The proper time interval between two events is measured from the frame of reference of an observer present at both events. Therefore, the proper time measurement of the decay of a neutron is measured by
A) an observer in the national lab at Los Alamos or any other certified nuclear lab.
B) an observer at the speed of light, relative to the neutron.
C) an observer who is emitting light at all frequencies.
D) an imaginary observer riding along with the neutron.
Fill in the Blank Questions

Question

Quizplus · Accepted Answer

The proper time interval is the time interval measured by an observer who is at rest relative to the event being observed. In the case of the decay of a neutron, the proper time would be measured by an observer who is moving along with the neutron, as if "riding" along with it, because this observer would be at rest relative to the neutron. Choices A, B, and C involve observers who are not at rest relative to the neutron and thus would not measure the proper time.

The Proper Time Interval Between Two Events Is Measured from the Frame