We USE GPS all the time on the Duke. In uncontrolled airspace it is so accurate a pilot has to be careful to use "off" altitudes and headings to prevent a collision with other aircraft using standard parameters in the opposite direction. Considering General Relativistic effects is critical to assuring the accuracy of GPS equipment. Any reader interested in knowing HOW essential it is that we "figure General Relativity into GPS" to assure even reasonable navigation accuracy is free to contact me for an eye-opener. I understand that one possible way, in times of war, for the military to make GPS worthless to the average person is to delete the GR corrections- and apply them manually only for the military!

I'm really interested in recent and not so recent experiments involving action at a distance and the topological implications. If one photon can instantly affect another at vast distances, and we are constructed of photons, moving vast numbers in coordination could in fact influence the universe...in ways we don't perhaps understand, but influence it none the less.

The fact that the speed of light is measured invariant to say 10 places in a vacuum, without regard to ANY motion of either a source or an observer has profound implications, not only with regard to the true essence of what we call force and motion, but also in the observed "ability" of light energy to reduce entropy, do work, and "create".

While highly counterintuitive, at the bottom line, SRT and GR closely match the reality we observe- and is the logic rigid, or is it not?

By the way, I saw "Contact" only a few months ago for the first time. I'm not a movie goer, but my children sent me a VCR copy (out here in the islands) where I don't even have cable.

It is clear that Carl Sagan did have a pretty fair concept of General Relativity. Any Physicist would understand the geometric meaning of the roughly spherical contraption with three rings simulating time, space and energy! The astronaut experiencing time travel along the axis at high energy levels is not Jodie Foster...the time traveling astronaut is US. The journey around the universe was interesting too.

Of course it was science fiction! Time travel in our universe doesn't require a 1.5 Trillion dollar contraption...it is built in. We call it "birth" and "death".

The engineering complexity we observe in the universe guarantees that even if we can't (or don't choose) to see it, we live in a universe alive with intelligent complexity, and in which almost everything which can be...HAS been done.

Our role lies in continuing the eternal completion of that "almost".

Best Wishes, Sam Cox