Physics updates

Has your GPS ever failed you? Perhaps it told you to turn in 100 feet or so, but once you were past a corner, on your way to the nearby next cross street, it decided you'd gone too far. Perhaps, at some critical juncture, it just failed to say anything, because reflections from nearby buildings confused it with too many signals. Or perhaps you were indoors, hoping for intra-building guidance, and -- of course -- there was no signal.

And it works!Then be of good cheer (especially if you're in...