# Colony on the moon - how fast can Santa deliver?

I sometimes tell my kid that when he grows up, he might be living on the moon. Last night he was worried that Santa won't be able to bring him presents there. To which I replied that sure, Santa can go quite fast, covering the entire globe in a 24 hour period.

So, Santa wouldn't have a problem reaching across a distance of a mere 30 Earths. Would he..? It's just a matter or time, right?

I'm no stranger to the various estimations of Santa's speed (different estimates of time he has and actual distance traveled):

http://www.telegraph.co.uk/topics/christmas/8188997/The-science-of-Christmas-Santa-Claus-his-sleigh-and-presents.html

http://www.daclarke.org/Humour/santa.html

http://www.fnal.gov/pub/ferminews/santa/

Let's say Santa gets a fresh bunch of reindeer, with their reindeer spacesuits and his jolly red santapacesuit, sets his sled's warp/wormhole/time distortion generator to max output, and heads out. Can I get a fair estimate of how long will it take him to reach the moon and my kid (How long will the boy be staying awake despite his father's protests).

And oh, my son (or his son, or his grandson, or his clone's grandson's robotic heir) isn't the only eagerly awaiting kid on the block - the moon's gonna be heavily popualated in a couple of years decades centuries. So make it snappy!

• With all these numbers, I begin to think, Santa's reindeer are fake. Either he has stolen the Heart of Gold or he's a Timelord. Dec 22 '16 at 14:31
• Alexander von Wernherr - read the links! They're interesting and might bring you to add to your answer below :-) There are a bunch of theories out there and a gazillion stack questions about the physics. Dec 22 '16 at 14:35
• @AlexandervonWernherr I thought everyone knew that Santa only visits select kids, about twice as many are visited by elves on reindeer, and the rest are mailed presents. Dec 22 '16 at 17:25
• The actual answer isn't what you think: worldbuilding.stackexchange.com/questions/32007/… ;-0 Dec 22 '16 at 19:38
• @AlexandervonWernherr would you say that reindeers being that fast is HIGHLY IMPROBABLE? Maybe that is what's actually powering the Heart of Gold's drive ;) Dec 22 '16 at 19:48

# How fast does Santa go now?

The population of the Earth is about 7 billion, and the land area is 150,000,000 km$$^2$$. Lets assume that people live in groups of 3.5 per 'household' on average (no idea if that is a good assumption), then Santa has to make it to 2 billion households over 150,000,000 km$$^2$$; or 13 per km$$^2$$. If those 13 per km$$^2$$ are neatly distributed within that square kilometer, we can approximate that he has 0.5 km to travel between each household (depending on how good Santa's traveling salesman algorithm is....say maybe I should ask for that for Christmas?).

At half a kilometer between households on average and 2 billion households to cover, that means it take him a billion kilometers to hit everyone on Earth in one night. Defining the night is tricky too, but lets say he has 24 hours as the night swings its way around the Earth. That means he has to be going at about 11.6 11574(!!!) km/s to make it everywhere on time, assuming zero seconds for delivery.

That is going to be a sun-of-a-gun for re-entry, but then given that he is already doing 0.039c (!!!!!!!!!!) in the atmosphere, and even at sea level, he's probably got some pretty great materials technology (definitely asking for that for Christmas). According to xkcd, he should be causing fusion of the air in front of him as he passes through it. Gnarly!

# How long does it take to get to the moon?

At 384,400 km away, it takes only 33 seconds to get to the moon.

# Conclusions

Totally do-able! Now Mars is going to make things a little harder...

• Was 'sun-of-a-gun' intended? If so: applause Dec 22 '16 at 14:13
• @JoeBloggs Tis the season for good cheer and bad puns. Dec 22 '16 at 14:16
• A Hohmann Transfering Santa Clause. A great name for a space christmans novel Dec 22 '16 at 14:21
• A moon night is ~30 days, he can take his time there.
– csiz
Dec 22 '16 at 17:29
• Santa confirmed this in his 1998 interview with NASA: "The Moon won't be too much of a challenge," Santa told us. "I figure the lunar colonies will keep Earth time, so I'll just add them to my route. The reindeer will gripe about having to put on spacesuits, but we'll get used to it." Dec 22 '16 at 17:38

It isn't the distance to the moon, which would worry me, but more the absence of atmosphere on the trip there and the presence of the atmosphere on the trip back.

Santa would need a complete new set of sleigh, space suit and space proof reindeer.

Currently Santa is moving 650 miles per second according to this link. So, since the moon is 238900 miles away, it'll take him 367 seconds there and 367 back.

With the training of new deers he may be able to beat the 6 minutes time.

