The look-back time is
A)the time it takes for the light from an object to reach Earth.
B)numerically equal to the distance in light-years.
C)smaller for more distant objects.
D)All of the other choices are correct.
E)the time it takes for the light from an object to reach Earth and numerically equal to the distance in light-years.

Question

Quizplus · Accepted Answer

The look-back time is defined as the time it takes for light from an object to reach Earth. It is also numerically equal to the distance in light-years. Therefore, E is the correct answer. The statement that it is smaller for more distant objects is incorrect as the look-back time increases with the distance of the object. Hence, D is incorrect.

The Look-Back Time Is