I know shadows in the ground prove how the Earth is positioned close the Sun and how the light reflects off the moon and something to do with the curvature of space and/or roundness of Earth but can someone give me a quick overview? Something to do with the roundness of Earth creates shadows.
Also, for the stupid Flat Earthers, I know flat land or flat surfaces don’t experience as many shadows or very rarely, but yeah can someone explain?
Thanks for helping the random thought.
In: 1
So many questions at once… I think I’ll have to oversimplify a bit.
About the roundness of the earth with shadows: When measuring the length of a shadow, you are also measuring the angle between the ground and a line towards the light source. If you do this in multiple places, you get multiple lines towards that light source and can calculate how far away they intersect.
But there is one assumption you have to make, and that is that the ground at those different locations is in one plane. If you do this with the sun and two measurements, you get something in the “a couple thousand miles” range. But if you then measure how parallel the run’s rays are at one point, you won’t get the result you’d expect if the sun was that close. And if you do the shadow angle measurements at more than two points, the lines won’t intersect at one point anymore.
But if you change your assumption of a level ground to be part of the surface of a sphere, et voila, all the measurements suddenly line up perfectly.
Moon is reflective: There’s not much to measure here, this one is just an observation. Once you have a telescope that is good enough to see that the dark part of the moon is still there (and doesn’t get eaten by some sky snake), you can figure out that it’d be very unlikely for the moon’s surface to light up and go dark in such a weird way. And once your telescope gets even better, you will notice that the bright side of the moon isn’t uniformly lit. There are shadows up there, and they move around—just like shadows from a moving light source. And they point away from where we just calculated the sun should be.
In addition, when looking at how the lengths of shadows change over time at different locations on the moon, we can see that it cannot be flat either. Otherwise, those shadows would get longer and shorter by the same amounts. But they don’t. The closer they are to the dark side, the longer they are. And when the dark side is the other side (i.e. 14 days later), they point in the opposite direction. When there’s a full moon, the mountains in the centre have no shadow at all, but those at all sides have very long ones. etc.
Earth’s shadow: Someone else already answered that.
Curvature of space: You mean how heavy objects bend the space around them? The moon is a bit light to see that, but with modern telescopes, we can watch plenty of really heavy objects. And there we see this lensing effect. Around those objects is a ring where the stars are very dense, i.e. where what’s behind the object is visible around the object, all smooshed together. In some cases, it’s so extreme that we can see the same star at multiple locations, once directly and once where the light from it into another direction got bent towards us. However, the step from “light is attracted by gravity” to “mass bends spacetime” is quite big and complicated. Too big and complicated for me to explain it here.
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