Quote (juliusjuice @ Wed, Apr 22 2009, 01:17pm)
dark matter has been used to explain pheonomena we cannot explain on paper otherwise. decades ago vera rubin, a cosmologist, discovered that there is not near enough matter in a galaxy to hold it in tact-the stars in the outer rim should just drift away from the center instead of holding in an orbit. the amount of matter missing is a startling 97%. solution: propose some kind of matter that has so far eluded detection -such as an unknown weakly interacting massive parcticle (WIMP) that has enough gravity to make up for the missing part of the equation. this has been the biggest slap in the face to scientists as we still have no idea what actually makes up this difference -decades after they were first proposed. -unless our idea of how gravity interact at great distances is incorrect.
modified newtonian dynamics (MOND) proposes that gravity is much stronger over long distances than previously thought. it could also explain why the univers appears to be expanding (not spreading apart but actually expanding according to a value called hubble's constant), the light travelling over these long distances may just be affected by gravity in ways we do not understand. the theory was created in the early 80's but hasnt got much publicity uuntil recently. part of the reason it is now being taken seriously is the pioneer 10 and 11 spacecraft phenomena.
-the pioneer craft are now at the edge of our solar system and have deviated from the course they are predicted to follow. some unknown force is redirecting their trajectory -their engines have been cold for decades, they should drift on according to gravitational pull of any bodies close enough to them, but they are a little off, and rocket scientists/cosmologists do not accept even the smallest deviation from predicted orientation. this is a very small difference. over its distance travelled over a year, 219 million miles, they drift off by 18 thousand miles.
MOND could possibly explain this problem with the pioneers, it could actually explain some of the wierdest phenomena in cosmology. the scientific community is reluctant to accept this theory as it would change newton's 2nd law of gravity -science books would be forever changed (forever?)
i highly suggest reading the book "13 things that dont make sense" by michael brooks. i also used the internet, memory from radio/television programs and a march '09 issue of astronomy monthly. -i am no cosmologist i just find this stuff interesting, i dont necessarily believe this theory, but at the same time it makes more sense than the existance of dark matter and universe inflation.
well I have touched on MOND quite a bit myself... I will have to go get that book by Michael Brooks, for sure.
But this is how I was lead to understand it (I give 90% of my insight into things like this to my Highschool Astronomy teacher, I can remember many hours of talking about things like this. Sure she wasn't "Qualified" to teach about physics this extreme, but then again, neither am I)
So here we go, you referring to things like, the Gravity train and things like that? but over massive distances, now MOND takes that to a whole new leveling, talking about how Gravitational forces can act upon eachother over great distances, much more strongly than ever thought before. Now, as we know gravity always effects everything, no matter how far away the source is. The furthest possible star in the universe is currently pulling you towards it... granted, so minutely its impossible to measure, but it is effecting you. Now, my problem with MOND is that, they are quick to point out how it effects small, standalone things, such as the Voyeur craft.
Now, the funny thing about all this, is that it was said that Universal expansion was slowing down... things where going to come to a stop, then slowly everything would come back together, colliding and condensing everything back into a singularity over a massive amount of time. But now they are saying that things are actually speeding up... and we are accelerating outwards in Universal expansion, and now everything is going to get so far apart it will grow dead and cold, Void of life.
Now Im not sure which to believe but DarkMatter is the best explanation for this so far, (in my opinion) Because... its the most unknown, we are able to measure and calculate Gravity, and distance, and the difference of effect. so I think its more likely that there is something that we cant see, something we dont know about, that is doing this, rather than us being wrong about something we Already "know"..
however your right, as our understanding grow's so does our knowledge about things we already "know"
Anyways Im probably rambling now, I just think that Understanding the shift in Matter domination, vs Darkmatter domination... is just alot more, idk... more simple?
Very interesting thankyou for putting up a post in here that got me to think a bit. I just spent a good few hours reading about all this.