<P> For an Earthbound observer, objects in the sky complete one revolution around the Earth in 1 day . Proxima Centauri, which is the nearest star outside the solar system, is about 4 light - years away . On a geostationary view, Proxima Centauri has a speed many times greater than c as the rim speed of an object moving in a circle is a product of the radius and angular speed . It is also possible on a geostatic view for objects such as comets to vary their speed from subluminal to superluminal and vice versa simply because the distance from the Earth varies . Comets may have orbits which take them out to more than 1000 AU . The circumference of a circle with a radius of 1000 AU is greater than one light day . In other words, a comet at such a distance is superluminal in a geostatic, and therefore non-inertial, frame . </P> <P> If a laser beam is swept across a distant object, the spot of laser light can easily be made to move across the object at a speed greater than c . Similarly, a shadow projected onto a distant object can be made to move across the object faster than c . In neither case does the light travel from the source to the object faster than c, nor does any information travel faster than light . </P> <P> Since there is no "retardation" (or aberration) of the apparent position of the source of a gravitational or electric static field when the source moves with constant velocity, the static field "effect" may seem at first glance to be "transmitted" faster than the speed of light . However, uniform motion of the static source may be removed with a change in reference frame, causing the direction of the static field to change immediately, at all distances . This is not a change of position which "propagates", and thus this change cannot be used to transmit information from the source . No information or matter can be FTL - transmitted or propagated from source to receiver / observer by an electromagnetic field . </P> <P> The rate at which two objects in motion in a single frame of reference get closer together is called the mutual or closing speed . This may approach twice the speed of light, as in the case of two particles travelling at close to the speed of light in opposite directions with respect to the reference frame . </P>

What is something faster than the speed of light