I usually get up early, but this morning was exceptional. As a result, I fell to wondering how many other people were up, and from there what would be the moment in time when there was least human activity on the planet. I should have gone to bed hours ago, but the question popped into my head again and the Internet was calling…
I think the answer is 8.30 pm in winter and 7.30 pm in summer (UK time). (Corrected after some sleep.)
Here’s my reasoning. At a guess, the core sleep time in any given time zone is 12 midnight until 6am (0000-0600). Looking at the map of time zones, the most populous group would be one that includes H (which contains the whole of China, and much of South-East Asia) and E* (containing most of the Indian subcontinent). These two zones are two and a half hours apart (E* is UTC+5.30 and I is UTC+8), so local times of 1am (0100) in E* and 3.30am (0330) in I would fit them both into the same core sleep time comfortably .
On these assumptions, and ignoring the effect of Daylight Saving Time, most humans are asleep around 2030 UTC. If DST is applied to these time zones, the quiet time is probably around 1930 UTC.
If I am right, Rives is probably wrong.