What is Dark Matter ( HD Space Documentary )
Δημοσιεύτηκε στις 14 Ιουλ 2015
What is Dark Matter ( HD Space Documentary )
Dark
matter is a hypothetical kind of matter that cannot be seen with
telescopes but would account for most of the matter in the universe. The
existence and properties of dark matter are inferred from its
gravitational effects on visible matter, radiation, and the large-scale
structure of the universe. Other than neutrinos, a form of hot dark
matter, it has not been detected directly, making it one of the greatest
mysteries in modern astrophysics.
Dark matter neither emits nor
absorbs light or any other electromagnetic radiation at any significant
level. According to the Planck mission team, and based on the standard
model of cosmology, the total mass–energy of the known universe contains
4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy.[2][3]
Thus, dark matter is estimated to constitute 84.5% of the total matter
in the universe, while dark energy plus dark matter constitute 95.1% of
the total mass–energy content of the universe.[4][5][6]
Astrophysicists
hypothesized dark matter because of discrepancies between the mass of
large astronomical objects determined from their gravitational effects
and the mass calculated from the observable matter (stars, gas, and
dust) that they can be seen to contain. Dark matter was postulated by
Jan Oort in 1932, albeit based upon flawed or inadequate evidence, to
account for the orbital velocities of stars in the Milky Way and by
Fritz Zwicky in 1933 to account for evidence of "missing mass" in the
orbital velocities of galaxies in clusters. Adequate evidence from
galaxy rotation curves was discovered by Horace W. Babcock in 1939, but
was not attributed to dark matter. The first to postulate dark matter
based upon robust evidence was Vera Rubin in the 1960s–1970s, using
galaxy rotation curves.[7][8] Subsequently many other observations have
indicated the presence of dark matter in the universe, including
gravitational lensing of background objects by galaxy clusters such as
the Bullet Cluster, the temperature distribution of hot gas in galaxies
and clusters of galaxies and, more recently, the pattern of anisotropies
in the cosmic microwave background. According to consensus among
cosmologists, dark matter is composed primarily of a not yet
characterized type of subatomic particle.[9][10] The search for this
particle, by a variety of means, is one of the major efforts in particle
physics today.[11]
Although the existence of dark matter is
generally accepted by the mainstream scientific community, some
alternative theories of gravity have been proposed, such as MOND and
TeVeS, which try to account for the anomalous observations without
requiring additional matter. However, these theories cannot account for
the properties of galaxy clusters.[12]
Dark
matter is a hypothetical kind of matter that cannot be seen with
telescopes but would account for most of the matter in the universe. The
existence and properties of dark matter are inferred from its
gravitational effects on visible matter, radiation, and the large-scale
structure of the universe. Other than neutrinos, a form of hot dark
matter, it has not been detected directly, making it one of the greatest
mysteries in modern astrophysics.
Dark matter neither emits nor
absorbs light or any other electromagnetic radiation at any significant
level. According to the Planck mission team, and based on the standard
model of cosmology, the total mass–energy of the known universe contains
4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy.[2][3]
Thus, dark matter is estimated to constitute 84.5% of the total matter
in the universe, while dark energy plus dark matter constitute 95.1% of
the total mass–energy content of the universe.[4][5][6]
Astrophysicists
hypothesized dark matter because of discrepancies between the mass of
large astronomical objects determined from their gravitational effects
and the mass calculated from the observable matter (stars, gas, and
dust) that they can be seen to contain. Dark matter was postulated by
Jan Oort in 1932, albeit based upon flawed or inadequate evidence, to
account for the orbital velocities of stars in the Milky Way and by
Fritz Zwicky in 1933 to account for evidence of "missing mass" in the
orbital velocities of galaxies in clusters. Adequate evidence from
galaxy rotation curves was discovered by Horace W. Babcock in 1939, but
was not attributed to dark matter. The first to postulate dark matter
based upon robust evidence was Vera Rubin in the 1960s–1970s, using
galaxy rotation curves.[7][8] Subsequently many other observations have
indicated the presence of dark matter in the universe, including
gravitational lensing of background objects by galaxy clusters such as
the Bullet Cluster, the temperature distribution of hot gas in galaxies
and clusters of galaxies and, more recently, the pattern of anisotropies
in the cosmic microwave background. According to consensus among
cosmologists, dark matter is composed primarily of a not yet
characterized type of subatomic particle.[9][10] The search for this
particle, by a variety of means, is one of the major efforts in particle
physics today.[11]
Although the existence of dark matter is
generally accepted by the mainstream scientific community, some
alternative theories of gravity have been proposed, such as MOND and
TeVeS, which try to account for the anomalous observations without
requiring additional matter. However, these theories cannot account for
the properties of galaxy clusters.[12]
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