Astronomy Question: Light and The Universe?
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David asks:
If I understand it right, If we look back to the Big Bang, 13.7 Billion l.y or so, and we look in the opposite direction we still can see the BB, 13.7 Billion l.y; no matter what direction we look, that is what we see. Seemingly one might think we are at the center of this Universe, but we know that is not so.
Would you be kind enough to de-confuse me on this?
Excellent question David!
Many people assume that since the Universe is estimated to be just under 14 billion years old, the universe is just under 14 billion light years in size. (A light year is the distance light travels in a year) Consider the radius of the Earth, at about 6,400 kilometers, yet on a clear day, the average person can only see to about 5km (distance to horizon).
With advances in science, we’ve learned that for a brief period of time, the Universe may have expanded faster than the speed of light. (Note: According to Einstein’s theory of relativity, while nothing with mass can travel through space faster than the speed of light, space itself has no such restriction) Given the theorized early superluminal (faster than light) expansion of The Universe and current expansion rates (Hubble Constant), our true “observable” distance estimates are closer to about 46 billion light years. Some of the most distant objects we’ve seen are around 30 billion light years away.
Keep in mind also, that we can’t “see” the Big Bang – only what we believe to be evidence for it.
If you are interested in learning more, you can read up on “Cosmic Microwave Background” and “The Hubble Constant”.
So, to a certain extent we ARE at the center of The Universe. More to the point, we are at the center of our OBSERVABLE universe, as there may quite possibly be no real “center”, “beginning” or “end” to The Universe, but those theories a more along the lines of theoretical physics and cosmology, which aren’t my specialty.
Ray Sanders is a Sci-Fi geek, astronomer and blogger. Currently researching variable stars at Arizona State University, he writes for Universe Today, The Planetary Society blog, and his own blog, Dear Astronomer
2012-12-04 08:05:35
Source: http://www.dearastronomer.com/2011/01/11/light-and-the-universe/
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