Michael Wolgemut, Danse Macabre (Dance of Death), 1493.
David Rumsey Historical Map Collection
1850 Star Chart
Vesica Piscis and the Flower of Life
Female IRA Fighter. County Armin, Northern Ireland. 1972.
An eruption on the volcano island of Gaua in the south Pacific, observed from the International Space Station, May 2013.
Spiral of Theodorus
First constructed by Theodorus of Cyrene, the spiral (also called the square root spiral, Einstein spiral or Pythagorean spiral) is composed of contiguous right triangles. It is begun with an isosceles right triangle with each leg having a length of 1 - then another right triangle is formed next to it with one leg being the hypotenuse of the prior triangle and the other leg having a length of 1.Thus, each successive nth triangle has side lengths √n and 1, with a hypotenuse of √(n + 1).