Current News



Q&A: She discovered the black hole at the center of our galaxy. This week, she finally saw it

Corinne Purtill, Los Angeles Times on

Published in News & Features

We’ve just discovered these objects at the center of the galaxy that seem to stretch out as they get close to the black hole, then become more compact. They’re called tidal interactions. If you think of the movie “Interstellar” with that big giant tidal wave, this would be like a big tidal wave that just lifts off the planet. If we’re seeing stars having those kinds of interactions, it means that the star has to be, I don’t know, a hundred times larger than anything we predicted to exist in this region. So that makes you scratch your head.

Does the new image of Sgr A* reinforce your finding that, for now, Einstein’s theory of general relativity seems to do the best job of explaining how gravity operates throughout the universe?

Yes. Absolutely. Black holes kind of represent the breakdown of our understanding of how gravity works. We don’t know how to make gravity and quantum mechanics work together. And you need those two things to work together to explain what a black hole is, because a black hole is strong gravity plus an infinitesimally small object.

Wait, what? I thought black holes were huge.

No. The image is of the phenomena that happens around the black hole. The black hole has no finite size, but there is this abstract size of the event horizon, which is the last point that light can escape. And then the gravitational interaction with local light gets concentrated in this ring that’s two-and-a-half times bigger that the event horizon.


Anyway, we know that black holes represent the breakdown of our knowledge. That’s why everyone keeps testing Einstein’s ideas about gravity there, because at some point you expect to see what you might call the expanded version of gravity, in the same way that Einstein was the expanded version of Newton’s version.

Is it fair to say that Newton’s laws do a decent job of explaining how gravity works here on our little planet, but we need Einstein once we head out into the universe?

Yes, except for what we take for granted today: our cellphones. The fact that we can find ourselves so well on Google or Waze or your favorite traffic app is because GPS systems position your phone with respect to satellites going around the Earth. Those systems have to use Einstein’s version of gravity. So, yes. We could use Newton until we cared about things like this.

©2022 Los Angeles Times. Visit at Distributed by Tribune Content Agency, LLC.


blog comments powered by Disqus