Simply put, a white hole can be described as a black hole where time is reversed, and the matter that enters the black hole will eventually come out of the white hole and appear in another universe. It is called a "white" hole because it has a completely opposite nature to a "black" hole. It has a closed boundary. The matter gathered inside the white hole can only move outward, not inward. Therefore, a white hole can supply matter and energy to the outer region, but cannot absorb any matter or radiation from the outer region. A white hole is a strong gravitational source with the same external gravitational properties as a black hole. A white hole can accrete matter around it to form a layer of matter on its boundary. The white hole doctrine is mainly used to explain some high-energy celestial phenomena. At present, astronomers have not actually found white holes, and it is still a theoretical term. Before we get into white holes, let's briefly introduce black holes:
Black holes
A black hole is a celestial body whose gravitational field is so strong that not even light can escape from it. According to general relativity, the gravitational field will bend space-time. When a star is very large, its gravitational field has little effect on space-time, and light from a point on the star's surface can be directed in a straight line in any direction. The smaller the radius of the star, the more it bends space-time around it, and light emitted at certain angles will return to the surface of the star along the curved space. Black holes do not allow anything within their boundaries to be seen by the outside world, which is why they are called "black holes". We can't see it through the reflection of light, but only indirectly through the objects around it that are affected by it. It is hypothesized that black holes are the remnants of dead stars or exploding gas clouds, created when particular massive supergiants collapse and contract. (