Light path B is shorter than path A. If the knot’s speed is close to the speed of light, B is almost a light-year shorter than A. This “head start” makes the light arrive sooner than expected, giving the appearance that the knot is moving faster than light. (Nothing actually needs to move that fast for the knot to appear to move that fast.) Thus apparent speeds larger than the speed of light can be obtained. The apparent speeds only turn out to be much in excess of the speed of light ifthe actual speed of the radio-emitting knots is pretty close to the speed of light.

Ejection speeds in astrophysics tend to be close to the escape speed of the object that did the ejecting. What has escape speeds near the speed of light?

• Neutron stars (but they can’t produce the quasar’s luminosity)
• Black holes - like the ones that can produce the quasars’ luminosities.