What's in a white hole

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To answer this question, we must first say what a black hole is. This is understood to mean an object that generates such a strong gravitational field in its immediate vicinity that, due to the associated gravity, neither matter nor light or radio signals can escape from this environment. Since even light (i.e. the light particles, so-called photons or electromagnetic waves) cannot leave this area, in principle one cannot look into it and therefore speaks of a "black" hole. The General Theory of Relativity (GTR) provides information about its origin, because according to it, a sufficiently compact mass deforms space-time so strongly that a black hole is formed. The process of gives a clearer idea of ‚Äč‚Äčthis
Gravitational Collapse: Stars have a very large mass, so their gravitational force tries to compress them. But when a star has used the energy to counteract the force of gravity with its internal thermal pressure and to keep itself in balance, it can collapse into a black hole. Since the mass is retained, the density of the star increases across all boundaries. Such bodies bend (according to the mathematical equations of the GTR) the space-time around them so strongly that one could speak of a "hole", which is more precisely called an exact singularity. This singularity is surrounded by a space-time area from which neither matter nor information can get outside and whose limit is the so-called event horizon.
From the outside, however, one would observe that the collapse progresses more and more slowly and the volume never contracts to a single point, because the ever increasing gravity locally distorts the space and the passage of time.

Despite their "invisibility", black holes can be detected indirectly through the effects of the gravitational field, which causes the mass that has disappeared inside them in the outside area. (The best known is Sagittarius A *, in the constellation "Sagittarius" and the center of the Milky Way with a mass of approx. 4 million solar masses.)

A white hole describes an astronomical object of a hypothetical nature, the opposite of a black hole, so to speak. It ejects mass and everything inside it, and it is impossible to cross the above-mentioned event horizon from the outside in, since a speed higher than the speed of light would be required for this, which is however physically impossible. However, the ART allows mathematical solutions for the underlying equations, which correspond to a time reversal of a black hole and would result in precisely such properties for a white hole. It would therefore consist of a visible (!) Singularity which, for no apparent reason, suddenly breaks out into a star whose radius increases inexorably beyond the event horizon. Despite this mathematical solution to the ART equations, there is currently nothing to indicate that white holes must actually exist, especially since they have not yet been proven experimentally.

In this context, the term wormhole, also known as the "Einstein-Rosen Bridge", is often used. This theoretical structure is a system consisting of a black and a white hole and connects two places in the universe with each other. Figuratively speaking, both worlds are connected via a hole in which extreme gravitational forces prevail; Matter that falls into a black hole would be ejected from a white hole in another universe (or perhaps even in another part of that universe). Here, too, an insurmountable problem quickly arises. Because in order not to be crushed by the gravitational forces at the wormhole, we would have to have negative energies available, which no one has generated yet.

A fundamental objection to any travel into the past is a violation of the causality principle, i.e. the fact that an effect cannot have taken place before its cause. Transferred to the journey through time, the mere presence after returning to the past would possibly change the world and thus the further course of things. An at least theoretically conceivable remedy for this paradox would be to make a time machine out of a passable wormhole; but then after the trip we would find ourselves in another world and no longer in our original world. All in all, these ideas all belong in the world of science fiction.

Another argument against the existence of white holes, which also has to do with the opposite time axis, is the following:
In order to be able to see white holes, they would have to have existed for an infinite amount of time, and the emerging particles would have to have been on the move for an infinite time. However, this is not possible in a world of finite (!) Past created by the Big Bang (as it has so far been in complete harmony with the knowledge of modern cosmology).