Evolution of the Universe According to the Big Bang

The discovery that the galaxies seem to be flying away from one another led astronomers to focus on a single model. According to this theory, our Universe began billions of years ago in a cosmic explosion known as the "big bang." The big bang set in motion the expansion of the Universe. As the Universe expanded it changed, giving rise to everything from webs of galaxies to stars to planets to you.

The Universe as a whole seems to follow the same physical laws that govern the world around us. Thanks to this fact, astronomers have been able to construct a robust theory of how the Universe began and evolved. Though they disagree about some aspects of this so-called big bang theory, most think it represents science's best effort to explain the nature of the Universe.

Like investigators at a crime scene, astronomers have been combing the Universe for physical evidence to test the big bang theory. The first evidence that turned up was predicted in advance but discovered by accident. Some scientists thought the big bang should still be visible as a faint glow of radio light filling the sky in all directions. In 1964 Arno Penzias and Robert Wilson discovered that light, called the cosmic background radiation. Other efforts were soon launched to confirm their discovery and to explore the nature of the background radiation.

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   Creation of the Universe