BBC Knowledge Channel: “BBC Facts” [01:00]# We forget 80% of the stuff we learn each day. Thankfully, however, we have pencils whose leads are big enough to draw lines 56 km in length. This distance is approx. 1, 500 greater than that covered by the Wright Brothers in their first flying machine. All this and more can be learnt in this stop-motion animation spot for the BBC Knowledge Channel.