I have heard that dark matter could possibly be the gravitational link between between distant galaxies. Could this possibly lead to the big crunch? Thanks
dark matter is believed existing whereever ammounts of matter are.
The relation between dark matter and galaxies is, that only the existance of dark matter would explain the odd rotation of those galaxies. Newtons law has predicted that the outer parts of galaxies would rotate much slower than it it is observed.
about dark matter and the universe itself…well… obviously most galaxies move away from each other even with dark matter in place. Reason: dark energy is believed to make the universe expand, or better the space between galaxies.
scientists think there is 73% dark energy, 23% dark matter and just 4% normal matter, these numbers may show why dark matter will not lead to a gravitational collapse.
January 29th, 2010 at 5:38 am
no…they believe that the galaxies are speeding up outwards because there is super dense yet invisible "dark matter" outside the universe that is pulling everything outwards
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January 29th, 2010 at 6:04 am
Nope. More like the "Big Rip", since the visible matter seems to be accelerating away. This stuff is still too new to know. The hypotheses may be interesting, but it’ll be some time before we have concrete data to prove them.
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January 29th, 2010 at 6:20 am
dark matter is believed existing whereever ammounts of matter are.
The relation between dark matter and galaxies is, that only the existance of dark matter would explain the odd rotation of those galaxies. Newtons law has predicted that the outer parts of galaxies would rotate much slower than it it is observed.
about dark matter and the universe itself…well… obviously most galaxies move away from each other even with dark matter in place. Reason: dark energy is believed to make the universe expand, or better the space between galaxies.
scientists think there is 73% dark energy, 23% dark matter and just 4% normal matter, these numbers may show why dark matter will not lead to a gravitational collapse.
References :
January 29th, 2010 at 6:25 am
Astro-physicists believe that that the Universe is critically balanced between being open and closed. They derive this fact from the observation of the large scale structure of the Universe. It requires a certain amount of matter to accomplish this result. Call it M.
One can estimate the total baryonic matter of the universe by studying Big Bang nucleosynthesis. This is done by connecting the observed He/H ratio of the Universe today to the amount of baryonic matter present during the early hot phase—when most of the helium was produced. Once the temperature of the Universe dropped below the neutron-proton mass difference, neutrons began decaying into protons. If the early baryon density was low then, it was hard for a proton to find a neutron with which to make helium, before too many of the neutrons decayed away—to account for the amount of helium we see today. So, by measuring the He/H ratio today, we can estimate the necessary baryon density shortly after the Big Bang, and, consequently, the total number of baryons today. It turns out that you need about 0.05 M total baryonic matter to account for the known ratio of light isotopes. So, only 1/20 of the total mass of the Universe is baryonic matter.
Unfortunately, the best estimates of the total mass of everything that we can see with our telescopes is roughly 0.01 M. Where is the other 99% of the stuff of the Universe? Dark Matter!
So there are two conclusions. We only see 0.01 M out of 0.05 M baryonic matter in the Universe. The rest must be in baryonic dark matter halos—surrounding galaxies. And there must be some non-baryonic dark matter to account for the remaining 95% of the matter required to give omega, the mass of the Universe, in units of critical mass, equal to unity.
For those who distrust the conventional Big Bang models, and don’t want to rely upon fancy cosmology to derive the presence of dark matter, there are other more direct means. It has been observed in clusters of galaxies that the motion of galaxies within a cluster suggests that they are bound by a total gravitational force due to about 5-10 times as much matter as can be accounted for from luminous matter in said galaxies. And, within an individual galaxy, you can measure the rate of rotation of the stars about the galactic center of rotation. The resultant "rotation curve" is simply related to the distribution of matter in the galaxy. The outer stars in galaxies seem to rotate too fast for the amount of matter that we see in the galaxy. Again, we need about 5 times more matter than we can see via electromagnetic radiation. These results can be explained by assuming that there is a "dark matter halo" surrounding every galaxy.
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January 29th, 2010 at 6:59 am
Dark matter was invented by cosmologists to explain something that mat not exist.
Solar systems are satellite systems,they must conform to newtons laws or the planets would fly off into space.
A galaxy is not a satellite system so some other force must be in effect to explain their behavior.
The outer arms rotate locked in step with the galactic center and do not fly away.
Gravity is the initial source that forms galaxies but some other force orchestrates their evolution.
The engine that drives the galactic center must be some sort of neutron star activity,which diminishes the density of space.
To fill this gap space from the exterior flows in pulling the galactic material with it.
Galaxies are the end stage in the evolution of a universe and this activity is the mechanism of a Galaxy’s demise.
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