How Much Warning Would We Have of an Earth-Shattering Comet? And More Questions From Our Readers

Q: In the film Don’t Look Up, scientists warn that a comet is about to hit the Earth. How much warning would we have in real life? Brendanis Rodriguez | Bronx, New York

If a large comet were on a direct trajectory toward Earth, the movie’s time frame of about six months would be realistic. But such impact events are unlikely to happen more than once in a hundred million years. In the last 20 years, dedicated survey telescopes have discovered almost all near-Earth asteroids larger than one kilometer. (The very smallest objects pose no threat, burning up as fireballs in Earth’s atmosphere.) If the large telescope surveys were to miss a threat, the ATLAS alert system could give us weeks of warning. The Near-Earth Object Surveyor, an infrared space telescope scheduled for launch in 2028, will increase these discoveries significantly. Meanwhile, in September 2022, NASA launched the first successful mission to nudge an asteroid off track. —Peter Vereš, astronomer, Center for Astrophysics | Harvard & Smithsonian

Q: Do American Indians have a written language? Nancy Snyder | Woodstock, Maryland

The Timucua were among the first to have a written system, though it was developed by Francisco Pareja, a Franciscan missionary who came to St. Augustine, Florida, in 1595. In 1821, Sequoyah, a Cherokee Indian, created a set of written characters to form the first written Native language using new characters. This syllabary allowed reading, writing and later printing to prosper in the Cherokee Nation. Today, many tribes in the United States, including the Navajo, have phonetically adapted their spoken languages using the Latin alphabet. —Dennis Zotigh, cultural specialist, National Museum of the American Indian

Q: Where did the Union Army get the blue to dye its uniforms during the Civil War? Christopher Newhouse | Waterloo, Wisconsin

The Union Army dyed its fabric with indigo, a plant that once grew abundantly in South Carolina but declined steeply by the late 1700s. During the Civil War, the Union Army had to import indigo, primarily from India by way of Great Britain. As demand for uniforms went up, the Army began using cheaper dyes for the thread that held the fabric together. Prussian blue was synthetic and manufactured domestically. Logwood, a natural dye, came from tropical plants and was easy to obtain from sources in the Western Hemisphere. —Frank Blazich, curator of military history, National Museum of American History

Q: What do astronauts do when they get sick in space? Sylvia Anderson | Hallsville, Missouri

Getting sick in space can be dangerous to the entire crew. A spacecraft is a “closed loop environment,” meaning the air can be filtered but not replaced. Astronauts quarantine before launch and take great care to avoid contaminating supplies. There are medical kits on board to treat small wounds, headaches and other minor problems. One astronaut who is also an M.D. says common health complaints in space include paper cuts. —Jennifer Levasseur, space history curator, National Air and Space Museum