Delta-P
by Jeff
Image 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.
This comic was posted late and now I'm late and I'm at work so I can't do as much explaining as I usually do, but I'll do my best. That's also why we have the best comment section on the Internet.
The basic idea of the formula and the comic are based on the books and movies of the Lion, the Witch and the Wardrobe in which a giant wardrobe contains a portal to a world known as Narnia. In the comic, someone connects an anchor to the wardrobe and throws it into the ocean which means that a steady stream of water at a velocity of 200 m/s will flow into Narnia.
The White Witch, the antagonist in the books and movies apparently won't know what hit her according to the caption.
The image 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.
The image text also references the fact that CS Lewis wrote the Lion, Witch and Wardrobe books as a thinly veiled allegory of Christ's crucifixion with Aslan, the Lion in the title, playing Christ's part. (Spoiler alert! Sorry!)
This is a classic xkcd based on the intersection of literature, math and video games.
October 26th, 2011
Traditionally, ’spoiler’ tags come before the spoiler.
October 26th, 2011
haha, thanks! I was writing stream of consciousness there and thought it was funny at the end.
Plus, if you get pissed about spoilers in an old young adult book…
October 26th, 2011
Especially when it’s as popular as the Lion, the Witch, and the Wardrobe.
October 26th, 2011
Can someone explain the title?
October 26th, 2011
I imagine delta P would stand for ‘change in pressure.’ As the Wardrobe sinks further into the ocean, the pressure increases on it due to the weight of the water pushing down.
October 26th, 2011
ΔP is the change in pressure (as
said). The formula for flow through an orifice is normally Q=A*sqrt(2*ΔP/ρ). In this case, ΔP/ρ simplifies to gd, to get Q=A*sqrt(2gd), as in the comic. ( ρ is the density of the incompressible fluid flowing.
The pressure on the ocean-side of the wardrobe is the mass of the column of water above it, divided by the area (or dAgρ/A => dgρ), while the pressure on the Narnia side of the wardrobe would be effectively 0. So the difference, δP = dgρ – 0 = dgρ. So ΔP/ρ = dg.
October 27th, 2011
All I saw was “orifice” and “sqrt”
…
Who says science can’t be fun?
October 27th, 2011
I think Randall failed to account for the different rate of time flows (i.e. a flow of 2 Lucies / 5 earth minutes = 2 Lucies / narnian day).
http://xkcd.com/821/ uses Narnian time to run seti@home and folding@home to greatly increase the rate of information flow out of Narnia. By the same logic, the rate of water flow into Narnia would be greatly reduced.
December 11th, 2011
The problem is the time ratio in the books at least was more or less random… At least from our side to Narnia.
October 26th, 2011
couldn’t he just as easily sent the wardrobe to space and had everyone die in the vacuum of space? You get the added hillarity of their heads potentially exploding
October 26th, 2011
What would you have to do to drop a wardrobe to the bottom of the ocean? Rent a boat, wrap a few weights around it, and kick it overboard.
Now what would you have to do to launch that wardrobe into space? Multi-million dollar space program and the combined efforts of a whole team of scientists.
These are not, “Just as easy” as one another.
October 26th, 2011
Adam: You’re confusing the real world with the wonderful world of xkcd (which only intersect when it suits Randall’s purpose). In xkcd, it would indeed have been “just as easy” to launch the wardrobe into space.
But Randall’s instinct for comedic absurdity is unmatched, and I’d have to vote for the unexpected 200m/s stream of seawater firing into Narnia over the blood-boiling antics of un-suited beings exposed to hard vacuum.
October 27th, 2011
I’d like to jump in and point out my first though upon seeing the comic. Under water the pressure would force the doors of the wardrobe closed, thus restricting the flow of water (at least). I am assuming that the wardrobe, which I (again) assume to be a magical construct, would not be crushed by the resulting oceanic pressures.
However, in space, the pressure from the Narnia side would fling and hold open the doors thus constituting greater negative flow than the resulting positive flow (from the Narnia perspective) from the ocean and better suit the purpose implied in the comic.
October 27th, 2011
The moment the wardrobe is filled with water (I refuse to believe it’s tight) the pressure “inside” the wardrobe will match the pressure from outside, which means the doors will be just as free as a dangling chain. It’s the same reason the top board of a table doesn’t buckle under the pressure from all the air resting on top of it. The doors themselves may get slightly thinner though.
