According to an internet site, presumably American, "Steel will expand from 0.06 percent to 0.07 percent in length for each 100oF rise in temperature. The expansion rate increases as the temperature rises."
Rough figures now. On a hot day, the temp might rise 20 DegC. This converts to 36F. For approximation, and ignoring the physics, let us call this .02%. So our 1K track would expand by 20 cm. and the calculation is sqrt(500.01 sq - 500 sq) = 3.16 m
This is still counterintuitive. Is the extra length taken up by those gaps in the track?
A good question - not mine, the original one.
Ed, Paul and Erin will touch on our favourite Whetstones, and even some things that didn't make it to a Whetstone.