It is claimed that Einstein’s Theory of General Relativity replaced Newton’s gravitational theory. Newton’s theory described the force of gravity, while Einstein said “Force, what force, space-time is distorted by embedded masses and so moving objects instead of moving in straight lines, move along the curved lines of space-time.
A common example used to distinguish these two ideas is an orbiting satellite, like the moon or the ISS. In Newtonian physics, the satellite moves in a straight line unless acted upon by a force. The force involved was gravity, which was a pull on the satellite causing its path to change. In effect the satellite is pulled “down” toward the Earth but it keeps missing it because of its “sideways” movement.
In Einstein’s physics, there is no force, the satellite is travelling along a “straight” line of curved space-time, giving the appearance of a force acting when there is really no force. (Think of a NASCAR race on a steeply banked track. When the cars enter the banked parts of the track, they don’t have to turn their steering wheels much or at all because the slant of the track imparts the turn needed.)
Okay, here is my problem with Einstein’s conception of “gravity.” Starting with a board at a slant (see illustration below). We all know if the ball is in such a position, if it is free to move, it will roll down the plane. But in the absence of gravity, what happens to the ball? <Jeopardy theme music playing>
In the absence of gravity or any other force the ball doesn’t move. It stays where it is (according to the Law of Inertia, or Newton’s First Law: an object will remain at rest or continue moving in a straight line at a constant speed unless acted upon by an external force.
Okay, now consider a larger experiment. The Earth orbits the Sun because of space-time being curved by the Sun, right? If we had access to a Star Trek like matter transporter and we “beamed” a round ball into a position stationary with regard to the Sun, what would happen to it? According to Einstein, it would not move because there would be no force acting upon it. Available paths, aka distorted space-time surfaces, to that ball may be myriad, but since it is not moving, it would take none of those.
According to Newton, it would move in a straight line directly into the Sun. According to Einstein, it would not move. Now, I ask you: would the ball move?
Postscript In a comment to a comment where I share this thought experiment, the commenter on my comment went on and on about how thee Sun was moving, along with the Milky Way Galaxy, rotating around the center of the Milky Way Galaxy, moving as part of a supercluster, etc. Apparently the phrase “with regard to the Sun” was insufficient, so may I clarify that it was stationary relative to the Sun or that it moved along with the Sun, not just relative to it? Sheesh.
Uncommon Sense 