What Is A White Hole And How Is It Different From A Black Hole?

The possibility of the existence of white holes was first suggested by a theoretical astrophysicist Igor Novikov in 1964.

A white hole is a hypothetical region in spacetime, which is predicted as part of a solution to the Einstein field equations.

But let’s begin with black holes because they are easier to explain. Black holes form when the center of a large, dying star collapses in upon itself. All the mass is squeezed into an infinitely small volume. Their gravitational pull becomes so large that even light cannot escape it.

White holes are exactly opposite of black holes: while nothing can escape from a black hole’s event horizon, nothing can enter a white hole’s event horizon. In simple language, a white hole spits out everything and nothing goes in.

The concept of a white hole is extremely complex. Thus we have tried to explain it in small sections. By the end of this article, you will learn a lot more about this intriguing phenomenon.

Do White Holes Exist?

A White hole is just a theoretical mathematical concept and it hasn’t been observed in the universe. Most of the discussions of white holes revolve around the words “hypothetical”, “unfeasible”, and “unrealistic”.

They are a potential solution to the laws of general relativity, which imply that if eternal black holes exist, then white holes should also exist in the universe.

They are expected to have properties like mass, charge, angular momentum, but anything approaching a white hole (even at speed of light) would never reach it. Theoretically, there isn’t enough energy in our universe that can get you inside.

They Violate the Second Law of Thermodynamics

One of the major reasons why white holes are considered unrealistic is the fact that they reduce entropy, which is against the law of thermodynamics.

The second law of thermodynamics states that the total entropy of the universe is continually increasing, so the change in entropy is always positive. That’s why white holes would not fit into our current model of the universe.

Evidence Regarding White Holes

Although evidence and information regarding white holes remain uncertain, a gamma-ray-burst — named GRB 060614 — detected by the Neil Gehrels Swift Observatory in 2006 has been considered as the first recorded occurrence for a white hole.

Unlike typical gamma-ray bursts that last for only a few seconds, GRB 060614 hybrid burst lasted for a remarkable 102 seconds but wasn’t associated with a supernova. It challenged a previous scientific consensus on black holes and other types of celestial bodies that can emit gamma-ray bursts.

White Holes Could Make Up Dark Matter

In 2018, scientists theorized that white holes with microscopic diameters could make up dark matter. Such tiny white holes wouldn’t emit any radiation, and since they are smaller than the wavelength of light, they would be invisible.

Dark matter makes up roughly 27% of our universe and its local density is approximately 1% the mass of the Sun per cubic parsec. To account for this density with white holes, the team evaluated that one microscopic white hole (about a millionth of a gram and much smaller than a proton) is required per 10,000 cubic kilometers.

White Holes May Even Predate The Big Bang

Another intriguing theory put forth by researchers is that white holes might explain the Big Bang, since this is another case where an immense amount of matter and energy spontaneously appeared.

In fact, it was argued that the Big Bang was a result of a white hole explosion, which presumably spewed out all the matter and information that had been consumed by a black hole.

Obviously, we don’t know whether the theory is true or not, but then again, it is amusing to think that life has emerged from a white hole.

White Hole and Black Hole Are Connected Via Wormhole

One of the main reasons to study the existence of white holes is that they could solve an open mystery: what happens at the center of a black hole. What happens to all of the information that gets sucked in?

A few theories suggest that there is a white hole at the other end of a black hole. All matter and information swallowed by the black hole is ejected by the white hole into a different universe.

The “entrance” of a black hole and “exit” of a white hole could be connected to two completely different universes. And what makes this connection possible is called a wormhole: it can be visualized as a tunnel with two ends, each at separate locations in spacetime.

The theory of general relativity have valid equations that consist of wormholes, however, they haven’t been observed in the universe yet. A wormhole could connect short distances (a few meters), extremely long distances (millions of light-years), or different universes.

In 1935, scientists discovered the first type of wormhole called Schwarzschild wormhole, using Einstein general relativity. The entire Schwarzschild metric is comprised of a white hole, black hole, and two separate worlds connected at their event horizons via a wormhole.

The Schwarzschild solution has two valid equations – a positive and a negative square root. The latter accounts for a black hole going backward in time, which also represents a white hole.

Read: What is Magnetic Wormhole and How It’s Useful?

White Holes Open Possibilities Of Time Travel

Wormhole travel as envisioned by Les Bossinas for NASA

In certain conditions, a wormhole could connect two points in time, instead of connecting two points in space. Thus, an object swallowed by a black hole could pass through a wormhole and be spewed out by a white hole in another region of time [or space].

However, the concept has numerous flaws. For instance, an object falling into a black hole wouldn’t be able to withstand its enormous gravitational pull. And since the wormhole is incredibly unstable, it would instantly collapse upon itself.

Still, some physicists have shown that a wormhole (if it exists) can allow travel in space as well as time. Professor Kip Thorne of the California Institute of Technology, who is also a Nobel laureate, has theorized that these three phenomena (black holes, wormholes, and white holes) may allow humans to travel back and forth in time (thousands of years).

Read: 18 Interesting Facts About Black Holes

Honestly, there are hundreds of theories regarding white holes, but scientists haven’t found solid evidence to prove their existence. Maybe in our vast mysterious universe, there is space even for them.

Written by
Varun Kumar

Varun Kumar is a professional science and technology journalist and a big fan of AI, machines, and space exploration. He received a Master's degree in computer science from Indraprastha University. To find out about his latest projects, feel free to directly email him at [email protected] 

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