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Jim,

I find Einstein's discussion clear, and more importantly, supported by a century of observation.

The "proof" you offer makes an assumption different from the thought experiment, which concerns, in Einstein's words, "a large portion of empty space, so far removed from stars and other appreciable masses that we have before us approximately the conditions required by the fundamental law of Galilei."

In such conditions, the convergence you describe would not happen.

Consider this: A person in free fall with no ability to observe the outside world, whether in orbit or in an elevator with a broken cable in an evacuated shaft, is "weightless." From the perspective of someone on the outside, that person is in a gravitational field and is accelerating. From the perspective of the person falling, the local "g" is 0.

Going further: We don't feel the Sun's gravity because we are falling toward/around the Sun with our planet. Nor do we feel the net gravitational attraction of the galaxy, even though the Sun and Solar System are moving in an orbit around the galactic center of mass and are bobbing up and down through the galactic plane.

We only know of such accelerations by making observations of the rest of the Solar System and the galaxy.

We don't even feel Earth's gravity when we are in free fall, but it is there.

As far as I can tell, your difficulty in understanding this leads to phrases that are muddled at best and incorrect at worst, like: "Gravitation is only involved with inertial acceleration when it is resisted." That seems based on the perception of gravity, not gravity itself.

And now I must close my part of this. I have a book to write based on my "Our Next Planet" school visit program.

Fred Bortz -- Science and technology books for young readers (www.fredbortz.com) and Science book reviews (www.scienceshelf.com)