I suspect that “trickier” is the proper word and that “tricker” is just a spelling error. “Trickier” means more difficult. “Science” is a tricky word because it derives from the Latin “scientia” which referred to knowledge in general. The English word “scientist” was not common, I think, until well into the 19th century and those we call “scientists” today were called “natural philosophers.” Today, “science” has a narrower meaning than it did before the 19th century.