Last week, we learned about two scientists who thought that their radio telescope was giving incorrect signals due to pigeon poop.
It turns out they discovered a kind of low intensity signal that permeates the entire universe, almost like a fog. It's called the cosmic microwave background. For this week's episode of Cosmically Curious, Nicole Gugliucci of Saint Anselm College tells us what that signal actually is.
Nicole Gugliucci: This signal all around the sky is kind of a glow, a leftover glow from a particular time in the universe, about 380,000 years after the Big Bang.
There's a whole lot of weird particle physics and stuff that happens in the early part of the universe. And early on, there are so many particles in a small region that light is bouncing off everywhere.
If you were standing in it, it'd be like standing in a fog. Light just bouncing off all these particles everywhere. You hit a point where the universe expands enough and cools down enough that some of these particles start to come together to form atoms. And the light now doesn't necessarily bounce between all the particles. It's now free to go flying throughout the universe. So that's like the edge of that fog from the early universe that we see in every direction that gives off this radio glow.
Patrick McNameeKing: That's super cool. But why was this an important discovery?
Nicole Gugliucci: At the time, there was still discussion about what the nature of the universe really was. The expansion of the universe — as discovered by Hubble and Humason earlier in the 20th century, from all these galaxies that they see flying apart from each other — indicated that, well, if they're all flying apart now, they must have all been really close at one point. And that glow is such a big feature of these models that it would be a really good piece of evidence that we were on the right track.
If you have questions about the night sky, send us an email at cosmic@nhpr.org.
