Figure 24-11: An Explanation of Superluminal Motion (a) If a blob of material ejected from a quasar moves at five-sixths of the speed of light, it covers the 5 ly from point A to point B in 6 years. In the case shown here, it moves 4 ly toward Earth and 3 ly in a sideways, transverse direction. The light emitted by the blob at A reaches us in 2014. The light emitted by the blob at B reaches us in 2016. The light left the blob at B 6 years later than the light from A but had 4 fewer light-years to travel to reach us. (b) From Earth we can see only the blob’s sideways, transverse motion across the sky, as in Figure 24-10. It appears that the blob has traveled 3 ly in just 2 years, so its apparent speed is 3/2 of the speed of light, or 1.5c.