Penguin voices distinct

Question: Penguins are big these days, especially with other penguins. But they've got a problem. After diving into the water and eating, an emperor penguin must return to its home and locate its mate among thousands of other penguins huddled together to avoid freezing in the harsh Antarctic winter. Besides, all penguins look much the same, even to other penguins, whose underwater-adapted vision likely leaves them nearsighted in the air. How then does Mr. Penguin find the Mrs., or vice versa?

Answer: Most birds vocalize with only one side of their vocal organ (syrinx) but penguins use both simultaneously, with each side setting up a different frequency, says Jearl Walker in "The Flying Circus of Physics." These form a strong net sound wave, plus a warble that varies from loud to soft and a beat frequency based on the difference between the two actual frequencies. Thus a penguin's cry can be rich with distinctive resonances and beats, allowing it to be recognized even among a thousand other penguin voices.

ID problem or no, the dense penguin huddle of 10 per square meter means survival as temps plunge to -40 C (-40 F) and winds hit 300 kph (180 mph). Saving on heat energy is critically important during the winter breeding season. Each resulting egg is incubated almost exclusively by the father, who keeps the egg from freezing by balancing it on his feet for months. During this time he must fast because his food is in the water, making his hudddling even more important to avert energy losses that could drive him into abandoning the egg to search for food.

Question: When during World War II incendiary bombs rained down on U.S. and Canadian forests and set them ablaze, what were the "fingerprints in the sand" to help pinpoint the source and stop the attacks?

Answer: The Japanese sent the bombs attached to balloons toward North America, where air currents would no longer hold them aloft and they would crash to the ground, say William J. Neal et al. in "Atlantic Coast Beaches."

Beach sand served as ballast to adjust the balloons' buoyancy for the cross-ocean trip. Because of the sand's unique mix of minerals in its heavy-mineral fraction, Allied geologists were able to deduce the balloon release site by poring over every available geologic map of Japan and noting the location of surface rocks the minerals could have come from. Then "the release site was bombed, and because the American news media had been ordered not to report fires resulting from the incendiary balloons, the Japanese assumed the effort wasn't working and abandoned the project."

Question: A busy dairy farmer, but maybe not quite busy enough, wonders: "How long would it take my Daisy to fill the Grand Canyon with her milk?"