Can theories change over time

Answer 1

yes, as more things are learned theories can be modified (theory of evolution) also sometimes theories can be thrown out (the theory that the earth is flat)

Answer 2

Theories don't technically change, they adapt themselves accordingly with improved data collection (and depending on how you interpret that sentence that could make the answer either yes or no). Example (taken from Isaac Asimov who commented on creationists): There are people who say that the earth is flat. They are called flat-earthers and they subscribe to the flat-earth theory. Their position is not wrong, but it is incomplete because the curvature of the earth is .00003.... so it is close enough to flat that it could be called that. We all know that the earth is not flat though, but it does appear to be flat when we look at it using only our eye. Then people discovered that the world was round and they thought that it was a circle, like a ball. These people had adopted the "round earth" theory. Then science progressed and the measurements were taken again and we discovered that the world was really spherical instead of round. Once this became accepted it was the "spherical earth" theory (it's not really known by that name though). Then in about sometime in the 60's - 80's they discovered that the bulge was greater at the south than at the north, so the earth is actually a pear shaped. The way I view it that is even an incorrect interpretation of the earth. I view the earth as something that I can only call erratic because there are lumps and bumps and indents everywhere (i.e. mountains, hills, holes)