Season 17, Episode 3: Are We Living Inside a Black Hole?

Hey StarTalkians! Season 17, Episode 3’s collection of “Cosmic Queries” saw Neil and Chuck tackle a lot of questions about black holes, and this question in particular stood out:

Alcubierre Drives, Antimatter Multiverses & More! | Cosmic Queries #103

Neil’s answer is solid. But lurking underneath that question is something they didn’t address in the episode: why would we be living in a black hole at all? This post takes a brief look at one recent paper making this argument as an example, but there are others .

Black Hole Universe: The Bounce Model

The paper investigated what happens when a cloud of matter collapses in on itself in curved space, taking into account quantum mechanics.

Quantum mechanics matters because of the Pauli Exclusion Principle, which says that no two fermions in the same system can occupy the same quantum state. There are two key parts to this definition:

• Fermions include electrons, as well as composite particles like protons and neutrons. Basically, it includes all the “regular” matter we’re most familiar with.

• Quantum states are defined by some key values. For example, in an atom, electrons occupy discrete “energy levels,” denoted by an integer physicists label n. So n = 1 is the lowest energy level. Other quantum numbers relate to magnetic properties and “spin.”

It’s like there are set seats for the particles, and if someone else has seat n = 1, ℓ = 1, m = 0 and s = 1/2, then the next fermion has to sit somewhere else.

So when all of the quantum numbers fill up, this limits how much the matter can be squashed. Some particles have to move to a different “seat.” This creates a kind of pressure that pushes the matter back outwards.

This bounce is what the paper investigates. While from the “outside,” an observer would see a black hole form, on the inside there would be a big bang. This is illustrated in the attached image.

• The good news: It would explain the initial inflation phase of the universe and dark energy.

• The bad news: It requires a curved universe, but most evidence says ours is flat.

So do we live in a black hole? Maybe! But probably not.