Some of the most amazing phenomena in nature, from electromagnetic radiation and infrared vision to subatomic particles and cosmic rays, are invisible, and we get to know them only through their various applications. This is true of Lagrange points as well – points in space between celestial bodies where a spacecraft stays more or less stationary, as if held in place by some cosmic magic.
The ‘magic’, of course, owes itself to the unseen forces of gravity exerted by these bodies. Lagrange points are found along the plane of two objects in orbit around their common centre of gravity, where their gravitational forces cancel each other, so that a third body of negligible mass will remain at rest between them.
For example, the combined gravitational force between the sun and the earth equals the centrifugal force required by a satellite or an asteroid to orbit the sun-earth centre of gravity. At this Lagrange point, a satellite will keep its position constant relative to both the sun and the earth.
