CS4FN Advent – Day 24: Santa’s Sleigh – track its progress through the skies

Updated for Christmas 2022.

We are nearly coming to the end of our CS4FN Christmas Computing Advent Calendar with one more post to come tomorrow. If you’ve missed any you can catch up by scrolling to the end where there’s a complete list so far.

Today’s advent calendar window shows Father Christmas’ sleigh with a sack full of presents ready for delivery. Today’s theme is about the many different online ways that you can now ‘track’ his movements around the world. This follows on from yesterday’s bonus post about how you can actually see (cloud permitting) his sleigh ‘in person’ as it flies overhead at 7:12am on Christmas Day. In reality it’s International Space Station whizzing past – but other interpretations are available.

You can track Father Christmas as he dashes through the sky, delivering presents.


1. NORAD Santa tracker

https://www.noradsanta.org/en/ (you can also track him on NORAD’s apps too)

In 1955, so the story goes, an American department store published a newspaper advert with a phone number for children to call so that they could speak to Father Christmas. Unfortunately a misprint meant that the wrong number was given and instead people found they were talking to the US military’s Air Defense Command (now called North America Air Defense Command or NORAD).

Realising the mistake, but also spotting a great public relations opportunity, the team capitalised on this and began to make an annual event of it.

NORAD uses radar and geosynchronous* satellites to monitor Father Christmas. The satellites are able to detect infrared (heat) radiation and apparently Rudolph’s red nose gives quite a strong signal. This data is then shared with everyone via their website, though they don’t know in advance what route he’ll take.

If you’re visiting the website hover over the different bits of the picture as there are linked activities and extra information too.

*geo = Earth, synchronous = matching / following (like when you sync devices), the satellite follows the Earth’s orbit and is always above the same spot, so effectively (from the Earth’s point of view) the satellite appears not to move (it is moving but it follows the Earth’s rotation).


2. FlightRadar24 Santa tracker


FlightRadar24 is a great website for telling you the answer to “what was that aircraft that’s just flown by?” It tracks the flight of aircraft all over the globe in real time, using a signal transmitted by the aircraft’s beacon (called a transponder) which announces where it is. Father Christmas’ sleigh has its own transponder too which is transmitting its location to receivers around the world.

An aircraft, or Santa’s sleigh, gets information about where it is from a GPS satellite (very similar to using a maps app on a smartphone and it telling you where you are and whether you should go left or right) and it then transmits this location info, along with other data, through its transponder.

There are thousands of receivers here on Earth, many of them in people’s homes and gardens (you can even apply to host a receiver antenna, or build your own with a Raspberry Pi) and whenever Santa’s sleigh passes over one of these ‘ground stations’ its signal is picked up and collected by FlightRadar24. The receivers are in different places so they are receiving the same signal at slightly different times and this information can be used to work out (by triangulation) how fast the sleigh is moving and in what direction.

Apparently Santa has been “able to extend the reach of his transponder by using the reindeer antlers as additional antenna” so the tracking should be fairly accurate.

FlightRadar24’s Santa Tracker animated icon.


3. Google Santa tracker


Google’s Santa Tracker has lots of games to play while you wait for Santa and his sleigh to take flight, including Code Boogie where you can try and program some dancing elves. You move little blocks (a bit like Scratch) to copy the dance moves and, if you get it right, it will show you the underlying JavaScript code.

Dave Holmes, a developer who works at Google and who works on the Santa Tracker project says “Santa Tracker launched in 2004, and has been an important project at Google ever since. While there’s a small core team dedicated to Santa, up to 20 or so Googlers volunteer to help make it happen every year, and it’s become a true community effort. It’s also a way for our developers to try things and see what Google products can do … I like to say that everything I’ve learned at Google, I learned from Santa.”

Google has also added some ‘Easter eggs‘ to its search page – try typing in Christmas or where is Santa to https://www.google.com/. You can also colour in some images online at their Christmas-themed Art Coloring Book, from Google’s Arts and Culture.

Further reading

The Googlers who help track Santa each Christmas (22 December 2021) Google Blog


4. Early internet Santa-themed humour

Back in the early 1990s email was very new but right from the start people used it to send each other amusing things. One of them was a rather literal consideration of the physics of a sleigh that is laden with gifts and a traditionally overweight Santa, led by a team of reindeer moving at unlikely speeds (after all Father Christmas has to get around the entire world to deliver presents, in just one day). The author (unknown) began –

No known species of reindeer can fly. BUT there are 300,000 species of living organisms yet to be classified, and while most of these are insects and germs, this does not COMPLETELY rule out flying reindeer which only Santa has ever seen.”

