Paradox of radiation of charged particles in a gravitational field fields. One of the first to study this problem was Max Born in his 1909 paper about the consequences of a charge in uniformly accelerated frame. Earlier concerns and possible solutions were raised by Wolfgang Pauli (1918), Max von Laue (1919), and others, but the most recognized work on the subject is the resolution of Thomas Fulton and Fritz Rohrlich in 1960. It is a standard result from Maxwell's equations of classical electrodynamics that an accelerated charge radiates. That is, it produces an electric field that falls off as formula_1 in addition to its rest-frame formula_2 Coulomb field. This radiation
Direction, position, or indication sign sign category into direction signs, which are only those giving distances or directions to a given location; road identification signs (also known as "reassurance signs"), which repeat the name or number of the road, and place identification signs, which give the name of a landmark, such as a town, river or border. Unlike the other classes of sign, direction signs remain broadly undefined by the convention; the only restrictions given are that direction signs must be either a rectangle or an arrow shaped pentagon, and that they may not contain placenames in more than two languages. Additionally, direction signs on