Editing Mean free path (section)

{{short description|Average distance travelled by a moving particle between impacts with other particles}}
[[File:Gamma ray mean free path.png|thumb|Mean free path of [[gamma rays]] ([[very high energy]] and [[ultra high energy]]) based on photon energy (expressed in [[electron-volts]] on horizontal axis). Mean free path is expressed on a <sup>10</sup>log scale of [[megaparsecs|mega-parsecs]] (i.e. "–1" indicates 0.1 Mpc, "3" equals 1,000 Mpc, etc.). The primary form of [[attenuation]] is [[pair production]] by collision with [[extragalactic background light]] (EBL) and [[cosmic microwave background]] (CMB).]]
In [[physics]], '''mean free path''' is the average distance over which a moving [[particle]] (such as an [[atom]], a [[molecule]], or a [[photon]]) travels before substantially changing its direction or energy (or, in a specific context, other properties), typically as a result of one or more successive [[collisions]] with other particles.