- The origin of this constellation is so ancient that its true identity was lost even to the Greeks, who knew the figure as Ἐνγόνασι (Engonasi) or Ἐνγόνασιν (Engonasin), literally meaning ‘the kneeling one’. The Greek poet Aratus described him as being worn out with toil, his hands upraised, with one knee bent and a foot on the head of Draco, the dragon. ‘No one knows his name, nor what he labours at’, said Aratus. But Eratosthenes, a century after Aratus, identified the figure as Heracles (the Greek name for Hercules) triumphing over the dragon that guarded the golden apples of the Hesperides. The Greek playwright Aeschylus, quoted by Hyginus, offered a different explanation. He said that Heracles was kneeling, wounded and exhausted, during his battle with the Ligurians.
- 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.