Exploring The Mystery Of The Black Hole | Universe | BBC Earth Science

Black holes are where two of our greatest theories collide and clash. So you've got these two primal forces in the universe, gravity, which we all understand and feel with our bones, and then you've got quantum mechanics, which governs the theory of the ultra small, how atoms and nuclei come together. The black hole is where gravity and quantum mechanics finally meet. When we try to take the mathematics of the very large and try to combine that with the mathematics of the very small, instead of matching, they get into a fight. And so we don't have a consistent way to describe both. We can begin to probe this deep mystery by investigating the heart of Sagittarius A star. Scientists have studied dozens of stars in its orbit, some passing just a few billion miles from the event horizon, a hair's width on galactic scales. And these flybys could have catastrophic consequences. Because some of these stars likely have planets in orbit. Planets that may stray too close, moths to a flame, pulled from their parent stars towards the abyss. So imagine you're some alien civilization looking up at your lovely home star S2 in the sky, and one day the thing starts wandering closer and closer to what we call the tidal disruption radius of Sagittarius A star, this four million solar mass black hole. If you fell into a black hole, you'd pass the event horizon. And actually, bizarrely, you'd see nothing. There's no physical barrier. There's no big line in space saying point of no return. You would just drift very casually, gently across the event horizon. If we could stand on such a planet and look outwards, we'd see something spectacular. You see a distorted universe. And in fact, you see it distorted in both time and space. You'd see it playing out at an amazingly fast speed. The rest of time would play out unbelievably fast in front of your eyes. But eventually, tidal and gravitational forces become too strong, stretching space and everything in it. Your feet would be pulled more strongly by gravity than your head. So you'd be stretched out into a giant string. And eventually, you'd be one long string, one atom thick. We call this spaghettification. Boulders become rocks. Rocks become sand, whose very atoms are then pulled apart. Gravity and the quantum world collide. Ahead, the heart of the black hole, the singularity. Where all journeys in terminate. Our idea of a singularity is that everything is compressed beyond what it can be until it's nothing, but yet still exists. That is wild.