Cookie Mysteries

I just finished up with my 1L finals. I'm one-third a lawyer! Well, kind of. Anyway, I've been studying for the past two weeks straight. The only culinary thing I accomplished was to bake a batch of cookies that was puzzlingly odd. Why did the cookies baked on the dark baking sheet turn out so different from the ones baked on the light baking sheet?! It's a mysterious world these days.