Comments by "Lawrence D’Oliveiro" (@lawrencedoliveiro9104) on "" video.

I have a problem with the idea that light can disappear into a black hole and be lost forever. Light travels along geodesics. And geodesics are time-symmetrical. That means a light beam can travel in either direction along a geodesic. Therefore, if there is a light path from outside the event horizon leading into it, then there is a path in the opposite direction leading out. So if light can enter, it can just as easily escape. Since there is no escape, that must also mean there is no entry. QED.
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@scottmanley Whatever it travels along, those trajectories are bidirectional. Either they cross the event horizon (which gives both entry and exit), or they don’t. Which is it?
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@scottmanley Geodesics are time-symmetrical. Consider the orbits of the planets -- flip the time axis, and they go round the orbits the other way, and everything still conforms to the laws of physics. Every trajectory under gravity is time-symmetrical. That carries over to General Relativity too.
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