Ram pressure is pressure exerted on a body due to its movement through a fluid. For the simplest case:
P = ρv²
(This equation for the simple case also indicates the scale and some of the proportionality for less simple cases.) Examples:
In the latter case, the pressure can strip away the galaxy's interstellar gas (ram-pressure stripping).
Compression from significant pressure can significantly heat the gas and this temperature increase and its consequences (thermal emission) are often what is of interest and constitute our means of detecting ram pressure. For objects entering the atmosphere, such as meteors or space vehicles, compression by ram pressure contributes more heat than does the friction.