American Solar Challenge: 6 months to go

Scrutineering for the 2018 American Solar Challenge starts on July 6. The chart below summarises the 39 solar car teams from 8 countries which have registered for the race. Many of them are frantically building or modifying cars – see my race information page. The race will run through the mountains from Omaha, Nebraska to Bend, Oregon. Follow the leadup to the race here and on the official ASC Facebook at  

Four worlds

The picture above shows four possible worlds: a (slightly oblate) sphere, a torus, a disc, and a Klein bottle (images © Anthony Dekker). The darkened end of the Klein bottle is shifted through the fourth dimension to connect with the other end, making it a one-sided surface (like the Möbius strip). How do we know which world we live in?