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Y
THERE ARE TWO HYPOTHESES to explain why
these insects, which measured over six feet, thrived
some 300 million years ago, says Conrad Labandeira,
curator of fossil arthropods at the National Museum
of Natural History. One is the absence of aerial and
land predators at that time. The other is the higher
concentration of oxygen in the atmosphere — 140
to 170 percent higher than levels today. This gave
the insects greater respiratory effi ciency than their
modern counterparts and, in turn, led to larger sizes.Q: Why do American drivers sit on the left
side of the car and drive on the right side ofMichael Reed | Allegan, MichiganIN 1792, on its newly established turnpike, Pennsyl-
vania required buggy or wagon drivers to keep right.
About a decade later, New York became the fi rst state
to mandate right-hand travel on all public highways.
As automobiles became more common at the turn of
the 20th century, safety proponent William Phelps
Eno wrote the world’s very fi rst traffi c code, adopt-
ed by New York City in the early 1900s. For the fi rst
decade or so of the automobile era, many cars had
the steering wheel on the right-hand side. Histori-
ans believe that’s because it was easier for drivers to
keep an eye on ditches and the sides of narrow bridg-
es they might be crossing, says Roger White , curator
of road transportation at the National Museum of
American History. That changed with the Ford Mod-
el T, which moved the steering wheel to the left. The
1909 brochure cited two benefi ts: letting a passenger
exit at the curb and giving the driver a better view
of oncoming traffi c. Other automakers were inspired
to follow suit when the Model T quickly became the
best-selling car of the era.Q: Why do male lions have manes growing
around their ears? What does this mean in
the animal kingdom?
Jeaneth Larsen | Mitchell, South DakotaIT COULD BE for protection, mate selection or both.
Male lions fi ght other lions, hyenas and other small-
er predators for territory, food and the right to stay in
the pride, explains Craig Saff oe, curator of the Great
Cats area at the National Zoo. Their manes, which
are very thick and extend to cover their necks, pro-
vide crucial protection, almost like medieval chain
mail. Also lionesses may be attracted to healthy
manes, and may even have preferred colors. The
mane may serve a similar purpose to the tail feathers
male peacocks use to attract mates.Q: I understand that scientists record
noises from the sun, but I thought
sound didn’t travel in a vacuum. How
do they record these sounds?
Frederick Vogt | Grand Rapids, MichiganOU’RE RIGHT: Sound waves cannot
travel in a vacuum. But scientists who
study the dynamics of the sun’s inte-
rior convert other kinds of signals into
audio fi les, explain the National Air
and Space Museum’s David DeVorkin
and Shauna Edson. Oscillations originating deep in-
side the sun become detectable only on the surface, at
which point scientists use optical, spectroscopic and
radio instruments to measure the phenomena. Those
readings are then converted into sound waves to help
the scientists analyze and fi nd patterns in the data.
Q: The National Museum of Natural History
features a giant prehistoric millipede. Why is
it so much bigger than today’s millipedes?
Anonymous