How Powerful Is a Volcanic Eruption and More Questions From Our Readers

You asked, we answered

Gina Triplett

Could a volcanic eruption blow ash out of the Earth’s atmosphere?

Arleigh Pudlick, Becker, Minnesota

No volcano has come close. The Earth’s atmosphere rises about 300 miles, in six layers. The highest volcanic column measured on Earth, from Mount Pinatubo in 1991, rose only 22 miles. But that was above the troposphere, or the lowest of Earth’s atmospheric layers, and “it’s hard for ash and particles to fall back through the troposphere,” says Ed Venzke of the volcanism program at the National Museum of Natural History. The Pinatubo debris circled the globe for years.

All the Mars photos I’ve seen look enhanced. How bright is it at high noon on Mars compared to on Earth?

Antonio Betancourt, St. Louis

It would look about like high noon on Earth on a cloudy day, says John Grant, planetary geologist at the National Air and Space Museum’s Center for Earth and Planetary Studies. As for those photographs: For scientific purposes, the cameras on the Mars rovers capture images in many wavelengths of light, some invisible to the human eye. When those images are processed here on Earth, they can be filtered to reproduce “approximate true color”—about what we would see if we were there.

How far down the animal-kingdom ladder does the ability to dream go?

Gene Goes, Cincinnati

Dreaming while sleeping is closely tied to the ability to think, and while thinking was once believed to be an exclusively human trait, “in the last 50 years we’ve shown that animals use tools, have a sense of self and have a mind,” says Don Moore, senior scientist at the National Zoo. Scientists have evidence that dogs and orangutans dream, and that rats, octopuses and even queen ants at least think while sleeping.

Was the silent “k” in English words such as “knot,” “knee” and “knowledge” ever pronounced?

Robert Stern, Seattle

It was—until the middle of the 15th century generally, though it persisted in some forms through the 19th century in northern England and Scotland. Why did it go silent? You create the “k” sound in the back of your mouth and the “n” just behind your front teeth. That distance, says Mary Linn of the Smithsonian Center for Folklife and Cultural Heritage, makes it hard to pronounce the sounds consecutively. Gradually, English speakers dropped the “k,” but speakers of other Germanic languages still pronounce it. 

The Civil War death toll was recently revised from about 640,000 to 750,000 or more. Where does the new number come from?

Thomas Hansen, Rolling Meadows, Illinois

The lower figure originated in the late 19th century with two Union veterans who combed through muster roles, says David Ward, senior historian at the National Portrait Gallery. The higher figure comes from a 2011 article published by historian J. David Hacker, based on 19th-century census data. Surviving records may never establish a definitive number of Civil War dead, Ward says, but the essential point—the extraordinary loss of life—remains clear.

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