[time-nuts] GPS disciplined Mars clock

Chris Albertson albertson.chris at gmail.com
Sun Jul 10 02:48:01 EDT 2016

Calculator here http://astroutils.astronomy.ohio-state.edu/time/hjd2bjd.html

Source code to do the conversion also on above site.  You should just use
their code as it is known correct .

BJD (date/time at the center of the solar system) is actually very commonly
used .  It is the best way to describe the time of an event outside the
solar system such as the timing of a variable star.  There is a huge amount
of published data in BJD.  But even within the solar system how do you
define when two events are simultaneous?   Obviously you need to pick a
vantage point where an assumed observer is.  The center of mass of the
solar system is not a bad choice of vantage point.

So when  you ask "what is the time on Mars?"  Is that what would you see if
you had a telescope good enough to read a Martian's wrist watch, or is it
what that watch would read if you brought it into your office.  Is either
of these of much practical use if you had friends living on Mars?   Yes, I
think the view of the clock through the telescope would be best that way
when your friend says he will call you at 8:00am your phone rings when you
see his watch reading 8:00am.   If you only had a clone of has watch then
you'd need a computer to make sense of it.    Always when looking at a
planet you want to know the observed time (reading watch through telescope)
so you can interpret what you see, what is the longitude that is directly
facing you.

On Sat, Jul 9, 2016 at 3:35 PM, Mark Sims <holrum at hotmail.com> wrote:

> I just added code to Lady Heather to calculate time in Terrestrial Time
> (TT) and Geocentric Terrestrial Time (TCG).   The difference is basically
> the time dilation effect of a time referenced to the center of the earth.
>  Now  I'm adding Barycentric Dynamic Time (TDB) which is TT referenced to
> the center of the solar system... basically another relativistic correction.
> Does anybody know of an online TT/TCG/TDB clock?  I can't seem to find one
> to check my math.
> I've also added Mercury/Venus/Pluto time/date... which I've arbitrarily
> defined as GPS seconds since the J1900 astronomical epoch divided by the
> orbital period.  I decided not to do times for those squishy gas-bag
> planets.
> ---------------------------
> > Hmm,  gravitational time dilation it might complicate things ...  I
> suppose it depends on whether your Mars clock is on the surface of Mars,
> Earth or somewhere else.
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Chris Albertson
Redondo Beach, California

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