October 27th, 2011
If the pressure “inside” were the same, there would be no stream of water launching into narnia. The whole point is that the pressure would create a stream which most certainly would pull the doors closed
October 27th, 2011
Well that is certainly a solid point, I had already forgotten about the whole bottom line of the comic.
November 1st, 2011
The actual portal to Narnia itself is in the back of the wardrobe, so I would assume that the pressure near the front of the wardrobe where the doors are would be closer to the pressure of the ocean, and it wouldn’t change much until closer to the “back” of the wardrobe.
November 10th, 2011
>But Randall’s instinct for comedic absurdity is unmatched,
you have to be fucking joking
October 26th, 2011
It would be hilarious if your head exploded, I think.
October 26th, 2011
I noticed that someone below didn’t like your comment and was modded down. It actually wasn’t until I read your comment that it occurred to me that this whole comic today might actually be rather offensive to some people. Before that, I thought it was just a physics joke, one of Randall’s common mash X, Y, and Z together and see if it’s funny.
A number of other people have made some interesting comments, like the one who pointed out that C.S. Lewis didn’t see Aslan as an allegory but rather, what Christianity would be like on another world.
To many people, the Narnia series is just an entertaining work of fiction. To others, it’s a lot more. Now, I’ve met some really annoying ‘Christians’ who wanted to tell me that Narnia was the work of the devil and that it was blasphemous. Those are the same people who don’t realize that Halloween was a Christian holliday. The Christians who really like Narnia are more often the intelligent ones who are able to think more flexibly about their religion. So let’s consider only the reasonable people. Some of them may be bothered by the idea of positioning that wardrobe such that a whole world full of people might be killed.
Oh, but it’s just a work of fiction! Yes, but if we’re considering the consequences here, let’s think it all the way through. I don’t think he intended it, but Randall is taking a pot-shot at C.S. Lewis and Christianity, first by postulating the idea of flooding Narnia.
Oh, but it’s just a work of fiction! Imagine the reaction of millions of fangirls of Twilight should you suggest that it would be funny to see what’s-her-face and those vampires and that werewolf were get get drowned or suffer explosive decompression. Actually, in this case, that might be funny. But the fans would still be offended!
Twilight is a bunch of crap, but to many people, many of the ideas in the Narnia series are a reflection of their faith. Personally, mainstream Christianity and may individual Christians drive me crazy. I hate the hell-scare-tactic thing, and how so many want to shove their “morality” down your throat. But the real Jesus (Yeshua), even the distorted one in the Bible, was a serious rabble rouser and a brilliant strategist. There’s plenty from Paul that I’d rather leave behind, but there’s no shame in believing in the anti-establishment, peaceful-but-fight-the-pharisees-and-romans person that Jesus was. C.S. Lewis had a knack for taking the GOOD parts of Christianity and packaging them up as enjoyable books that one might even learn something from if you don’t try too hard not too.
So, here are a few questions to consider:
What if you were to take a portal gun and point it on the ground in South Park, and then take it to an asteroid in deep space. I’m sure Matt and Trey could create all kinds of hilarity. Just imagine Cartman’s head popping, or just everyone slowly suffocating as the atmosphere is slowly sucked away.
Ok, now imagine that happening in the REAL (South) Park, Colorado. Perhaps we would reach some equilibrium, where earth’s gravity will balance out against the negative pressure of the vacuum on the other end of that portal. But by then, the Earth would be devastated. Would that be funny?
Now connect this back to Narnia and consider that although we all know that Narnia is fiction, some of us have a soft-spot in our hearts for it, and we’re not too keen on imagining the deaths of all the people there. (Or the role of Aslan being trivialized.)
No one’s saying that you can’t make the joke. But it’s still kindof offensive.
October 27th, 2011
This is a “comment” and not an “essay” section.
October 27th, 2011
But the essay wasn’t exactly off-topic, and not exactly bad either. I liked being able to read it.
October 27th, 2011
You can thank a teacher (or your parents) for that (Being able to read it).
October 27th, 2011
I’ve always had a thing for TL;DR’s more people should use them.
October 27th, 2011
OH MY GOD! You killed Kenny!
October 27th, 2011
Narnia is a whole huge world, with its own mountains and cliffs… I seriously doubt even a whole ocean of flooding would kill everyone there. The sea level there would rise extremely slowly, particularly considering the time dilation effect.
So the Narnians would be fine, I think.
Of course, WE would probably die without the massive CO2 and temperature sink of our oceans. Whee!
