What is true about muons?
A) They are always moving at high speed, so they test relativity.
B) Relativity explains why we can see short-lived muons that are produced high in the atmosphere from cosmic rays.
C) We can see them being deflected from straight lines by the gravity of black holes.
D) They have a mass that does not increase if they are moving fast.
E) They are examples of Hawking radiation from black holes.

Question

Quizplus · Accepted Answer

Muons are short-lived particles that are constantly being produced by cosmic rays colliding with particles in Earth's atmosphere. They are able to reach the Earth's surface because of time dilation, a concept in special relativity. Due to their high speed, time is slowed down for the muons, allowing them to survive long enough to reach the surface of the Earth.

Answer: D 
 According to special relativity, as an object approaches the speed of light, its mass appears to increase. However, studies of muons have shown that their measured mass remains the same, regardless of their velocity. This is one of the key pieces of evidence supporting special relativity.

What Is True About Muons