My brain was working overtime when I was wondering:
OK we’ve got our 24 hour time, but would it do us any good on another planet if we were to inhabit it or would we have to make new clocks/watches for Saturn for instance. Since we basically all operate on the 16/8 cycle - we’d be in complete confusion trying to wake/sleep on the Saturn day/nite cycle.
I’ve come to the conclusion that motor-vehicles, planes, etc. are a form of crude time travel machines since we get to a destination much faster than if we had walked or swam. Even though we’re not experiencing a theoretical time surge, we’re still traveling faster than “human speed” but not even close to light speed.
Before the astronauts went to the moon, did we know what the dark side looked like? If so, how was this obtained since we always see the light-side (man-in-the-moon).
Even if the moon rotates when is this dark-side visible?
The length of the day is arbitrary by physical standards. Physiologically, though, we might have problems. However, humans are notoriously interesting for their ability to adjust to different cycles. Experiments have been done in the land of the midnight sun whereby folks have been asked to get rid of their clocks for a long period of time. Some people end up shortening their days, other people end up legthening them. All this says, in short, is that humans don’t make for accurate clocks.
The answer to this question is similar to the answer to question 1. Humans don’t make accurate clocks. Indeed, if you bring your quartz time-piece along with you (or it’s digital analog – I’ve always wanted to write that!) you will find that time is still proceeding at one second per second. Other than effects of special relativity, motor-vehicles are really not physically significant time machines.
The first view of the FAR side (not the dark side… we astronomers get antsy when you say “dark” side of the moon) was had by the Ruskies from a probe. Indeed, Apolo 13 was the first time a human laid eyes on the far side of the moon without “reinterpretation” from a probe.
The time the moon takes to orbit the earth is the same as the time it takes to rotate on its axis. So, although the moon rotates on its axis, the same side of the moon always faces the earth.
This is not a mere coincidence by the way and neither has it always been so. The gravitational relationship between the earth and the moon eventually caused the moon to get locked into a rotational period that always keeps the same face pointed at the earth as it orbits (the earth was likewise getting its rotation adjusted by the moon but the earth significantly outweighs the moon so the moon inevitably lost that battle).
The moon rotates just the way the earth does, around a line drawn from pole to pole. The timing works out so that the same side is always facing us, as explained by W-a-M.
Or, to put it another way: Suppose you’re standing on the spot of the Moon that’s closest to the Earth. If you look up in the sky, you’ll see some stars. Wait two weeks and look up again, and you’ll see a completely different set of stars. The spot on the Moon you’re standing on was pointing at one set of stars, now it’s pointed at another set. It changed the direction it was facing, so it rotated.
Meanwhile, though, it also moved around the Earth, so the Earth stayed in the middle of the sky.
Visual aids:
The Moon orbiting the Earth, and keeping the same side to us: