The Canadian Broadcasting Corporation has a smart and engaging radio show, Quirks & Quarks. Yesterday’s show focused on a big question: What happened at, and before, the Big Bang? Mavens queried included Robert Brandenberger, Paul Steinhardt, Justin Khoury, and of course me (otherwise it’s somewhat less likely that I’d be blogging about it, I guess). The blurb:
The Big Bang theory of the origin of our universe is widely accepted by the physics community. The idea that our universe started out as some infinitesimally small point, which expanded out to what we see today, makes a lot of sense. Except for one small thing. That initial point, called a singularity by physicists, is a physical impossibility. According to the models we have today, the temperature of the universe at that first moment would have had to be infinite, which mathematically makes no sense. Also, the singularity doesn’t do a good job of explaining where all the matter and energy we see today in the universe came from. So, physicists are increasingly starting to look at other branches of physics to see what they can do to replace the singularity with a more reasonable proposition, one which can actually be explained by existing science.
Listen here. As we’ve talked about on this very blog, the time is right to push our understanding of the universe back before the Big Bang and ask what was really happening. Current ideas are understandably vague, but the only way to improve them is to keep exploring.
One slight clarification, to those who listen: in the interview, I give an entropy-based argument against bouncing cosmologies. That’s appropriate for the ekpyrotic universe, but not necessarily for the most recent versions of the cyclic universe. In these models, the universe never really crunches; it keeps expanding, but at some point flares back to life — particles are created without space ever contracting. Some sort of thermodynamic sleight-of-hand is still being pulled — the entropy of the whole universe rises monotonically for all of eternity, which seems a bit fishy — but the argument is somewhat different.