Allan Adams: MIT Associate Professor with focus on Theoretical Physics.
(Illustrated by Randall Monroe, of http://www.xkcd.com fame, a former NASA employee who now writes a science-themed webcomic)
If you look at the sky you see stars, but if you look further and further you see nothing. Beyond that nothingness is the afterglow of the Big Bang. This afterglow is nearly completely uniform at 2.7 degrees, but has cooled slightly in small patches (20 ppm). These tiny discontinuities are caused by Quantum Mechanical ‘wiggles’ during the Big Bang, that have been stretched across the universe.
Before the Big Bang, our universe was extremely dense like a metal bell. On March 17 something new was discovered. Like a metal bell, this original universe could be ‘rung’ by quantum mechanics, then it could produce gravitational waves (like the sound from a bell). Nowadays these gravitational waves have faded, but early on the waves caused small twists in the structure of light that we see. By searching the sky from the South Pole, researchers recently discovered these wiggles in the light coming from distant stars.
What this implies is that our universe is in a ‘bubble’. It is then possible that our ‘bubble’ is just one of many, even though we may never see the others.
further reading here: http://www.space.com/25100-multiverse-cosmic-inflation-gravitational-waves.html . The big key here was that in the first fractions of a second, the universe was expanding faster than the speed of light, with our ‘uniform’ universe an expansion of a very tiny point in the original tiny dense mass. Gravitational waves were an important feature of this model, but could never be identified until recently. If our universe condensed around one region and expanded outwards, it is likely others did likewise, hence the ‘bubble’ analogy.