Welcome to Palo Alto- public domain (photograph)
- The sign itself was created by an unknown person and should assume to be protected by copyright.
- Sphere (Wikipedia)
A sphere (from Greek σφαῖρα, sphaîra) is a geometrical object that is a three-dimensional analogue to a two-dimensional circle. Formally, a sphere is the set of points that are all at the same distance r from a given point in three-dimensional space. That given point is the center of the sphere, and r is the sphere’s radius. The earliest known mentions of spheres appear in the work of the ancient Greek mathematicians.