Halloween and astronomy
- From: Rich <none@xxxxxxxx>
- Date: Fri, 28 Oct 2005 22:36:54 -0400
According to the National Retail Foundation, the most popular
Halloween costume last year was Spiderman. Next was "a princess,"
followed by witches and vampires, SpongeBob, Barbie and Harry Potter.
Sounds about right. But if you read the complete list of top costumes,
you'll notice something missing: astronomers. There are no Sagans, no
Galileos, not even a Hubble.
And that's funny, because Halloween is an astronomical holiday.
It has to do with seasons: Halloween is a "cross-quarter date,"
approximately midway between an equinox and a solstice. There are four
cross-quarter dates throughout the year, and each is a minor holiday:
Groundhog Day (Feb. 2nd), May Day (May 1st), Lammas Day (Aug. 1st),
and Halloween (Oct. 31st).
Long ago, "the Celts of the British Isles used cross-quarter days to
mark the beginnings of seasons," says John Mosley of the Griffith
Observatory in Los Angeles. "Winter began with Halloween, [or as they
called it, 'Samhain']. Halloween marked the transition between summer
and winter, light and dark -- and life and death."
"On that one night, according to folklore, those who had died during
the previous year returned for a final visit to their former homes.
People set out food and lit fires to aid them on their journey -- but
remained on guard for mischief the spirits might do."
And, so, something astronomical became something spooky. It's not the
first time. Have you heard that comets are bad omens? Or that a full
moon brings out werewolves? Astronomy and superstition are old
friends.
This year Halloween has a new astronomical significance:
On Oct. 31st, the planet Mars is making its closest approach to Earth
for the next 13 years. (13 years? Cross your fingers.) Technically
speaking, the moment of closest approach occurs on Oct. 30th, a day
before Halloween, but the difference in distance between the 30th and
the 31st is too slight to matter.
Trick or Treaters will notice Mars rising in the east at sunset: sky
map. It looks like a pumpkin-colored star, so intense that people in
brightly-lit cities can see it. Some say it's blood red, but maybe
that's just Halloween talking.
Mars will soar almost overhead at midnight (as seen from North
America) and stay "up" all night long. Halloween 2005 is truly the
night of Mars.
Because Mars is so close--only 69 million km away, which is close on
the vast scale of the solar system--it looks great through a backyard
telescope. Lately amateur astronomers have been watching dust storms
swirl around Mars. They've seen icy-blue clouds gather over the
Martian north pole, where it is winter. And they been sketching and
photographing strange dark markings that dapple the planet's surface.
So--nothing against Spiderman, mind you--you might wish to reconsider
your costume. Grab a telescope and be an astronomer. It is Halloween,
after all.
Source: Science@NASA (by Dr. Tony Phillips)
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