3 things we learned about black holes

There are about 2 million black holes buried in the galaxy and though we've know about their existence for about two centuries, it's only in the last few decades that we've begun to understand how important they actually are to the universe.

So what did we learn from today from our guest Caleb Scharf, astrobiologist and author of 'Gravity's Engines?'

1) Blackholes are surprisingly small, although their mass is enormous. "They live in the center of pretty much every galaxy in the universe," said Scharf. "Some are a few million times the mass of our sun, but some of them are billion of times the mass of our sun. But they are incredibly compact. A super-massive blackhole, containing the mass of millions of suns, would only extend to the orbit of Neptune in our solar system." Which, in the universal scheme of things, is pretty small.

2) There are a heck of a lot of black holes out there. "In pretty much every large galaxy there is a super-massive black hole in the center. There is something about the way that galaxies grow and the way they generate stars that is intimately linked to black holes. There has been a joint evolution of these two things. They are linked somehow." We just don't know how.

3) We will probably never understand black holes. "When black holes consume matter, it vanishes for good. They have shut themselves off from the normal universe. We'll never know what is really going on inside. They are forever sealed off from us."

--Stephanie Curtis, social media host

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