November 10th, 2011
you’re seriously OFFENDED someone made a joke about the characters from narnia being smushed by water
what a fucking faggot-ass fag. get over yourself you fat neckbeard
October 26th, 2011
Delta-P probably refers to the change in water pressure. Just a guess though.
@JT I like the space idea!
The wardrobe inhabitants get to die either by being flooded (solves our rising oceans problem yes?) or having all their air sucked out of their lovely world.
October 27th, 2011
http://www.youtube.com/watch?v=AEtbFm_CjE0
October 26th, 2011
Of course, time travels much faster in Narnia. So, even if it only takes a few hours to send a dangerously large amount of water into the wardrobe, in Narnia they’ll be watching the corresponding slow flooding that takes decades or centuries. The White Witch will have time to prepare.
Plus, can’t the witch make it really, really cold in Narnia? If I remember from the book (spoiler alert), one of the reasons Narnia was in a perpetual cold winter when the four children arrived was because of the power of the White Witch. When her power began fading, the snow melted and it was spring again.
I know there will be a lot of water pressure shooting into the ocean from Earth, but because the water is coming in slowly into Narnia (because of the time warp), I think the White Witch will be able to freeze it as it comes in, jamming up the portal with ice and stopping water from flowing into the wardrobe on our side.
I’m almost concerned that the White Witch would freeze our oceans.
October 26th, 2011
End to Global Warming perhaps? (assuming that it’s actually happening)
October 26th, 2011
Everyone knows that Global Warming is a myth…but this could explain why the Earths ocean levels are dropping…all that water flowing into Narnia
October 26th, 2011
I don’t know that everyone knows that
October 27th, 2011
Ohh yeah… everyone knows that the oceans are dropping… but only some of them, in particular the Atlantic ocean have been partly drained and the water was moved over in the Pacific Ocean. I was told that this water migration was partly caused by better water real estate prices due to better schools, but that the scientist who discovered this needs more money to futher reaserch and confirm.
November 6th, 2011
I suspect that everyone DOES know this. Most of the public now disbelieve the ‘CO2-driven Global Warming’ hypothesis. But there is now too much invested in the scare for those involved to back down…..
October 27th, 2011
Phil — you’re speaking ironically, right? I find it hard to believe that the xkcd readership has a high percentage of people who would agree with your first statement.
Just to do a quick survey, I suggest those who agree with Phil’s statement vote my comment DOWN, and those who disagree vote it UP.
October 26th, 2011
What happens “in-between” with high velocity water flowing`in and low velocity water coming out? Will the actual flooding happen in another dimension (poor Dorothy) or does it come out as one massive stream of black holes?
October 26th, 2011
There is no fundamental change in the velocity of the water in this case, only in the frame of reference of the observer. Conversely to this statement, if the Witch was able to slowly freeze an amount of water at time on “our side” of the wardrobe without herself crossing the boundary then whatever happened would happen so quickly from our point of view to appear almost instantaneously.
October 26th, 2011
I slapped my forehead so hard after reading that. Thanks, I needed it.
October 26th, 2011
This troubles me. Since time flows differently there versus here, the rate of flow in Narnia should be much slower — but this equation has no factor that can be adjusted to account for the time differential. This implies that new seawater would be created from nothingness on the Narnia side at an alarming rate so that the observed flow can be the same on both sides of the portal.
Oh, my aching head!
October 27th, 2011
The acceleration (i.e. g) depends on the time frame.
October 27th, 2011
Aside from the time issues, it should be noted that sea water is quite a bit harder to freeze than fresh water. Or, more precisely, it freezes at a lower temperature. I would assume a proper witch can figure it out…
October 26th, 2011
But it says the portal gun lock space and time together. Doesn’t that make time flow the same on both sides?
October 26th, 2011
In the Narnia books, sometimes the children went back and it had been no time at all, and sometimes it had been 500 years. Time doesn’t necessarily flow slower in Narnia… Sometimes it goes much faster. In which case, the water would be instantaneously there. If it was slower, then I’d have to agree with you, but there’s an equal probability that one minute, there’s no water in Narnia, and suddenly the whole place is flooded in a matter of minutes or even seconds.
October 27th, 2011
There must be a way of exploiting this chronological instability.
