What is Hubble's Law? What is the significance of Hubble's Law?

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Hubble's Law states that galaxies are moving apart from each other and that the farther away they are, the faster they are moving.

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In 1929, Edwin Hubble made an announcement that has become foundational for modern astronomy. His announcement said that almost all galaxies were moving away from Earth. He additionally said that the universe was expanding, which could be seen by the fact that all galaxies were in fact moving away from each other as well. He determined this by examining the redshift in the light that was coming from those galaxies. The redshift was not uniform, either. The shift was larger for galaxies that are farther away; therefore, Hubble posited that the further away a galaxy is, the faster it is moving away from Earth. The velocity of each receding galaxy can be calculated mathematically by using this equation:

v = H x d.

V is the galaxy's outward velocity, d is the galaxy's distance from Earth, and H is Hubble's constant.

Hubble's discovery is important, because it gave astronomers foundational data for an expanding universe. The universe is not static with set boundaries. Hubble's work also applies to the current Big Bang theory. The idea is to rewind the universe's expansion, and the result is that all of the matter in the universe would have been contained at a point that then exploded and scattered all of the material throughout the universe. The expansion from that explosion is still happening, and things like cosmic background radiation add evidence to the theory. Hubble's expanding universe also gave cosmologists new ideas about how the universe will come to an end.

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