# The Reason Scientists Can Calculate the Distance and Velocity of Galaxies and Stars

Scientists understand the immense distance between galaxies and stars because of American astronomer Edwin Hubble’s theory of the expanding universe, as it is now understood that galaxies drift from the observer proportional to their distance, meaning the further a star is, the faster it continues to move away from the observer. This phenomenon is referred to as “Hubble–Lemaître’s Law”. Astronomers can calculate how fast a star is moving away from the Earth by observing the Doppler shift of the light it projects, as yellow light becomes red light as a star moves away and yellow light becomes blue light as it approaches closer. A formulae is then used to calculate the distance from the source point. Redshift is observed throughout the universe which confirms that the universe is indeed expanding at a phenomenal rate of speed

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