Also, maybe the “portal” to Narnia opens and closes when the time flows are different? After all, stepping through it for even a brief instant, while time flows are in flux, would likely kill you (blood be pumped for a year in one part of the body before flowing to other parts of the body for a relatively small amount of time – even if it’s a small difference, accumulation for a day or even 20 minutes or less could still make a massive difference), and I’m assuming the wardrobe isn’t mortally, horrifically dangerous.
October 27th, 2011
Yeah, let’s just say that time gets synced up for as long as there’s a portal open. Makes everything much simpler.
October 27th, 2011
I don’t remember the books well enough to say this for certain, but maybe only one side of the portal can be active at any given time (the doors or the back of the wardrobe). If true, I’d assume that the process of closing one portal and opening the next instantly syncs you up with the opening portal.
Of course, that kind of ruins the comic, since you couldn’t have a constant flow of matter through both portals.
October 28th, 2011
No, the first time that Lucy, the youngest, went through on her own, she purposefully left the wardrobe door ajar; the book says even she knows it is foolish to lock oneself in a wardrobe. The second time, when the second youngest followed her, he foolishly closed the door completely, but I’m pretty sure the third time (when everyone went in and the story progressed), they made sure to keep it slightly open again.
October 27th, 2011
>> “Time doesn’t necessarily flow slower in Narnia… Sometimes it goes much faster.
The rate of the time difference may vary (hard to tell):
- Lucy spends an afternoon with Mr Tumnus, and only a few seconds pass here. (2-4 hours = 10 seconds)
- The children spend years growing up in Narnia, and return here minutes after they left. (15? years = 2-3 minutes)
- Caspian has become an old man while only a few months pass between Eustace’s visits to Narnia. (60? years = 4-6? months)
but it always flows faster in Narnia.
October 27th, 2011
So that means Narnia moves close to the speed of light and acelerates and desacelerates?
So if water flows 10 seconds here then It flows 4 hours in narnia. So aceleration is reduced, so water flow slower.
So time is faster but water flow slower????????????????????????????????????????????????????????
October 28th, 2011
Time in Narnia flows at the speed of plot.
October 28th, 2011
Exactly right! Well said!!
October 28th, 2011
The actual point would be that time flows faster in narnia relative to Earth. Years in narnia is equal to hours or so on earth. This would mean that narnia would have to be moving slower and have considerably less gravity than Earth. Though, even at no speed and no mass, or a complete lack of gravitational force, I doubt that the time dialation effect would that many times less than that of the Earth.
October 28th, 2011
Or… Narnia has magic.
October 28th, 2011
Of course this assumes that the wardrobe is dropped in the ocean while the children are in Narnia. What about the time difference when nobody has “crossed over”? Have not read the books, would imagine time stands still when no-one is there to observe it..?
October 31st, 2011
Hardly. All sorts of things happen in Narnia when the children aren’t there.
October 26th, 2011
Plus we have the benefit of the water level being a few inches (or possibly feet) lower to help combat the rising sea level due to global warming.
October 26th, 2011
This is funny. Nice.
October 26th, 2011
Um, he specifies that the wardrobe is under 2 kilometers of water. Does that mean that the seas would drop by 2 km? Or would they only drop 1 km, assuming that the portal on the other side is at sea level? Either way, that’s a lot of water to lose, and it might result in the extinction of all life on this planet. You need to be careful with these inter-dimensional portals!
October 30th, 2011
Earths sea level will fall by about 1 pm/s or about 0.033 mm/year.
It’ll take millennia to get to inches.
October 26th, 2011
I think ‘difference in pressure’ (between the two sides of the orifice) is a better reading.
October 26th, 2011
Just to quibble, Narnia is neither “thinly-veiled” nor an “allegory.” It is rather explicitly a question of what the Gospels might look like in a many-worlds situation.
October 26th, 2011
Source of this claim?
October 26th, 2011
http://www.rapidnet.com/~jbeard/bdm/exposes/lewis/cs-lewis.htm
C.S. Lewis used a very strict definition of the word “allegory” — after all, one of his most important academic books was a study of this subject. He wrote to some Maryland fifth graders in 1954:
“I did not say to myself ‘Let us represent Jesus as He really is in our world by a Lion in Narnia’; I said, ‘Let us suppose that there were a land like Narnia and that the Son of God, as he became a Man in our world, became a Lion there, and then imagine what would happen.’”
October 27th, 2011
You mean allegory as a form of rethoric?
