Frostbit grasshoppers, nearest and
farthest moons, most poisonous mammal
Q: How do grasshoppers survive the winter? (Lane, Somewhere,
USA)
A: It was wintertime, the ants' store of
grain had got wet and they were laying it out to dry. A hungry
grasshopper asked them to give it something to eat. 'Why did you not
store food in the summer like us?' the ants asked. 'I hadn't time', it
replied. 'I was too busy making sweet music.' The ants laughed at the
grasshopper. 'Very well', they said. 'Since you piped in the summer, now
dance in the winter'. — Aesop's Fable
Most grasshoppers winter over as eggs. The buried
eggs get some protection from the soil insulation.
"Some species (even in Wyoming) overwinter as
nymphs," says
Jeff Lockwood, professor of natural sciences and humanities at the
University of Wyoming.
The first heavy frost kills the adults. American
grasshoppers (Schistocerca americana), however, found in the warm USA
south, are an exception. These grasshoppers pipe and dance the winter
long, surviving as adults.
How do eggs and nymphs get through the winter?
That "hasn't been directly addressed in grasshoppers to my knowledge,"
says
Greg Sword, research ecologist at the USDA Agricultural Research
Laboratory in Sidney, Montana.
They must supercool — either with anti-freeze
type compounds protecting their cells or by pushing water outside the
cells where it can freeze harmlessly, says Sword. Another strategy is
cold hardening. Some insects make "heat shock" proteins when it gets
cold. The proteins then protect the bugs later when the weather turns
freezing cold.
Eliminating water from cells is tricky says
Lockwood. The insect has to do it just right: rid enough water so the
cell doesn't freeze, but not so much that the high concentration within
the cell harms the cell's metabolism or protein structure.
What strategy do grasshopper eggs and nymphs
pick? "I'm not really sure," says Lockwood. "My money would be on the
chemical antifreeze strategy (as a minimum) for both eggs and nymphs."
Further reading:
• WonderQuest:
Grasshopper life span
• North
Dakota State University Extension Service: Grasshoppers by Ron Smith
• University
of Wyoming: Grasshoppers of Wyoming and the West by Jeffery Lockwood,
Scott Schell, Kiana Zimmerman
Q: Is the Harvest Moon
when the moon comes closest to Earth? When is the moon farthest away?
(William, Albuquerque, New Mexico)
A: No, the Harvest Moon is the Full Moon
that occurs closest to the autumnal equinox, when the day and night are
equal length. The Harvest Moon, therefore, occurs within several days of
September 23, the fall equinox.
The closest Moon, though, occurs at various
months through the years.
When the Moon comes closest to Earth depends on
the Moon's inconstant orbit about Earth. (Actually, the orbit is about a
common center of gravity, which lies inside Earth — but let's ignore
this nicety.)
The Moon's orbit isn't a perfect circle but
rather a fat ellipse. Therefore, the Moon's distance from Earth isn't
always the same (as it would be for a circular orbit). Instead it varies
by about 5.49% from its average distance. Each time the Moon orbits
Earth (approximately monthly), it has a closest point (perigee) and a
farthest point (apogee) in its orbit, as you can see in the images at
left.
So, what is its closest point? We're getting
there. The inconstant Moon is well named because the closeness of the
Moon to Earth changes with the Sun's tidal force — its differential
gravitation.
The Moon experiences different pulls from the Sun
and Earth depending on whether or not the Sun, Earth, and Moon are
aligned.
When the three bodies are aligned and the Moon is
closest to Earth (perigee), "the Moon comes a whole Earth-diameter
(about 13,000 km) nearer, toward us," says
Guy
Ottewell, author of The Astronomical Companion.
In 2004, the Moon got closest to Earth (221,980
mi or 357250 km) on Jun. 3 and will get farthest from Earth (252,580 mi
or 406490 km) on Dec. 26. Over the time span from the year 1750 through
2125, the Moon came closest (221,441 mi or 356375 km) on Jan. 4, 1912.
The farthest apogee has yet to occur: it will be 252,724 miles away
(406720 km) on Feb. 3, 2125.
The Full Moon is much larger and brighter when it
is closest, compared with farthest away. It's 30% brighter! It also
moves noticeably faster across the sky because it moves fastest at
perigee.
By the way, the Harvest Moon stays more nearly
full over a few days than other Full Moons and that's why it's called
the "harvest" moon. It gives the northern farmer more night light to
harvest crops.
Further reading:
• Ottewell, Guy. The Astronomical Companion.
Cambridge, MA: Universal Workshop, 1979.
•Fourmilab
Switzerland: Inconstant moon by John Walker
•Distance
of the full moon from Earth by Jürgen Giesen
•NASA:
Harvest Moon
Q: What is the
name of the most poisonous mammal living today? (Ariana,
Albuquerque, New Mexico)
A: The egg-laying platypus of Australia is
the world's most poisonous mammal. Males have hollow spurs connected to
venom glands on the ankle of each hind leg. The extremely painful poison
can harm a man but won't kill him.
•Discovery.ca:
The dream of the platypus
(Answered November 5, 2004) |
