Mosquito teeth and why stars move

Q: How many teeth do mosquitoes have on the proboscis? (Molly, Senatobia, Mississippi)

The tip of a mosquito’s snout, showing two of her four sets of serrated teeth. Magnification: x60. Dennis Kunkel , Dennis Kunkel Microscopy, Inc., used with permission

A: Four sets. Mosquitoes have four knife-like tools of serrated teeth that surround a pair of fine tubes — one for dripping a pain suppressor and one for sucking blood. See figure for a good view of one knife tool and a glimpse of a second one.

A common house mosquito (Culex sp.) stabs the skin with her sharp snout and saws in with her four knife tools to draw blood. She shoots in saliva laced with anesthetic (to escape notice) and an anticoagulant (to keep blood flowing). Then she sucks blood.

In 90 seconds, she sucks enough blood to nourish 100 eggs or more — and is too heavy to fly. She makes a controlled descent to a close safe spot where she squeezes in on her abdomen. Water oozes out of the blood, filtered through the abdominal wall, and forms a large drop. Light again, she takes off.

During her short adult life (two weeks to a month) she bites one to three times, says Larry Weber, naturalist and author of Spiders of the North Woods.

As all my (male) editors point out, only female mosquitoes draw blood (for needed protein). The males feed on nectar and plant juices.

Mosquito — designed by God to make us think better of flies.— Anonymous.

Further Reading:

Trivia Queen Enterprises: Let's slap at mosquitoes by J. Spencer

Minnesota Department of Natural Resources: Minnesota's biting flies by Larry Weber

Q: What causes stars to move? Why don't they just stay in the same place? I know the different kinds of movements stars have, but WHY do that do that? WHAT causes them to? (Jillian, Charlottesville, Virginia)

A: A star moves for the same reason that nebulae and galaxies move — because of momentum left over from the impetus of the Big Bang (the beginning of the Universe).

Courtesy of the author A planet orbits a star, tracing an egg-shaped elliptical path.

"A star cannot just stand still in space. When it was born [from a cloud of moving dust], it was already in motion and it cannot just stop," says Guy Ottewell in The Astronomical Companion. Bodies can't stop unless acted upon by a force, as Sir Isaac Newton stated in 1665.

The primary force that acts on a star is gravity due to its mass. Other bodies with mass tug the star and can change its velocity because of mutual gravitational attraction. The same force causes Earth to orbit the Sun instead of flying off on a straight line.

Also, an impact (such as colliding stars) can change a star's movement.

A star is usually born in a cluster, such as the Pleiades cluster (which contains about 500 stars). Eventually, it may break free of the parental cluster's gravity and wander off on its own.

How a star moves, even routinely, gets complicated. In 1609, Kepler observed for a simple two-body motion — such as the Earth and Sun: the orbit of a planet about a star is an ellipse with the star at one focus. See figure.

NASA, ESA, and the Hubble Heritage Team (STScI/AURA) We can’t see our own Milky Way galaxy in its entirety — only the disk around us. We’re too close to see the “forest.” Here’s a picture, though, of an entire galaxy (NGC 3949, 50 million light years away) that has a similar shape and structure to ours. Stars in the disk whirl around the hub.

But throw in the Moon and consider an Earth-Moon-Sun system. The math gets so complex that even Newton (the developer of calculus and modern mechanics) said it gave him a headache. A galaxy swarms with about 500 billion (500 thousand million) stars. Exactly how a given star moves due to the jillion other stars in its galaxy defeats our best computers.

"Although predicting the motion of a particular star is hard over a long period, many astronomers seek to model the general motion of stars around the galaxy," says astronomer Robert Massey of the Royal Observatory Greenwich. We've deduced in this way that the Milky Way galaxy has absorbed several smaller galaxies during its lifetime.

Our Sun, like other stars in the "wheel" part of our spiral galaxy, revolves about the center hub. It takes Sol 200 million years to make the trip, going about 560,000 mph (900,000 kph). In comparison, Earth orbits the Sun at almost one-tenth the speed.

The last time when the Sun was at this point in its revolution, dinosaurs roamed Earth.

Further Reading:

Cornell University: How stars move in a galaxy

Guy Ottewell, The Astronomical Companion. Middleburg, VA: Universal Workshop, 2002.

Greenwich Royal Observatory: What is a star?

Fred Hoyle, Astronomy and Cosmology. San Francisco: W.H. Freeman and Company, 1975.

Cornell University: How fast Earth orbits the Sun

(Answered Sep. 9, 2005)

April Holladay, science journalist for USATODAY.com, lives in Albuquerque, New Mexico. A few years ago Holladay retired early from computer engineering to canoe the flood-swollen Mackenzie, Canada's largest river. Now she writes a column about nature and science, which appears Fridays at USATODAY.com. To read April's past WonderQuest columns, please check out her site. If you have a question for April, visit this informational page.