Effects of gravity in precision measurements

Abstract

lomb) and the units of magnetic- and electric-field strength and electric and magnetic induction and thus becomes a part of the system of electromagnetic units. In an ampere balance, the electromagnetic force of the interacting currents, which is proportional to the square of the current I flowing through the electromagnetic system, is balanced by a weight on the other pan of the balance: i/c 2 I2f = mg. Here, f is a dimensionless function of the geometric parameters of the system, c is the velocity of light, m is the mass of the weight, and g is the free-fall acceleration. Finally, the scale of the ampere unit is determined by a combination of fundamental physical constants - the gravitational constant G and the velocity of light c: I = cr - and by two standard units (mass and length) and a dimensionless function. The dependence of the dimensions of units of physical quantities on the fundamental constants is not single-valued; it is determined by the operative system of physical units. Recently (in 1983), the unit of length (the meter) was redefined as the distance traversed by light in some portion of a second: ~s = cat. The second is defined as the frequency of hyperfine splitting of a cesium atom. As a result, as is readily apparent, the velocity of light disappears from the units of the electromagnetic quantities (ampere, coulomb, tesla, etc.): I = ms ~s f~- The gravitational constant, however, re~ains in the system of electromagnetic units. Obviously, quantum units of the volt~ ohm, and ampere will be used in the near future, but this gives rise to a new problem ~which is automatically solved in the present definition of the ampere) - the problem of consistency of the systems of electromagnetic and mechanical quantities. It is possible that the ampere balance (or a variation of it) will continue to be used for this purpose for a considerable period of time. Explicitly or implicitly, the gravitational constant is a part of a number of standards of mechanical units: pressure, acoustic pressure, etc.