FeedA component that "feeds" the signal from the optical system to the amplification electronics. Also called a "feed horn" or "horn".
FiniteHaving a set amount. A barrel of 30 apples contains only 30 apples. However the number of times one can divide a meter into two parts is infinite.
FissionThe splitting of heavier atomic nuclei into lighter ones. In the case of heavy atoms (e.g., uranium, plutonium), this will release energy.
Flat UniverseA universe where the geometry of space does not curve but is flat like a tabletop. In a flat universe the total energy density equals the critical density.
Flatness ProblemUnder normal gravity, any slight deviation from flatness should quickly get larger : for example a closed universe should recollapse or an open universe…
FluctuationThe deviations from expectation in a player's bankroll.
FluxThe amount of energy passing through a unit area (for example, 1m2) per time. On this website, we will be discussing the flux of light energy due to…
Frame of ReferenceThe perspective from which an event is viewed. For example a man is standing on the side of the road, and he sees a woman drive past him in a car.
Fundamental InteractionsIn the Standard Model the fundamental interactions are the strong, electromagnetic, weak, and gravitational interactions (forces).
Fundamental ParticlesA particle with no internal substructure. In the Standard Model the quarks, leptons, photons, gluons, W+ and W- bosons, and the Z bosons are fundamental.
FusionThe combining of lighter elements into heavier ones. For lighter elements (e.g., hydrogen, helium) this process releases energy.