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Welcome to the first episode of Science with Sam, hosted by 51���� social media editor Sam Wong, who will explain some of the biggest topics in science every week. From microbiomes to vaccines, quantum theory to consciousness, and much, much more. If you’ve ever idly wondered whether it would be possible to escape from a black hole, questioned whether there are multiple universes or wanted to understand exactly how a vaccine works, this video series is for you.

First up: Black holes, objects so massive and dense that not even beams of light, the fastest things in the universe, can escape their gravitational pull. First predicted by Albert Einstein’s theory of general relativity, the first image of a black hole was captured in 2019, when scientists turned Earth into one giant radio telescope, created by the Event Horizon telescope network.

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Video transcript: Science with Sam: What is a black hole? And could you survive one?

Imagine you’re floating in space. It’s quiet and cold, serene but slightly terrifying. Suddenly, you feel a tug. It starts out faint, but gets stronger, pulling you towards an empty region of the sky. Before you know it, you have entered a black hole. That’s not good. Could you survive? Maybe, but it gets pretty weird. To find out, we need to know more about black holes.

Black holes are objects so massive and dense that not even beams of light, the fastest things in the universe, can escape their gravitational pull. Essentially any object sufficiently compressed can be a black hole. If an evil alien empire decided to squash Earth down, it would form a black hole about the size of a peanut.

The existence of black holes was predicted by Albert Einstein’s theory of general relativity, which states that matter warps space and time, creating what we call gravity. The theory also predicted that when black holes collide, they send out ripples in the fabric of space-time, called gravitational waves. These ripples were first detected in 2015 by an incredibly sensitive experiment called LIGO, proving Einstein right. Then in 2019, we managed to photograph a black hole for the first time, by using observatories around the world to turn Earth into one giant radio telescope. On the picture we can see a bright ring of material circling the black hole itself, silhouetted in the centre. Pretty amazing, huh? And there’s even more exciting research happening all the time.

If you were unfortunate enough to get sucked into a black hole, it would be a spectacular, if devastating thing. As you circle down the drain of this cosmic plughole all the photons being pulled alongside you would create a stream of blinding light. Then, a looming darkness would wash over you and the surrounding stars would start to distort and bend. This is your last opportunity to escape. Any further, and you will cross the event horizon, the line where the black hole’s gravity is too large to resist. Beyond here gravity increases so quickly that it wouldn’t just crush you but pull apart every part of your body at different speeds, resulting in what physicists delightfully call “spaghettification”. If you fell in feet first, your ankles would stretch away from your knees before your neck elongated into a strand of pasta.

Once inside the black hole, it gets a bit harder to work out what happens, perhaps unsurprisingly, because general relativity’s equations fail catastrophically here at the black hole’s centre, known as its singularity. This is where quantum physics comes into play, but quantum theory and General relativity don’t really get along. General relativity states that when matter falls into a black hole, information is destroyed, but quantum mechanics says that can’t happen. We need a unified theory to reconcile the two.

One way to do that is with string theory, which says that matter isn’t made of fundamental particles, but instead is composed of tiny strings. If that’s the case, black holes aren’t really black holes at all, but fuzzy balls of tangled string. You would still die a pretty terrible death if you fell into a fuzzball like this, but instead of becoming part of nothing, you would become part of this bundle of strings.

Still not much of a consolation. Is there a way to survive a black hole? Well, sort of. Black holes come in a range of sizes, from as small as a single atom to a million times the mass of the sun. If you have a choice, your best bet is to fall into a large one: their gravity is bigger, but the stretching tidal force is less, meaning you might just live to tell the tale. Unfortunately, you wouldn’t be able to escape to tell anyone what you’d seen. Or could you?

There is one possible way you could make it back out, through a hypothetical object called a white hole. Just as black holes allow nothing to escape their pull, white holes can’t hold anything together. One idea is that every black hole is connected to a white one via an inter-dimensional tunnel known as a wormhole. Fall into one, and you will, eventually, get thrown out the other end where space-time bounces back outwards, vomiting you up with it. Alternatively, you could wait for a black hole to turn into a white one. To an outside observer, this process would take billions of years, but inside, thanks to the enormous gravitational pull, time would be speeded up, taking you mere milliseconds.

So maybe there is a way to fall into a black hole and survive, but I don’t fancy the risk myself – spaghettification doesn’t sound very nice at all. How about you? Let us know in the comments and don’t forget to for more Science with Sam.