Black Holes: Gravity's Relentless Pull

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Black Holes: Gravity's Relentless Pull
What happens when black holes collide?

It is possible for two black holes to collide. Once they come so close that they cannot escape each other's gravity, they will merge to become one bigger black hole. Such an event would be extremely violent. Even when simulating this event on powerful computers, we cannot fully understand it. However, we do know that a black hole merger would produce tremendous energy and send massive ripples through the space-time fabric of the Universe. These ripples are called gravitational waves.

Nobody has witnessed a collision of black holes yet. However, there are many black holes in the Universe and it is not preposterous to assume that they might collide. In fact, we know of galaxies in which two supermassive black holes move dangerously close to each other. Theoretical models predict that these black holes will spiral toward each other until they eventually collide.

Gravitational waves have never been directly observed. However, they are a fundamental prediction of Einstein's theory of general relativity. Detecting them would provide an important test of our understanding of gravity. It would also provide important new insights into the physics of black holes. Large instruments capable of detecting gravitational waves from outer space have been built in recent years. Even more powerful instruments are under construction. The moment they detect their first gravitational wave, you are sure to hear about it!

Image illustrating: What happens when black holes collide?
One of the two LIGO gravitational wave observatories (Hanford, WA, USA). In two 2.5 mile long pipes laser beams are used to search for gravitational waves.