from the this-is-glue.-strong-stuff. dept.
sciencehabit writes: Planetary scientists have found an asteroid spinning too fast for its own good. The object, known as 1950 DA, whips around every 2.1 hours, which means that rocks on its surface should fly off into space. What's keeping the remaining small rocks and dust on the surface? The researchers suggest van der Waals forces, weak forces caused by the attraction of polar molecules, which have slightly different charges on different sides of the molecule. For example, water molecules exhibit surface tension because of van der Waals forces, because the negative charge of one water molecule's oxygen atom is attracted to nearby water molecules' hydrogen atoms, which have a positive charge at their surfaces. Similar attractions could be occurring between molecules on the surfaces of different pieces of dust and rock. Such forces would be comparable to those that caused lunar dust to stick to astronauts' space suits.
If you push the "extra ice" button on the soft drink vending machine, you won't
get any ice. If you push the "no ice" button, you'll get ice, but no cup.