What Do Black Holes And The Big Bang Have In Common?

At first thought, black holes and the big bang seem to be unrelated phenomena. But if we choose to look underneath the hood, these two seemingly unrelated phenomena have more in common than you might think.

In my previous essays on black holes, I covered the intuition behind the notion of black holes and the rich history behind their discovery. You just happen to be reading the third essay in the hitchhiker series.

In this essay, I will be exploring the notion of how our entire universe could reside inside a gigantic black hole. Let us begin.

This essay is supported by Generatebg

What Do Black Holes and the Big Bang Have in Common?

Let us get straight to the most obvious fact. Both of these phenomena are singularities. To be more precise, Einstein’s theory of relativity is unable to mathematically handle them both. What this also means is that black holes and the big bang have mathematical similarities.

The big bang could be perceived as a singularity in the past that occupied all space. A black hole could be perceived as a singularity in the future (of an entity venturing towards it) that occupies all space beyond its event horizon. Since the big bang, the universe has been expanding at such a rate that there are objects in our universe that we will never reach.

This means that there exists a cosmological horizon, beyond which we are not able to retrieve any information. If you are familiar with the notion of a geodesic, the big bang represents the global starting point of all geodesics in our universe whereas a black hole represents the local end-point of geodesics in its space beyond the event horizon.

---

Can a Universe Exist inside a Black Hole?

For a universe to exist inside a black hole, the mathematics between the two needs to be indistinguishable for any entity residing inside the black hole. This is the point at which we start moving from speculation into science fiction. You see, for one of the mathematical possibilities, we would need a time-reversal of sorts.

Russian cosmologist Igor Novikov proposed the possibility of the existence of entities known as while holes. Conceptually, a white hole is the opposite of a black hole. It allows entities to flow in one direction only: outward (beyond its event horizon). Space from inside the white hole flows outward across the event horizon at the speed of light.

If you think about it, that sounds an awful lot like the big bang.

Spacetime Beyond the Event Horizon

Theoretical physicist Raj Kumar Pathria showed in 1972 in his scientific article titled “The Universe as a Black Hole” that it is indeed mathematically possible for a universe to exist inside of a black hole. This led to the Black Hole Cosmology Theory which took this idea further and linked it with the Big Bang.

As one of the potential explanations for the big bang, the black hole cosmology theory suggests that the big bang could have been a supermassive white hole caused by a supermassive black hole. This supermassive black hole would in turn have been at the core of a galaxy from our parent universe.

What Can We Know?

Using the Schwarzschild metric and the Friedmann-Lemaitre-Robertson-Walker metric, physicists have shown how it is possible to model flat spaces within collapsing stars. We can see this mathematically.

Having said this, we have thus far only three properties to assess a black hole from the outside: its mass, its charge, and its angular momentum. Consider one hypothetical black hole that holds an unstable space and another one that has a stable flat space.

If these two black holes feature the same mass, charge, and spin parameter values, we would not be able to tell them apart. Even though our mathematics enables us to peek into possibilities inside a black hole, the fact remains that we might never know what is inside. Or for that matter, we might never know if we are inside a black/white hole either!

---

Reference: Dr. Matt O’Dowd.

If you’d like to get notified when interesting content gets published here, consider subscribing.

Further reading that might interest you: Why Is A Black Hole Really So Special? and Where Does The Black Hole Get Its Name From?