Samantha Weinberg considers the choices:
How do you measure the wheel against the space shuttle? I am taking the greatest to mean the invention that has had the greatest impact on the most people in a relatively immediate sense; power equals energy over time. And for that, we don’t have to look very far back at all. If I had been writing this article 22 years ago, it would have taken much longer. I would have had to traipse around libraries, wade through encyclopedias and newspaper cuttings, and bother a host of people with a stack of questions. Instead, I’ve been sitting at home, in front of a flickering fire (c. 1.4m BC), drinking tea (first recorded in the 10th century BC; teabags patented 1903), tapping at my laptop (1983), and distilling what I’ve found by trawling the world wide web.
The Dish 