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What is the Big Bang?

November 13, 2012

Hi, I’m Emerald Robinson, and in this “What Is” video, we’re going to discuss the Big Bang: the most accepted scientific theory of the origin of the universe.

According to the Big Bang theory, all of the matter that existed at the beginning of time was concentrated in an infinitely small, hot, dense mass called a “singularity.” About 13.7 billion years ago, the singularity suddenly expanded, and all of the matter was carried away from this point.

About one millionth of a second after the big bang, matter had cooled down to about ten thousand million degrees, cool enough to form protons, neutrons, and electrons, the building blocks of atoms. For the next three hundred thousand years the universe continued to expand and cool until the first atoms of hydrogen, the most abundant element in the universe, finally formed.

About one thousand million years after the big bang, the gravitational attraction between particles caused the accumulation of matter in large familiar formations such as stars, gas clouds, galaxies, and, later, planets and solar systems.

The first theory of an expanding universe was proposed by astronomer Georges Lemaitre. Three years later, another astronomer, Edwin Hubble, actually observed that galaxies were, in fact, moving away from one another by looking at the light coming from them. If a star is moving away from earth, its light becomes stretched into longer and longer wavelengths, toward the red end of light’s color spectrum. Evidence of this “redshift” is a major reason why many scientists accept the big bang theory.

Research suggests that the universe is still expanding. We’re not sure if the effects of the Big Bang will ever have an end point – that is, whether the universe will stop expanding, expand forever, or start to collapse back towards its center.

But we continue to look deep into space to answer this – and many other – questions about our universe.



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