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 form of energy whose nature is unknown but which, theoretically—and unlike gravity—would repel matter, causing the expansion of the universe to accelerate. It is thought to make up the majority of the cosmos. However, some scientists challenge this theory. (See ordinary matter and dark matter.)