- Von Neumann paradox (Wikipedia)
In mathematics, the von Neumann paradox, named after John von Neumann, is the idea that one can break a planar figure such as the unit square into sets of points and subject each set to an area-preserving affine transformation such that the result is two planar figures of the same size as the original. This was proved in 1929 by John von Neumann, assuming the axiom of choice. It is based on the earlier Banach–Tarski paradox, which is in turn based on the Hausdorff paradox.
- Copenhagen (Wikipedia)
Copenhagen (Danish: København [kʰøpm̩ˈhɑwˀn]) is the capital and most populous city of Denmark, with a population of 1.4 million in the urban area. The city is situated on the islands of Zealand and Amager, separated from Malmö, Sweden, by the Øresund strait. The Øresund Bridge connects the two cities by rail and road.