The "science" that all those cowardly "scientists" used here is a simple observation/evaluation scheme: "Hm, if we go against this brute in close combat, we don't stand a chance." Even big bad King Saul wasn't described as a giant like this one.
David used a different approach, based on the same observations, using a slightly different evaluation: "If I can't kill him up close, I'll kill him from afar."
What, you don't understand such an easy concept? Challenges amongst single fighters were quite common, and followed some rules of honour. Presenting a brute as Goliath is described to have been is a little... unsporting. Yet it is within the rules: the Israelites were free to chose a champion of their own.
Consider it as a duel. You have challenged your opponent to a duel with swords. Now if you know that you are an excellent swordsman and he cannot match you, this might be considered unfair. But if he comes to the field with a pistol and shoots you... he is cheating.