When spiders get sucked into a vacuum cleaner, can they eventually crawl back out, or do they suffocate in all that dust?
Pamela Wyatt, San Diego
Almost every spider sucked into a home vacuum cleaner will die—either immediately, from the trauma of ricocheting through the machine’s narrow tubes, or eventually, from thirst. Arachnologists collect living specimens with leaf blowers reversed to suck rather than blow, but the machines are modified to make the spiders’ landings less perilous.
- Jonathan Coddington, curator of arachnids and myriapods, National Museum of Natural History
“Pittsburgh” ends with an h, but not “Harrisburg.” Why?
Patrick Ian, Philadelphia
Amid America’s rampant growth in the Gilded Age, the United States Board on Geographic Names and postal authorities tried to standardize place names. “Borough” became “boro,” and “centre,” “center.” Possessives were dropped (“Crary’s Mills” became “Crary Mills”). Towns ending in “-burgh” dropped the “h.” Thus Pittsburgh lost its “h”—but got it back, through forceful lobbying, in 1911.
- Nancy Pope, curator, National Postal Museum
Human ancestors originated in Africa, where skin color is dark. So why do other populations have lighter skin?
Norbert Stogniew, Sunnyvale, California
The color of early modern humans in Africa had the benefit of protecting the skin against the sun’s rays—which can strip away folic acid, a nutrient essential to the development of healthy fetuses. Yet when a certain amount of UV rays penetrate the skin, they help the body use vitamin D to absorb the calcium necessary for strong bones. As people moved to areas farther from the Equator with lower UV levels, natural selection favored lighter skin, which allowed more UV rays to penetrate.
- Rick Potts, paleoanthropologist, National Museum of Natural History
For spiral galaxies to remain spirals, stars on the outside must travel around the center faster than stars closer in. Doesn’t this violate Newtonian gravity?
Mark Dormann, Palm Coast, Florida
As they are understood today, those spiral structures are not “arms” of stars traveling around a core, but transient regions of increased gravity density. Higher gravity density enhances star formation, which is why those regions have more stars than others. Astronomers speculate on various causes for spiral-shaped gravity density waves, but none of these would bring Newton’s laws into question.
- David DeVorkin, curator of space history, National Air and Space Museum
Which animals survived the Permian/Triassic extinction other than snails and sea urchins?
Bickley Simpson, New York City
Among marine lineages, two major survivors were the mollusks and echinoderms (which include sea urchins, starfish and sea cucumbers). Here on land, the arthropods and vertebrates survived.
- Conrad Labandeira, curator of fossil arthropods, National Museum of Natural History
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