The Holes in Our Space-Time
Are wormholes unstable? And is it because of black holes?
To begin with, let’s do a small recap.
What is a Black Hole?
On grounds of intuition, we’ve all been explained the concept using a piece of fabric and a ball. A ball placed in the middle of the stretched fabric bends it. Then if you roll a marble, it follows a curved path; and that the bend of the fabric resembles gravity.
The picture depicts the true warping (bending) of space-time, as opposed to our intuition.
Black holes are defined as extremely compact and massive objects in the cosmos; they warp space-time so dramatically that objects crossing the surface of no return can never escape.
Coming to wormholes, we all have heard of them as fancy portals which give us access to far-away places in a matter of seconds. You get sucked in and spit out in a different place. And then you wonder how does that happen? Suddenly, that one person comes up with a sheet of paper and folds it into half and creates one hole through the fold. Boom! Wormhole! Two faraway points connected due to a fold!
Keeping wormholes aside (for a moment), we need to look at one important thing about Black Holes. You see, a lot is unexplained about Black Holes. Einstein’s theory, albeit a great one, does miss a few markers. A big one being — It fails to be quantized.
Now, as it happens to be, black holes are excellent test cases for applying the quantum theories. Gravity is a much weaker force compared to the electromagnetic and nuclear forces. It dominates on a massive scale. But it is negligible when accounted on for a quantum scale where the other forces dominate. An important thing to remember here is that gravity is a function of ‘curvature of space-time’ and not directly of mass, mass distribution, and/or density. In black-holes, the curvature increases rapidly as we approach the singularity. With that, the gravitational pull strengthens. Hence, when black holes are subjected to quantum analysis, the gravitational force becomes significant and it becomes simpler to apply the quantum laws and get an outcome.
And Hawking did apply this quantum theory to black holes. He found that black holes have a temperature, but more importantly and counter-intuitively, they also give out a sort of radiation known as the Hawking radiation, and shrink in size doing this. Slowly, they vanish away. Now, the information that was consumed by the black hole would have vanished. This would mean a violation of the quantum theory that we started with (because information entering a black hole never escapes, or so we know). The only possible place all the information could have gone is getting emanated as the hawking radiation. BUT, information inside a black hole can simply not get out. Then how does Hawking Radiation carry the information? It is possible that copies of the information exist, inside and outside the black hole.
We shall explore more later in the article.
The White Hole
And I thought this question couldn’t have taken another turn. Well, if black holes exist, then a so-called White Hole must exist, right? It does exist. In theory. We haven’t yet been able to observe one.
The Schwarzschild solution to the Einstein’s Field equations gave a non-rotating and uncharged black hole. It was soon realised that the other possible solution (using the Schwarzschild method) gives a white hole. (It’s pretty famous. If you’re curious, a quick google search should satisfy you.)
In simple terms, a white hole is the theoretical opposite of a black hole. Where a black hole consumes everything, a white hole spurts out all information, and the force of repulsion increases as we come closer to the point of singularity. Meaning that it is impossible to reach its center. A simpler way of saying would be to say: ‘White holes are time-reversed black holes.’
But the reason why we say white holes do not exist is because of entropy. Entropy is, in simple terms, a variable which defines the degree of disorder. While black holes increase overall entropy, white holes decrease it. According to our physical laws, overall entropy should increase, always. This also happens to be the reason why we theorize that we can travel to the future but not back to our past. At least, yet!
Here’s a brain twister! If black holes do emit radiation (discussed earlier), then it technically behaves like a white hole, or it is a white hole (Whaaat?!). Here’s the catch. Having two copies of information is not valid in quantum theory. Many scientists believe it is the limitation of General Relativity. However, the concept of ‘complementarity’ was introduced to explain the anomaly.
An observer outside the black hole sees the information located at the event horizon, and the observer inside the black hole sees the information inside. Since there is no mode of communication possible between the two observers, there is no question of duplication or rather, the existence of such a paradox.
The concept of complementarity requires a large number of strange and odd assumptions and them to hold true. Amongst this is the concept of ‘holography’, details of which we shall not get into.
There have been theories (Novikov, 1964) which suggest that white holes and black holes are mutual. That when you enter a black hole, you come out of a white hole. (Ahaa! Portals, finally!)
Einstein — Rosen Bridges
Popularly known as wormholes, they serve as ‘gateways’ for travel in space. They bend space-time and create an alternate route to places in space. Wormholes have been known to be capable of space AND time travel but the latter is a little dubious. It has been theorized that one black hole and one white hole form one wormhole. However, the factor of stability prevents its existence. White holes have so far been explained in a complete vacuum. The moment we add mass to the system, white holes cease to exist. And this makes the wormholes unstable.
If one were to travel through a wormhole, they would be on a trip to the event horizon of a black hole and crossing it just very slightly to emerge to the other side. This would mean stretching and warping of the body to unimaginable extents. The force of gravity would tear it apart. Withstanding that, one would be safely transported to the other side, provided it exists. Amazing, though you probably knew it wasn’t safe to go near a black hole anyways.
Another possible explanation is to have two black holes at the ends of a wormhole. Whatever the case, one cannot simply ‘build’ a wormhole. Something known as quantum entanglement is involved before a wormhole is created. As said, so far we have analyzed the simplest of black holes, the Schwarzschild black holes, static and uncharged. As we start introducing more parameters, the complexity increases exponentially making analysis difficult.
There is little to no observational proof of the existence of the assortment of the aforementioned holes. Mathematical simulations seem to prove some while breaking laws. It is completely possible that all the theories used so far lack some parameters or make different assumptions. An interesting attempt to merge two popular theories (General Relativity and Quantum Theory) is being formulated. It’s the LQG or Loop Quantum Gravity. It is based directly on the geometrical formulations given by Einstein.
While we may have explained black holes to a comfortable extent, there still remain all the different paradoxes. While explaining these Holes in our Space-Time is proving to be very challenging, we are pushing our boundaries and expanding our reach to the unknowns of this universe.
