It would be nice if you use spoiler to hide the OA

Here HAS BEEN SHIFTED is appropriate as the light is not shifting on its own.
The rapid motion of the galaxy is shifting the light.

Hope it helps.

prachich1987 wrote:It would be nice if you use spoiler to hide the OA

Here HAS BEEN SHIFTED is appropriate as the light is not shifting on its own.
The rapid motion of the galaxy is shifting the light.

Hope it helps.

the light can shift, move, jump and do many ample jobs much much faster than any super speedy flying object of an engineer's mind ; now we need to analyze the whole sentence to understand why here the passive tense (has been shifted) is prevalent over the active tense (has shifted)

In astronomy the term "red shift" denotes the extent to which light from a distant galaxy
stop here: we speak about a term definition "red shift" --> it means the extent to which light from a distant galaxy (the galaxy is not close by, either moving itself or located at distance)

has been shifted toward <-- click this off for the time being to understand overall meaning

the red, or long-wave, end of the light spectrum by the rapid motion of the galaxy away from the Earth.
so we found that the light is actually stretched towards the end of its spectrum, as the galaxy moves away and leaves such shift (here finally we understood the meaning of shift, it's stain or simply red spot at our eyesight).

So this is actually light (of the distant galaxy) in its movement which may be shifted towards the end of its spectrum, as a person or any object traveling by oneself may be reallocated in the space.

May be it was very technical explanation, but here's my take-away from this problem - by reading entire sentence once, we should be able to understand its meaning better and to express the ideas more clearly.