Why Do Only Men’s Bicycles Have Crossbars? And More Questions From Our Readers

Q: Why do men’s bicycles have crossbars but not women’s? I’d expect it to be the other way around. —Joan Rosenberg | Annapolis, Maryland

Bicycle designs have gone through many changes. In the early 19th century, velocipedes had low frames that could fit women’s skirts. The penny-farthing bicycles introduced in the 1870s were easier to ride over rough roads, but their enormous front wheels made them hard for women to mount. Safety bicycles did away with those giant wheels in the 1880s, introducing chain-powered rear-wheel drive. Women’s safety bikes had sloping bars, while men’s had crossbars to support more weight. As materials evolved, crossbars became less structurally necessary, and women stopped cycling in big skirts. But old gender conventions still win over comfort, as men may find if they slip forward off their seats. —Arthur Daemmrich, director, Lemelson Center for the Study of Invention and Innovation

Q: When we find artifacts, they’re buried deep in the earth. Does that mean the earth is getting fatter?  —Dawn Evans | Black Mountain, North Carolina

The Earth is not expanding. Instead, its surface is constantly shifting. Plate tectonics and surface processes may bury historical artifacts—either suddenly (as with the volcanic eruption that buried Pompeii in A.D. 79) or gradually over time, as when eroding gravel and sand from mountains are deposited in low-lying areas by streams and rivers. The state of Florida is slowly becoming a historical artifact due to sea-level rise caused by human-induced climate change. —Elizabeth Cottrell, research geologist, National Museum of Natural History

Q: Why did animals, even insects, evolve to play? —Stella S. Rogers | Sherman Oaks, California

When we describe animal play, we generally mean behavior performed without a normal stimulus or a direct, immediate benefit. Play has been well documented in mammals, birds, reptiles and fish. Larger animals might play to engage and develop their brains. But even small invertebrates can be seen playing: Some jumping spiders will chase laser pointers as cats do, while some young wasps engage in play-fighting. They may be practicing skills they’ll need later to defend territory, attract a mate or take down prey. But insect behavior is difficult to tease apart because their neuroanatomy and physiology are so different from our own. —Floyd Shockley, entomology collections manager, National Museum of Natural History

Q: Who is a science fiction writer you hold in high esteem? —Paul Schatz | Havre de Grace, Maryland

Octavia Butler was an Afrofuturist author who was born in 1947 and died in 2006. In her Patternist novels, published during the 1970s and ’80s, she foresaw many aspects of our current era—climate change, pandemics, ethical questions about genetic engineering, struggles for racial justice—yet she struck a chord of hopefulness, especially for Black and women readers. Her body of work, which is featured in Smithsonian’s current FUTURES exhibit, grapples deeply with what it means to be human and inspires us to build a more equitable future, no matter what obstacles lie in the way. —Monica O. Montgomery, special projects & programs curator, FUTURES exhibition