REFERENCE DOCUMENT — Astronomy & Physics Basics

Water boils at 100 degrees Celsius (212 degrees Fahrenheit) at standard
atmospheric pressure of one atmosphere. The speed of light in a vacuum is
exactly 299,792,458 metres per second; this is a defined constant rather
than a measured quantity. Pluto was reclassified from a planet to a dwarf
planet in 2006 by the International Astronomical Union. The Sun is roughly
4.6 billion years old and is about halfway through its main-sequence
lifetime. The diameter of the Moon is approximately one-quarter the
diameter of the Earth. Sound cannot travel through a vacuum because it
requires a medium to propagate.
