I understand some of the basic concepts of curved space, flat, positive, negative, spheres, saddles, etc. In flat space, if one measures the angles of a triangle, the sum adds to 180 degrees. In spherical space, the sum is greater than 180.(adsbygoogle = window.adsbygoogle || []).push({});

OK, how do things work in spherical space? If I shine a light in front of me, does it curve around as on a great circle and hit me in the back? How do I determine the length of a curve (I suppose assuming I'm not attached or standing on anything, but am free to float with a jetpack) or the radius of the circle it makes? Put down a marker and walk (jet) through "space" trying somehow to keep a "straight" path? What's straight here? Does it need to be a great circle or can I pick any old circle?

If you and I are in flat space, and I see you, then someone throws a switch to turn it into spherical space, do you look the same to me?

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# What Do I Observe Moving Around in Curved Space

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