The End of Cosmology?
http://www.sciam.com/article.cfm?id=the-end-of-cosmologyAn accelerating universe wipes out traces of its own origins
By Lawrence M. Krauss and Robert J. Scherrer
A decade ago astronomers made the revolutionary discovery that the expansion of the universe is speeding up. They are still working out is implications.
The quickening expansion will eventually pull galaxies apart faster than light, causing them to drop out of view. This process eliminates reference points for measuring expansion and dilutes the distinctive products of the big bang to nothingness. In short, it erases all the signs that a big bang ever occurred.
To our distant descendants, the universe will look like a small puddle of stars in an endless, changeless void.
What knowledge has the universe already erased?
One hundred years ago a Scientific American article about the history and large-scale structure of the universe would have been almost completely wrong. In 1908 scientists thought our galaxy constituted the entire universe. They considered it an ?island universe,? an isolated cluster of stars surrounded by an infinite void. We now know that our galaxy is one of more than 400 billion galaxies in the observable universe. In 1908 the scientific consensus was that the universe was static and eternal. The beginning of the universe in a fiery big bang was not even remotely suspected. The synthesis of elements in the first few moments of the big bang and inside the cores of stars was not understood. The expansion of space and its possible curvature in response to matter was not dreamed of. Recognition of the fact that all of space is bathed in radiation, providing a ghostly image of the cool afterglow of creation, would have to await the development of modern technologies designed not to explore eternity but to allow humans to phone home.
It is hard to think of an area of intellectual inquiry that has changed more in the past century than cosmology, and the shift has transformed how we view the world. But must science in the future always reflect more empirical knowledge than existed in the past? Our recent work suggests that on cosmic timescales, the answer is no. We may be living in the only epoch in the history of the universe when scientists can achieve an accurate understanding of the true nature of the universe.
A dramatic discovery almost a decade ago motivated our study. Two different groups of astronomers traced the expansion of the universe over the past five billion years and found that it appears to be speeding up. The source of this cosmic antigravity is thought to be some new form of ?dark energy? associated with empty space. Some theorists, including one of us (Krauss), had actually anticipated this new result based on indirect measurements, but in physics it is direct observations that count. The acceleration of the universe implies that empty space contains almost three times as much energy as all the cosmic structures we observe today: galaxies, clusters and superclusters of galaxies. Ironically, Albert Einstein first postulated such a form of energy to keep the universe static. He called it the cosmological constant [see Cosmological Antigravity, by Lawrence M. Krauss; Scientific American, January 1999].
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