What Would We Experience If Earth Spontaneously Turned Into A Black Hole? - Forbes

If a black hole were to form from the Earth itself, it would create an event horizon just 1.7 centimeters in diameter.

One of the most remarkable facts about the Universe is this: in the absence of any other forces or interactions, if you start with any initial configuration of gravitationally bound masses at rest, they will inevitably collapse to form a black hole.

If, somehow, the electromagnetic and quantum forces holding the Earth up against gravitational collapse were turned off, Earth would quickly become a black hole.

[+] forces or effects present (or they're all negligible compared to gravity), that mass will always inevitably collapse down to a black hole.

Right now, the reason Earth is stable against gravitational collapse is because the forces between the atoms that make it up — specifically, between the electrons in neighboring atoms — is large enough to resist the cumulative force of gravity provided by the entire mass of the Earth.

In the cores of stars that are massive enough, however, neither the electromagnetic force nor even the Pauli exclusion principle can stand up to the force inciting gravitational collapse; if the core’s radiation pressure (from nuclear fusion) drops below a critical threshold, collapse to a black hole becomes inevitable.

After just a few minutes more — 21 to 22 minutes total — the entire mass of the Earth would have collapsed into a black hole just 1.75 centimeters (0.69”) in diameter: the inevitable result of an Earth’s mass worth of material collapsing into a black hole.

Either way, the first thing that would happen would be a transition from being at rest — where the force from the atoms on Earth’s surface pushed back on us with an equal and opposite force to gravitational acceleration — to being in free-fall: at 9.8 m/s2 (32 feet/s2), towards the center of the Earth.

Both inside and outside the event horizon of a Schwarzschild (non-rotating) black hole, space flows ...

At the event horizon, even if you ran (or swam) at the speed of light, there would be no overcoming the flow of spacetime, which drags you into the singularity at the center.

Outside the event horizon, though, other forces (like electromagnetism) can frequently overcome the pull of gravity, causing even infalling matter to escape.

In Newtonian gravity, which is a good approximation as long as you’re very far away from the event horizon (or the equivalent size of the event horizon), the gravitational acceleration you experience will quadruple every time your distance to a point halves.

While, overall, you (as the falling object) would experience an average force over your entire body, these tidal forces would stretch you along the direction towards the black hole and compress you in the perpendicular direction.

That’s because your body, as you fall closer and closer to the center of the collapsing Earth, starts to experience enormous increases in tidal forces.

Here on the surface of Earth, these tidal forces on a human being are minuscule: a little less than a millinewton, or the gravitational force on a typical small earring.

If we subtract that force out (Fr) from every point, the red arrows showcase the tidal forces experienced at various points along the object.

[+] spaghetti-like structure as they approach the event horizon of a black hole.

In order to approach the actual event horizon itself, you’d have to somehow shield yourself from these tidal forces, which would rip your individual cells apart and even the individual atoms and molecules composing you before you crossed the event horizon.

In the end, like everything on Earth, we’d be absorbed into the black hole, simply adding to its mass ever so slightly.