Complex sentence: After returning to LM site, Scott performed an experiment with a feather and hammer to demonstrate Galileo's theory of objects in gravity fields in vacuums: he dropped the hammer and feather at the same time.
Split into simpler sentences: After returning to LM site, Scott performed an experiment with a feather and hammer to test Galileo's theory of objects in gravity fields in vacuums. To test this, he dropped the hammer and feather at the same time.