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Spiral nebulae
Vesto Slipher began examining the "spiral nebulae." -
Nebulae outside of the Milky Way
Carl Wirtz discovered a systematic redshift of nebulae and discovered that there are nebulae outside of the Milky Way. -
Theory of Relativity
Einstein published the Theory of Relativity, which is the geometric theory of gravitation. It states that when spacetime stretches around a massive object, the light travelling through that spacetime stretches too. -
Redshifting discovered
Vesto Slipher had now examined 25 "spiral nebulae" and found that most of them were highly redshifted. (most were moving away from earth at a high speed.) -
Expanding universe theory
Georges Lemaitre proposed a theory that everything in the universe was expanding or contracting. He believed that the universe was getting bigger, which would explain the Redshift. -
Radio waves in the Milky Way
Karl Jansky was supposed to find out what made a certain sound that was interfering with radio signals. He traced some of the noise to a certain region in the sky and his colleague discovered that the period of the signal corresponded to a sidereal day, which is the length of time that the stars come back into the same alignment as the day before. They turned out to be radio waves emitted from the center of the Milky Way galaxy. -
Hubble's Law
Edwin Hubble proved the universe was expanding in a paper he wrote. He proved this by working with Milton Humason to measure the Doppler shift of several galaxies, proving that the spiral nebulae were galaxies, and measuring their distances by observing Cepheid variable stars. -
Light from the atoms's creation theory
Ralph Alpher and Robert Herman believed that if the Big Bang theory was accurate, we could see the glow of light from when atoms first formed, when the universe was about 300,000 years old. Since the universe has been expanding for billions of years,the light would have been redshifted by a factor of 1,000, and would only be able to be detected as microwaves now. -
Atomic nuclei theory
George Gamow published a paper called "The Origin of Chemical Elements." The paper explains his theory that after the big bang, atomic nuclei were built up by the successive capture of neutrons by the initially formed pairs and triplets.He advocated and developed Lemaitre's big bang theory. -
Microwave wavelengths theory
Robert Dicke and his colleagues hypothesized that the entire universe is pervaded by a background radiation of microwave wavelengths—the remnant of the intense thermal radiation associated with the big bang -
Light from the atoms's creation confirmed
Arno Penzias and Robert Wilson of Bell Labs announced they had identified the light Ralph Alpher and Robert Herman were talking about, which provided very strong evidence to support the Big Bang theory. -
Holmdel Horn Antenna
Arno Penzias and Robert Wilson used this in 1964 and 1965 to map signals from the Milky Way, and it helped them discover the CMB. The CMB is "noise" left over from the creation of the universe. -
Cosmic Background Explorer (COBE) is launched
COBE precisely measured and mapped the oldest light in the universe, which is the cosmic microwave background. The cosmic microwave background radiation is a remnant of the Big Bang. COBE proved that the big bang theory was how the universe was created. -
Hubble Space Telescope launched
The Hubble is one of the world's most powerful space telescopes. It has been measuring the distances between nearby galaxies and the recent rate of the universe’s expansion since it was launched. The measurements allow scientists to predict how the early universe would have evolved to the expansion rate it now has. -
Wilkinson Microwave Anisotropy Probe (WMAP) is launched
The purpose of WMAP was to create extremely precise full-sky maps of the cosmic microwave background and improve on maps created by COBE. During each six-month orbit, WMAP took a complete picture of the sky. It proved the universe is flat and is 13.77 billion years old.