October 26th, 2011
http://thinklings.org/?post_id=6275
October 26th, 2011
Also – don’t forget about the End Of the World – seems that there is some sort of dimensional shift that happens at the edge of the sea, so in theory there could be infinite space for the water to fill. Narnians would just see a new river form (coming from the Western Woods) flowing into the sea. The river would eventually run dry (the time would depend on the above-mentioned difference in time flow in Narnia and our world).
October 26th, 2011
Anyone think that there may also be tie-in/reference to the Wicked Witch of the West from ‘The Wizard of Oz’ given that (spoiler alert
) she melts when water is thrown on her?
October 26th, 2011
Anything could be a tie-in or a reference, but I think that in this case p>.05 and it’s likely to either be subconscious or nonexistent (coincidental).
October 27th, 2011
I think Randall actually got his books mixed up. The Wicked Witch of West is vulnerable to water, but the White Witch isn’t.
October 27th, 2011
Maybe not *as* vulnerable, but we’re not talking about a bucket here – an ocean is devistating with or without a ‘vulnerability’
October 26th, 2011
Don’t the doors of the wardrobe open outward – against the ~200 atm of water pressure?
October 27th, 2011
I doubt the wardrobe is water tight. Even if dropped in with doors closed, eventually the doors would either be smashed in by the pressure, or water would force its way inside through any gaps/cracks and once the pressure is equalized, nothing really to stop the doors from being in any particular position.
October 27th, 2011
The pressure would never equalize, since the back of the wardrobe is open to (much lower-pressured) Narnia. But at this level of pressure, the doors would be smashed as soon as they closed — unless, of course, they were somehow magically reinforced.
October 27th, 2011
I doubt the back is open to Narnia.
.
see http://www.explainxkcd.com/2011/10/26/delta-p/comment-page-1/#comment-15651
October 26th, 2011
I think this is a terrible idea. Even if you say that the wardrobe will combat the problem of rising sea levels, I am very disturbed at the prospect of never being able to find and recover the wardrobe from the ocean floor. Once put in motion, this hole might never be plugged. So if in the future the sea levels stop rising, there could still be this bottomless flush mechanism slowly robbing the ocean of its water. Shorelines expand. Coral reefs are exposed to the air and sun. Land bridges open up allowing the mass migration of pest species from one continent to the other. River deltas silt up. Meanwhile, humans are scratching their heads. “Find and neutralise a magical wardrobe to a hidden land that some idiot dumped under the sea” could be the last plan they might think of.
Or am I being a little too melodramatic?
October 26th, 2011
It’s a legitimate concern. I’m right there with you.
October 26th, 2011
Legitimate, of course, in the sense of fictional…
October 27th, 2011
Humans have quite the mean to stop high pressure leaks down in the ocean
October 31st, 2011
Maybe that’s where all the unaccounted for oil from the spill went…
October 27th, 2011
We’ll have to deploy amber.
April 9th, 2012
That was funny, made me laugh unexpectedly because it took me a second to realize what you’d said. I wonder how far between chaos and order narnia would fall- 2/3 of the way towards chaos? less, probably.~1/2 if 1/4 is earth…
October 26th, 2011
damn! its difficult to kill this (b|w)itch, what if whe rapidly send the wardrobe to the sun, that way she can’t melt.. oh wait, the mass slow the time to give her much more time, what if we just wait a few hours for her to die or at least grow old
October 28th, 2011
She is immortal…you could wait forever and she wouldn’t grow old!
October 26th, 2011
I believe Space sphere in the image text, refers to the same Space sphere in the end of Portal 2
October 27th, 2011
http://theportalwiki.com/wiki/Space_Sphere
October 27th, 2011
If you’ve never seen Delicatessen, it’s worth watching. There’s a deluge scene in it that is a delight. I can’t find it on YouTube, but the trailer is up there.
October 27th, 2011
But wouldn’t that flow rate just cause the doors on the wardrobe to close, closing the portal almost instantly?
November 2nd, 2011
Nope. If you look at all of times the kids cross over, the second time when Lucy takes the second youngest with her through to Narnia, it mentions very explicitly that he closes the door all the way. So the portal is open regardless of the position of the doors.
One more point, I think that all Wardrobe doors open out. I don’t see how it would be a very useful wardrobe if they opened in…
October 27th, 2011
I suspect that the pore ole wardrobe doars would not be able to handle said atmospheres.
October 27th, 2011
Now we just need the you know explanation of the mouse-over text. How would the portal gun knot space and time together (or is he firing it into the wardrobe, space and a time knot?), and what is the space sphere??
