Explain xkcd: It's 'cause you're dumb.
Title text: If you fire a Portal gun through the door of the wardrobe, space and time knot together, which leads to a frustrated Aslan trying to impart Christian morality to the Space sphere.
The Lion, the Witch, and the Wardrobe is a book in which four children accidentally wander into a world known as Narnia through a wardrobe that only allows passage through to Narnia when you aren't looking for it. In the comic, someone connects an anchor to the wardrobe and throws it into the ocean. The formula describes the flow of water through the open doors, which means that a steady stream of water at an approximate velocity of 200 meters per second will flow into Narnia.
The evil White Witch, who has made it "always winter, and never Christmas," could not have anticipated that the wardrobe portal would suddenly begin spewing approximately 400,000 liters of water per second into Narnia which would presumably freeze very quickly and make the whole world very slick.
Delta-P is a mathematical expression for the difference in pressure. Here the difference is between the depths of the ocean and the open air of a forest that creates the flow of water.
The title text references the video game "Portal" in which you fire a portal gun into walls and etc. to make "portals" that can open holes in other places so that you may portal through. In the game you cannot shoot a portal through a portal, but Randall is saying that if you try to create a portal with the portal gun through the wardrobe, space and time knot together. Aslan, the lion in the title, was written by Lewis to be an actual representation (scroll to the section "Is Narnia an allegory?") of Jesus Christ. The Space Core is a Personality Core from Portal 2 that doesn't care about anything but wanting to go to space.
This is a classic xkcd based on the intersection of literature, math and video games.
[A wardrobe, with a boat anchor attached to one corner, falling towards water]
Q = A * sqrt(2 * g * d)
Q = flow rate
A = area of opening
d = ocean depth (2 km)
g = Earth gravity
Flow: ~400,000 liters/s
Water jet velocity: ~200 m/s
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Caption: The White Witch didn't know what hit her.
First, it is worth noting that water jet velocity = (Q/A) = sqrt(2 * g * d).
As such, it is not dependent on the opening size of the wardrobe.
The figures given appear to assume the wardrobe is 2 square meters, which is probably fairly large.
Second, there is also the matter of momentum.
The water mass is ~400,000 kg/sec, at ~200 m/sec, for a net of 80,000,000 kg meter/sec.
If the receiving portal is subject to conservation momentum and is another wardrobe, it will be traveling at over 99% of the water jet speed.
(The reduction would actually be less than the adjustment for the correct gravitational force.)
So part of what the white queen would have to worry about is this wardrobe darting all over the place at ~700 km/hour or ~440 miles/hour.
Of course, the sending wardrobe will be zipping around the ocean as well, which might make "Glass Half Empty" relevant.
Divad27182 (talk) 15:39, 5 October 2012 (UTC)
Well, the suction of the vacuum might increase the momentum of the wardrobe AND the jet.--Jimmy C (talk) 15:01, 12 November 2012 (UTC)
I have a feeling that the inconstant passage of time, between the two realms, should factor into this somehow. At the start, Lucy is in Narnia for a whole evening, and returns moments later. By the end the whole group stay for many years and are hardly away for much longer (while the 'tour' is still passing). So the amount of water that leaves Earth's oceans in a short time can probably afford to trickle out into the Lantern Wastes at a much lower volume/time.
In reverse, would the passive thermal energy of Narnia (even during its snowbound period) over a long Narnian period now be exiting Earthside in a compressed form (if not in frequency, certainly in rate) making the open wardrobe door furnace, like?
Or, given the above, and that nobody seems to notice any strange dilation effects during transition, and the fact that Edmund enters shortly after Lucy yet is not several days later in arriving (though possibly up to an hour or two) there may be a "time lock" facility, which means that one or more transitional areas betwixt Earth and Narnia are sealed shut behind one traveller while they start travelling further into (or out of) the furs/firs hybrid areas. We already know that the 'normal' wardrobe back can present itself at times when transit isn't required, so who knows whether it's an active compartmentalising, or just passively not wormholing betwixt the relevent domains.
And for my next
essay, I shall be discussing how to automate the use of the rings made by the original Magician (the Professor's Uncle) in order to transfer spent nuclear waste to Charn, or some other, similar dead world. (And the security measures needed to ensure that Jadis does not obtain the necessary material to make radiologically-active weaponry in her conquests of other worlds brought into being by Aslan.) 220.127.116.11
16:24, 23 April 2013 (UTC)