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William Cron San Antonio, Texas — Sat, 11 Aug 2007 03:35:34 GMT

Time is based on earth's rotation about its axis and its rotation around the sun. When humans live on Mars, will they age slower since its rotation is slower and it takes longer to revolve around the sun? Humans on the Moon- will they age since the moon appears to not rotate around an axis? Will scientists creat a new clock based on Mars rotation? How long will an hour be? A day be? A year be? Billy

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steve smyth lynn ma — Sat, 11 Aug 2007 20:53:15 GMT

Time is based on Human perception...beyond our reach, it does not exist...stop worrying about it, and get going!

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Des Emery, St. Thomas, ON, Canada — Sun, 12 Aug 2007 04:26:41 GMT

Hi, Billy -- I do not expect to be your only reply but here's some info to think about. Time is set by longitude and latitude which is why we have so many lines on a map. That accounts for hours,minutes and seconds on Earth, a circle having 360 degrees around its centre. Earth travels in its orbit around the sun in an ellipse,not a circle, but it still takes one year (four seasons) to complete each orbit. The rotation of the Earth upon its own axis does not coincide exactly with the solar orbit, and we add a day every four years, leap year, to keep it all on time. Except that is still not enough juggling to make the process smooth, so we take the leap year out when the century year (e.g., 1700, 1800, 1900, 2000) is not evenly divisible by four. This measurement of time is generally agreed upon by most nations, and includes 'daylight savings time' when the clock is pushed ahead in spring and backwards in the fall.

The reason you see the same face of the moon all the time is that the rotation of the moon upon its own axis coincides with the month (a word derived from 'moon') the moon takes to complete its orbit of Earth. The moon also regulates the tides of the oceans of Earth by its gravity (high tide) and resonance (low tide) and its waxing and waning depends upon its position relative to Earth and to the sun. The moon is responsible for other things that regulate life here.

You can see that some things are whatever they are by nature, and other things are invented by mankind to be more useful to us. But time is essentially the same all over the universe (as far as we can determine, anyway) so we will probably continue to count time intervals by Earth standards regardless of where we are in the future, be it the moon or Mars or Alpha Centauri.

A Mars year will be the time it takes for the planet to complete one orbit of the sun, and a day will be how long it takes for the planet to complete one rotation on its axis. Martian hours, minutes and seconds will be determined by the planet's own latitude and longitude. It will still be 360 degrees around but the distance between the lines will be much less than we have on Earth. There will be no Martian months since the moons of Mars are comparatively insignificant.

Humans will still age as fast as we do here on Earth, but birthdays will be celebrated there by Earth standards so you would celebrate sometimes twice in one 'year' if you were living on 'Martian time.'

If your name is actually 'Cron' your ancestors probably were the timekeepers of their tribes, and your interest in 'time' is indeed timely.

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Lars Jonsson from ol EU — Sun, 12 Aug 2007 05:23:01 GMT

Time on the moon & mars will theoretically run slower due to the relativistic influence as the gravitation is lower.
I´m not sure how this will affect a human considering the effect of all sorts of radiation in the otherwordly environment...
Perhaps an new article of Mr Boyle could shed light on this?

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Wayne, TN — Sun, 12 Aug 2007 08:14:15 GMT

"Time is based on earth's rotation about its axis and its rotation around the sun."
Time is not based on the Earth's rotation, only our method of measuring the passage of time.

"Will scientists creat a new clock based on Mars rotation? How long will an hour be? A day be? A year be? Billy "
Since a day on Mars is a bit longer than 24 hours its been suggested that the extra minutes be designated a rest period where the Marsbase personnel just kick back and relax.

There have been alternative time measurements suggested and/or implemented in the past. The Calendar of the French Revolutionary council is an example. And several cultures have used a thirteen month year.

I expect all spacecraft will try to stay within Greenwich Mean Time with anomalies caused by variations in speed used to measure those speeds and distances and allowed for in calculations with Earth time broadcasts compared to onboard atomic clocks as part of the navigation system.

Since those broadcasts will be limited to the speed of light the times received onboard will be earlier than actual time on earth at any given moment according to the distance traveled. There will be constant adjustment for such factors.

Since biological aging is not according to any time measurement, but rather according to the internal changes in the individual cells due to environmental factors and the individual's state of health with cell repair and replacement being the deciding factor, there's really no way of knowing the exact rate that anyone might physically age under those conditions.

Just as here on earth identical twins who lead very different lifestyles may look and feel either younger or older than their twin and have a different life expectancy.

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T Nathe — Sun, 12 Aug 2007 16:36:06 GMT

One of the most useful applications that I use to plan my astronomy activities, is the 'Clear Sky Clock'. It can give you about 48 hours of advanced information on night sky conditions. Plus it shows you how powerful one pixel's worth of data can be.

http://www.cleardarksky.com/csk/index.html

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Alan Boyle — Sun, 12 Aug 2007 22:01:23 GMT

Strangely enough, I've been clicking through the Clear Sky Clock a lot, looking for the best place for Perseid viewing. I settled on Cle Elum, as detailed in this story I just wrote:

http://www.msnbc.msn.com/id/20187088/

The questions about time on Mars came out of the blue, but they're really thought-provoking. Thanks, Billy! My guess is that there will be 24 hours in the Martian day and 24 months in the Martian year (because Mars takes roughly twice as long to go around the sun), but the hours and months will be measured differently to fit the different length of the day and the year. Each "hour" will be a bit longer, and each "month" will be a bit shorter. On Earth, months used to reflect the phases of the moon, but now they're more of a timekeeping convenience ... and I'm sure the concept of the month will be used in the same way on Mars. There'd have to be conversion programs to translate "Earth time" into "Mars time" at a given moment.

The question of time dilation is also intriguing, and more complex than you might think. The way I see it, if you had two Earth-calibrated clocks, and you took one of them to Mars for a long time, then brought it back to Earth ... you would find that the time on the clock from Mars would be later than the time on the Earth clock.

This is because of general relativity. The usual (and not completely well-stated) rule is that clocks
tick "slower" in a gravitational field. Mars is farther out from the sun, thus it's "higher up" in the sun's gravitational well. Mars is also less massive than Earth, so its own gravitational field is not as strong as Earth's. Thus, the clock on Mars should run "faster" than the clock on Earth.

In the case of clocks orbiting Earth, there is a special relativity factor as well as a general relativity factor. The SR factor partially cancels out the GR factor. This interactive provides more information on that:

http://www.msnbc.msn.com/id/7423298

So just how much faster would a clock on Mars run? That kind of math makes my head hurt, but some kind soul out there might be willing to perform the calculations for extra credit. ;-)

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Frank, Dallas, TX — Mon, 13 Aug 2007 18:57:54 GMT

Mars' period of rotation is 1.026 Earth days, or 24 earth hours and 37 earth minutes. If they want a "mars clock", all units of time will have to be an extra 2.6% longer, if they want the clock to have an even 24 hours in it. To make a system of longitude work on mars, it would need to be either 24 hours or some other number that is evenly divisible into 360, since there will still be 360 degrees.

Perhaps they could use "metric time", where each unit is one 360th of the period of revolution. On earth, each "metric minute" would be 4 minutes, on mars it would be 4 earth minutes and 6.24 earth seconds, but it would still be just 4 mars minutes.

And you thought converting central time to pacific standard time was tough.

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Frank Glover rochester, NY — Mon, 13 Aug 2007 21:17:40 GMT

In most cases, expect humans to live by either GMT/UTC, or the the Houston (central) time zone...