On May 17, 9:04*am, "Androcles"
*Spacetime is curved so the Earth travels in a straight line in
spacetime, no acceleration or GR needed.
So, now, why won't *you* answer *my* question,
you ignorant anti-Celtic Jewish *******?
Wow! I didn't know that you were a Geocentrist! Have you ever
talked to Tony Pagano?
The earth is a massive body generating a gravitational field.
Therefore, it warps the space time. Objects on the surface of the
earth are in a region of space that have a slight curvature.
Objects on the surface of the earth are under the influence of
contact forces that keep them from falling. Therefore, they are not
truly in free fall. Therefore, their world lines are not perfectly
straight. So objects on the surface of the earth are undergoing an
acceleration relative to the free fall (i.e., straight world line)
condition.
These features don't make a difference for most relativistic
experiments. They could not affect the Michaelson Morley experiment,
for instance. However, they cause an effective centripetal
acceleration that is measured in a number of experiments. The Foucault
pendulum and the Sagnac interferometer have both been used to measure
the centripetal acceleration of objects on the surface of the earth.
Very often, the result is expressed as an "effective velocity" of the
earths motion. This is a derived quantity with units of velocity that
actually characterize centripetal acceleration.
Furthermore, the sun and the center of the galaxy both generate a
gravitational field. So earth is in a region of space that has a
slight curvature due to the mass of these objects.