I stumbled upon the following sentence while browsing a Spanish translation website today:
Podríamos volver atrás y ver los dinosaurios.
We could go back and see all the dinosaurs.
Question is, is it appropriate to use atrás with volver given the latter already means "to return" or "to go back"? In English, it would be incorrect grammar to say something like "return back." Isn't it the same in Spanish?
This is known as pleonasmo.
Depending on the circumstances it can be considered an erroneous and ugly redundancy:
Por favor bajen para abajo. (Please drop down)
I do not know if the effect is maintained in English, but in Spanish it is redundant because the action ("bajar") includes direction ("hacia abajo").
Or it can be considered a stylistic resource to emphasize something.
Lo vi con mis propios ojos. (I saw it with my own eyes)
Voló por los aires. (He flew through the air)
It seems acceptable to me. It's not really redundant, because "volver" is a quite generic term that has little spatial meaning -it can mean "do something again", or "go back"- and even in the later case, "back" does not necessarily alludes to a direction in the current spatial frame.
For example, if we are walking along some path in some exhibition, to simply say "Podríamos volver a ver los dinosaurios" might allude to a place that is still in front of us: we are only meaning "volver a ver" = "ver otra vez" (as we did in a previous visit).
Adding "atrás" we are making clear that we mean to go back along the current path.
