Space might seem like an empty place, but the area surrounding Earth is constantly being bombarded by waves of charged particles released by the Sun: The solar wind. Luckily, thanks to Earth's swirling, molten core (and the magnetic field it provides), we are protected from this planet-sterilizing onslaught like an invisible force field.
All that science has a beautiful side effect: It makes the auroras! The Northern and Southern lights are the result of the solar wind and its dance with Earth's magnetic field and polar atmosphere. It's Earth's own cosmic light show!