The Astronautics Vocabulary is a glossary of terms that pertain to the science and technology of spaceflight. This alphabetical list can be navigated by clicking on the letters A-Z displayed on this page.
Definition: A worldwide standard time-scale, the same as Greenwich Mean Time. Universal Time is the mean solar time on the meridian of Greenwich. It is defined as the Greenwich angle of the mean sun plus 12 hours, so that the day begins at midnight rather than noon.