sit back vs sit by

sit back and sit by both are verbs.

Word	Noun	Adjective	Verb	Adverb
sit back	No	No	Yes	No
sit by	No	No	Yes	No

As verbs, sit back and sit by are synonyms defined as:

sit back and sit by: be inactive or indifferent while something is happening

sit back (verb)	sit by (verb)
settle into a comfortable sitting position	be inactive or indifferent while something is happening
be inactive or indifferent while something is happening