Why Twitter expanded to 280 characters

What can you say in 280 characters that you couldn't in 140?

The world's going to have to figure that out now that Twitter has signaled it will expand its infamous limit to just how many letters, numbers, spaces, punctuation, and emoji you're allowed to fit into a tweet. Technically, the change is just a test at this point, seeded to a few (lucky?) users, but such a fundamental change to the service was big news, and any backtracking at this point would not be a good look for Twitter. So it seems likely that, going forward, 280 is the new 140.