[Mee-n-Mac]

Originally Posted by SIKSUKR

Smith Point brings up an interesting point.I always thought of water as being the most accurate level.Over a long span I guess it's not but, what is level?Relative to the curvature of the earth apparently.Level actually is not a straight line then is it?Oh boy,thanks RG!

Correct, level and straight aren't the same thing. Even worse straight ain't what you think straight is. Imagine a perfect laser out in space far from anything. You'd think it would project a straight beam and you'd be correct. But bring that laser to Earth and it's straight line isn't the same line you'd see in far off space. Just as the Sun curves space-time so a star behind it (the famous 1919 confirmation of general relativity) the Earth will curve space-time (ever so slightly) so the laser isn't as straight as it would be in non-curved space-time. Of course the refraction effects mentioned earlier would far outweigh this effect. Good thing that I'm an engineer and not a physicist because that allows me to say "close enough".