The biggest problem will be the re-entrance into earth atmosphere, where he'd probable turn into a huge ball of Christmas plasma, but at this point, I'd like to hand over to the real rocket scientists.

• Now I want a ball of Christmas Plasma. Dec 22 '16 at 14:07
• We call it Sylvester :o) Dec 22 '16 at 14:09
• Obviously, he has already solved the reentry problem, since his 650 mi/sec takes place at ground level, or near enough (chimney level). What really has the military salivating is the technique he has developed for suppressing sonic booms. Dec 22 '16 at 14:38
• @WhatRoughBeast That's why I think this whole Santa thing is just scam... Dec 22 '16 at 14:41
• @WhatRoughBeast No, wait. He's working for the military! What better cover could material tests have than the cover of a friendly old chap bringing presents! Santa doesn't come from north pole, but Area51! Dec 22 '16 at 14:42

I think Santa would have more difficulty with lunar delivery than other answers suggest. We can't model Santa as a mere physical projectile and expect the results to be meaningful; the Santa-reindeer-gifts system is known to obey a set of additional rules which constrains his behavior beyond the ballistic model. In particular, while Santa is capable of impossible velocities, this ability has only been shown to function at night- more precisely, on that one special night of the year.

We'll ignore possible effects from the inevitable encounter with sunlight as Santa travels between the Earth and the Moon; it is unclear if this would count as "day" in any event, and if Santa has some vampiric aversion to the Sun he could at least use a big parasol or something.

The more direct problem is that a "day" on the moon (a synodic day, as we use on Earth) is as long as 29.5 Earth days. So, assuming a roughly even distribution of human colonists around the Moon, and supposing that Moon Christmas starts with the whole of the night side of the Moon on December 25th and progresses from there, there will still be Moon Cookies left out waiting for Santa's arrival on January 8th.

That is of course a worst-case scanario; careful astrological calculations before you position your lunar homestead will ensure that Santa can reach your grandson roughly in time with the lucky Earth kids. And in either event, they'll be better off than Venusian colonists, for whom the old "Twelve Weeks of Christmas" will be roughly true.

• "...waiting for Santa's arrival on January 8th." Easily solved if you make sure all the colonists are Orthodox Christians on the Julian calendar. Dec 22 '16 at 18:14

Reindeer cannot cross the vacuum of space. Not to mention Santa himself. That's why the elves keep posting questions to this forum about building physical bridges between planets, and why having a retractable one is so key. They'll be able to extend the bridge on Christmas Eve and take it down after Santa's return, before our sensors detect anything. Don't you worry -- the elves are well aware of our tech progress. They'll handle this just like the year they had to start making Atari game consoles in what used to be the wood shop.
Is it possible to build a bridge between planets?

• And building the bridge at the North Pole would handle the issues of planetary rotation. Nice. Dec 22 '16 at 19:51
• Those pesky elves, man. Them and their questions, on a site meant for Wbuilding, sheesh :-) Dec 25 '16 at 9:05
• Yes, but how long would it take to extend/retract? ;) May 9 '17 at 15:45
• @Draco18s with sleigh technology built in? Not long at all.
– SRM
May 9 '17 at 15:51

# Tunneling

This question and of course the answers I have seen thus far have all assumed "classical" mechanics. Instead, if we consider the Quantum Mechanical Santa Claus, we get much more sensible results. http://www.amsat.org/amsat/archive/amsat-bb/200812/msg00543.html

In the case of a Quantum Mechanical Santa, he would be able to cross over to the moon via tunneling assuming

• There is a potential preventing him from being observed in the space been Earth and the moon.
• His Wave function decay is slow enough to reach the moon
• There are observers on the moon

Under such circumstances, Santa would instantaneously find himself on the moon.

There is a special Moon-Santa who stays on the moon and because of the lower gravity is able to jump anywhere he needs to go

• Welcome to the site. We generally expect a bit more in the way of content and supporting reasoning/logic (as silly as that may be for this kind of question) Please elaborate a bit. When you have a chance check out the help center and tour. Dec 22 '16 at 17:07
• That's actually a good answer to shut my boy up, but if I were to write up an essay (which I may well end up doing) I'd need a full reindeer_sled setup, low grav no atmo transportation system, and what about laughing "Ho Ho Ho" in space? Santa can't go without the ho ho Dec 25 '16 at 9:08

Santa is a mythic role, much greater than a single man. Santa doesn't need to break the laws of physics and move so fast; he merely occupies millions of physical bodies simultaneously to accomplish his task.

As such, Santa needs zero time to get to the moon as long as there already exists there a generous soul to manifest through.