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Why are so few flowers and fruits blue? And more questions from our readers | At the Smithsonian

A reader wonders why more flowers and fruits are not bluish.
Illustration by Marilyn Foehrenbach

Question: Why are more fruits and flowers red, orange or yellow than blue?

—Robert L. Morrison | Poughkeepsie, New York

There is in fact no true blue pigment in nature. A pigment creates color by absorbing certain wavelengths of light and reflecting others. Chlorophyll makes plants green, carotene makes them red or orange, and xanthophyll makes them appear yellow. Plants make fruits and flowers look blue by changing acidity levels, adding molecules, or mixing pigments. Even then, it is rare to see a blue plant without a reddish tinge: a blueberry is slightly purple. So why do plants turn blue? Most likely to attract specific pollinators – blue is highly visible to bees.

Rose Gulledge, museum specialist, Department of botany, National Museum of Natural History

Q: Why do military helicopters have Native American names?

—Eli Cash | New York City

The US military began naming advanced weapon systems, as well as helicopters, after Indigenous nations in the early second half of the 20th century. Apparently this was done as a tribute to the valor and “warrior spirit” of Native Americans. However, this was done without the participation or agreement of the tribes and many felt it perpetuated a simplistic 19th century notion of Native Americans. Today, the military not only consults with Indigenous groups and seeks their approval before using their names, but also recognizes the many sacrifices and contributions that Native Americans have made while serving in the US military.

Cecile Ganteaume, co-curator of “Americans” exhibition, National Museum of the American Indians

Q: How would Earth be affected if we had more than one moon?

—Darrel Riesterer | Kiel, Wisconsin

Even a small moon traveling within the orbit of our current orbit would have a gravitational effect on the earth’s tides, inundating coastal cities where a large percentage of humans live. A bigger moon would cause more flooding, submerging even more land. The two moons would also affect each other. Earth’s gravity causes tides on the Moon, bending or stretching the lunar soil. A second moon could amplify this small effect, contributing to stronger moonquakes. The greatest calamity would be if the two moons migrated into each other. Large fragments could find their way to Earth, causing an extinction level event.

Thomas watters, senior scientist, National Air and Space Museum

Q: How can sharks have such a high concentration of mercury and still be alive?

—Michael Anderson | Fort Kent, Maine

Mercury and others the toxins are found in the blood and organs of not only sharks, but other aquatic species as well. The concentration of these elements increases along the food chain, with those at the top having higher amounts than those at the bottom. Because many sharks are top predators, they have particularly high concentrations of mercury – they get it from their prey, which got it from their own food sources. But despite the fact that sharks accumulate so much mercury, they seem to be immune to its harmful effects. Studies suggest that sharks have a physiological mechanism that protects them from mercury poisoning, but this mechanism is not yet clear.

Catalina Pimento, research associate, Smithsonian Tropical Research Institute

It’s your turn to ask the Smithsonian.