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Vesto Slipher
Vesto Slipher studied the universe. In 1912, he calculated the speed and direction of “spiral nebulae” by measuring the change in the wavelengths of light coming from them. Due to this, He discovered that most of them were moving away from us. At the time astronomers believed these to be stars in the Milky Way but later discoveries have showed that these were indeed galaxies. -
William De Sitter
William De Sitter was a Dutch Mathematician whose discoveries helped prove that the universe is expanding. In 1916-1917, he published a series of when he published a series of papers in London that expanded on Einstein's general theory of relativity. De Sitter believed that instead of the universe being static and unchanging in size, it was constantly expanding. This theory was later supported by Edwin Hubble and even Einstein himself. -
Georges Lemaître
Georges LeMaitre proposed the Big Bang Theory stating that the universe was initially a singular "primeval atom" that later exploded. This explosion allowed for the formation of space, time and the continuous expansion of the universe. -
Edwin Hubble
Edwin Hubble was able to prove that galaxies are moving away from us. By studying the light emitted by several different galaxies, he discovered that the light disordered around the red end of the spectrum. Through this, he concluded that our universe was expanding outward causing the galaxies to move away as well. This phenomenon is now known as the redshift. He also made a discovery known as "Hubble's Law" which stated that the further away a galaxy is, the faster it is moving away from us. -
Arno Penzias and Robert Wilson
In 1964, Arno Penzias and Robert Wilson discovered the Cosmic Microwave Background. They were experimenting with a 6-meter radio telescope when they identified a hiss in all directions of the sky. According to their findings, the sky's temperature was a few degrees above absolute zero. They later recognized this as cosmic radiation from the start of the universe. This proved theories that predicted after the big bang there would be a release of radiation. -
COBE
On November 18, 1989, COBE also known as "Cosmic Background Explorer was launched into the universe. Its purpose was to provide accurate measurements of the radiation in the universe referred to as the "Cosmic Microwave Background Radiation." This information helped NASA map out the earliest hot and cold spots throughout most of the radiation. -
Hubble Space Telescope
On April 24, 1990, the Hubble Space Telescope was launched. This helped scientists learn more about the solar system and the beginning of the universe. It has provided images of space which helped with estimating the age of our universe.