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  • Before the big bang, scientists believe the entire vastness of the observable universe, including all of its matter and radiation, was compressed into a hot, dense mass just a few millimeters across.
  • This nearly incomprehensible state is theorized to have existed for just a fraction of the first second of time.
  • Big bang proponents suggest that some 10 billion to 20 billion years ago, a massive blast allowed all the universe’s known matter and energy”—even space and time themselves—to spring from some ancient and unknown type of energy.

What Is the Big Bang Theory?

” The universe originated billions of years ago in an explosion from a single point of nearly infinite energy density .
  • The Big Bang Theory is the leading explanation about how the universe began.
  • At its simplest, it says the universe as we know it started with a small singularity, then inflated over the next 13.8 billion years to the cosmos that we know today.
  • In the first second after the universe began, the surrounding temperature was about 10 billion degrees Fahrenheit (5.5 billion Celsius), according to NASA. The cosmos contained a vast array of fundamental particles such as neutrons, electrons and protons. These decayed or combined as the universe got cooler.
  • This early soup would have been impossible to look at, because light could not carry inside of it. “The free electrons would have caused light (photons) to scatter the way sunlight scatters from the water droplets in clouds,” NASA stated. Over time, however, the free electrons met up with nuclei and created neutral atoms. This allowed light to shine through about 380,000 years after the Big Bang.
    This early light — sometimes called the “afterglow” of the Big Bang — is more properly known as the cosmic microwave background (CMB). It was first predicted by Ralph Alpher and other scientists in 1948, but was found only by accident almost 20 years later. 
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  • An explosion implies that something exploded, or expanded, from one center point outward into space. In fact, the Big Bang theory suggests that space itself expanded.
  • The maps give rise to new mysteries, however, such as why the Southern Hemisphere appears slightly redder (warmer) than the Northern Hemisphere. The Big Bang Theory says that the CMB would be mostly the same, no matter where you look.
  • Examining the CMB also gives astronomers clues as to the composition of the universe. Researchers think most of the cosmos is made up of matter and energy that cannot be “sensed” with conventional instruments, leading to the names dark matter and dark energy. Only 5 percent of the universe is made up of matter such as planets, stars and galaxies.
  • The cosmic microwave background has been observed on many missions. One of the most famous space-faring missions was NASA’s Cosmic Background Explorer (COBE) satellite, which mapped the sky in the 1990s.
  • The theory maintains that, in the instant—a trillion-trillionth of a second—after the big bang, the universe expanded with incomprehensible speed from its pebble-size origin to astronomical scope. Expansion has apparently continued, but much more slowly, over the ensuing billions of years.
  • The glow of cosmic microwave background radiation, which is found throughout the universe, is thought to be a tangible remnant of leftover light from the big bang. The radiation is akin to that used to transmit TV signals via antennas. But it is the oldest radiation known and may hold many secrets about the universe’s earliest moments.
  • Scientists can’t be sure exactly how the universe evolved after the big bang. Many believe that as time passed and matter cooled, more diverse kinds of atoms began to form, and they eventually condensed into the stars and galaxies of our present universe.
  • The big bang theory leaves several major questions unanswered. One is the original cause of the big bang itself. Several answers have been proposed to address this fundamental question, but none has been proven—and even adequately testing them has proven to be a formidable challenge.
Categories: space