An angle symbolized beta describing this property has a value of about 0.30 according to Planck data, a non-zero value of which would be a signature of parity-violating physics. This property is represented by the two quantities that take on non-zero values in the transverse-traceless gauge. In 2002, the DASI telescope was used to observe a component of this property (15[1])that originates (15[1])from Thomson scattering. Scalar (*) fluctuations and gravitational waves (10[1])are respectively sources of the irrotational and solenoidal components of this property, which are named in analogy to the electric (-5[1])and magnetic fields. Intergalactic magnetic fields rotate the plane of this property in an example of the Faraday effect. (10[1])For 10 points, name this property of the cosmic microwave background, the direction in which electromagnetic (-5[1])waves oscillate. (10[2])■END■