- Alphecca (stars.astro.illinois.edu)
ALPHECCA or GEMMA (Alpha Coronae Borealis). One of the very few stars with two commonly used names, Alphecca is the dominant (mid- second magnitude, 2.23) Alpha star of the delightful constellation Corona Borealis, the Northern Crown, a semicircle of stars to the east of Arcturus that truly reminds the viewer of a heavenly crown, the constellation representing the crown of Ariadne.
- Spacetime (Wikipedia)
In physics, spacetime is a mathematical model that combines the three dimensions of space and one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why different observers perceive differently where and when events occur.
