- Speed of light (Wikipedia)
The speed of light in vacuum, commonly denoted c, is a universal physical constant that is important in many areas of physics. The speed of light c is exactly equal to 299,792,458 metres per second (approximately 300,000 kilometres per second; 186,000 miles per second; 671 million miles per hour). According to the special theory of relativity, c is the upper limit for the speed at which conventional matter or energy (and thus any signal carrying information) can travel through space.
- Messier 28 (Wikipedia)
Messier 28 or M28, also known as NGC 6626, is a globular cluster of stars in the center-west of Sagittarius. It was discovered by French astronomer Charles Messier in 1764. He briefly described it as a “nebula containing no star… round, seen with difficulty in 31⁄2-foot telescope; Diam 2′.”