The existence of a white hole, a colossal cosmic structure that repels all objects towards it, remains a subject of debate and is regarded as the “phantoms” born from the mathematics of the theory of general relativity.
The Event Horizon Telescope captures an image of the supermassive black hole at the center of the M87 galaxy. Photo: EHT Collaboration
Black holes are regions of complete gravitational collapse, where gravitational forces dominate all others in the universe, compressing matter into an infinitely dense point called a singularity. Surrounding the singularity is an event horizon, not a solid physical boundary but a boundary around the singularity where gravitational forces are so strong that nothing, not even light, can escape.
When a massive star dies, its tremendous weight crushes its core, leading to the formation of a black hole. Any matter or radiation that comes too close to a black hole is intensely attracted and pulled down beneath the event horizon, leading to oblivion.
Experts understand the formation of black holes and how they interact with their surroundings through Einstein’s theory of general relativity. General relativity doesn’t concern itself with the flow of time; its time-symmetric equations work mathematically whether time moves forward or backward.
If one were to film the formation of a black hole and then play it in reverse, you would see an object emitting radiation and particles. Eventually, it would explode, leaving behind a massive star. This is the concept of a white hole, and according to the theory of general relativity, this scenario is entirely feasible.
White holes are a theoretical cosmic structure that operates in the opposite way to black holes. Photo: Future/Adam Smith
White holes are even more peculiar than black holes. They still have a singularity at their center and an event horizon at their outer edge. They remain massive objects with strong gravitational forces. However, anything that approaches a white hole is immediately pushed away at a speed faster than light, causing the white hole to shine brightly. Anything outside the white hole cannot enter it because it would need to move faster than light to breach the event horizon.
Nevertheless, the existence of white holes remains contentious because general relativity is not the only theory in the universe. There are other branches of physics that explain how the universe operates, such as electromagnetic theory and thermodynamics.
In thermodynamics, there is a concept called entropy, which is essentially a measure of disorder in a system. The second law of thermodynamics states that the entropy of closed systems cannot decrease.
For example, if you throw a piano into a woodchipper, the output will be a series of fragments. The disorder in the system increases, satisfying the second law of thermodynamics. But if you were to randomly throw those piano fragments back into the woodchipper, the output would not be a complete piano because that would reduce the disorder. Thus, it is not as simple as reversing the process of black hole formation to obtain a white hole because it would decrease entropy, and stars cannot form from a violent explosion.
Therefore, the only way for a white hole to form is through some exotic process occurring in the early universe, avoiding the complication of decreasing entropy. They simply exist from the dawn of the universe.
However, white holes are still highly unstable. They draw matter towards themselves, but nothing can cross the event horizon. Anything, even a photon (a particle of light), would be annihilated as it approaches the white hole. The particle cannot surpass the event horizon, causing the system’s energy to skyrocket. Eventually, the particle has so much energy that it causes the white hole to collapse into a black hole, ending its existence. Therefore, although fascinating, white holes seem not to be a real structure in the universe but rather “phantoms” born from the mathematics of the theory of general relativity.