Which Came First, the Galaxy or the Black Hole?

Theoretical Physicist, Author, and Science Educator
At the heart of every galaxy like our own Milky Way lies a supermassive black hole, but scientists are unsure which develops first.
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TRANSCRIPT

Question: Are the supermassive black holes at the center of galaxies involved in the formation of those galaxies? (Submitted by Andy Speight)

Michio Kaku:  Well Andy, you ask a very touchy subject.  What came first, the chicken or the egg, the galaxy or the black hole?  We still don’t know.  First of all, if you want to see the black hole at the center of our own Milky Way galaxy go out tonight and look in the direction of Sagittarius.  That is where we have a super-massive black hole at the very center or our own backyard, the Milky Way galaxy.  It weighs two to three million times the mass of our sun. 

Now the latest theory about which came first is the following: First, we think that out of the big bang came dark matter, invisible matter.  If I held dark matter in my hand it would literally ooze its way right through my fingers, go right to the center of the earth, go to China and then go back and forth between China and my hand.  That is dark matter.  We think that dark matter begins to clump first because of gravity, then matter was attracted to the clumpiness creating the super-massive black hole and then later the galaxy itself began to form.  We have computer simulations about this, but still the relationship is not yet clear. 

Now remember, stars—we know almost everything about stellar evolution.  That is because the Pentagon has given us physicists billions of dollars to model hydrogen bombs and a star is nothing but a hydrogen bomb.  However, a galaxy consists of over a hundred billion stars, so it’s much more difficult to tell which came first, the black hole or the galaxy itself.