Introduction

For a century, scientists have theorized about mysterious white holes—but what exactly are they?

E = mc^2! Everybody knows Einstein’s famous equation, and it comes from his most famous, groundbreaking work: the theory of relativity. He had two theories of relativity, special and general (published in 1905 and 1915, respectively) and they both significantly changed the field of physics. To keep it simple, special relativity focuses on phenomena without gravity, while general relativity strived to rework gravitational laws on a grander scale, where Newton’s physics failed.

The Basics

Sometime in 1916, physicist Karl Schwarzchild published the first exact solutions (solutions without approximations) to Einstein’s equations, trying to explain how space time functions around a very dense ball of mass. This “ball” is what we call a singularity: an infinite mass concentrated in a single point, which is commonly thought to be the centers of black holes (sadly, we can’t see inside them— yet). This was the first suggestion that black holes could exist: celestial bodies with gravitational forces so strong not even light could escape its pull. For a while, this was just a possibility, the fancy of a theoretical physicist. 

Six decades later, scientists found the first black holes and were able to prove its existence. Six decades! In the late 1970s, rockets were able to detect extremely strong X-rays from a distant source: this was Cygnus X-1, the first black hole to be discovered. It’s part of a binary star system consisting of a blue supergiant star and an invisible companion, the black hole. As mentioned before, these are very dense balls of mass; Cygnus X-1 has 22 times the mass of our sun, but mostly concentrated in an area only 78 miles across. That’s a little over half the distance from Mitty to Sacramento!

This characteristic, along with the fact that they emit no light, is what makes black holes so difficult to detect. They can only be seen by the mass and light they draw in with their extremely strong gravity, which forms a layer around it around 120 miles in diameter. We still don’t know a lot about black holes, like what they eat, what happens to the things sucked in, and exactly how they form, but we learn more every year. In fact, we only got the first picture of a black hole in 2019! 

Now let’s go back in time, to Einstein’s theory. It was able to predict and prove something long before we were even able to look for it. So, what else did this theory predict?

White Holes.

What are they?

Ultimately, these equations also provide the solution to a different type of singularity. Instead of everything being pulled in by its immense gravitational pull, as it would be in a black hole, a white hole acts in the opposite way; nothing can get past its barrier, protected by an ”anti-gravity” barrier. Just as black holes absorb information past their event horizon (the “edge of black holes” where the gravity is impossible to escape), white holes “eject” this information. 

However, there is one caveat to this: for this equation to work, time must flow…backwards? In the mathematical sense, time is not always a unidirectional dimension; equations could be tweaked to do things that wouldn’t really make practical sense. I mean, sure, time is relative—but we haven’t really thought of a way to go back in time. So then, wouldn’t this suggest that white holes couldn’t exist, at least within the rules of our universe?

Unfortunately, this is true; as cool as it would be to have an information-spitting celestial body, there has been no evidence that these exist. There are still theories on how these could have formed, though.

Where do they Come From?

One such theory suggests that white holes are the leftovers from the life-cycle of a black hole. After it was discovered in the 1970s that black holes leak energy in the form of Hawking radiation, some wondered what would happen when it had all been depleted—and what would happen to the information stored inside it. This white hole theory suggested that after a black hole’s death, it leaves behind a white hole with all of its absorbed information stored inside, and would possibly be emitted back into the universe.

Due to the inverse relationship between mass and the amount of radiation emitted, the black holes we’ve discovered so far would take magnitudes longer to evaporate than the age of our universe, suggesting that there are no sizable white holes to be discovered as of right now. There is also the possibility of mini-black holes, which would theoretically degrade into a white holes at a much faster rate than its larger counterparts. People are working hard to search for evidence for these bodies, but so far, haven’t found any yet.

Now, I’ve mentioned that white holes are an infinitely dense point that emits a lot of information… Does that ring a bell? For many theoreticians, the Big Bang Theory immediately comes to mind! This theory describes the universe coming into existence through an explosion coming from an infinitely small point of mass, similar to how a singularity works. So, one school of thought is that the universe started from a white hole, as the description of the two seem to line up.

This, in conjunction with the previous theory, would suggest a cyclical nature of our universe, as eventually all things may be consumed by a supermassive black hole, eventually turn into a white hole, and then re-explode back into a fresh universe.

So, what’s the Point?

While white holes may not actually exist, it’s a lesson on how math can describe and predict parts of our universe. Math is essentially a language used to describe phenomena, and it can go beyond how we can (currently) perceive our world; there are some equations that utilize more than 10 dimensions! In the end, things may not practically work, but we can continue to craft theories that unravel the inner workings of our universe.