Just over two years http://www.buscadichos.com/bin ge-drinking-essays yourselves essay my favourite subject english sergeant The radar systems set up around the world can track such motion. The meteors collide with atoms in the atmosphere and leave behind a path of electrons and charged particles. This electrically-charged region acts as a perfect mirror for radar waves, so the radar bounces back carrying both position information and Doppler shift information. This can be used to measure the speed and direction of background atmospheric winds at the altitudes where the meteoric tails are produced, between 40 and 60 miles high in the sky. Because there are so many such trails, they can be used to measure the velocity and direction of the winds continuously, helping to map out very complex wind patterns on a minute-by-minute basis.