Why do black holes emit high energy photons ?

Black holes are very dense objects living in the universe. Their density is about 10¹⁰ times the density of our sun. Such a density means that close to their core, under a given radius, nothing can escape, not even light.

A lot of scientists imagined such ‘holes’ where nothing can escape. Einstein was the first to actually find a good scientific theory to model them, one century ago. However, we have only been recently able to observe them directly (the famous photo of a black hole, April 2019).

In this article, we’ll discuss how a black hole can still emit a lot of energy (in the form of light). This paradoxical phenomenon shows that black holes are really strange and fascinating objects !

Galileo, Newton or Einstein ?

A bit of history

Ancient civilisations (egyptians, greeks, chinese) already had a rather good understanding of the law of physics, and especially gravity, since we can observe its effect every single second in our lives. Copernic and then Galileo advocated that objects movements in a gravitational field do not depend on their mass. As a consequence, every object thrown from a tower will arrive at the bottom at exactly the same time (+- epsilon because of air). Also, Earth is turning around the Sun, as every other…