# Deck the halls with Christmas lights all the way to space

University of Leicester students have calculated how many Christmas lights are needed to decorate a house to be visible from space.

In the 2006 Christmas film Deck the Halls, Danny DeVito's character, Buddy Hall, sets himself a mission: to use Christmas lights to make his house visible from space. Now, students in the Department of Physics and Astronomy at the University of Leicester have calculated how many LED Christmas lights Buddy would have needed to achieve this feat.

Buddy is inspired to undertake his mission when he discovers his house is not visible on MyEarth, a fictional version of Google Earth that uses satellite images from space. The film follows him as his display grows bigger – including live animals and music – to try to make it visible using Christmas lights.

University of Leicester physics students Ryan Bradley-Evans, Razzia Gafur, Ryan Heath and Matthew Hough have calculated that Buddy’s house would have needed precisely 2,638 LED Christmas lights in order for it to appear on MyEarth and be seen from space.

Matthew Hough explained: “Given our results regarding whether light from a house’s Christmas lights could reach the ISS, we have proven that for such a distance, it would be possible to make your house bright enough to be seen from space.”

Ryan Heath said: “Physics often stretches the limits of what is physically possible for entertainment purposes. By applying known physics to these scenarios we often get unrealistic answers. These values calculated are a rough approximation as we considered an ideal case based around the assumption of zero light pollution.”

This calculation was based on the following:

• The point at which a house is visible in space is at the altitude of the International Space Station (ISS)
• The house must have an apparent magnitude of at least +6.5 (the minimum value detectable by the human eye)
• The luminosity of a single LED is 4 lm
• The luminosity required for a house to be visible from space is calculated to be approximately 10.6 X 103 lm
• This corresponds to 2,638 LEDs focused on a point

Razzia Gafur said: “As scientists, we’re always looking for new ways to engage people in STEM and this paper is a prime example of how we can make science relevant outside of the lab/office. It explores physical concepts in a more fun, captivating way by relating it to a popular Christmas movie and showcasing how knowledge of physics can help us understand and answer some of the most exciting and complicated questions – even in fictional situations.”

Ryan Bradley-Evans said: “Although we oversimplified the factors involved, it was great to see this beloved Christmas film hold up to the physics involved, as often this is not the case. And who knows, maybe somebody reading this will actually try it someday!”

The students presented their findings in a paper for the 2017 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 leader, Dr Mervyn Roy, a lecturer in the University’s Department of Physics and Astronomy, said: “The aim of the module is for the students to learn about peer review and scientific publishing. The students are encouraged to be imaginative with their topics, and find ways to apply basic physics to the weird, the wonderful and the everyday.”