Are QR Codes Safe and Other Questions From Our Readers

Do the barcodes or QR codes on my bank statements and utility bills carry any sensitive personal information?

Diane Hunt, Burlington, Washington

The alphanumeric characters stored in a barcode or QR code could convey anything—I’ve sent some nerd friends birthday greetings as QR codes—but they commonly just contain a website address, sometimes with a tracking code. You can get a free barcode reader app on your smartphone and read the code, but I’d generally recommend caution in checking any link that comes up before following it.

Sebastian Chan, director, digital and emerging media, Cooper Hewitt, Smithsonian Design Museum

If you are standing exactly at the North Pole, can you walk away in any direction other than south?

Penny Bennett, Seneca, South Carolina

No. Any step would be toward the south. After that first step, you could go east or west by walking around the pole. But finding the exact spot would be tricky on the ice floating on the Arctic Ocean. It is simpler at the South Pole, where the Antarctic ice rests on land and moves much more slowly. An actual pole marks that spot.

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

In early color photography, were the Lumière brothers’ autochrome system and Eugene Ives’ photochromoscope system essentially the same?

J.D. Sutton, Orlando, Florida

Both were developed roughly at the turn of the 20th century, but they differed substantially. The Lumières’ method, patented in the United States in 1906, used plates coated with an emulsion containing dyed grains of potato starch to act as color filters; Ives’ used glass color filters within a stereoscopic camera and produced 3-D images. Autochrome was much more popular.

Shannon Perich, curator of photography, National Museum of American History

Does dieting deteriorate muscle?

Cassondra Hunt, Albuquerque, New Mexico

It can. If you reduce caloric intake severely and lose weight too quickly, the body will switch to “starvation” mode, conserving fat stores and deriving energy from muscle. But moderate decreases in caloric intake stimulate the loss of much more fat than muscle. When we formulate weight-loss diets at the zoo, we make incremental decreases over long periods of time to ensure slow, steady and healthy changes in body condition.

Erin Kendrick, clinical nutritionist, Department of Nutrition Science, National Zoo

Why do tree species lose their leaves at different times?

Jack A. Elder, Midvale, Utah

Cooler and shorter fall days trigger a hormonal response in deciduous trees, including the production of the hormone auxin in leaves and branches. The balance of branch and leaf auxin affects when leaves drop, and that balance varies from species to species.

Greg Huse, arborist and tree collection manager, Smithsonian Gardens