Glossary of Astronomical Terms/dust

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In astronomy, the term dust specifically applies to clouds of powdery matter floating in space. Viewed from a distance, such clouds seem rather dense, but on a human scale, one could float for centuries in a space suite in many such clouds without ever encountering a single speck of dust. (In Earth science, the term dust applies to matter which can be airborne and which passes through a 200-mesh seive with 76-micrometer openings.)