Newbie needs book advice
Roy Smith
roy at panix.com
Mon Apr 16 08:34:16 EDT 2001
"Steve Holden" <sholden at holdenweb.com> wrote:
> An ephemeris is a chart of planetary positions at certain times, used (among
> other things) to construct horoscopes.
M-X Soapbox-Mode
Steve,
You do astronomy a disservice if the only example of the use of an
ephemeris you can come up with is horoscopes. That's kind of like saying
python is a cool language because you can use it to pick Zippy The Pinhead
quotes randomly out of a file.
An accurate table of planetary motion is essetial for celestial navigation
(i.e. figuring out where you are with a sextant and chronometer). Up until
WW-II, this was the ONLY way sailors (and aviators) out of sight of land
could know where they were. Polar explorers, too. Since WW-II, electronic
navigation systems have slowly reduced the importance of celestial, but it
continued to be an important skill up until the past decade or so, when GPS
really made it obsolete.
In fact, an ephermeris is really a table of positions of any body in space,
not just the planets. The GPS system itself depends on the receivers
having an accurate ephemeris of the satellite orbital positions.
We would have never put a man on the moon without an accurate ephemeris.
Nor been able to send probes to visit other planets in our solar system.
M-X Soapbox-Mode-Off
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