The clumps will grow, becoming more massive, and attracting more particles.Īs these compacted clumps of hydrogen and helium grow in density, they'll also heat up. Little knots, wrinkles, and flaws will begin attracting nearby particles of matter. Upon a star's death, matter will spill out into space in the form of new elements, creating new star-forming nebulae, continuing its circle of life. Others, like our Sun, will burn more slowly, and probably expire less dramatically. The heaviest and densest of these will die in massive supernova explosions. Some will be lucky to reach a few billion or trillion years of age. When stars are born in nebulae, lighting up in fusion, they will race through life. In this way, scientists discovered evidence and claim tested the Big Bang. He pointed them to mathematical calculations by astrophysicists that showed if the Universe did, in fact, begin with a Big Bang, it would have released a huge amount of energy in just the same frequency as this low, static hiss.
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They were baffled.įinally, a colleague at Princeton suggested the hiss might have something to do with the start of the Universe. They were surprised to hear the same low, static hiss wherever they aimed it.
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In 1964, two scientists in New Jersey, Arno Penzias and Robert Wilson, aimed a new, extra-sensitive radio antenna at outer space to discover what they could hear. In 1929, astronomer Edwin Hubble made observations from a powerful telescope showing that galaxies sped away from each other at an ever-increasing velocity. When the theory of an expanding Universe was first proposed by Georges Lemaître in the 1920s even the great physicist Einstein did not believe it. In Big History, we call this process of gathering evidence that supports a theory or idea "claim testing." It took decades from the time a few scientists proposed that the Universe was expanding until the point where the Big Bang hypothesis was generally accepted.