How long does light take to reach us from Proxima Centuri
A)4.2 ly
B)4.2 years
C)8.4 AU
D)8.4 km

Question

Quizplus · Accepted Answer

Light takes 4.2 years to reach us from Proxima Centuri, as it is located 4.2 light years away from Earth. Choice A (4.2 ly) and C (8.4 AU) are incorrect because they only indicate the distance, whereas we are interested in the time taken for light to travel that distance. Choice D (8.4 km) is too small a distance, as light can travel 8.4 km in less than a few milliseconds.

How Long Does Light Take to Reach Us from Proxima