Comma splices

A comma splice occurs when two independent clauses are connected by a comma:

　　Planck's ideas seemed incredible, many scholars simply ignored him.

　　Fix comma splices in a variety of ways. Easiest is to put each independent clause in its own sentence:

　　Planck's ideas seemed incredible. Many scholars simply ignored him.

　　You may also use a semicolon:

　　Planck's ideas seemed incredible; many scholars simply ignored him.

　　A dash can sometimes do the job, especially if the second clause is short （see below for more on dashes）:

　　Planck's ideas seemed incredible—many scholars simply ignored him.

　　A coordinating conjunction will also work:

　　Planck's ideas seemed incredible, and many scholars simply ignored him.

　　Or subordination:

　　Since Planck's ideas seemed incredible, many scholars simply ignored him.

　　Or rewriting, to turn one of the clauses into a phrase:

　　Many scholars, finding Planck's ideas incredible, simply ignored him……

　　Some good writing, especially in British English, uses comma splices. If both independent clauses are short and lack internal commas, you may be able to get away with a comma splice. But since they act as a red flag for most academic readers, I recommend avoiding them altogether.