October 27th, 2011
Indeed. Just what the heck is the Space sphere?
October 27th, 2011
This is an internet term referring to Corrupt Core #1 at the end of Portal2. I’m not going to explain why this core is important to the storyline, as that would be a spoiler. However, the Space Sphere is basically a round robot (for those of you who have played Portal1, it looks a lot like the curiosity core) that is absolutely obsessed with outer space. It is responsibly for lines such as “What’s your favorite part about space? Mine is space.”
I think even Aslan would have a hard time explaining Christian morals to that little dude.
October 27th, 2011
check Pete’s link above. A character from the ending of Portal 2, where (spoiler alert) the final boss is defeated by sending a portal to the moon and depressurising the room. Relevant to the mention of a portal gun, and a similar pressure change situation
October 27th, 2011
Warning: This might end up being an essay-type comment. I think I’ll post what I want to say, and then have another tiny comment filled with the usual senseless crap.
Time dilation problems are something that have always been plaguing my mind ever since the most recent time I watched the Stargate SG-1 episode “A Matter of Time.” There were some things in there that bothered me.
To simplify time dilation problems, we can think of it, not as a continuous system that slows down as you go to a certain destination, but as a series of distinct “event horizons” in which time slows down. We can simplify this further by thinking of only one big event horizon. Then it basically become a time change question rather than a time dilation question. (Which, I suppose, is what we had here originally. If we wanted to talk about water around the wardrobe, that would be different.)
For the sake of discussion, let’s pretend that Narnian time runs exactly four times as quickly as our while a portal to Narnia is open.
As I understand it, if we had an observer in the water flowing through the event horizon (wardrobe door), that observer would report no difference. (Other than a “Hey, those aren’t coats!” of course.) Because of this, I think it would be safe to say that the water must continue to flow at 40,000 liters per second (let’s call that lps in case I need to use it again), with only the value of a second changing. If someone was able to observe the situation without being affected by the event horizon, I believe that he/she (the “casual observer”) would see the water increase in speed. Because of this increase, the water pouring into Narnia should be about 40,000 lps.
To the earth observer, the water would appear to be moving at normal speed, because he/she would be observing a slowed version of fast light that bounced off of fast water.
So, basically, although Narnian time is quicker than our time, the nature of the event horizon would cause Narnia to flood just as quickly anyway. I think that’s everything, really. Please tell me if I missed something or didn’t explain it properly.
October 27th, 2011
I don’t think the writers of SG1 cared about the physical implications of their writing…
You are right that Narnia would flood as quickly, but only when observed from our side. Think of it this way, the water is flowing at a constant rate, and therefore will take a certain amount of time to flood it’s destination – doing the maths relative to our time. This time t to flood (again, from our side) is then affected by the dilation, and is a larger value when observed inside Narnia – therefore the water *seems* to be coming in slower on the inside.
Does that make sense? The amount of ‘our side’/'narnia side’ in there is making my head hurt
October 27th, 2011
I’d say you’re correct about SG-1.
As to the observation of water flowing in from the Narnia side, I believe they would observe a quickened version of slow light that bounced off of slow water. The “slow” balances out the “fast” in the case of both Earth and Narnia, so the water seems to be flowing in at normal speed from both sides as observed from either side.
What you’re saying makes sense; I just always thought that it was incorrect. My reasoning for this thought is what I like to call the “elevator scenario.”
The elevator scenario, in short, is that you have an elevator that experiences time dilation as it goes up/down. Time is slowest at the bottom, and fastest at the top (because the elevator is on a really, really big planet or something). The cable that pulls the elevator must continually move at a “constant” speed, pulling the elevator with it. I make the assumption that, from inside the elevator, the elevator always seems to move at exactly 8 meters per second (I figure that’s really fast for an elevator, but what the hey), with the value of a second being all that changes. Under this assumption, the cable must “speed up” and “slow down” relative to a casual observer to preserve its own physical integrity.
This “elevator scenario” occurs with every elevator in existence, but only on a very small scale, as time dilation across, say, 40 meters on Earth is rather minimal. However, I suspect that it is changes in speed, and not this minimal change in time, that prevents the elevator cables from snapping upon use.
One could then ask if energy was being created or destroyed as matter or energy passed through the event horizon. However, if my understanding is correct, energy is being preserved by causing matter to speed up/slow down relative to the new time frame. The energy of speed is as dependent upon the material as it is upon how efficiently the energy of time is being used in that material’s environment.
