[paul.fr]

how many hours are there in a day on the moon? when astronauts visit the moon what system for telling the time do they use?

[another_someone]

Since the moon shows only one face to the Earth as it orbits the Earth, and it takes about 29 days to orbit the Earth, and its orbit around the Earth is very much less than the time the Earth takes to orbit around the Sun, thus one must assume that a day on the moon is very approximately about 29 Earth days (very approximately because the moon actually takes longer than 29 days to orbit the Earth, and one also has to allow for the fact that the Earth does not remain stationary around the Sun during this period).

Since astronauts are in close touch with their controllers on Earth, it is more important for them to synchronise their time with the time used by their controllers on Earth than it is for them to adjust to local time (which in any case they are only briefly exposed to, and would be unlikely to easily biologically adapt to anyway).

[paul.fr]

if in the future we were to colonise the moon, what would you guess we would do about the time, days months etc? use moon time or an earth standard, GMT for instance.

[another_someone]

if in the future we were to colonise the moon, what would you guess we would do about the time, days months etc? use moon time or an earth standard, GMT for instance.

A similar question was previously discussed pertaining to timekeeping on Mars:

http://www.thenakedscientists.com/forum/index.php?topic=4953.0

Given the close proximity of the Moon to the Earth, and the unlikelihood for a lunar society to ever be totally self sustaining, I would doubt they would ever use a purely lunar clock (I think it unlikely that astronauts would ever become permenant lunanauts (or should that be lunatics []), but just visitors for a time - either based on Earth, or in the space in between).

[that mad man]

Although there is no conclusive evidence I have often thought about the implications, if any, of human biorhythms.

For instance, we know that a human females menstrual cycle is moon based and rhythms of light and darkness also influence hormonal physiology. It can cause depression and other mental and physical problems.

How would that differ in non earth based living (colonising a planet) or prolonged space travel?

How would the body cope with a change in rhythms, can the rhythms be changed or would it matter?

I would think that the 24 hour system would have to be used as although not on earth our bodies biorhythms would still need to keep to the same rhythms and we would be in sync.

TMM

[another_someone]

For instance, we know that a human females menstrual cycle is moon based

It happens to be approximately the same duration, but it is not synchronised with the lunar cycle.

It is debatable if it ever was synchronised with the lunar cycle, and why should it be.  In nature, females would normally expect to conceive on almost every cycle, and thus one would not expect them to have to flush out their uterus on a monthly basis.

It is true that historically the moon was more significant to us (full moon would have been the time when there was most nocturnal light available, and so one could perform some tasks at night where at other times in the month it would simply be too dark), but it would be doubtful if this had much pertinence to the female menstrual cycle.

The moon also effects tides, and if one believes in the aquatic ape hypothesis, then tidal variation may have had some pertinence to early human development.

In modern terms, since there is no synchronisation between the female menstrual cycle and the lunar cycle, it would continue at roughly the same rate whether we had a lunar cycle or not.

and rhythms of light and darkness also influence hormonal physiology. It can cause depression and other mental and physical problems.

How would that differ in non earth based living (colonising a planet) or prolonged space travel?

How would the body cope with a change in rhythms, can the rhythms be changed or would it matter?

I would expect that over generations one could adapt to a degree to differences in levels of light, but even peoples who have lived for centuries within the Arctic circle are still afflicted by depression during the winter months.

Then again, the bigger problem is that even here on Earth, we ever more live in societies that ignore the solar cycles, and even in the height of summer, we spend much of our lives deep inside open plan offices, with little access to natural light.

I would think that the 24 hour system would have to be used as although not on earth our bodies biorhythms would still need to keep to the same rhythms and we would be in sync.

If a population becomes truly detached from Earth, then I would agree that they would probably retain a daily cycle of approximately 86,400 seconds; but there is a lot of latitude as to exactly what duration that might be (it could be stretched out to 100,000 seconds, or reduced to 50,000 seconds).

One problem that would very likely arise is that if these peoples are spread across a number of independent communities, there is no reason why all of the communities would retain synchronised circadian rhythms, unless the operate as closely linked communities (bear in mind the widely different calendars that different societies on Earth used, that despite their having the same astronomical cues).  The best one can hope is that if they are all using similar atomic clocks, they will at least have a common count of the number of seconds using that atomic clock - but this assumes that there is minimal time variation caused by relativistic effects (including differences in gravitational influence on time).

[that mad man]

Cheers another_someone, I find this interesting.

Circadian rhythms and any problems while in space are something that is obviously recognised well by NASA especially sleep abnormalities. I just been reading that they even take them into account on the shuttle missions.

TMM

[daveshorts]

You get the same problem if you are living in the arctic or antarctic - it is day or night for several months of the year. I think their solution is to pick an arbitrary timezone (eg where the scientists come from) and work to roughtly that.

[another_someone]

You get the same problem if you are living in the arctic or antarctic - it is day or night for several months of the year. I think their solution is to pick an arbitrary timezone (eg where the scientists come from) and work to roughtly that.

That problem only arises if you are actually on the axis of rotation (the actual pole itself).

If you are simply near the pole, then except for the time actually around midsummer, and midwinter, you will have some day, and some night, even if it is only 23hours day and 1 hour night, or visa versa, thus you do actually have a natural daily cycle, even if there is an extreme shortage of daylight within it (and even during the time of daylight hours, one does see a shifting of the sun, and a change in the quality of the light during the day).

[paul.fr]

You get the same problem if you are living in the arctic or antarctic - it is day or night for several months of the year. I think their solution is to pick an arbitrary timezone (eg where the scientists come from) and work to roughtly that.

That problem only arises if you are actually on the axis of rotation (the actual pole itself).

If you are simply near the pole, then except for the time actually around midsummer, and midwinter, you will have some day, and some night, even if it is only 23hours day and 1 hour night, or visa versa, thus you do actually have a natural daily cycle, even if there is an extreme shortage of daylight within it (and even during the time of daylight hours, one does see a shifting of the sun, and a change in the quality of the light during the day).

George, some places around norway, i think, don't have darkness. the sun is out all 24 hours long at some point in the summer

[Seany]

Paul, I think it's like that in the Antarctic as well. 9 months of darkness and 3 months of complete light. I think that was it.. I'm not sure. []