Q) When will the next ice age occur?
Ned Durden, Charlotte, North Carolina
A)YOU CAN RELAX, Ned. Glaciers aren't expected to swallow up major real estate on the continents for another 80,000 years. Over the last 2.5 million years or so, ice ages have returned, fairly consistently, every 100,000 years. They're caused by subtle changes in the earth's orbit and its distance from the sun, factors that decrease the amount of sunlight striking the planet, which allows the ice to creep south. But that's not the whole story, says NOAA paleoclimatologist David Anderson. An ice age also requires "feedbacks," which amplify the cooling. One prime example: the albedo effect, whereby ice reflects sunlight, causing more cooling, which makes for bigger glaciers. Other variables play a part, like the amount of carbon-dioxide-consuming plankton on the ocean surface. Since we humans are in the process of increasing CO2 amounts, you might wonder whether global warming will ever make ice ages a thing of the past. Good question! Anderson says. Chillingly, nobody knows.
Q) I recently climbed 14,162-foot Mount Shasta, and had a hard time eating. What happens to appetite up high?
John Adams II, Fremont, California
A)IT DISAPPEARS into (ahem) thin air. Researchers are largely stumped as to why, but they know that hypoxia, or oxygen deprivation, can cause drastic bodily changes. On the appetite front, scientists are focusing on three hormones that regulate hungergalanin, neuropeptide Y, and leptin. Leptin seems to be especially crucial: As you climb above 9,000 feet, your fat cells start overproducing it, which tells the hypothalamus that you're full. Careful acclimatization may ameliorate the problem, but that takes time. And since there are no drugssave cannabisproven to stimulate appetite, you've simply got to force those nibbles. Even if it seems impossible, stresses altitude specialist Dr. Peter Hackett, you need to choke down something, in small portions, the more calories the better: energy gels, sweets, pastas dripping with chutney. If you don't, you'll start burning muscle, and that can be catastrophic.
Q) How did elephants get trunks?
Asa Tapley, Washington, D.C.
A)SINCE A TRUNK doesn't contain bones, it doesn't leave behind fossils, and without fossils, paleontologists have to get creative about studying the trunk's evolution. By tracing changes in two cavities on the front of the skull, they've found what they think is the granddaddy of all elephants, a dog-size creature called Phosphatherium escuilliei, which lived 55 million years ago. But this tapirlike animal seems to have been trunkless. So what happened? Natural selection. As Hezy Shoshani, a biology professor at Eritrea's University of Asmara, explains, most scientists believe that elephants are a product of Cope's Law, which states that most species get bigger as they evolve. Over time, as elephants grew away from the ground, they had a harder time reaching down to get their food. So the trunk was bornprobably morphing out of the lip and noseand soon the big guys had the ultimate browsing tool.
Q) How many trees does it take to supply enough oxygen for one person to survive?
Steve Yates, Sugar Land, Texas
A)FIRST YOU NEED to figure how much oxygen one person consumes. Southern Oregon University biology professor John Roden estimates that the average human requires about 130,000 liters per year. Trees both produce and consume O2, but in a productive tropical rainforest, the average tree releases a net 273,000 liters of oxygen per year. At the other extreme, a desert juniper produces only 6,000 liters or so. So you'd need 21 junipers to keep one human aerated, while a single rainforest specimen produces enough oxygen for two. Next time you see a tree, take a deep breath and say thanks.