It is the theory that the earth rotates about its axis, once per day, and at the same time revolves around the sun once per year.
(It; is; the theory that the earth rotates about its axis, once per day, and at the same time revolves around the sun once per year) (the earth; revolves; around the sun; T:once per year; T:at the same time)
It the earth
is revolves
the theory that the earth rotates about its axis, once per day, and at the same time revolves around the sun once per year
around the sun T:once per year T:at the same time