Last week, Birmingham, Alabama got treated to a special cloudy day, thanks to some Kelvin-Helmholtz waves, shown above. When a layer of faster moving fluid shears a slower moving fluid, this instability can form and cause some spectacular mixing. In this case, the lower, slower fluid was cool and moist enough to contain clouds, enabling us to see the effect with the naked eye. The same mechanism is responsible for the shape of breaking ocean waves and can even be seen in the atmospheres of gas giants like Saturn and Jupiter. (submitted by David B)
Expiry Date / The Things Far Away Beyond Numbers - a milk carton that changes its color to indicate the freshness of its content.
A vintage Maybelline ad from 1971.
This is quite possibly the best thing that I have ever seen.