Before our universe gave birth to any of the stuff that fills it -- the particles that make up stars and planets and people, and the radiation they produce -- there was only space. And in the first tiny fraction of a second, it expanded at a staggering rate, pushed outward by an unknown form of energy.
That period of cosmic inflation ended quickly. The universe continued to expand, but at a much slower rate. And in fact, the rate of expansion slowed down until the last few billion years, when it seems to have picked up again -- the result of a mysterious "dark energy."
Today, scientists are studying both eras of expansion -- cosmic inflation and the modern era of dark energy. And one question they're pondering is whether dark energy is a sort of "watered-down" version of inflation. University of Texas physicist Sonia Paban explains:
PABAN: Probably it is a similar mechanism that's causing both periods. The difference is that the scale ... is many orders of magnitude smaller now than it was during the period of cosmic inflation. It's a similar feature, just the energy scales are much different. And we don't know if what we have now will be something that continues forever, or if it's something that is going to end like the cosmic inflation did.
Several experiments are probing the mystery of dark energy. Their findings will tell us not only about the fate of the universe, but perhaps something about its beginning as well.
Script by Damond Benningfield, Copyright 2011