Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Atomic-S on 31/07/2006 06:14:45
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If activities on Mars become more common, at some point it will become cumbersome to keep time there by Earth clocks. Has anyone given any thought to how to keep time on Mars?
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It would not make sense to ignore Earth clocks entirely, so long as Earth and Mars remained linked (i.e. there is communication and transport between the two).
Earth has several units of time. Some of these are relevant to the Earth's rotation and orbit, while others are more arbitrary.
The second is a wholly arbitrary unit that is purely there for convenience at a human scale. It is a very logical time unit to continue to use in all aspects of our lives, on any planet. It is increasingly the only unit of time used in computing (most computers now only measure absolute time as the number of seconds since the 1st of January 1970). Where there still remains much debate, and much political conflict between different interest groups, is the issue of leap seconds – and ultimately, these leap seconds would have no consistency between Mars and Earth (as it is, they are regarded as a problem for much of the computer industry, but are still favoured by Earth bound astronomers).
The year was really important for farming societies to know when to perform farming activities and how that will relate to where the Earth is in relation to the Sun. Since it is very unlikely that we will be doing any natural farming on Mars, it really is of little consequence which year, if any year, is actually kept on Mars. In terms of measuring the orbital position of Mars, it is probably going to be at least as significant for people to know the relative orbital position of Mars relative to the Earth (i.e. when is Mars closest to and furthest from the Earth), rather than measuring its position around the Sun in absolute terms.
The month is another arbitrary time unit that approximates to the orbital time of the Earth's moon around the Earth, but it does not even represent that accurately, so it must be regarded as arbitrary on Earth, and would be just as arbitrary if retained on Mars.
The most interesting unit of time is the day. Clearly, on whichever planet we are on, the hours of daylight and the hours of darkness will be important, and so the length of the local day will be important. What is interesting is how this will effect the internal biological clocks on human beings, which have been programmed to be approximately synchronous with the length of the Earth's day.
George
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The day length wouldn't be a problem on mars because on mars the day length is 24 H 37 m so its only about 40 mins longer than an earth day.
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So this raises the question of how a Mars clock might be designed. There are obvious advantages to keeping the concept of 24 hours, each divided into 60 minutes, each divided into 60 seconds, because that is the way innumerable devices are set up to reckon time. Obviously we cannot do that on Mars using the present second, and have it come out evenly. However, the Mars day is so similar to the Earth day that it seems somewhat logical to divide the Mars day up into 24 pieces as on Earth, etc. Whkich would necessarily require the definition of a new unit of time, a Mars-second, which would be a little different from that on Earth. Of course that is objectionable in that all our physical laws, measurements, and instruments are set up in terms of the second we know, and that would be a mess to deal with. One could keep the present second, and still have 24 hours in a Mars day, by making the hour and minute a bit longer than 60; but that would create many computational problems. One possible solution might be to keep time there using Earth-sized hours, minuts, and seconds; but add at the end of each day about half an hour of leap time, which could be built right into the clock dial by having it marked off to allow for it. (It would look dorky, but it would work). Then, since even this would not come out to an exact number of seconds, there would have to be some leap seconds thrown in every once in a while.
One other complication that occurred to mi as to do with the eccentricyt of Mars' orbit, which has the effect of having the length of the solar day vary, depending on whether mars is accelerating or decelerating angularly around the Sun. The same effect on Earth causes the noon transit of the sun to vary from exactly 12:00 standard time, at different times of the year. Not a big problem on Earth, but Mars' orbit is mor eccentric as I recall, which means the effect might be more pronounced. Would it be pronounced enough to cause trouble?
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There is absolutely no reason I can see for having 86400 seconds in a day – this is an inheritance from the Babylonians, and really has more to do with their astrological charts and base 60 numbering system. In modern terms, it is mere custom, and has no true contemporary significance.
It would also create many many problems if we tried to redefine the second, since seconds are a basic scientific and computational unit.
How you define minutes and hours – if those are the units you wish to retain, is up to you.
Whether you even need fixed length days is again dependent upon how you run your life. Certainly, there is no requirement to worry too much about exact timing of noon, since even here on Earth, aside from the slight natural drift, variations such as standardised time zones and daylight saving times means that few people have any real concern for exactly where the Sun is at any given time, and really are only concerned with one sunrise and one sunset per day, at very approximately similar times. We already mess around with the timing of the day so much, we can scarcely regard that as a unit of measure that is sacrosanct.
George
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Perchance then, a reasonable approach would be to begin the clock at midnight of each mean solar day, and simply count seconds till the next midnight, with leap seconds thrown in then as needed. No hours, no minutes.
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With regard to a Martian calendar, there actually are two phenomena which warrant taking account of the Martian year: meteorology and astronomy. The state of Mars' atmosphere varies significantly with the position in its orbit, apparently chiefly due to the distance from the sun. And, if any astronomical observations or activities are to be conducted from the Martian surface, the positon of Mars in its orbit is of significance.
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Probably would make sense to reset the clock at each quarter day (i.e. dawn, dusk, midnight, and noon).
It is likely that tradition would still dictate that they would retain a base 60 set of superior units of minutes and hours, as has been traditional since Babylonian times, even though such does not necessarily even have any meaning to us other than mere tradition.
It is also likely that, just as our calenders typically tell you phases of the moon, even though they are predominantly solar calenders; so to the Martian calenders would still give the date on Earth, even though on a daily bases the date on Mars might be more pertinent. It may even be that years will be continued to be counted as Earth years, even though this would not be in sync with the local seasons (after all, the Muslims are quite happy to retain a calender that drifts through the solar year). In many ways, the seasons are likely to be less important for Martians than they were for our ancestors because the Martians will not be undertaking natural farming, and will in any case have to be substantially isolated from their environment.
George
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Great thread Atomic-S.
great comments and observations by all contributors. Thanks.
Would they just not have two calenders ?..abide by the Earth one and keep the Martian one for local reference.
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