Fog

[Panic Button]

If fog is made up of tiny water droplets, what keeps them up in the air?

Why don't they fall to the ground like their cousins, the raindrops.

[Clanad]

Fog droplets are so small, the force of air molecules bumping into them almost nullifies the force of gravity... (Thanks to The Engines of Our Ingenuity )

[mibn2cweus]

An interesting thing happens when you group particles together. The combined mass or volume of the resulting object grows faster than the surface area. Especially in a spherical grouping, the most efficient geometry for volume versus surface area, as the volume increases more of the particles become internal to the overall structure. Because of this property of grouped particles a single particle will have the greatest surface area per volume than a grouped structure. This greater surface area per mass relationship makes smaller particles easier to retain in suspension than larger groupings of particles.

interactivity

[Panic Button]

3 stars mucus, but a bit beyond me that one!

[yinmorrison]

The reason is because the air temperature is above dewpoint. This being the point when the air cannot support the weight of the water molecules. Dry Bulb temperature and wet bulb temperatures are used to calculate the relative humidity of the air and if you look at a psychrometric chart you can see that at very low temps it is possible to have mist forming because of this. Try walking into a commercial freezer and you will be confronted with a similar foggy experience especially if the door has been open for a while allowing more moisture laden air to enter.