Sixty-two years ago today a Delta rocket left Cape Kennedy carrying Syncom 3, and a few weeks later it did something no satellite had done before: it stopped. Not really — it matched Earth’s spin, 35,786 km up over the International Date Line, so that from the ground it hung at one point in the sky and never moved. The first geostationary satellite. Syncom 2 had come close the year before but drifted north and south through a daily figure eight; Syncom 3 simply stayed.
A thing that sits still in the sky is a thing you can point a dish at and never touch the dish again. That is the whole trick, and it is most of modern television. Look up tonight: somewhere along that arc a few hundred of its descendants are holding very, very still.
The idea was published in Wireless World in October 1945 by a young RAF radar officer named Arthur C. Clarke, who worked it out on paper, didn’t patent it, and spent the rest of his life being asked why not. Here’s the clever bit: the altitude falls straight out of Kepler’s third law and a one-day orbit. The hard part was never the maths. It was the rocket.