Of course, my understanding is entirely based on one major assumption (that the value of a second changes, and that the speed of an object related to itself is constant), which may or may not be consistent with the original Theory, both of which may or may not be consistent with actual fact.
October 28th, 2011
People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint – it’s more like a big ball of wibbly wobbly timey wimey stuff.
October 27th, 2011
Key point I haven’t noticed mentioned yet: You can’t get to Narnia thru the wardrobe if you’re looking for it. You have to wander into it by accident, unconsciously.
.
Granted, water lacks consciousness so I suppose the case could be made that it would flow thru the wardrobe into Narnia without any problem. But I expect that wouldn’t really work as the person causing the water to flow into the wardrobe is consciously trying to get something into Narnia via that route, and I expect it’s the awareness of the person that matters.
(If the intent of the object is all that matters, you get the scenario where you can’t see/feel anything other than a solid back to the wardrobe because you’re trying to find Narnia, but the ball you throw at the back of the wardrobe goes thru without any problem. Vanishing from your point of view.)
.
Bottom line: Flooding Narnia via ocean-dumped wardrobe won’t work because the passage isn’t a constantly opened portal.
October 27th, 2011
See, the problem is that the portal doesn’t really exist. Aslan controls when you go, where you go, and how you go. While he might do so by manipulating basic rules of physics and magic, he created those rules, so it all works out. If Aslan wanted the wardrobe flooding trick to work, it would. The portal isn’t there when you’re looking for it because Aslan doesn’t just do what you want him to.
But, still, yeah, it was a point that needed to be brought up.
November 2nd, 2011
But if the wardrobe became portal-less, the back panel or the top would be blown off, presumably breaking the portal as well. So would the portal open as a defense mechanism to itself?
That’s a whole other question fraught with various points of conflict…
October 27th, 2011
Could there be a tie in to this comic and the end of the world in the final Narnia book? (spoiler) The sea rose up to cover the land. With the time flow disconect it is possible that the jet of water blasted through at that moment.
October 27th, 2011
I think the explanation for the Portal references in this comic weren’t properly explained. I thought that it would be okay, until I saw how many people were asking what in the heck a space sphere is. Apparently, not everyone has played Portal and Portal2 the whole way through. So, on to explaining xkcd.
The portal gun is a fictional device capable of firing a portal pellet (PoPe) that will generate one event horizon (”portal”) for a stable wormhole when it strikes a large, solid, flat object (esp. walls, but includes floors and ceilings) that is not made of some material that the makers of the game arbitrarily decided wasn’t “portal-able.” There are two colors of PoPe: orange and blue. The orange PoPe will create an orange portal, and the blue PoPe will create a blue portal. If you collide with the blue portal for any reason, you will exit the orange portal with the “same” velocity at which you entered the blue portal. The portal system is 2-way, so you can exit the blue portal by entering the orange, as well.
A PoPe is not capable of passing through a PoPe-generated portal (PoPePo). The energy signatures cancel out, and nothing happens. However, if a PoPe was fired at a different type of portal, the PoPe would pass through without harm and continue beyond. However, if one PoPePo is in one dimension, and its corresponding PoPePo is in another dimension (in this case, Narnia and Earth), then the two wormholes would tangle and form a sort of knot. (Maybe this knot would jam the wardrobe open?)
The Space Sphere, more accurately called Corrupt Core #1, is a spherical robot (spoiler)that is built in the same way that GLaDOS’s various cores are made(spoiler). This core, however, has become extremely corrupt and is unable to express anything other than an extreme passion for outer space. Because of this, it would likely be very difficult for Aslan to teach it Christian morals in a manner that could be verified.
… Wow. My comments today are all really long.
October 27th, 2011
>… Wow. My comments today are all really long.
I bet that’s what you tell all the girls.
April 9th, 2012
I thought it meant the spaceland sphere from the flatland short book.
October 27th, 2011
Practically, would this mean that our ocean levels would drop considerably? Would this be a solution to rising sea levels on this world? What is the impact on fish and other things that live in the ocean? Would our oceans run dry until we we drained? The wardrobe is a 2-way portal, so would we achieve hydrostatic equilibrium with Narnian water?
October 27th, 2011
Comic says this is dropped to 2 km. I think you’re right that it would be two-way, otherwise there wouldn’t be a pressure differential to start the siphon effect at all. So if we assume the Narnia side is at or near sea level (we don’t really know) the siphon would take away about 1 km of our ocean, but not all of it.
