Earth experiences seasons because the spin axis of our planet is not at right angles to our orbit round the Sun, but is tilted by over 23 degrees. When it is summer in the northern hemisphere, the north pole is tilted towards the Sun. First you see how it looks from the direction of the Sun, and then from one side. Six months later, Earth has traveled around its orbit to the opposite side of the Sun. Now the south pole is tilted towards the Sun and it is southern summer. Looking from the direction of the Sun, you see how Antarctica is in sunlight the whole time as Earth spins.
