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# Study shows how Santa’s sleigh takes to the skies

Posted by ap507 at Dec 18, 2015 10:30 AM |
University of Leicester students calculate the lift force required for take-off under the weight of the world’s presents

Issued by University of Leicester Press Office on 18 December 2015

Santa Claus’s reindeer will be in need of a good rest after their Christmas Eve capers based on a study by University of Leicester physicists, who have estimated the velocity required to provide enough lift force to get his sleigh to take flight given the large mass of presents in tow.

Santa is expected to visit every household by travelling speedily through the sky in his sleigh during Christmas Eve. In order to take off with sacks of presents on board his sleigh, fourth year Master’s students from the University of Leicester’s Department of Physics and Astronomy worked out the velocity needed to provide enough lift force, concluding that it would be around 0.76% of the speed of light.

To calculate this, the study assumed that everyone on Earth receives one present and that each present has a mass of 0.5kg to create an average.

The current population at the time of the study was recorded by the students as being 7,380,707,146, meaning that Santa would need to be carrying a large number of parcels to satisfy demand - a feat a little Christmas magic could aid in.

The students then calculated the small amount of time dilation and length contraction of Santa and his sleigh given he was travelling at this speed – although feasibly he could travel even faster.

The students estimate that, given Santa is travelling at 0.76% of the speed of light for 12 hours on one day of every year, over all the years of Santa delivering presents since his origin in 1821, he would have reduced his age by 242 seconds.

Because the velocity affects the length of the sleigh the students then reworked their initial estimate for the lift using a more sophisticated model and recalculated the relationship between the lift force and the velocity – concluding that the lift force goes to zero as the velocity approaches the speed of light.

The students presented their findings in a paper for the Journal of Physics Special Topics, a peer-reviewed student journal run by the University’s Department of Physics and Astronomy. The student-run journal is designed to give students practical experience of writing, editing, publishing and reviewing scientific papers.

Course tutor, Dr Mervyn Roy, a lecturer in the University of Leicester’s Department of Physics and Astronomy, said: “Every year we ask each student to write around 10 short papers for the Journal of Physics Special Topics. It lets the students show off their creative side and apply some of physics they know to the weird, the wonderful, or the everyday.”

The paper, ‘Santa’s Relativistic Journey’, is available here: https://physics.le.ac.uk/journals/index.php/pst/article/view/901

Read an article on why it is important to make physics and science education relevant and accessible to the public here: http://www2.le.ac.uk/offices/press/think-leicester/education/2015/zany-science-projects-help-students-learn-how-to-communicate-research-findings

ENDS