At the local science fair at IPFW recently, students got to try their hand at testing scientific hypotheses. Most of the ideas were tested pretty much immediately after the students thought about them. The astronomy community just got a lesson in how the testing of an idea sometimes takes a bit longer.
The astronomers who made this discovery built a specialty radio dish at the South Pole. The air there is especially dry and still, making it wonderful for precise observations. However, it also required astronomers to spend many months there every year doing the observations. The group built their own equipment because they needed instruments more sensitive and stable than had ever been built before. The instruments were sensitive to temperature changes less than a millionth of a degree. I am somewhat amazed that they were able to build and run something so exquisitely precise.
What they detected was phenomenal. For the first time, this group was able to measure a special, slight twisting of the afterglow of the Big Bang. Light like the afterglow can have an orientation. When the afterglow’s orientations from different directions are compared, the orientation appears to twist around, forming small circles. This twisting can only be caused by a couple of things. Through careful measurement, they were able to determine that it was caused by a super-fast expansion of the universe when it was less than a second old.
This super-fast expansion is called inflation. It was first proposed in the 1980s (I think the word was intended as a bit of a joke) It describes the currently visible universe when it was much, much younger and smaller. Our currently visible universe is about 90 billion light-years across. In the past, our part of the universe was significantly smaller. When the universe was about 10 to 36 seconds old, our part of the universe was smaller than an atom. Inflation describes how it grew to about the size of your arm. This rapid growth affected many things about the universe that are observed. However, it made a very specific prediction about the twisting of the Big Bang’s afterglow. It actually took about 16 years of work by astronomers to realize this connection. Even then, it required extrapolating far beyond standard laboratory physics. The energies are about a trillion times larger than what we can create in the most powerful lab experiments.
When astronomers do extrapolations, the need to have some prediction confirmed is especially strong. The fact that so many scientists spent so much time building equipment and operating it in a place as difficult as the South Pole is a testament to their perseverance. Nature, however, does not always reward perseverance. Alan Guth, one of the physicists who developed inflation, summarized much of the feeling in the astronomy community when he said: Nature did not have to be so kind, and the theory didn’t have to be right.