5 Facts about Gravity Waves from the Big Bang – The Countdown #44


Scientists have just spotted gravitational waves from the Big Bang! But, what are these waves? And why should we care about them? Here are five things you should know! I’m Sophie, and welcome to The Countdown. If you’ve been following the news, you may have heard about BICEP2. This stands for Background Imaging of Cosmic Extragalactic Polarization 2, a telescope located in Antarctica. BICEP2 uses 512 radiowave detectors to observe the cosmic microwave background, or CMB, which is the light leftover from the Big Bang. At the South Pole, BICEP2, and it’s sister detector, the Keck Array, can avoid noise that might disturb the CMB signal. The air is thin and dry, which makes it easier to detect microwaves. And without a large human population, there are no competing signals from cell phones or televisions. BICEP2 wasn’t just looking at the CMB, it was measuring the orientation of the CMB’s photons. Specifically, it was looking for a particular kind of curl in the light, called B-mode polarization. By mapping the polarization of the cosmic microwave background, over an area of the sky, researchers found a signature, left behind by gravitational waves. So, what are gravitational waves? According to Einstein, our universe is made up of a fabric called space-time. Heavy objects deform space-time, creating a curve that funnels smaller bodies towards bigger ones. This is how gravity works. But the deformation caused by larger objects doesn’t stay put, it can travel through the fabric of space-time, like a wave travelling down a string. These ripples are called gravitational waves, and they zip through space-time at the speed of light. The ripples can be produced when large objects accelerate quickly, like when two black holes spiral towards each other. But the gravitational wave detected by BICEP2 come from the time immediately after the Big Bang, and they prove that an event called “inflation” really occurred. With the Big Bang, our universe began expanding, a slow, even expansion would have created a universe with an uneven distribution of density and temperature. But, our universe is relatively even. So, in 1981, Alan Guthe proposed the expansion must have accelerated almost immediately after the Big Bang. This theoretical speed up, called inflation, would explain the smooth universe we see today. And it would also have produced gravitational waves strong enough to impact the cosmic microwave background. You can see how BICEP2’s discovery is a big deal. It reveals the presence of gravitational waves, and it proves the theory of inflation. Oh, and it also hints at the existence of a multi-verse. Inflation predicts the same forces that made space expand super quickly, also created pocket universes within our own. In fact, infinite pocket universes, giving us a multi-verse. Which means that somewhere out there, there might be exact copies of our galaxy, and our planet, and you! I’m Sophie Bushwick, and that’s your Countdown. For more space-y stuff, subscribe to the spacelab channel on youtube, or follow us on twitter @sa_spacelab. And if you’ve got any topics you’d like to see in the future, let us know in the comments. [Music]