That rock in your shoe, along with others lying around, may come from space

Q. Have you ever noticed a two-digit number embossed into the bottom of a pop or beer can? It’s shallow and hard to read, but it’s there if you look closely. What’s it for? A. A typical can production line runs 24/7 at a rate of 30 cans per second, so a factory with multiple lines produces tens of millions of them per day. Each container starts life as a small disk of aluminum and is formed (“punched” and “ironed”) into the shape of a can (sans top) by a machine called a body maker. Since there may be a dozen or more of these body makers on the floor, each has a unique ID number that gets embossed into the bottom of the cans it forms — vital in quality assurance. Typically, a few cans per thousand end up with defects such as dents or coating voids that may cause leakage or product spoilage. So the body maker ID tells the quality assurance folks which machine needs repair. (Look for a molding machine ID on the bottoms of glass bottles.)

Reassuringly, every metal, glass and plastic container we use is thoroughly inspected by sophisticated high-speed computer vision equipment. Nowadays the body maker and mold IDs are generally read by machine, not humans, and factory personnel are alerted when defects correlate with the forming process. Q. What does the sentence “John stood before me” mean to you? A. The 18th-century nursery rhyme “Sing a Song of Sixpence” (about a pie full of blackbirds) ends with “Wasn’t that a dainty dish to set before the king?” Here the word “before” means “in front of.” But in 21st-century English, this meaning of “before” is nearly extinct. In his book, “The Crucible of Language: How Language and Mind Create Meaning,” linguistics professor Vyvyan Evans considers the sentence, “John stood before me.” Informal experiments with native speakers suggest that what first comes to mind is the idea of time, meaning “John rose to standing position prior to me”; nowadays, the “John is in front of me” interpretation seems to demand more effort. “But the historical evidence demonstrates that the earliest meaning associated with ‘before’ was the spatial meaning, rather than the temporal one which has come to usurp it.” Q. They’re nowhere near the category of bird poop or raindrops or hail pellets, but they just might be dropping onto your roof sometime soon. Got a guess what these are? A. They’re small pieces of outer space — micrometeorites that have made their way Earthward and found a new home of sorts — often in the ocean, at times on city or suburban rooftops, says Jennifer Hackett in “Scientific American” magazine. When it rains, this rooftop debris can be swept into gutters. Taken all together, NASA estimates that maybe 100 tons of space dust, gravel and rock of various sizes hit our planet every day. (Massive meteorites are mercifully quite rare.)

According to civilian astronaut and meteoritehunter Richard Garriott, a marble-sized micrometeorite can be “picked up about every square kilometer across Earth’s surface”; at the size of a grain of rice, “they’re incredibly common.” Garriott uses a strong magnet to locate the nickel- and iron-laden rocks, perhaps where a gutter downspout terminates. Of course, not everything the magnet attracts will come from space. But micrometeorites are distinctively spherical in shape with a telltale coating of glass created under fusion, which can readily be confirmed with a microscope.

Citizen scientists have already submitted more than 3,000 photographs of candidate space rocks to Project Stardust, hoping for a celestial find. Interested in joining the search?