the Kalvi Institute at the U. of Chicago is doing a lot of studies in this area concerning the tidal streams in our galaxy and results from
WMAP and the Digital Sky Sloan Survey.

She appears to suggest that the DM is moving at very slow speeds (non-relativistic) and has ruled out any possibility of it being composed of any baryonic
material...

She studies alternative theories and has an entire room where she does all of her
studies on MOND..She was quite receptive to questions concerning alternative theories and didn't rule out their possibilities although she did have a few questions
she returned at our club meeting a few months back..

Do a google search and you'll find her site..Digital Sky Sloan gets renewed next year and will be resolving the motion and spectra of 250 million low metal stars in the outer halo. ESA will be launching a program around 2007 that will study a billion stars in the same area..

blueshift

bossman20081
2004-Nov-29, 08:38 PM
Originally posted by blueshift@Nov 28 2004, 03:58 PM
bossman,

The reason for proposing DM was because of Kepler's laws that hangs over our observations..While you may see this clearly, someone like OLDGIT might drop in on your post and take in the wrong impression..

First, who is OLDGIT? And how can you get the wrong impression from what I wrote? You basically said the same thing as me, only I didnt mention Kepler's Laws.