Dark Matter
[Key Words]
[General] [Composition of Dark Matter]
[Who
Proposed the Existence of Dark Matter]
[Where is Dark Matter]
General
Over 90% of the universe is invisible. This invisible
stuff is known as dark matter. Dark matter holds together galaxies
that spin very fast and controls the rate at which the universe
expands. Because of this, it has a nick name of "cosmic
glue." Until very recently, cosmologists did not know the
composition of dark matter. The main way dark matter was detected
was by viewing its gravitational effects on other objects.
Composition
of Dark Matter
There are many different theories of the composition of dark
matter. One is that dark matter is the remnants of white
dwarfs known as black dwarfs. Brown
dwarfs may also be a type of dark matter. Black holes
are another element that might make up dark matter.
Who
Proposed the Existence of Dark Matter?
In the 1930s, the Swiss astronomer Fritz Zwicky deducted
that dark matter must exist after realizing that the known mass
of the matter in galaxies is not enough to a cluster of galaxies
together. Each independent galaxy moves too fast for the galaxies
to stay in a cluster, yet they were not spinning away from each
other. Extra gravity must be coming from somewhere.
In the 1970s, Vera Rubin found the same thing to
be true in a single galaxy. Stars that were on the outside of the
galaxy were rotating at the same speed as stars that were closer
in to the middle. She concluded that there must be some
invisible, massive substance sounding the galaxy, creating
gravitational forces on all the stars.
Where is
Dark Matter?
Dark matter can be found in may places throughout the universe.
There may be huge superclusters full of dark matter. Dark matter
also may form halos around galaxies, and are spread all
throughout galaxies. Hence there word dark in dark matter.
Because this matter is so dark, it is very elusive and very
difficult to detect. scientists have not discovered any absolute
facts about dark matter, although recent discoveries such as
black holes and Brown and Black Dwarfs seem to support the theory
of dark matter.
Previous Topic: The
Expanding Universe
[Key Words]
[General] [Composition of Dark Matter]
[Who
Proposed the Existence of Dark Matter]
[Where is Dark Matter]
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