It is possible to tell if objects in space are moving closer to us or father away based on which of the following?

a. the high qualities of light that they emit.

b. their appearance through a telescope.

c. their size and other changes in appearance on satellites

d. the redshift or blueshift

I can't eliminate the wrong answers. I can only tell you what the answer is. You can look up the Doppler Effect. You will find that D is the answer.

The correct answer is "The red shift or blue shift".

Explanation:

Scientists use the Doppler effect to understand the universe by determining the motion of the object. Doppler effect phenomenon occurs when there is relative motion between the source and the observer.

Red shift: the light is shifted to red color when the object in space (such as star) moves away from us. In this case, the light is shifted to longer wavelength.

Blue shift: the light is shifted to blue color when the object in space (such as star) moves towards from us. In this case, the light is shifted to shorter wavelength.

It is possible to tell if object in space are moving closer to us or farther away on the basis of red shift or blue shift.

Therefore, the correct option is (D).

trig 15.3 cos