One of the more exciting results of Einstein’s theory of gravity – the so-called general theory of relativity – is the possibility of gravity waves. The force of gravity is in some respects like the force of electricity between charged particles, or the attraction between magnets, but with mass playing the role of charge. When electric charges are violently disturbed, such as in a radio transmitter, electromagnetic waves are generated. The reason for this can readily be visualized. If an electric charge is pictured as surrounded by a field, then when the charge is moved the field must also adjust itself to the new position. However, it cannot do this instantaneously: the theory of relativity forbids information to travel faster than light, so the outlying regions of the field do not know that the charge has moved until at least the light-travel time from the charge. It follows that the field becomes buckled, or distorted, because when the charge first moves the remote regions of the field do not change whereas the field in the proximity of the charge is quick to respond. The effect is to send a kink of electric and magnetic force travelling outward through the field at the speed of light. This electromagnetic radiation transports energy away from the charge into the surrounding space. If the charge is wobbled to and fro in a systematic way, the field distortion wobbles likewise, and the spreading kink takes on the features of a wave. Electromagnetic waves of this sort are experienced by us as visible light, radio waves, heat radiation, x-rays and so on, according to their wavelength.
In analogy to the production of electromagnetic waves we might expect the disturbance of massive bodies to set up kinks in the surrounding gravitational field, which will also spread outwards in the form of gravity waves. In this case, though, the ripples are kinks in space itself, because in Einstein’s theory gravity is a manifestation of distorted spacetime. Gravity waves can therefore be visualized as undulations of space, radiating away from the source of disturbance.