DARK ENERGY

My roomate just bought a ticket to go to London in September and was so excited--she was sitting by the printer, trying to figure out how to print her boarding pass so she could nail it to her bedroom wall and anticipate the trip all summer long. I had to let her down easy. You only really get a confirmation number and receipt now--you get your boarding pass later, at the airport. Tangible proof is often very satisfying. But, in physics, almost everything is found out through indirect evidence, since our eyes cannot see all the way into deep space or inside of an atom. But, how indirect is too indirect? I recently saw Dr. Radu Popa speak at USC, and he had a very pessimistic view of dark energy as a suitable scientific theory. "Dark energy is a placeholder," he said, "physicist simply sub the word for a hole in their calculations about gravity and our universe." As far as i understand, the reasoning that led to the naming of dark energy was this: for everything in the universe to keep expanding like it does, some force must exist that opposes gravity which holds planets together. Dark energy is this force. It kind-of acts like a field, keeping our universe relatively flat. But, we have not observed direct evidence of it, only the fact that gravity is not crunching the universe together and a mathematical hole that might correspond to this. So, that led me to think....how much and what kind of indirect evidence is needed to debunk a theory? I think Popa's point was that it is limiting to human thought to let a timid hypothesis become a theory or paradigm--people will trust your authority and stop questioning it. It's a good point, but, in this case, i think putting some sort of semi-tangible name on a theory is a necessary part of progress-- in the case of dark energy, or the Greek concept of ether and humors, it gives working scientists something to disprove.