# Is there a relationship between Black Holes and the Big Bang?

As the question mentions, is there a relationship between the Big Bang and Black Holes? It appears the Big Bang is a ‘tacked on’ theory that doesn’t align with current theories (since we don’t know or observe dark energy, a mysterious force that explains why matter is accelerating outward). Is it possible that once we understand what happens inside black holes that it could explain our origin? If you can imagine what it’s like to someone inside a black hole event horizon, would they observe matter accelerating outward in a similar manner to our universe? Maybe it’s possible to view the singularity inside the event horizon as the exterior (by flipping the black hole inside out in a mathematical sense) - so to an observer inside the event horizon everything is accelerating outward).

I come from a non-physics background, pls excuse my ignorance or seek further clarification on question.

• More on Big Bang & black holes. – Qmechanic Apr 23 at 4:34
• Why have you downvoted? – Christian Apr 23 at 4:35
• The gist - Black holes were created "long" after the Big Bang. Physicists have a good idea of what happened after the Big Bang, but no solid idea what caused the Big Bang itself. Also physicists have no solid idea on what dark matter and dark energy are. Maxwell's equations relate magnetism and electricity, but gravity can't yet be connected. Physics has long hoped for a theory of everything that would tie all these desperate parts together. – MaxW Apr 23 at 4:40

Both exist in mathematical models using General Relativity, and both are successful in describing astrophysical observations up to now. That is where the similarity ends, because the singularity at the beginning in the Big bang model is mathematically a different singularity than the ones modeling black holes.

An every day example is the singularities used to mathematically model a bathroom siphon, where the bath water will disappear into the hole, and the mathematics used to model an explosion. Both models have a singularity ( i.e. an infinity at a (0,0,0) point) both use classical mechanics and classical gravitation, but they are not the same type of singularity. This is because the data to be modeled in one case disappear into a hole, and in another a lot of matter appears from a small region.

The data that induced the Big Bang model resemble in the four dimensions of general relativity an explosion, whereas the data of black holes resemble a sink.

The relationship is that the same mathematical theory, General relativity, can model with singularities both black holes and the observable universe.

• What if you flipped the black hole inside out? So the singularity of a black hole is the exterior to an observer inside the event horizon? Would that make any difference? – Christian Apr 23 at 4:52
• @Christian There are two separate points in your comment. (1) A time reversed black hole is called a white hole that has many similarities with the Big Bang. In fact, the Oppenheimer-Snyder white hole singularity is mathematically the same as the Big Bang. This makes Anna's answer incomplete. (2) In the Milne model of cosmology, the universe expands inside the Big Bang singularity, such that the singularity appears like a sphere expanding with the speed of light while we are inside. While there are some arguments against this model, it cannot be completely ruled out today. – safesphere Apr 23 at 5:04
• In a sense, classical sources and sinks are flipped mathematically, but the solutions describe two different physical states. One models outgoing (explosion,source) the other inflow (sink) .As safespeare says, if you flip a black hole you will get a white hole, buti it will be modeling different observations( like a small Big Bang). The observations are what separates ingoing from outgoing in the model, One cannot explain the observations related to black holes by a source singularity, it is a sink. White black holes have not been observed. – anna v Apr 23 at 5:49
• @annav could an observer tell the difference between the Big Bang and being inside a white hole? Safespear stated that a white hole is mathematically the same as the Big Bang which makes me think that an observer couldn’t tell the difference. – Christian Apr 23 at 6:58
• Mathematically no, a source is a source, that is why there are all these many universes models floating around, but white holes have not been observed in outruniverse. – anna v Apr 23 at 7:12