Still, that’s a lot of ocean to lose. Like I said above, the effect of losing our CO2 and heat sink would be Bad. Ecologically, the fish should initially survive, even the shallow-water ones, but habitat destruction (no more coral reefs, etc.) will make feeding and breeding problematic.
October 28th, 2011
I stopped reading the comments at about the middle, but here’s my two cents:
Imagine a clock here and a clock in Narnia. Every second that goes by here, a minute goes by there. The two time frames are labeled on both clocks. So, when X liters go trough the portal here in one second, the same X liters get out there in one minute. That’s how I see it.
Also, I don’t think the bottomless pit would drain all our oceans, sooner or later both our hydrosphere and Narnia’s hydrosphere would eventually get ‘even’ and stop flowing, I guess. If it doesn’t, searching for a magical wardrobe lost in the bottom of the sea wouldn’t be too hard: everything dropped on the ocean would drain to there, a bunch of boulders could eventually clog the hole.
Talking about that, the rapid speed of water running by the sea floor towards the wardrobe would cause some nice erosion to that floor, it could form a hole and make the wardrobe fall deeper and deeper, beyond the crust into the magma and eventually the core? Now I’m going too far.
October 28th, 2011
Should also have intersected with SATLTSADW, but would have become too complex.
October 28th, 2011
What a shame they didn’t think of this for the Deepwater Horizon oil spill. Just trim the tube and pop the wardrobe on and bingo — billions of gallons of toxic guck flowing into the White Witch’s realm instead of the gulf. Simple!
November 6th, 2011
Umm….
This idea has already been explored in SF – I recall a story in which an inventor was forced by the Nazis to develop a space portal for troop transfer, and instead committed suicide and destroyed the project by opening the first demo portal deep into the ocean…can’t recall the story title, however…
It should be noted that the wardrobe portal was NOT always open, but only seemed to open when required. In any case, Aslan was capable of creating new portals as required, and could presumably control the operation of the wardrobe.
So I suspect that all that would happen if you dropped the Narnian wardrobe into the ocean is that you would get a wet wardrobe.
PS – what do we know about air pressure in Narnia? Is it reasonable to suppose that it is 1 bar? And note that Narnia is not a spherical world (see Prince Caspian), which means that G might be a little odd as well….
November 8th, 2011
Actually, only the first book is an allegory to the crucifixion (he is crucified, then rises again all in that book), the rest are simply him being an allegory for Jesus (well, more or less, sometimes hes just a wise lion)
November 8th, 2011
Also should be noted
Dropping the wardrobe into the sea is a terrible way to kill the white witch. It wasn’t like it was her world, she was just ruling it. If anything she was a dictator. Dropping the wardrobe into the ocean to kill the white witch is equivalent to nuking russia because you hate putin. Not to mention that I’m pretty sure she lived a long way away from the wardrobes location, so you would probaly just end up drowning mr.tumnas and some furry woodland creatures while she ran to the edge of the world or something.
Sorry, guess that was kind of pedantic, o wait, this is xkcd, so I guess it’s all fine.
November 11th, 2011
I first assumed that the “Space Sphere” was a reference of The Sphere from Spaceland, from “Flatland” by Edwin A. Abbot
April 9th, 2012
me too -lalalan blah length
December 29th, 2011
If this could work, then we could take a teleporter that opens onto the reservoir above a hydroelectric dam, and drop it into the river below the same dam, and get a constant waterflow that generates electricity – a perpetual motion machine of the first kind (violating conservation of energy), which is impossible. Therefore it can’t work.
Since characters traveled freely back and forth through the wardrobe without having to “push” either way, then both sides had to be at the same gravitational potential (i.e. altitude). If the wardrobe were lowered into the ocean on this side, our seawater would have to climb to get into Narnia’s upland Lantern Waste – which it wouldn’t. A mountain lake here would work better, but its volume is more limited, and you’d probably just get a new river in Narnia, anyway. See also Larry Niven’s essay in “All the Myriad Ways”, 1971, and story “Flash Crowd”, 1973 and others, on the subject.
And, also anyway, all this is academic: the White Witch is already dead since sometime in our 1940s, and the Narnia universe itself ended in our 1950s (see “The Last Battle”, 1956 – incidentally, the earlier “The Magician’s Nephew”, 1955, mentions how the White Witch herself destroyed all life in her homeworld in order to defeat an enemy, and suggested this was a bad thing). The way is shut.