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  2. Speed of electricity - Wikipedia

    en.wikipedia.org/wiki/Speed_of_electricity

    The speed of this flow has multiple meanings. In everyday electrical and electronic devices, the signals travel as electromagnetic waves typically at 50%–99% of the speed of light in vacuum. The electrons themselves move much more slowly. See drift velocity and electron mobility.

  3. Absorption cross section - Wikipedia

    en.wikipedia.org/wiki/Absorption_cross_section

    One GM is 10 −50 cm 4 ⋅s⋅photon −1. [ 1 ] [ 2 ] In the context of ozone shielding of ultraviolet light , absorption cross section is the ability of a molecule to absorb a photon of a particular wavelength and polarization .

  4. Motion - Wikipedia

    en.wikipedia.org/wiki/Motion

    One can also speak of the motion of images, shapes, and boundaries. In general, the term motion signifies a continuous change in the position or configuration of a physical system in space. For example, one can talk about the motion of a wave or the motion of a quantum particle, where the configuration consists of the probabilities of the wave ...

  5. Cross section (physics) - Wikipedia

    en.wikipedia.org/wiki/Cross_section_(physics)

    Although the SI unit of total cross sections is m 2, a smaller unit is usually used in practice. In nuclear and particle physics, the conventional unit is the barn b, where 1 b = 10 −28 m 2 = 100 fm 2. [1] Smaller prefixed units such as mb and μb are also widely used. Correspondingly, the differential cross section can be measured in units ...

  6. Gallium - Wikipedia

    en.wikipedia.org/wiki/Gallium

    Gallium is one of the four non-radioactive metals (with caesium, rubidium, and mercury) that are known to be liquid at, or near, normal room temperature. Of the four, gallium is the only one that is neither highly reactive (as are rubidium and caesium) nor highly toxic (as is mercury) and can, therefore, be used in metal-in-glass high ...

  7. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    Similarly, a time dilation factor of γ = 10 occurs at 99.5% the speed of light (v = 0.995 c). The results of special relativity can be summarized by treating space and time as a unified structure known as spacetime (with c relating the units of space and time), and requiring that physical theories satisfy a special symmetry called Lorentz ...

  8. Interstellar medium - Wikipedia

    en.wikipedia.org/wiki/Interstellar_medium

    Within our galaxy, by mass, 99% of the ISM is gas in any form, and 1% is dust. [2] Of the gas in the ISM, by number 91% of atoms are hydrogen and 8.9% are helium, with 0.1% being atoms of elements heavier than hydrogen or helium, [3] known as "metals" in astronomical parlance. By mass this amounts to 70% hydrogen, 28% helium, and 1.5% heavier ...

  9. Nuclear cross section - Wikipedia

    en.wikipedia.org/wiki/Nuclear_cross_section

    Nuclear cross sections are used in determining the nuclear reaction rate, and are governed by the reaction rate equation for a particular set of particles (usually viewed as a "beam and target" thought experiment where one particle or nucleus is the "target", which is typically at rest, and the other is treated as a "beam", which is a projectile with a given energy).