But then goes on to point out that such a gift-delivery system would be working far beyond normal levels and would probably end in disaster, suggesting that –

In short, they will burst into flame almost instantaneously, exposing the reindeer behind them, and create deafening sonic booms in their wake. The entire reindeer team will be vaporized within 4.26 thousandths of a second. Santa, meanwhile, will be subjected to centrifugal forces 17,500.06 times greater than gravity. A 250-pound Santa (which seems ludicrously slim) would be pinned to the back of his sleigh by 4,315,015 pounds of force.”

Fortunately Father Christmas has his own magic, meaning that we don’t need to worry too much about him disobeying the laws of physics. But he and his reindeer really deserve those cookies, milk and carrots!

You can read the full post here: The Physics of Santa and His Reindeer Snopes.com


The creation of this post was funded by UKRI, through grant EP/K040251/2 held by Professor Ursula Martin, and forms part of a broader project on the development and impact of computing.



4. Previous Advent Calendar posts

CS4FN Advent – Day 1 – Woolly jumpers, knitting and coding (1 December 2021)


CS4FN Advent – Day 2 – Pairs: mittens, gloves, pair programming, magic tricks (2 December 2021)


CS4FN Advent – Day 3 – woolly hat: warming versus cooling (3 December 2021)


CS4FN Advent – Day 4 – Ice skate: detecting neutrinos at the South Pole, figure-skating motion capture, Frozen and a puzzle (4 December 2021)


CS4FN Advent – Day 5 – snowman: analog hydraulic computers (aka water computers), digital compression, and a puzzle (5 December 2021)


CS4FN Advent – Day 6 – patterned bauble: tracing patterns in computing – printed circuit boards, spotting links and a puzzle for tourists (6 December 2021)


CS4FN Advent – Day 7 – Computing for the birds: dawn chorus, birds as data carriers and a Google April Fool (plus a puzzle!) (7 December 2021)


CS4FN Advent – Day 8: gifts, and wrapping – Tim Berners-Lee, black boxes and another computing puzzle (8 December 2021)


CS4FN Advent – Day 9: gingerbread man – computing and ‘food’ (cookies, spam!), and a puzzle (9 December 2021)


CS4FN Advent – Day 10: Holly, Ivy and Alexa – chatbots and the useful skill of file management. Plus win at noughts and crosses – (10 December 2021)


CS4FN Advent – Day 11: the proof of the pudding… mathematical proof (11 December 2021)


CS4FN Advent – Day 12: Computer Memory – Molecules and Memristors – (12 December 2021)


CS4FN Advent – Day 13: snowflakes – six-sided symmetry, hexahexaflexagons and finite state machines in computing (13 December 2021)


CS4FN Advent – Day 14 – Why is your internet so slow + a festive kriss-kross puzzle (14 December 2021)


CS4FN Advent – Day 15 – a candle: optical fibre, optical illusions (15 December 2021)


CS4FN Advent – Day 16: candy cane or walking aid: designing for everyone, human computer interaction (16 December 2021)


CS4FN Advent – Day 17: reindeer and pocket switching (17 December 2021)


CS4FN Advent – Day 18: cracker or hacker? Cyber security(18 December 2021)


CS4FN Advent – Day 19: jingle bells or warning bells? Avoiding computer scams (19 December 2021)


CS4FN Advent – Day 20: where’s it @? Gift tags and internet addresses (20 December 2021)


CS4FN Advent – Day 21: wreaths and rope memory – weave your own space age computer (21 December 2021)



CS4FN Advent – Day 22: stars and celestial navigation (22 December 2021)



CS4FN Advent – Day 23: Father Christmas – checking his list, spotting the errors (23 December 2021)


CS4FN Advent – Day 23: Bonus material – see “Santa’s sleigh” flying overhead (23 December 2021) – this was an extra post so that people could get ready to see “Father Christmas” passing overhead on Christmas Day at 6:48am)


CS4FN Advent – Day 24: Santa’s Sleigh – track its progress through the skies (24 December 2021) – this post




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