Why Are So Few Flowers and Fruits Blue? And More Questions From Our Readers

Flower illustration
One reader wonders why more flowers and fruits aren’t blue-hued. Illustration by Marilyn Foehrenbach

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

—Robert L. Morrison | Poughkeepsie, New York

There is actually no true blue pigment in nature. A pigment creates color by absorbing certain wavelengths of light and reflecting others. Chlorophyll makes plants look green, carotene makes them look red or orange, and xanthophyll makes them look yellow. Plants make fruits and flowers look blue by shifting acidity levels, adding molecules or mixing pigments. Even then, it’s rare to see a blue plant with no reddish tint: A blueberry is slightly purple. So why do plants go 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 U.S. military began naming advanced weapons systems, as well as helicopters, after Native nations early in the second half of the 20th century. Ostensibly, it was done as a tribute to the valor and “warrior spirit” of Native Americans. However, it was done with neither the involvement nor agreement of tribes and many felt it perpetuated a simplistic 19th-century notion of Native Americans. Today, the military not only consults with Native groups and seeks their approval before using their names, but also in doing so acknowledges the many sacrifices and contributions Native Americans have made serving in the U.S. armed services.

Cécile Ganteaume, co-curator of the “Americans” exhibition, National Museum of the American Indian 

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

—Darrel Riesterer | Kiel, Wisconsin

Even a small moon traveling inside the orbit of our current one would have a gravitational effect on Earth’s tides, flooding the coastal cities where a large percentage of humans live. A bigger moon would cause bigger floods, submerging even more land. The two moons would also affect each other. Earth’s gravity causes tides on the Moon, flexing or stretching the lunar ground. A second moon could amplify this small effect, contributing to stronger moonquakes. The biggest 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 other toxins are present in the blood and organs of not only sharks, but also other aquatic species. The concentration of such elements increases along the food chain, with those at the top having higher amounts than those at the bottom. Because many sharks are apex predators, they have especially high concentrations of mercury—they obtain it from their prey, which have obtained 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 some physiological mechanism that protects them from mercury poisoning, but it’s not yet clear what that mechanism might be.

Catalina Pimiento, research associate, Smithsonian Tropical Research Institute 

It’s your turn to Ask Smithsonian.

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