Why Smaller Black Holes Can Have Stronger Tidal Forces

Small black holes can have much stronger tidal forces at their event horizons, while supermassive black holes may let you cross the horizon without being torn apart.

Astronomy

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Black holes are not equally violent at their event horizons. The key difference is tidal force, which measures how much gravity changes across an object. Around a stellar-mass black hole, the event horizon is relatively close to the center, so the difference in gravity between your head and feet can become enormous. That can stretch an object lengthwise, a process often called spaghettification. Around a supermassive black hole, the event horizon is vastly farther from the center. The gravitational pull is still extreme, but its change across a human-sized body at the horizon can be surprisingly small. In principle, someone could cross the event horizon of a sufficiently large black hole without immediately feeling the tidal forces. Crossing the horizon is still a point of no return, and the environment around a real black hole can contain intense radiation and other hazards. The exact physics deeper inside remains an area where current theories are incomplete.

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