A circle is what you get if you take a straight line and bend it around so that its ends touch. You can demonstrate this by taking a piece of stiff wire and doing just that: bring the ends of the wire ... Continue reading
A Mobius Strip is an amusing three-dimensional object whose surface has only one side. Huh? Well, most objects you can imagine have a surface with two sides. For example, an ordinary piece of paper ... Continue reading
Cones are used every day for a variety of purposes. Perhaps the most useful application of the cone shape is as a funnel. For finding the volume, a cone is best viewed as a stack of circles, each one ... Continue reading
Originally, each country had its own, and rather poorly reproducible, unit of luminous intensity; it was necessary to wait until 1909 to see a beginning of unification on the international level, when ... Continue reading
