Portal:Physics/Selected picture/July 2007

Image credit: A.Greg

The translational motion of fundamental particles of nature such as atoms and molecules gives a substance its temperature. Here, the size of helium atoms relative to their spacing is shown to scale under 1950 atmospheres of pressure. These room-temperature atoms have a certain average speed (slowed down here two trillion fold). At any given instant however, a particular helium atom may be moving much faster than average while another may be nearly motionless. Five atoms are colored red to facilitate following their motions.