Q: Given the havoc Kilauea has wreaked in Hawaii, would an active volcano make an effective trash dump, with the lava acting as a natural incinerator?

— Rebecca Adams | Natchez, Mississippi

In a word, no. Lavas like those in Hawaii can reach temperatures a bit over 2,000 degrees Fahrenheit. That’s hot enough to incinerate organic material, such as wood, says Liz Cottrell, a research geologist with the Global Volcanism Program at the National Museum of Natural History. But it’s not hot enough to incinerate many metals, nor would it do anything to mitigate the hazards posed by radioactive waste. Human engineering has produced more effective incinerators. Besides, it would be terrible to turn a natural wonder like a lava lake into a dump.

Q: What’s the highest altitude a bird has been known to fly?

— Jonathan Goodnough | Jersey City, New Jersey

The highest observed flier is a Rüppell’s griffon, a kind of vulture native to a large swath of Africa. In November 1973, one was sucked into a commercial aircraft engine at 37,000 feet over Ivory Coast. (The plane landed safely.) Bar-headed geese have been observed at 29,500 feet as they migrate over the Himalayas, and demoiselle cranes can reach about 26,000. These birds can fly so high, says Gil Myers, assistant curator at Smithsonian’s National Zoo, in part because a special type of hemoglobin in their blood makes oxygen intake more efficient.

Q: Do galaxies generally rotate clockwise or counterclockwise? Most of the ones I’ve seen in photographs go clockwise.

— Justin M. Ruhge | Lompoc, California

They don’t generally go in either direction. The universe shows no preferred direction for galactic rotation, says Avi Loeb, a theorist at the Harvard-Smithsonian Center for Astrophysics. In principle, half of all galaxies rotate clockwise, the other half counterclockwise—and a 2008 study of some 37,000 galaxies confirmed that belief. However, our perception of the direction depends on our vantage point; an object seen as rotating clockwise from above will be seen as rotating counterclockwise from below. What you see in photographs from space depends on the angle from which they were shot.

Q: Who was the first U.S. president to go abroad while in office? And who was the first foreign head of state to visit the U.S.?

— Drew Oliver | Hamtramck, Michigan

President Theodore Roosevelt was the first; he visited Panama in 1906. It took 116 years for a president to travel abroad because the United States avoided European entanglements through its first century, says Jon Grinspan, a curator at the National Museum of American History. But the end of the 1800s marked an interest in imperial expansion, and rough-ridin’ Roosevelt led the way; his administration maneuvered to engineer Panama’s independence from Colombia, largely so the U.S. could build the Panama Canal. The first foreign leader to visit our shores in an official capacity was King David Kalakaua of Hawaii, in 1874, shortly after he’d been elected (yes, elected) to the throne, at a time when several foreign nations eyed the islands as a takeover target. He saw the trip as a way to assert his leadership and his kingdom’s independence, and he traveled widely during his reign. In fact, when Kalakaua died, in 1891, he was in San Francisco.