Special relativity predicts that the velocity of light is modified by travelling through a
moving medium. •
For a moving particulate body, light moving through the body's structure is known to move faster in the direction of the body's motion than it does in the opposite direction (
Fizeau experiment). This effect was originally predicted by
dragged-aether theories (
see: e.g. Fresnel). Light aimed transversely through a moving transparent body is also seen to be translated in the direction of the body's motion (R.V. Jones, J.Phys A 4 L1-L3 (1971) ). General relativity predicts that the
acceleration of a body in a straight line will cause light to drag, an effect known as
Frame dragging (or
gravitoelectromagnetism). •
For a moving gravity-source the gravitational field can be considered as an extension of the object, and carries inertia and momentum - since a direct collision with the moving object can impart momentum to an external particle, interaction with the object's gravitational field should allow "momentum exchange" too. Consequently,
a moving gravitational field drags light and matter. This general effect is used by
NASA to accelerate space probes, using the gravitational
slingshot effect. ==Rotation-dragging effects==