The Leonids is a meteor shower associated with the comet Tempel-Tuttle. It gets its name from the location of its apparent radiant in the constellation Leo and has been famous for its most spectacular meteor storms since its identification in 1833. Since comet Tempel-Tuttle is a periodic comet with an orbital period of 33 years, people on Earth are expected to see such magnificent astronomical phenomenon only once every 33 years. The superlative strength of the Leonids, which is approximated to be over one hundred thousand meteors an hour, forced scientists to revise their previous ideas that meteors were only atmospheric phenomena. Although most Leonids are only 10mm across with a mass of half of a gram, they are able to generate bright meteors due to their fast moving streams when encountering the path of the Earth (up to 72km/s, which is 100 times faster than that of a bullet). And according to what we learn in the class, the high speed of the Leonids may pose a threat to artificial satellites and spacecrafts orbiting the Earth. And in the case of meteor storms that happens once every 33 years, long-distance telecommunication may also be severely disrupted.