My rough calculation based on what I quickly looked up of Mars's orbit eccentricity suggests that solar noon won't be off from clock noon by more than an hour. --Joshua On Fri, Dec 10, 2010 at 8:35 AM, Cordwell, William R <wrcordw@sandia.gov> wrote:
As long as the clocks are set for 24:00 Mars time = 24:40 Earth time (i.e., each Mars minute would be a bit longer than an Earth minute), then almost certainly, the sun would never rise at midnight.
As the planet moves in its orbit, the clock is such that after 1 day of clock time, the planet has actually rotated a bit more than 360 deg, so that it will still face the sun directly at noon, clock time. The extra rotation compensates for the movement along the orbit. If the clock were on sidereal time, noon at perihelion would be midnight at aphelion, and you would have your sunrise at midnight, but, even with an elliptical orbit, the extra daily rotations will compensate for most of the sidereal vs. clock time difference.
-----Original Message----- From: math-fun-bounces@mailman.xmission.com [mailto:math-fun-bounces@mailman.xmission.com] On Behalf Of Schroeppel, Richard Sent: Friday, December 10, 2010 8:17 AM To: 'math-fun' Cc: 'rcs@xmission.com'; Schroeppel, Richard Subject: Re: [math-fun] Analemma
A puzzle for the computationally minded ... The orbit of Mars is much more elliptical than Earth's. So the analemma effect is much stronger. On the Earth, we simply use mean solar time in our daily affairs, and ignore the slight difference between clock noon and local physical noon. The difference is only +- ten minutes or so, and is swamped by the effect of time-zone quantization. (Never mind daylight savings.)
The puzzle: Could future Mars colonists ignore the analemma? The day length is about 24:40, so the natural thing to do is simply live by the longer day. Most of us could use an extra forty minutes a day. But would the Martians sometimes find the sun rising at (clock) midnight?
Rich
-----Original Message----- From: math-fun-bounces@mailman.xmission.com [mailto:math-fun-bounces@mailman.xmission.com] On Behalf Of Bill Gosper Sent: Thursday, December 09, 2010 8:43 PM To: math-fun@mailman.xmission.com Subject: [math-fun] Correction; Analemma
<stuff about pendula removed>
Doug Dodds at Symbolics used to send the following every year at this time. If you haven't seen one, check out "analemma" in Google images for one of those 365-exposure sky pix. There's even one for Mars!.--rwg --- Received: from ELEPHANT-BUTTE.SCRC.Symbolics.COM by RUSSIAN.SPA.Symbolics.COM via CHAOS with CHAOS-MAIL id 52312; Tue 8-Dec-87 13:52:55 PST Received: from YUKON.SCRC.Symbolics.COM by ELEPHANT-BUTTE.SCRC.Symbolics.COMvia CHAOS with CHAOS-MAIL id 244027; Tue 8-Dec-87 16:18:32 EST Received: from ANNISQUAM.SCRC.Symbolics.COM by YUKON.SCRC.Symbolics.COM via INTERNET with SMTP id 303771; 8 Dec 87 16:11:04 EST Date: Tue, 8 Dec 87 16:11 EST From: Doug Dodds <DODDS@YUKON.SCRC.Symbolics.COM> Subject: Rejoice, the light returneth! To: BBoard@YUKON.SCRC.Symbolics.COM, Fun@YUKON.SCRC.Symbolics.COM File-References: SCRC|Y:>Dodds>analemma.mss.newest, SCRC|Y:>Dodds>analemma.text.newest Message-ID: <19871208211112.0.DODDS@ANNISQUAM.SCRC.Symbolics.COM>
The sunset today in Boston is at 16:11 EST, which is Plenty Early. But take heart, today's sunset is the earliest of the year! (Everywhere in the northern hemisphere, regardless of the actual sunset time.) The sunset starts to become later tomorrow, even though the shortest day is still two weeks off.
If you haven't yet learned of this fascinating phenomenon, take a look at one of the referenced files. The first is formattable (m-X Format File); if formatting is not available to you, then print the second referenced file.
Enjoy the increasing afternoon light!
0,, *** EOOH *** _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
_______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
_______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun