Question

At noon, the sun and the earth pull the objects on the earth's surface in opposite directions. At midnight the sun and the earth pull these objects in the same direction. Is the weight of an object, as measured by a spring balance on the earth's surface, more at midnight as compared to its weight at noon?

Answer 1

The distance of the sun from the earth is R = 150x10⁶ km while the diameter of the earth is 12800 km only. So the variance of distance R between the noon and the midnight is comparatively very small (about 0.0085%). The force on an object by the sun is inversely proportional to R², so the change in the force between the noon and the midnight is even smaller or say negligible. So, the weight measured by a spring balance at the earth's surface at these two times will not differ as the spring balances are not sensitive enough to detect such negligible changes.