Take this paper as an example. The way a paper shredding machine shreds the paper which increases the entropy in the same way, black holes shred everything in the universe. Black holes swallow the entire planets and stars and only radiation is left behind. This increases the entropy in the universe. But if you try to imagine that it is happening in reverse, with the entropy decreasing, this is not possible. And if white holes do exist, then essentially this is what they will aim to do. So, as per this logic, perhaps they cannot exist.
But despite this, some scientists believe that not only do white holes exist, but that in 2006, scientists saw a white hole. On 14th June 2006, a space satellite named Neil-Gehrels Swift Observatory captured an astronomical event. Scientists saw an explosion of a white light which suddenly disappeared. This event was named GRB 060614. It was a gamma-ray burst. Gamma-ray bursts are basically are highly energetic explosions observed in distant galaxies.
Usually, these events occur when a black hole swallows a big star. You can see very bright explosions of light. But in this case, no evidence of a star was found. So, it was hypothesized that this was an observation of a white hole. Since then, we have not seen such an event again. And that’s why till now, white holes is only a theoretical concept.
