Present tense for general truths

General truths or scientific principles should appear in the present tense opens in new window, unless such principles have been disproved.

Example sentence with editing. Original sentence: Galileo taught that the earth revolved around the sun. Revised sentence: Galileo taught that the earth revolves around the sun. Explanation: The past-tense verb 'revolved' has been replaced by the present-tense 'revolves.'

Since Galileo’s teaching has not been discredited, the verb should be in the present tense. In the following sentence, however, the past-tense verb is acceptable:

Example sentence: Ptolemy taught that the sun revolved around the earth.