Using the opinion of an authority figure or someone in a position of authority in place of a real argument.
We know that abortion in the early stages is morally permissible because Bill Nye the Science Guy said that the fetus at this point is "just cells".
While Bill Nye is in some position of authority, what he claims should be backed by data if we are to make an argument or a claim of some sort. Arching back to the example, when the egg and the sperm meet, they form a zygote, which is a cell that is genetically distinct from all others. These cells are not ordinary and therefore, it may be disputed that his claim is actually false.