Mathematics
The Law of Large Numbers
Quick fact
The law of large numbers guarantees that if you repeatedly flip a fair coin, the proportion of heads will approach 50% as the number of flips grows. Yet, it also means that the difference between the number of heads and tails can grow without bound—so don't expect a 'balancing' effect in the short term.
Why this is interesting
Ever wondered why casinos always win in the long run? The law of large numbers is the secret behind their business model.