13. According to mathematics and other theories, white holes are entirely possible. A white hole is a hypothetical feature of the universe. It is considered the opposite of a black hole. As black holes don't let anything escape from their surface, white holes are eruptions of matter and energy and nothing can get inside them. The laws of general relativity imply that if eternal black holes exist in the universe, then a white hole should also exist. It is a time-reversal of a black hole. They are expected to have gravity, so they attract objects, but anything on a collision course with a white hole would never reach it.
