Earlier today, a team of Harvard astrophysicists announced that, as part of their high-resolution BICEP2 experiment, they had discovered curls in the cosmic microwave background indicative of gravitational waves. NANOGrav physicist Michael Koop explains gravitational waves here (this video was produced before today’s press conference, back when we were still looking for evidence of gravitational waves, but the same theories apply):
Most media reports emphasize that the discovery of these curls further strengthens the case for the Big Bang, and it does, but the existence of the cosmic microwave background had already established an ironclad case. More relevantly, the finding makes the case that faster-than-light inflation, and not mere explosion, was the mechanism by which the Big Bang created the universe as we know it. But what today’s discovery does that might be more directly relevant to our day to day life is that it clearly establishes, on a cosmic scale, that gravity itself exists only in a purely relational sense—that it is something that can be given or taken away—and is not an intrinsic background property of the cosmos. The vast majority of theoretical physicists already believed this, but it hasn’t caught on among the general public because most of us aren’t conversant in theoretical physics.
Now that we have direct evidence that gravitational waves exist—now that it’s sensible to talk concretely and in a non-speculative sense about time before gravity, gravity moving outward, and so forth—we know that space itself is something that can expand or contract. The universe itself becomes something flexible, something malleable, as do all of the properties with which it is associated. And its status as such is no longer controversial, no longer assumed. It is simply the story that the evidence tells.