Dark Mysteries: Energy and Matter
By Dr. Richard Hammond
Posted: 12:40 June 3, 2008
It is the Roaring Twenties and the great telescopes of the day open a new window to the universe revealing strange and unpredictable behavior across the vast space of our cosmos. Astronomers discover entire new galaxies as we come to realize our majestic Milky Way is no more unique than a tree in a forest. Stranger yet, these great “island universes,” as galaxies were once called, millions of light years away, are speeding through space.
By the end of the decade, in 1929, the astronomer Edwin Hubble made an extraordinary discovery, bringing some order to flying galaxies as they rocket through space. He found that all of the distant galaxies are moving away from us, and equally intriguing, the farther the galaxy, the faster it moves. The only sensible interpretation of these bizarre revelations is to assume the universe itself is expanding.
Before this, for century after century, it was believed that the universe was a static, unbending framework. Although planets and other celestial objects may move, the cosmos, on the whole, is as rigid as granite. In the preceding decade Albert Einstein developed his famous General Theory of Relativity. He even went so far as to apply his equations to the entire cosmos, giving a mathematical structure for our universe as had never been done. But he failed! Unable to let go of the abiding model of a static universe, Einstein went so far as to alter his theory, adding a “cosmological constant,” so that his theory could accommodate a frozen universe. But Hubble’s observations destroyed this age-old notion, as we finally came to understand our universe is growing every day.
In the decades following Hubble’s result, the evidence piled higher and higher, and Hubble’s ideas were validated. The only debate that remained dealt with the rate of expansion. Since gravity is an attractive force, it was realized that all of the countless galaxies pull on each other, and so, the expansion was expected to be slowing down. Astronomers were so confident that the expansion was slowing down they coined the term deceleration parameter, which would describe the quantitative rate of deceleration. The biggest remaining debate was whether the universe, though slowing, would expand forever, or at some future time reach a maximum size and stop, and then begin its inevitable journey to final collapse—the big crunch.
Astronomers continued making careful measurements of the most distant galaxies in the universe, using every scrap of physics and ingenuity to calculate the speed of these distant worlds. Nothing shocked the community more than a paper published in 1998, describing the results of these meticulous measurements: the rate of expansion of the universe is increasing!
All of the mass and energy in the universe should act like cosmic brakes, slowing the expansion and pulling all of the galaxies together, but now we had to wonder if some new, mysterious force could be pushing everything apart. All of the mass and energy that we have ever observed tends to pull things together, and no one has ever observed the kind of energy that could push our far-flung galaxies apart at ever increasing rates. This was so shocking that even the deceleration parameter was misnamed, so now we find that this number is in fact negative, the mathematical way of saying we are suffering a positive acceleration.
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