I went to my local planetarium recently and learnt that the earth to moon distance increases by 38mm each year, while the earth rotation slows down very slightly. Obviously not a significant amount to mean anything right now, but what will happen in the future when it will make a difference? How will people just “add time” to hours/days/weeks/months and so forth?
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Most people don’t know, and it’s largely invisible to them so why would they, that we often add a leap second to compensate for the difference between our standard time and “real time”. Since the early 1970s this has happened almost 30 times.
Now that we have computers and mobile devices synchronizing time over the Internet to Standard sources which are themselves synced to atomic clock sources this happens quickly and transparently.
The rate at which earth’s rotation is slowing down is absolutely miniscule. Since the 8th century, it’s only been slowing 2.3 milliseconds *per century*. 43,000 years from now, a day will be just 1 second longer than it is today. And since today, our days are actually 3 minutes and 56 seconds shorter than 24 hours, it’s going to be over 10 million years before we’re even *at* 24 hours a day, let alone significantly *past* 24 hours a day. Humans are going to be *long* dead 10 million years from now.
Most likely the same way we do now. The earth takes 365 days and a bit for a year. So every four years that extra bit adds up to a full day and so we just have an extra day in February. Until the extra time is significant, it will be ignored until it can be added up to make an extra period of time. So we will probably just have a permanent 29th Feb and then maybe a 30th every three years or something. It would be too chaotic trying to add it in smaller increases.
Engineer here: we deal with this today by adding leap seconds, usually after big earthquakes slow down the earth a bit. Every few years on midnight the 60th second happens twice. You’ve never noticed because we did our jobs right. It’ll be a long, long time before this strategy stops working and we need to officially do something more drastic like slow down the second.
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