Editing Circular orbit (section)

==Energy==
[[File:Gravity Wells Potential Plus Kinetic Energy - Circle-Ellipse-Parabola-Hyperbola.png|thumb|250px|A circular orbit is depicted in the top-left quadrant of this diagram, where the [[gravity well|gravitational potential well]] of the central mass shows potential energy, and the kinetic energy of the orbital speed is shown in red. The height of the kinetic energy remains constant throughout the constant speed circular orbit.]]

The [[specific orbital energy]] (<math>\epsilon\,</math>) is negative, and
:<math>\epsilon=-{v^2\over{2}}</math>
:<math>\epsilon=-{\mu\over{2r}}</math>

Thus the [[virial theorem]]<ref name=lissauer2019/>{{rp|72}} applies even without taking a time-average:{{cn|date=August 2019}}

*the kinetic energy of the system is equal to the absolute value of the total energy
*the potential energy of the system is equal to twice the total energy

The [[escape velocity]] from any distance is {{radic|2}} times the speed in a circular orbit at that distance: the kinetic energy is twice as much, hence the total energy is zero.{{cn|date=August 2019}}