Arcadia links time to entropy – the idea that everything in the universe is getting more and more randomly distributed, until it's all total disorder (think about a bag of cookies in your backpack slowly getting crushed to crumbs – or what would happen to your room if you never cleaned it). No matter what we do to create order, in the long run it's doomed to be destroyed – so why do anything at all? Arcadia's surprisingly cheerful struggle to answer this question may even make you want to go home and do some tidying.
By showing the passage of time producing more and more disorder, Arcadia counters the narrative of continuous scientific progress.
Valentine says that "there's an order things can't happen in" (2.7), but the play's jumping between different historical periods suggests that order is more flexible when it comes to storytelling. Juxtaposing these different models of time suggests that order is an interpretation imposed on events rather than inherent in the events themselves.