What do they mean when they say space time is curved? I keep hearing a lot of talk about Space Time being the 4th dimension, and no matter how many trampoline examples I see, I just don’t get it.
In: Physics
They mean what they say, that it’s curved.
You can see this around objects with high gravity fields. Best examples are so called gravitational lenses. This is where something like an entire galaxy bends the space around it to such an amount that you can see what is behind it. If the space wasn’t curved then the galaxy would block the light. By the space around the galaxy being curved the light from the objects behind it travel in a straight line, because that is what light does, but it’s travelling in a straight line through curved space. Sometimes this means you can see the same object multiple times.
If you’ve seen Interstellar you would have seen it with the black hole.
Example http://assets.cdn.astronomynow.com/wp-content/uploads/2015/02/02153356/Interstellar_black_hole_940x400.jpg
That’s a flat disc but the high gravity has bent the space around it so you can see behind it.
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