How Do Seals Find Their Prey and More Questions From Our Readers

How do diving animals that lack sonar, such as sea lions, detect their prey in water with poor visibility?

Anthony Clayton, Wilmington, Delaware

The short answer is that they use their very sensitive whiskers, called vibrissae, to detect movement in the water.

Rebecca Miller, biologist, American Trail, National Zoo

Are there any foods besides corn that have seeds that can be “popped”?

Stan Zukowsky, Syosset, New York

Yes, there are. The key thing here is the relationship between the amount of moisture in the seed and the strength of the seed covering—the covering has to be weak enough to give way when the moisture expands under heat. In addition to corn, sorghum, amaranth and quinoa seeds have that felicitous relationship, so they will “pop,” or puff, in a skillet. Happy snacking.

Cindy Brown, horticulturalist, Smithsonian Gardens

Why could Hiroshima and Nagasaki be rebuilt so soon after they were destroyed by the A-bomb? Wouldn’t the fallout remain unsafe for years?

Nancy Davison, Sebastopol, California

Those two bombs were deliberately exploded high in the air; as a result, much of the radioactive debris was carried aloft and dispersed by the mushroom cloud. Moreover, the amount of fissionable material in both bombs was only about two pounds. In contrast, the meltdown at Chernobyl involved some two tons of material released at ground level with no mechanism for rapid dispersal. Today, Hiroshima and Nagasaki have background radiation levels well within the world average.

Tom Crouch, curator, aeronautics, National Air and Space Museum

Why is there a lag between the winter and summer solstices and the coldest and warmest months of the year?

Jennifer Latzgo, Fogelsville, Pennsylvania

Seasonal changes in sunlight don’t instantly alter air temperatures because the earth’s oceans and land masses are slower to cool down and warm up than the atmosphere. As the days shorten in winter, the oceans release heat they absorbed when the days were longer; as the days lengthen in summer, the oceans absorb the heat they will later release. The time lag between each solstice and the maximum high or low temperature varies with latitude and proximity to the oceans.

Andrew Johnston, geographer, Center for Earth and Planetary Studies, National Air and Space Museum

Why are most homes no longer equipped with lightning rods?

Paul Agathen, Washington, Missouri

Lightning rods have always been optional equipment; though lightning can strike erratically, tall trees or structures tend to protect shorter structures nearby. Buildings in open spaces are at higher risk and often have lightning rods. Today, homes at higher risk do have lightning-protection devices; they’re just not as obvious as a rod jutting into the sky.

Harold Wallace, curator of electricity, National Museum of American History

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