NASA has released a photograph of the black hole known as Sagittarius A* which spins at the centre of our galaxy. With a mass of only 4.3 million suns, it is relatively small for a supermassive black hole, especially when you consider that the black hole at the centre of the galaxy M87 has a mass of 6 billion suns. Strictly speaking, the photograph doesn’t show us the black hole since a black hole captures all information and releases nothing back to observers outside it; more properly, it’s a photograph of illuminated gas surrounding the black hole.
Whenever I read news stories like this, it sends my mind reeling, partly speculation, partly existential musing. Thankfully, neither of these tendencies need be limited by the fact that I know absolutely nothing about theoretical physics. In fact, my general ignorance probably makes the speculation more fun and free-wheeling.
What I do know is that the technical term for a black hole is singularity. Extreme gravity pulls matter to a single point in spacetime. Because we’re talking about spacetime and not just space, the extreme gravity also affects the flow of time. Observed from outside, as something approaches the singularity’s event horizon, time appears to slow. Beyond the event horizon (the boundary beyond which no information returns to outside observers), it’s impossible to say how time flows within the singularity. This is where speculation comes into play. Maybe time stops. Maybe time flows backwards. Maybe time flows randomly. Maybe we get time soup.
Another speculation that occurs to me: maybe we already know what happens inside a black hole because, in effect, that’s what our universe is. Like a black hole, the universe has a limit beyond which no information can escape. It’s limits appear to us dark and empty, not because there’s nothing there, but because whatever is there is unknowable. And if our universe is like a black hole, then maybe the flow of time in our universe is likewise fluid.
In his book, A Brief History of Time, Stephen Hawking wonders why time appears to move in only one direction. There doesn’t appear to be a reason why time can’t move backwards. An incidental consequence of Hawking’s observation is that the physical laws of our universe offer no reason why psychics shouldn’t be able to do what they claim they can do. This suggests a different kind of singularity: a convergence between theoretical physics and theoretical psychics.
