Four questions, classic or eccentric, with astrophysicist Jean-Pierre Luminet

Jean-Pierre Luminet, astrophysicist, world specialist in black holes, was a guest of “The Square Earth”. On this occasion, he answered some usual or eccentric questions about black holes. Some of these questions and many more are in his latest book, Black holes in 100 questions (Thailand, August 2022).




53 min

1. Why are black holes so fascinating?

They are truly fascinating objects! There are three main subjects which have always held the public’s favor. There is obviously the one about the plurality of inhabited worlds, extraterrestrial life. There is the subject on big bang because it touches deeply on a question of origin. It is a very strong topic.




53 min

And black holes touch on the question of the end of everything. As these are still poorly understood items that bring into play bizarre laws of physics, distortions of space and time, there really is a power of fascination. Jean-Pierre Luminet has noticed this fascination since he has been working with black holes, that is, for 45 years.

2. What is at the bottom of a black hole?

Some wonder where this matter and light go, including information, because information is related to matter and light. Does it get trapped in the black hole? Jean-Pierre Luminet answers immediately: We do not know!

At the moment, we can only send equations, which are necessarily imperfect, until we have a complete theory of gravitation, which would become quantum. At the bottom of a black hole there is what is called a singularity, i.e. a moving space-time node. Everything accumulates indefinitely in this node.

It is physical nonsense. So you have to be imaginative! There are possible scenarios that are not yet well-established theories. Scenarios, one of which is developed in several issues: the famous wormhole scenario, the kind of corridor doors, the stargate. These wormholes would allow us to pass through a large black hole and emerge elsewhere in spacetime. At the moment, we cannot know what is at the bottom of a black hole!

3. Could we be eaten by a black hole on Earth tomorrow?

For Jean-Pierre Luminet, it is far from being a far-fetched question – it is even relevant! The nearest known black hole is already fifteen light years away, so there are none absolutely no risk. Black holes are rare objects. Could a black hole burst into our solar system, devour the Earth and consume the Sun? The answer is clearly no. The probability is absolutely zero.

Black holes, like other objects in the universe, are subject to general gravitational motion. We don’t know all the black holes, but for the ones we do know, we know their trajectories. There are no black holes anywhere near our solar system.

4. Are there black holes of all sizes?

It is a question that Jean-Pierre Luminet particularly develops in his book. The answer is yes!

There is what is called stellar black holes. These are the black holes formed by the collapse of the cores of massive stars. They form only up to ten, thirty or forty times the mass of the Sun, for relatively modest sizes of a few tens of kilometers.

And then there is giant black holesthem supermassive black holes which is absolutely fascinating, with the latest breaking news, the giant black hole at the center of the galaxy, which is 4 million times the mass of the Sun. Earlier, there was the first telescope image of 2019, Messier 87, which is 6 billion times the mass of the Sun, 40 billion kilometers in diameter. But these are extraordinarily far away.

🎧 Listen to this exciting show in its entirety.




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