Computer model of the radio waves emitted from a small antenna. This is a Hertzian dipole, an antenna whose length is much smaller than the wavelength of its emitted radio waves. The antenna comprises a conductor carrying oscillating electric charges. At the start of the clip, far away from the antenna, the waves resemble a regular sine wave radiating from the antenna. In the middle part of the clip, as we approach the antenna and the dipole becomes visible, the picture is far more complex: the radiation is not uniform, instead being emitted mainly to the sides of the antenna, with none in the direction of the antenna axis. The antenna is represented by a rod carrying a positive (red) and negative (green) charge, whose oscillation is the source of the radiation. This part of the clip shows a cross-section of the field at its origin, with black and white bands showing regions with the same energy density. The last part of the clip shows the absolute energy density, from black through blue, green and yellow to white. This reveals the lack of emission along the axis, seen as a black wedge.