Sciences that differences in buoyancy and viscosity force small creatures to
use more energy as they swim. — Alexandra Witze
layer

Depth (meters)

300

Pycnocline \PIHC-noh-kline\ n. A boundary or layer with varying water density caused by changes in temperature or salinity. In oceans and lakes, these stratifications help control which organisms live in which water layers, for instance by concentrating plankton that attract predators.

600

900

1200

Deep layer

1500

60° 30° 0° 30° 60° North South

Latitude

SOURCE: AMERICAN METEOROLOGICAL SOCIETY
Now, researchers have found that the density changes have a fundamental
effect on marine creatures. Using calculations of how a pycnocline
physically affects a single cell, scientists at the University of Notre Dame
and MIT report March 6 in the Proceedings of the National Academy of

Surface Pycnocline

SN Online www.sciencenews.org

EARTH

Horizontal motion makes a magnitude 8. 6 quake less dangerous. Learn more in “Indonesian quake passes without major tsunami.”

DELETED SCENES BLOG A video game puts birds into orbit. Read “The Newtonian physics (or not) of Angry Birds Space.”

Science Past | FROM THE ISSUE OF MAY 5, 1962

CANCER CAUSE IN TOBACCO — “You might as well ask a per-
son if he believes the earth is round as to ask him if he is one of
those who believes cigarettes cause cancer,” Dr.
Charles B. Huggins, director of the Ben May
Laboratory for Cancer Research, University of
Chicago, told SCIENCE SERVICE.... Sixty
known cancer-causing compounds have been
tested…. Two components of deoxyribonucleic
acid — guanine and cytosine — were made into
a molecular model and a plastic frame was constructed to sur-
round it. In this frame, Dr. Huggins showed, in slides, how all
known cancer-causing aromatic hydrocarbons fit neatly. Also
similar atomic models of the steroids testosterone (male hor-
mone) or progesterone or estradiol (female hormones) fit.

Science Future

May 16 Test your mettle at science trivia night at Washington, D.C.’s Kosh-land Science Museum. Prizes go to the winning team. See bit.ly/SFtrivia

GENES & CELLS Altering gene activity may make chemotherapy more effective. See “Old cancer drugs offer new tricks.”

May 19 The Orlando Science Center holds a Science of Wine event, with educational events and wines from around the world. More information at bit.ly/SFoscwine

The (-est)

Reaching speeds up to 29 kilometers per hour ( 18
miles per hour), a new robot is the fastest of its kind.
Called Cheetah and designed by DARPA, a U.S.
Department of Defense research agency, the device
breaks the previous record of about 21 km/ h for land-
based, legged robots. Cheetah’s leg movements mimic
the strides of some of nature’s speediest runners.
Though there is no immediate application planned
for the robot runner, a DARPA spokesperson says
that scientists are
interested in building
speedy machines for
a variety of purposes,
such as assisting in
dangerous military
missions.

SCIENCE & THE PUBLIC BLOG Recent U.S. record warmth was not shared globally. Read “March: American heat vs. global temps.”

Science Stats | FAT TER THAN YOU THOUGHT About a third of Americans are estimated to be obese, based mostly on measurements of body mass index, or BMI. But new research shows that BMI underestimates obesity compared with directly measuring the percentage of body fat. Underestimates are most common in older women, who lose more muscle with age than men do.