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Mike Follows
Sutton Coldfield, West Midlands, UK
Gravity is a force that acts between all objects with mass. It can even act on light, which is massless in the conventional sense, but still responds to gravity because of its energy (which, according to Albert Einstein, is equivalent to mass).
The force between two objects gets stronger as their masses increase or as the distance between them decreases, but gravity acts between all particles in the universe, no matter how small or far apart they are.
The only difference with black holes is that they are incredibly dense, so that if another object gets closer than the event horizon, it cannot escape. Black holes still exert a gravitational influence on objects beyond the event horizon.
Of course, this picture might suggest that gravity somehow “escapes” from the black hole. But in general relativity, gravity isn’t really a force. Instead, mass curves the fabric of space-time, and a black hole is where this curvature becomes so extreme that, inside the event horizon, all possible paths lead inward – so nothing can escape.
The space-time outside the black hole is still curved, and this curvature is what we experience as gravity. It doesn’t emerge from inside the black hole; rather, it is a feature of the space-time that already exists around it.
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