> Earth rotates around its axis – one rotation is called a day
A [solar] day is the time between noons, which is slightly more than one rotation on our axis. A single rotation is a [sidereal day] — the Wikipedia article has a good animation.
(The ellipse part of our orbit means the length of a solar day isn't consistent, as the rotation required to get back to pointing at the sun isn't the same throughout the year, which is what leads to mean solar time. The the article doesn't want to do ellipse orbits, which is fine… for a moment… but…)
> When the tick comes directly under the sun, that's (solar) noon, and one full rotation is one day.
But this is sort of where if you do you MST (if you have a fixed day length, you are), then when the tick is directly under the sun it won't necessarily be noon. The difference (between MST & solar) is like 17 minutes at its peak. The aliens will be looking at this going "it's uh… close? But off."
I still think "solar time" is a cultural assumption, though I do think there's a high likelihood of aliens sharing that assumption. But one might also imagine a species on a tidally locked world (maybe having grown up in the twilight region) with no concept of "days".
Thanks for the detailed explanation, I love this - exactly the sort of "geek out" mode I was in when tinkering with the clock.
I had a fuzzy sense of these differences but had no idea that MST/solar is 17 minutes off - that's a lot! Of course there's also the difference between this and proper clock time (depending on where in your timezone you're located), and the clock shows clock time.
> Long or short days occur in succession, so the difference builds up until mean time is ahead of apparent time by about 14 minutes near February 6, and behind apparent time by about 16 minutes near November 3.
> Of course there's also the difference between this and proper clock time (depending on where in your timezone you're located), and the clock shows clock time.
"Standard time", yes, will be different yet. I didn't comment on that b/c the whole article is, of course, building a clock that unmoors us from cultural conventions, and I think Standard Time falls very squarely in the "cultural convention" bucket. So it's more of a solar clock in that sense.
I regret not learning about this before, but apparently "sidereal" is from Latin, and not what I always assumed, i.e. "side real" as in "kinda not quite real, wtf?!" day.
A [solar] day is the time between noons, which is slightly more than one rotation on our axis. A single rotation is a [sidereal day] — the Wikipedia article has a good animation.
(The ellipse part of our orbit means the length of a solar day isn't consistent, as the rotation required to get back to pointing at the sun isn't the same throughout the year, which is what leads to mean solar time. The the article doesn't want to do ellipse orbits, which is fine… for a moment… but…)
> When the tick comes directly under the sun, that's (solar) noon, and one full rotation is one day.
But this is sort of where if you do you MST (if you have a fixed day length, you are), then when the tick is directly under the sun it won't necessarily be noon. The difference (between MST & solar) is like 17 minutes at its peak. The aliens will be looking at this going "it's uh… close? But off."
I still think "solar time" is a cultural assumption, though I do think there's a high likelihood of aliens sharing that assumption. But one might also imagine a species on a tidally locked world (maybe having grown up in the twilight region) with no concept of "days".
[sidereal day]: https://en.wikipedia.org/wiki/Sidereal_time