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What is gravity? (mander.xyz)
submitted 3 years ago by to c/science_memes@mander.xyz
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[–] 25 points 3 years ago (1 child)

Stars that were behind the sun (within the radius of the sun, geometrically speaking) were visible due to gravitational lensing

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  • [–] 11 points 3 years ago (4 children)

    Oh ok. That messed me all up.

    I’ll have to look into that.

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  • [–] 9 points 3 years ago (1 child)

    It isn't directly analogous because one is gravitational and the other is not, but if you've ever watched a ship sail beyond the horizon, sometimes you can see a reflection of the sail after it is no longer in direct sight, because the way that light can reflect around the curvature of the earth. It's a pretty crazy phenomenon.

    https://en.m.wikipedia.org/wiki/Mirage#Superior_mirage

    In the case of the OP, as light from distant stars approach the sun, some of their light that may normally have passed to the side of the sun and beyond the earth, thus rendering them invisible, are instead 'bent' back towards the earth by the sun's gravitational well. But since the sun is so luminous we normally cannot see those stars. If the sun were somehow dark we would see a collection of tiny, distorted stars around the perimeter of it.

    To metaphorize: imagine a ball rolling straight from a point directly in front of you, but at an angle such that it won't roll to you. Now imagine a dip in the ground, not deep enough to cause it to fall in and not escape, but enough to cause the ball to curve as it rolls, sending it to you instead. The sun acts in a similar manner on light.

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  • [–] 6 points 3 years ago*

    An analogy I've used with my children.

    Sit in the middle of our trampoline. Roll a ball in a straight line beside you. Watch it roll around you and fall into the depression you make in the trampoline surface.

    This is a primitive 2 dimensional simulation of gravity.

    The ball "thinks" the surface is a flat plane, as far it knows it's rolling in a straight line.

    You are the heavy object curving space(time). Your eyes are a higher (3rd) dimensional observer and can see the curvature and it's effect on the ball.

    If you roll them ball fast enough, it curves slightly and then escapes your "gravity well". It has changed course slightly. This the gravitational lensing simulation.

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  • [–] 7 points 3 years ago

    Yeah it sounds silly but like it's a weird thing to see stars that are literally behind another object because it weighs enough and it's a interesting story for Einstein who has a moment discovering it.

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  • [–] 2 points 3 years ago (1 child)

    If you really want to be messed up, absolutely nothing is where we think it is because gravitational lensing affects the light of every object in the universe, while we observe. The further away it is, the more light is warped by the masses along the path, and we can't know what those many masses are or where they are either.

    Our observability of the universe is a guessing game as large as the universe, and there is no conceivable model to assess it all and the interrelations between...everything.

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