Editing YORP effect (section)

== Physical mechanism ==
In principle, [[electromagnetic radiation]] interacts with the surface of an asteroid in three significant ways: radiation from the [[Sun]] is (1) [[Absorption (electromagnetic radiation)|absorbed]] and (2) [[Diffuse reflection|diffusively reflected]] by the surface of the body and the body's internal energy is (3) [[Emission (electromagnetic radiation)|emitted]] as [[thermal radiation]]. Since [[photon]]s possess [[momentum]], each of these interactions leads to changes in the [[angular momentum]] of the body relative to its [[center of mass]]. If considered for only a short period of time, these changes are very small, but over longer periods of time, these changes may [[Integration (mathematics)|integrate]] to significant changes in the angular momentum of the body. For bodies in a [[heliocentric orbit]], the relevant long period of time is the [[orbital period]] (i.e. year), since most asteroids have [[rotation period]]s (i.e. days) shorter than their orbital periods. Thus, for most asteroids, the YORP effect is the secular change in the rotation state of the asteroid after averaging the [[Solar Radiation|solar radiation]] torques over first the rotational period and then the orbital period.