molecules collide
41Formation and evolution of the Solar System — Artist s conception of a protoplanetary disk The formation and evolution of the Solar System is estimated to have begun 4.568 billion years ago with the gravitational collapse of a small part of a giant molecular cloud …
42fusion reactor — Physics. a reactor for producing atomic energy by nuclear fusion. Cf. reactor (def. 4). * * * Introduction also called fusion power plant or thermonuclear reactor a device to produce electrical power from the energy released in a nuclear… …
43dating — I In geology and archaeology, the process of determining an object s or event s place within a chronological scheme. Scientists may use either relative dating, in which items are sequenced on the basis of stratigraphic clues (see stratigraphy) or …
44meteor and meteoroid — ▪ astronomy Introduction respectively, a glowing streak in the sky (meteor) and its cause, which is a relatively small stony or metallic natural object from space (meteoroid) that enters Earth s atmosphere and heats to incandescence. In modern… …
45Collision — For other uses, see Collision (disambiguation). A collision is an isolated event which two or more moving bodies (colliding bodies) exert forces on each other for a relatively short time. Although the most common colloquial use of the word… …
46Mass spectrometry — (MS) is an analytical technique that measures the mass to charge ratio of charged particles.[1] It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical… …
47Entropy (statistical thermodynamics) — In thermodynamics, statistical entropy is the modeling of the energetic function entropy using probability theory. The statistical entropy perspective was introduced in 1870 with the work of the Austrian physicist Ludwig Boltzmann. Mathematical… …
48nuclear weapon — an explosive device whose destructive potential derives from the release of energy that accompanies the splitting or combining of atomic nuclei. [1945 50] * * * or atomic weapon or thermonuclear weapon Bomb or other warhead that derives its force …
49Energy level — A quantum mechanical system or particle that is bound that is, confined spatially can only take on certain discrete values of energy. This contrasts with classical particles, which can have any energy. These discrete values are called energy… …
50Ice — This article is about water ice. For the broader concept of ices as used in the planetary sciences, see volatiles. For other uses, see Ice (disambiguation) …
