Electrodynamics of Radiating Charges

Figure 4

The figure shows the difference between a Lorentz contracted sphere (dashed line) centered at the instantaneous current (cur) position of the charge, 𝑥(𝑡), and the retarded (ret) sphere (solid line) with the same radius 𝑟=𝑐(𝑡−𝑡_𝑟) centered at the position, 𝑥(𝑡_𝑟), of the particle at time 𝑡_𝑟<𝑡.