The animation below from Wikipedia shows the standing waves of voltage and current on an ideal center fed resonant half wave dipole in free space.

[![Dipole standing waves animation](https://i.stack.imgur.com/8niio.gif)](https://i.stack.imgur.com/8niio.gif)

The red and blue curves show the change in amplitude of the actual voltage and current which exists on the antenna at each point during one cycle of the applied RF energy. The arrows are the AC current which flows through the antenna and the source. The voltage depicted is the amplitude of the electric potential at each point, and the current is the amplitude of the AC current which flows along the antenna elements at each point. The amplitude of both voltage and current changes in sinusoidal fashion at the same frequency as that of the applied RF energy, and as can be seen the voltage and current are 90 deg out of phase in time and space, in fact the voltage lags the current by 90 deg (you can't see this in the animation) which makes sense because the dipole is a big capacitor in which the voltage also lags the current by 90 deg.

But everyone knows that the voltage and current are in phase at the feed point of a resonant half wave dipole and the animation shows that the voltage and current are clearly not in phase, so it all seems very self contradictory and incestuously mutually exclusive. The phase difference between the standing waves cannot be the condition which determines the reactance present on the antenna, even though the amplitudes of the standing waves at the feed point determine the real part of the impedance of the dipole at the feed point ie: Z = E / I.

The amplitudes of the standing waves of voltage and current vary in sympathy with the sinusoidal change in amplitude of the applied RF energy at the feed point. The positions of the peaks and troughs of the standing wave remain stationary and fixed in space along the length of the antenna. The standing waves result from the vectorial addition of the amplitudes of voltage and current of the traveling wave emanating from the feed point towards the ends of the dipole, and that of the reflected wave, and are the actual conditions present on the antenna which can be measured. The original incident and reflected traveling waves cannot exist independently of each other and cannot be measured as their existence is obscured by the vectorial addition of each to the other.

Even though the voltage and current of the incident and reflected traveling waves can't be seen because they have been added together and so result in the standing waves present, they must exist otherwise there would be no standing waves.

Is it the difference in phase of the voltage and current which results from addition of the incident and reflected traveling waves at any point along the lengths of the dipole elements which determines the amount of reactance present at each point ?