Q: How did the earth get its name?
--Emily Hansen, Ellensburg, Washington
A: The word "earth" is older than dirt (dirt being from the Middle English drit), and the meaning of "earth" has changed with its spelling: from the flat land underfoot to the round planet we live on. The modern spelling dates from the 16th century, possibly appearing first in R. Eden's 1555 English translation of Decades of the Newe Worlde, an account of Spanish explorations. The first Old English version cropped up nearly 500 years earlier in a number of texts, such as Beowulf and this passage from the homilies of the 11th-century monk Ælfric: And God gecigde tha drignisse eorthan ("And God called the dryness earth"). But then eorthan's just a rendering of the Old Testament Hebrew for earth--erets. And before that were words such as erda, from ninth-century Old High German, and era, from eighth-century b.c. Greek. We lose the thread at the Proto-Indo-European tongue spoken beginning in 4,000 b.c. and since vanished. Meanwhile, some people might say God coined the term on Genesis day one. As Oxford University Press etymologist Samantha Schad points out, "Who knows what language God was speaking when he created the world?"
Q: My vet recently gave my dog a vaccination to prevent giardia. Is there a vaccination for humans?
--Natalie Segall, Park City, Utah
A: No, because drug companies argue that humans don't need the vaccine as badly. Researchers at Fort Dodge Animal Health Company in Kansas brought to market your dog's vaccination, a kindly protozoan called GiardiaVax, in January of 1999 because they found that Giardia intestinalis infects approximately 43 percent of all puppies and virtually all animals in kennels and shelters. The animals contract the disease by eating or drinking anything contaminated with the single-celled parasite--be it water or another animal's feces. Humans contract it the same way, but far less frequently. According to the Centers for Disease Control, only 2 to 5 percent of Americans harbor giardia and many of them don't show symptoms. Because of this, and the ready availability of the curative antibiotic metronidazole, drug companies haven't created a similar vaccine for humans--useful as it would be. "Giardia is by far the most common intestinal parasite found in humans," says Hugh Lewis, the former dean of Purdue University's school of veterinary medicine. And it's a fair bet that all who've suffered explosive diarrhea in a fly-swirled Third World latrine would pay top dollar to never get it again.
Q: Can a person get sunburned through the windows of a car?
--Michael Blazek, Brisbane, Australia
A: Nope, just wrinkly and cancerous, thanks to glass molecules' only absorbing half the spectrum of ultraviolet light. In 1995, physics professors Fred Loxsom and Richard Bartels, from Trinity University in San Antonio, Texas, measured UV light passing through auto windshields and found that the quarter-inch-thick laminated glass absorbs almost all UVB rays (short-wavelength ultraviolet radiation) and some UVA rays (long-wavelength ultraviolet radiation)--enough that windshields could carry an SPF label of 100. The few UVA rays that do get through aren't strong enough to sunburn drivers, but as American Cancer Society dermatologist Susan Boiko testifies, they can still singe the epidermis and cause what's politely known as photoaging--the leathery skin found poolside in Phoenix. Side windows, with a hypothetical SPF of 15, are thick enough that UV radiation doesn't scorch drivers, but thin enough that long commutes in blazing sun can prove harmful. Even when tinted, says Loxsom, like cheap sunglasses they're not UVA-proof (only adding an SPF of 3). Boiko adds, "I see many more skin cancers--actinic keratosis and squamous-cell cancers--on drivers' left sides of faces and necks, and left ears and arms."
Q: A friend says his pet peacocks drowned by looking skyward during a rainstorm. Is that possible?
--Geoff Witt, Hickory, North Carolina
A: "To suggest that a vertebrate would drown itself while looking up into the rain isn't consistent with what I know about animals," says Stefan Hames, a Cornell University ornithologist who knows a lot about animals and is himself a vertebrate. The most plausible explanation (out of many implausible explanations) for the peacocks' deaths is that their legs got stuck in mud and the birds died from hypothermia. That said, the tall tale, also associated with turkeys, is so common that it deserves investigation. It's likely the myth is based on a physiological truth: The bird's stiff and bony tongue can't seal the trachea off from the mouth. If rain falls into the bird's mouth, theoretically it could sluice down the windpipe past the larynx and into the lungs. Of course, notes Hames, even if the bird were so dumb as to gaze skyward in a torrential storm, and even if the larynx didn't instinctively close off the trachea, the bird would probably sneeze out the rainwater long before it drowned. Robert Kauffman, who raises 80,000 turkeys per year on his Illinois farm, agrees. In 20 years he's never witnessed a bird die by downpour.