Nicolien Janssens

Black holes: spending some more time on time

In the latest episode of Talk That Science, I talked with Sera Markoff about black holes. I knew black holes especially for their ability to absorb infinite amounts of matter. I was thinking of all sorts of physical matter, like stones, planets and stars. What I had not thought of, however, was that black holes even absorb time!

Roughly, this works as follows. As I just said, black holes can absorb infinite amounts of matter. As more and more matter goes into the black hole, the black hole becomes heavier and heavier. This means a black hole is a very tiny point, with lots of weight. Now the thing is that weight influences time: weight curves space-time. This might sound strange but we are actually familiar with it. This is what we call gravity! This is the force that ensures that we stay on earth and prevents us from floating around in the air. Because space is curved, the time to travel from a certain distance becomes longer. You can see this in the image below.

Of course, the difference is so small that we are not going to notice this. But still, is the idea not already mind blowing?! Making this podcast has really opened my eyes regarding time and taught me a lot about the relation of space, time and gravity. I had always thought that time was a static fact, but I now know that this is not the case. Yet, new questions arise in my head. Because what does this mean for our notion of time? What is time exactly, is it something invented by humans or something out there in the world? And what does it mean for space and time to be curved? Well, I guess a good topic for a future podcast episode, whatever ‘future’ may mean ;)