Father Christmas and his reindeer must travel at incredible speeds to deliver presents to all the good boys and girls in one night. A recent study calculates that Santa needs to travel at a whopping 8.2 million kilometers per hour, or 0.8% of the speed of light, to drop off all the presents.
The concept behind this calculation is based on the Doppler effect, which describes how speed affects the length of waves, such as sound or light. When light changes color due to speed, it can be measured using spectroscopy and telescopes.
The study assumes that Santa only delivers presents to those who truly believe, leaving approximately 690 million children to receive gifts. With about 2.3 children per household worldwide, he needs to visit roughly 300 million households.
By spreading these households evenly across 69 million square kilometers of habitable land area on Earth, Father Christmas has to travel nearly the same distance as the distance from Earth to the sun.
The study’s hypothesis is that Santa needs to travel at this speed to deliver all the presents in time. However, measuring his speed with Rudolph’s nose is not a straightforward task.
A standard speed camera wouldn’t work, but telescopes on Earth could be used to measure the color of Rudolph’s nose using spectroscopy. The Doppler effect would show that if Rudolph’s nose were red due to traveling at high speeds, it would appear more “redshifted.”
Recent studies have shown that the Doppler effect has a crucial role in astronomy. Astronomers use it to measure how things move in space and find exoplanets using a method called radial velocity.
While science can’t explain the magic of Father Christmas, this study is an entertaining way to think about the physics behind his journey. If astronomers ever catch Rudolph with their telescopes, they’ll be sure to let everyone know.
Source: https://phys.org/news/2024-12-santa-christmas-eve-rudolph-nose.html