Is household dust the same as the cosmic dust that falls from outer space?

It’s a plausible theory, on the face of it. Dust does seem like some sort of weird alien thing, in that it appears from nowhere and doesn’t seem to be the same dirt, sand, and other stuff you find blowing around outside.

Furthermore, it’s a known fact that about a thousand tons of cosmic dust fall on Earth every day, the residue of comets and other space entities. So its easy to think that maybe a thousand tons would be enough to account for all the dust bunnies around the world. You’d be wrong, but at least it sounds more likely than some theories we’ve heard.

The truth is that your household dust is an individualized thing. Your dust is not exactly the same as the dust of your neighbors—in fact, your house dust can even vary in composition from room to room.

Laboratory analysis finds that dust consists of a mixture of things. For example, up to 70 percent of all house dust comes from the tens of thousands of skin cells we each shed every minute of every day. There are zillions of tiny mites eating all that loose skin, and their excrement and corpses also make up some of your dust.

The good news is that the mites do a pretty good job of cleaning up most of the dead skin; the bad news is that they’re the cause of almost all of the allergens that make some people sneeze and wheeze when exposed to dust.

In heavily trafficked public buildings, bits of shoe leather make up a large proportion of the dust. Other stuff in your household dust might include topsoil, industrial pollution, pillow feathers, lint from clothes, pollen, yeast, mold spores and yes, probably even a little bit of cosmic dust.

Libraries run by the National Trust in England have been plagued by a corrosive dust that’s slowly eating away the bindings of books. The dust is made up largely of natural fibers shed by visitors’ jackets and sweaters. “Visitors to stately homes tend to wear their outdoor clothes.

Upper garments are far more prone to shedding fiber than lower ones, as they are more likely to be made of soft material such as wool,” said a National Trust representative.