Why Earth has day and night, What is the difference between a groundhog and
a gopher
Q: Why does Earth have day and night? Do all planets have the same?
---Charlene, Auckland, New Zealand
Sunset over Earth with Venus in shining above [NASA]
![Sunset over Earth with Venus in shining above [NASA]](images/2003-08-22-sunset-venus-big.jpg) A:
Earth’s spin causes night and day. It makes a complete revolution in 24 hours (a
solar day). Imagine spinning a top in a darkened room. Shine a flashlight at the
whirling top. A tiny bug crawling on the gyrating top experiences day and night
as he passes into and out of the light — much like we do on rotating Earth.
All the planets in our solar system spin and therefore have night and day but
the length of day varies greatly. Venus rotates through a "day", with respect to
the Sun (not the stars), in 117 Earth solar days. A day on Mars is about the
same as ours (24 hours and 40 minutes). Giant Jupiter whips through its day in
only 9 hours and 57 minutes.
The giant planets (Jupiter, Saturn, Uranus, and Neptune) contain most of the
angular momentum of our solar system (even more than the Sun) and therefore spin
faster than the inner planets. The Sun rotates slowly, only once monthly.
The Sun, Moon, and the planets formed from a huge spinning gas cloud that
collapsed into a gyrating disk. The whirling disk gave its spin to the planets,
which started them orbiting about the Sun and spinning on their axes. Using the
Hubble Space Telescope, we have observed similar proto-planetary disks, for
example, in the Orion nebula, says Robert Massey, astronomer at the Royal
Observatory Greenwich. All objects that we know spin — the Sun, the Moon, stars,
black holes, galaxies, planets inside and outside our solar system.
"There are circumstances in which planets wouldn’t have night and day
although we don’t know of any yet," says Massey. A planet close to a star could
experience "captured rotation" (like our Moon relative to Earth). Then, it would
always keep one face turned to its sun. One hemisphere would be bathed in
everlasting light and the other, never ending darkness.
Further Surfing:
WonderQuest:
How Earth started orbiting the Sun
Royal Observatory Greenwich: Timekeeping by the Earth, Moon, and Sun
Griffith Observatory: Sunrise/sunset and the Sun’s path across the sky
Groundhog dwarfs the gopher
Q: What is the difference between a groundhog and a gopher? — Janice
A: The big groundhog is about 24 times heavier than the little gopher. The
animals look somewhat similar, however, with short neck, legs, and tail.
The groundhog (also known as a "woodchuck" and "whistle pig") is a marmot —
essentially, a giant North American ground squirrel. The gopher is, like the
groundhog, a burrowing member of the rodent order but its closest living
relatives are kangaroo rats and pocket mice.
The pocket gopher gets its name from large fur-lined cheek pouches that
border its face down to its shoulders. These weird roomy pouches function much
like jeans pockets. They open to the outside and can be turned inside out for
cleaning.
The groundhog hibernates and the gopher does not. By the end of
October, the groundhog descends into her hidden burrow beneath a stump or a
rock, curls into a relaxed ball, slows her heart from 75 to 4 beats a minute,
and drops her body temperature to that of her home. She is so far "asleep" that,
even if we warm her, she needs several hours to waken.
Groundhog:
species Marmota monax from the squirrel family, Sciuridae, order
Rodentia
up to 13 pounds, 6 kg
head and body 20 inches(50 cm) long; tail 18 inches
found in eastern and central United States, across Canada, and into Alaska
along forest edges abutting meadows, open fields, roads, and streams.
good swimmers, can climb tall shrubs and sizable trees
Gopher:
any of 38 species from the family Geomyidae, order Rodentia
0.5 pound (250 g)
head and body 6 inches (15 cm) long; tail 3 inches (8 cm)
range from southern Canada and the United States, south through Mexico and
Central America, to northwestern Colombia. Found from coastal areas to above
the timberline in high mountains.
two to three-year lifespan
Further Surfing:
University of New Mexico: Botta’s pocket gopher
Missouri Conservation Commission: Woodchuck
(Answered Sep. 26, 2003)
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