When Apollo 8 first went behind the back side of the Moon, it was traveling at 7,777 feet per second (https://history.nasa.gov/afj/ap08fj/12day3_lunar_encounter.html). Was the speed being all 7s (the traditionally lucky number in western culture) intentional or just a coincidence? How was it possible to control the speed (or even measure it) down to a specific ft/s level?

  • $\begingroup$ My apologies for not answering directly, but this reminds me of D.G. Fahrenheit's scale. While in the process of inventing his scale, he supposedly wanted people to get a nice and clean 100 degrees on it, so he measured his own body temperature and then marked "100 F" at whatever point his thermometer prototype was showing. Later it turned out that he must have had a fever while calibrating his device, because normal body temperature is actually 98.6 F, but also varies a few degrees depending on the body's site you stick a thermometer in. {continues} $\endgroup$ Commented May 9, 2022 at 15:47
  • $\begingroup$ And still, if one just plays and tweaks around a little with a thermometer, one probably could eventually get a clean 100 F as well. Hence I guess it could had been some aesthetically driven person who intentionally adjusted the speed, or "upgraded" the speed reading during the measurement itself or during metric conversion. 2370 m/s actually amounts to 7775.6 feet/s, but who said that the 2370 figure was exact itself? No harm done by aesthetically "upgrading" it to read 7777 after conversion :} $\endgroup$ Commented May 9, 2022 at 15:47
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    $\begingroup$ The error of speed was at least some feet per second, so not all four digits are exact. The speed will change before and after orbit entry anyway and the orbit will not be a perfect circle with constant speed. The gravity field of the Moon is not precisely described by a point mass at the center of the Moon, so a circular orbit is not possible. $\endgroup$
    – Uwe
    Commented May 9, 2022 at 16:34


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