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Cosmology GapFill
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When discussing interstellar distances, measuring distances in metres starts being unhelpful. Instead, astrophysicists use units of distance like light years (= 9.46 × 1015 m, the distance travelled by light over the course of one year),
(= 1.50 × 1011 m, the average distance between the Sun and Earth) and
(= 3.09 × 1016 m, the distance to an object which subtends a distance of 1 arcsec over the course of the year as viewed from Earth).
Much of astrophysics relies on the principle, which states that the universe looks roughly the same at all locations; with this principle, scientists can't make predictions about other areas of the universe, or even assume that physics works the same way!
During the 1920s, something strange was noticed about distant galaxies - the further a galaxy was from Earth, the more the wavelength of light from that galaxy seemed to stretch out. This is due to an effect known as the effect, where the wavelength of a wave changes with the motion of the wave source relative to an observer; an increase in wavelength is known as red shift, and the furthest galaxies have the highest red shift.
This means that the distance to a galaxy can be determined from its red shift (and its recessional velocity), a relationship called law. This can be explained by the space between all galaxies expanding, so that the furthest points in space expand away from each other the quickest, implying that at some point the universe was once much smaller and more dense, in what is known as the .
The universe may even be expanding more quickly than expected, with causing inflation of space.
Much of astrophysics relies on the principle, which states that the universe looks roughly the same at all locations; with this principle, scientists can't make predictions about other areas of the universe, or even assume that physics works the same way!
During the 1920s, something strange was noticed about distant galaxies - the further a galaxy was from Earth, the more the wavelength of light from that galaxy seemed to stretch out. This is due to an effect known as the effect, where the wavelength of a wave changes with the motion of the wave source relative to an observer; an increase in wavelength is known as red shift, and the furthest galaxies have the highest red shift.
This means that the distance to a galaxy can be determined from its red shift (and its recessional velocity), a relationship called law. This can be explained by the space between all galaxies expanding, so that the furthest points in space expand away from each other the quickest, implying that at some point the universe was once much smaller and more dense, in what is known as the .
The universe may even be expanding more quickly than expected, with causing inflation of space.