White Holes
You might have heard of the “Demons of the dark”, the mysterious and terrifying black holes.
Think of it, a large hole that sucks everything that crosses the event horizon, and even light cannot escape. Whatever goes inside, goes through gruesome spaghettification and is lost forever.
But have you ever thought if there exists something “opposite” of black holes? Something that instead of swallowing everything, pours out whatever was initially eaten by black hole? This might sound possible. Since General Relativity and Newtonian physics are time-symmetric concepts. This hypothetical “reverse” black hole is termed “White hole.”
What are white holes?
White holes are a hypothetical concept, first proposed by Russian cosmologist Igor Novikov[1] . White holes are predicted as part of a solution to the Einstein field equations known as the maximally extended version of the Schwarzschild metric[2] describing an eternal black hole with no charge and no rotation. In simple language, they are opposites of black holes.
According to Physicist Sean Carroll[3] ,
A black hole is a place where you can go in but you can never escape; a white hole is a place where you can leave but you can never go back”.
So if black holes represent a one way entrance into oblivion, white holes can be thought of the exit from this hell. Theoretically, a black hole and a white hole has the same geometrical structure, since they’re just opposite of each other. However, the existence of such white holes are yet to be proven.
Origin of White holes
The next question that comes up is how white holes are formed. There are a lot of interesting theory concerning this.
One model developed by Carlo Rovelli and Hal Haggard[4] suggests the transition of a black hole to a white hole would occur right after the formation of the former.
According to this theory, when a black hole is formed, it’s guarded by the event horizon, beyond which nothing can escape. However, the star that is collapsing under its own gravity will soon reach a point beyond which it cannot shrink further. At this point, it experiences an outward pressure, termed as “quantum bounce” which causes it to transform into a white hole.
The calculations of the team concluded that this transition occurs instantaneously. But it seems black holes exist for billions of years due to their intense gravitational pull, which makes time appear to go slower to an observer.
However, there’s a large obstacle in the way of the existence of White holes -
Second law of Thermodynamics
Second law of Thermodynamics says that the entropy (chaos) in the universe is always increasing.
Black holes follow this law pretty well. They swallow celestial bodies over long time, thereby spreading their matter over a large space and adding to the chaos of the universe.
But white holes, on the other hand, would theoretically do exactly the opposite—they would bring objects or scattered materials into arrangement or order, which would go against the second law. So, can White holes exist?
Let’s the a look at a similarly interesting concept -
Eternal black holes
The theory of eternal black holes was presented by Stephen Hawking. It was believed that whenever information enters a black hole is lost forever. Hawking predicted that black holes should gradually lose energy by radiation—in accordance with the second law of thermodynamics. Hence, black holes continuously radiate energy beyond their event horizons, ultimately losing all their energy and ceasing to exist.
So, can there be an eternal black hole? A black hole which can swallow as much as it wants without radiating part of it? Kind of like a “cosmic safe”?[5] It’s easy to see that this will violate the 2nd law.
So, actually eternal black holes are the theoretical opposite of White holes. An eternal black hole can swallow matters without letting it escape, and a white hole throws stuff out without letting anything enter. Hwever, both the concepts are still not proven to exist.
Big bang is caused by a white hole
We all have idea about Big bang. It is believed that around 13.7 billion years ago, the universe was compressed into a single point, which exploded to form the universe as we know it.
A 2011 paper suggests that the Big Bang was caused by a white hole. That might explain how the gigantic amount of matter and energy suddenly appeared. This paper also suggests “Small Bang” which is the emergence of a white hole and argues that this event is spontaneous and all the matter is ejected in a single pulse which is the reason we can’t observe a white hole continuously, rather their effect can only be observed around the event itself.
GRB 060614
On 14 June, 2006, NASA’s Swift Satellite observed a powerful Gamma Ray Burst. Gamma Ray Bursts are nothing special, but this one was.
Codenamed as GRB 060614. [6] , this burst was different from others since unlike normal GRBs this couldn’t be linked with any regions or low star formation or supernovae. And unlike others which last a few seconds, it lasted for a whooping 102 seconds!! and was trillions of times powerful than our own star!
Since it wasn’t linked to a supernova, scientists concluded that this might have come from an infinitesimally small speck which collapsed after those 102 seconds.
The features of this burst perfectly matches with the concept of white holes. (i.e. spewing out matters for a while before disappearing into oblivion). Does that mean that white holes exist? Hope we will get an answer soon!
White holes and worm holes
Along with the concepts of white holes, an intriguing idea has been perceived. It has been hypothesized that at the end of a black hole, there’s a white hole which vomits whatever the black holes eat. What’s interesting is that this “exits” can be situated in other universe!! Which means you enter a black hole and come out of a white hole in another universe.
This idea, published in 1935 is known as Einstein-Rosen bridge (or a Lorentzian wormhole or Schwarzschild wormhole). A wormhole[7] may be defined as a hypothetical area of warped space-time with enough energy to create tunnels through the fabric of space-time.
Time travel anyone?
The concepts of wormholes open a possibility of time travel. Can there be a wormhole which, instead of connecting two points at space, connects two points in time?
However there are some certain obstacles for the existence of this kind of wormholes. And there are a number of theories concerning this. You can read an interesting theory suggested by Nobel laureate Kip Thorne here (String Theory: Travel through a Wormhole - dummies)
Although White holes are still a hypothesis, who knows, maybe in future, their existence will be proved. And if they really exist, think of all the doors of possibility they might open.
This also makes one wonder, how little knowledge we have regarding the universe. Even seemingly impossible things are perfectly possible in the realm of reality!!
The seven articles I used for researching this article are :
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