We all loved Christmas gifts by Santa Clause in our childhoods and then we grew up and wondered, how is it possible that Santa delivers gifts to so many kids around the world! Is he even real? There you've it - the mystery of how Santa Clause arrives without being seen or heard is solved by Physics!
Dr. Katy Sheen, a physicist at Exeter University has given a physical (it's pretty cool!) explanation for why Santa is so rarely seen and can also fit down the chimneys. The physicist has calculated that Santa would need to travel at about 6.2 million miles per hour to deliver presents to every child expected to celebrate Christmas in 31 hours - taking into account world time zones. According to Einstein's special theory of relativity, traveling at such high speeds shrinks Santa and his bag of gifts. Such speed would make him change from red to green and, at greater speeds, and eventually disappear entirely. This is another physics phenomenon(which we've studied in 12th Physics) - Doppler Effect.The Doppler effect also explains why children cannot hear Santa arrive. As he and his sleigh approach, the sound of bells and his deep "ho, ho, ho" would get higher and higher in pitch and then become completely silent, as his voice moves move beyond human hearing range. So, he is neither seen nor heard when he delivers gifts to all the kids at night.
Only if Physics was taught to us this way! Physics is amazing, ain't it?
Merry Xmas and a happy new year to all!
Read more about Einstein's Theory of Relativity real life applications :- http://www.livescience.com/48922-theory-of-relativity-in-real-life.html