Does space dust fall on the roof of my house? (opens in new tab)

I don't have a SO account, so I'll post here. I'm having trouble finding the reference, but there's an IKEA in Sweden or Norway that is really far away from industrial pollution, and so gets basically no soot deposited on its perfectly white painted roof. Some intrepid amateur astronomer put 2 + 2 together and realized it's a perfect collection mechanism for space dust. They thoroughly cleaned the roof, then came back a week later and carefully collected the accumulated dust. Looking at it under a microscope confirmed minerals that only form in microgravity environments.

I thought everything was space dust, in the final reckoning of things, wasn't it?

Probably, but neutrinos definitely pass through your house (and you).

Cover a baking tin with transparent film and put it outdoors. Micrometeorites have enough velocity to punch through, but windblown dirt rarely does. Classic grade school experiment.

It was demonstrated to me a a young kid that running a strong magnet through beach sand would collect tons of black magnetite, at least some of which is likely meteorite derived.

The micro-meteorites.com website appears to be down, but you can see pictures from the book on the Internet Archive here[0]

[0]https://archive.org/details/insearchofstardu0000lars/mode/1u...

> An article by Phil Plait (The Bad Astronomer) says that each square meter of surface is hit by 1 - 2 micrometeorites per year.

A much cooler way to put this is that if you spend 1 hour per day on average not under a roof, and if we ignore some complications, your expected micrometeorite-strikes-per-lifetime is about 0.5:

    (1/24 of the time outside) * (1.5 per meter squared per year) * (80 years) * (pi * 8 inches * 6 inches) = 0.486 [1]

where the last term here is an approximate cross-sectional area of the human head as viewed from above. (Micrometeorites reach terminal velocity at a very high altitude, so they should be falling almost vertically as they strike the ground, minimizing your cross-sectional area unless you happen to be lying down.)

Someone doing manual labor or other primarily-outdoor work has an expected-micrometeorites-per-lifetime much greater than 1, and therefore is overwhelmingly likely to have space dust in their hair at least once in their life. If you spend 8 hours outside per day (so your workday + some miscellaneous non-work time that covers days you're not working), your expected lifetime impacts is ~4, so your chance of >= 1 impact is 1 - Pois(0; 4) = 1 - e^-4 = about 98%.

A better calculation would account for the fact that Earth's orbital motion makes the relative motion of impacts non-uniform in the same way the front of a moving car is hit by more raindrops than the rear. This means most strikes occur around dawn, because that's the time when you're on the "front" of the Earth as it moves in its orbit.

Early-morning workers, like agricultural, sanitation, or custodial workers, might be out for the peak of impacts nearly every day, while the average reader here who drifts into the office hours after dawn (if at all) and spends most of their outdoor time in the evening might almost entirely miss their opportunity to have a bit of space fall on their head. (I think this is rather poetic: if you want to touch the stars, go pick up trash!)

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[1] https://www.wolframalpha.com/input?i=%281+hour%2F24+hour%29+...

For anyone interested in an archive link of the meat of this: https://web.archive.org/web/20240414181406/https://micro-met...

I read about the magnet method when I was young. I always thought that was so cool. It never occurred to me until now that I never tried it!

More likely the roof than your basement, though in the latter case, you'd likely not need me to tell you ...

A prime meteorite and meteoric-dust hunting ground is Antarctica. With an ice cap that's kilometres thick, odds are high that all rocks, and much dust, found on the surface of the snow are meteoric in origin.

2018 story on that: "Hot on the trail of Antarctic meteorites" <https://www.snexplores.org/article/hot-trail-antarctic-meteo...>

And yes, there's a global warming angle on this as well: "Thousands of hidden meteorites could be lost forever as they sink in Antarctic ice, taking their cosmic secrets with them" <https://www.livescience.com/space/meteoroids/thousands-of-hi...> (2024)

Clearly explains the crumbs around be office chair

Here's a good video running through one way to do this at home - https://www.youtube.com/watch?v=9q3uNcJh4pc (I really like the ending, it's real science which is rare these days)

There are a heap of better links to micrometeorites stories than this stackexchange. Discussed many times on HN.