Ron Dippold
San Diego, California, US
If you believe Albert Einstein 鈥� and he has never been wrong about gravity after many experiments 鈥� gravity isn鈥檛 a 鈥渢hing鈥� that emits from an object, like light. Rather, the mass of an object like a black hole, a planet or even you and me warps the fabric of space and time itself. Objects being attracted to each other is just a consequence of that space-time warping.
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Imagine you have an almost infinitely wide trampoline. That鈥檚 a 2D space-time. Now drop a bowling ball on it and call that our sun. Add a golf ball for Earth, a baseball for Jupiter, a speck of dust for you and me, and so on. The bowling ball sunken into the trampoline forms a funnel with the sun at the bottom.
If nothing is moving, our golf ball Earth, which is inside the bowling ball sun鈥檚 funnel, will just roll down and smack the bowling ball. That鈥檚 gravity. But if you pretend the trampoline is frictionless, like the vacuum of outer space, and you give the golf ball a good sideways nudge, the frictionless golf ball will circle the frictionless funnel around the bowling ball forever if nothing else interferes.
Now, if you try to flick a marble past the spinning baseball, spinning golf ball and bowling ball, you will see that it naturally curves to follow the dips they have made in the trampoline that is our space-time. This is how light and comets and space ships have their trajectories bent by gravity 鈥� they are just following the path of least energy expenditure on that warped surface.
Then, a black hole would be dropping Mount Everest squeezed into the size of a pea onto the trampoline. It would create an incredibly deep funnel. If you got far enough down the funnel, you couldn鈥檛 possibly get out, no matter how hard you tried to accelerate, and that鈥檚 the event horizon. But it鈥檚 not because anything is actually escaping the pea, it鈥檚 because space (the trampoline) around the pea is warped. Gravity doesn鈥檛 escape the black hole; the black hole has just warped the space-time around it.
Gravity doesn't actually escape from a black hole; the black hole has just warped the space-time around it
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