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South Pole lit half time, Some lizards lack legs, Star
books to enthrall kids (and people)
Q: What is the average number of days the South Pole has no
sunlight? —Nella, Naples, FL
![[NOAA / P. Roberts] The sun sets for six months of darkness](images/sunset-dome.jpg) A: The South Pole has about six months of darkness and
six months of light. Technically, the Sun sets on one equinox (March 21) and
rises on the next (September 21). That amounts to 184 "dark" days. Sunrise and
sunset occur when the apparent upper limb (edge) of the Sun is on the horizon.
[NOAA / P. Roberts] The sun sets for six
months of darkness
However, if you’re at the South Pole, you see it differently
because Earth’s atmosphere bends the low light. You see the Sun peeking over the
horizon for another four to five days after March 21. Likewise, the Sun appears
earlier than September 21, at sunrise. This adds about nine days of light; the
no-sun days diminish to about 175. Absolute darkness (when the sun is more than
18° below the
horizon and twilight has deepened to night) blankets the South Pole for about 80
days.
However, often it’s not dark even then. Sunlight bounces off
the Moon and then off grainy polar ice that looks like white wind-blown sand in
the desert. "Anytime within about six days of the Full Moon, you can easily find
your way about outside in the ‘dark’," says Don Neff, physicist at NOAA’s
Climate Monitoring & Diagnostics Laboratory (CMDL), who spent three years at
their South Pole facility.
The Full Moon appears to wheel overhead each 24 hours during
winter’s night just as the stars do. The Moon goes through its phases and rises
and sets each month. It’s above the horizon continuously for a dozen days each
winter month. Most star constellations never rise or set; they just circle
overhead. Our closest star, the Sun, does much the same during summer at the
South Pole.
"The sun appears to revolve about you every 24 hours just like the stars do
in the winter but it also moves vertically a small distance each day, sort of
spirals up for three months and then spirals back down the next three months,"
says Neff. It never climbs higher than 23.5 degrees above the horizon: Earth’s
tilt to its plane of orbit.
The Sun rises and sets slowly since the Sun’s apparent
vertical motion is small. So, if the weather cooperates, the green flash (so
elusive elsewhere on Earth) lasts sometimes a day or more at the South Pole.
Earth’s atmosphere bends the low sunbeams and a blue or green light shines from
the Sun’s upper limb. Neff says it’s "spectacular."
Further Surfing:
USA Today: South Pole locked in winter darkness, cold
WonderQuest: Green flash at the South Pole
NOAA/CMDL: South Pole life—live camera
U.S. Naval Observatory: Sunrise and sunset data
Department of Commerce/NOAA: Sunrise and sunset calculator
Ethan Dicks: Sunrise and sunset around the world
U of Chicago Astronomy: Photos of the Sun circling the horizon at the South
Pole
The Royal Observatory Greenwich: Time Keeping
![[Jeff LeClere www.herpnet.net/Iowa-Herpetology] Slender glass lizard— legless!](images/glass-lizard.jpg) Q: Is there a lizard with no legs? —Sarah Columbia, Maryland
A: Yes, both the glass lizard (aka glass snake) and the slow -worm have
no legs and propel themselves somewhat like snakes yet are, indeed, lizards.
[Jeff LeClere
www.herpnet.net/Iowa-Herpetology] Slender glass lizard— legless!
Glass lizards (some of whom are four feet long) don’t move with the wriggling
expertise of true snakes. Instead, they twist across the land and have to
rest-stop every two or three yards (2 - 3 meters). Like most lizards, they can
detach their tail to escape. A grass lizard’s long tail (two-thirds of her
length) is peculiar. When it comes off—the tail breaks into several pieces and
the pieces wriggle off (to distract a predator while the lizard scoots away).
The main part of the lizard is about the same length as the pieces. Hence, the
name "glass" snake. A legend says if you hit the snake with a stick, the snake
breaks into many pieces and magically reassembles later into a whole grass
snake.
Slow-worms, like glass lizards, look like snakes but have lizard
characteristics: movable eyelids, external ear openings, and a notched tongue,
not forked like a snake’s. Inside the foot-long (30 cm) slow -worm, are
vestigial shoulder- and hip-girdles—remnants of legs. Their ancestors once
walked.
Further Surfing:
Jeff LeClere’s Iowa Herpetology: Slender glass lizard
Suite U: Legless
lizard
![[Guy Ottewell, Universal Workshop] A star book that delights children down to age 8](images/to-know-the-stars.gif) Q:
I am looking for a good book to help with star gazing and teaching our
grandchildren the names of some of the stars or constellations. Can you suggest
a fairly simple one or where to look for one? — Peggy S.
[Guy Ottewell, Universal Workshop] A star book that delights
children down to age 8
A: A favorite of Sky & Telescope magazine for the past 40 years is
H. A. Rey’s The Stars. It costs $12 (from Sky) and is written for
older kids and adults: "classy cartoon illustrations and star charts round out
this fine guidebook," says Sky.
I like the $10 Night Sky: A Field Guide to the Heavens, a Golden Field
Guide Series. It got a 5-star rating from readers on Amazon.com’s website. "This
book takes you from ignorance to comprehension painlessly," says a reader from
Leesville, Louisiana.
Another good choice, written on a more advanced level but crammed with
information and illuminating sketches, is Guy Ottewell’s The Astronomical
Companion. This costs $22 from Universal Workshop (see Further Surfing). "It
is one of the most inspired non-textbook introductions to the cosmos that has
ever appeared," says Sky & Telescope.
Ottewell authored another book ($8 from Amazon.com) that’s especially good
for kids: To Know the Stars. A Maine reader says it’s the "most complete
introduction to astronomy for any child that you can find." Adds Scientific
American, "There is no more straightforward guide to the stars of the sky."
Further Surfing:
Sky &
Telescope: Astronomy basics
amazon.com: books
Universal Workshop:
Ordering Guy Ottewell’s books
Richard McCray’s
online course: Stars & galaxies
(Answered Feb. 28, 2003)
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