The Origin of the Universe – Space Documentary

The Big Bang Since the early part of the 1900s, one explanation of the origin and fate of the universe, the Big Bang theory, has dominated the discussion. Proponents of the Big Bang maintain that, between 13 billion and 15…

The Big Bang

Since the early part of the 1900s, one explanation of the origin and fate of the universe, the Big Bang theory, has dominated the discussion. Proponents of the Big Bang maintain that, between 13 billion and 15 billion years ago, all the matter and energy in the known cosmos was crammed into a tiny, compact point. In fact, according to this theory, matter and energy back then were the same thing, and it was impossible to distinguish one from the other.

Adherents of the Big Bang believe that this small but incredibly dense point of primitive matter/energy exploded. Within seconds the fireball ejected matter/energy at velocities approaching the speed of light. At some later time—maybe seconds later, maybe years later—energy and matter began to split apart and become separate entities. All of the different elements in the universe today developed from what spewed out of this original explosion.

Big Bang theorists claim that all of the galaxies, stars, and planets still retain the explosive motion of the moment of creation and are moving away from each other at great speed. This supposition came from an unusual finding about our neighboring galaxies. In 1929 astronomer Edwin Hubble, working at the Mount Wilson Observatory in California, announced that all of the galaxies he had observed were receding from us, and from each other, at speeds of up to several thousand miles per second.

The Redshift

To clock the speeds of these galaxies, Hubble took advantage of the Doppler effect. This phenomenon occurs when a source of waves, such as light or sound, is moving with respect to an observer or listener. If the source of sound or light is moving toward you, you perceive the waves as rising in frequency: sound becomes higher in pitch, whereas light becomes shifted toward the blue end of the visible spectrum. If the source is moving away from you, the waves drop in frequency: sound becomes lower in pitch, and light tends to shift toward the red end of the spectrum. You may have noticed the Doppler effect when you listen to an ambulance siren: the sound rises in pitch as the vehicle approaches, and falls in pitch as the vehicle races away.

To examine the light from the galaxies, Hubble used a spectroscope, a device that analyzes the different frequencies present in light. He discovered that the light from galaxies far off in space was shifted down toward the red end of the spectrum. Where in the sky each galaxy lay didn’t matter—all were redshifted. Hubble explained this shift by concluding that the galaxies were in motion, whizzing away from Earth. The greater the redshift, Hubble assumed the greater the galaxy’s speed.

Some galaxies showed just a slight redshift. But light from others was shifted far past red into the infrared, even down into microwaves. Fainter, more distant galaxies seemed to have the greatest redshifts, meaning they were traveling fastest of all.

An Expanding Universe

So if all the galaxies are moving away from Earth, does that mean Earth is at the center of the universe? The very vortex of the Big Bang? At first glance, it would seem so. But astrophysicists use a clever analogy to explain why it isn’t. Imagine the universe as a cake full of raisins sitting in an oven. As the cake is baked and rises, it expands. The raisins inside begin to spread apart from each other. If you could select one raisin from which to look at the others, you’d notice that they were all moving away from your special raisin. It wouldn’t matter which raisin you picked, because all the raisins are getting farther apart from each other as the cake expands. What’s more, the raisins farthest away would be moving away the fastest, because there’d be more cake to expand between your raisin and these distant ones.

That’s how it is with the universe, say Big Bang theorists. Since the Big Bang explosion, the reason, the universe has been expanding. Space itself is expanding, just as the cake expanded between the raisins in their analogy. No matter whether you’re looking from Earth or from an alien planet billions of miles away, all other galaxies are moving away from you as space expands. Galaxies farther from you move faster away from you because there’s more space expanding between you and those galaxies. That’s how Big Bang theorists explain why light from the more distant galaxies is shifted farther to the red end of the spectrum. In fact, most astronomers now use this rule, known as Hubble’s law, to measure the distance of an object from Earth—the bigger the redshift, the more distant the object.

#documentary #universe #space #spacetime

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