Showing posts with label Narnia. Show all posts
Showing posts with label Narnia. Show all posts

Tuesday, January 14, 2014

Sailing Away to Narnia


I stumbled upon an article a few months ago that I've been meaning to blog for a while and never got around to.

The original article is by Chris van den Broeck, and deals with the subject of warp drives.

Yes, warp drives.  The Alcubierre warp drive engine is a device that stretches the spacetime around a spaceship, forming what is known in scientific literature as the "warp bubble" (really, that's what we call it).  Within the warp bubble, the ship is moving at "normal speeds", but outside of the bubble, the ship is moving faster than the speed of light.  The geometry for this is known and well understood, and the means of producing it are also fully understood.

You're probably wondering, if we know how to make a warp drive, why we haven't actually... you know... made a warp drive.  And that's a wonderful question.  We haven't made a warp drive because it requires a lot of stuff that probably doesn't exist, namely negative energy mass.  It requires a whole lot of it.  Like, ten times the positive mass of the entire universe in negative mass.

Van den Broeck proposed an idea to get around this, one elegant in both its simplicity and apparent absurdity.

Here's what you do: Take a bag.  Distort space, so that the inside of the bag is bigger than the outside of the bag.  The inside is big enough to hold a spaceship, and the outside if around the Planck length.  Now stick your spaceship inside of the bag, and then put a warp bubble around the bag.   It requires a lot less negative energy.  Voila!  Crisis averted.
Schematic from original article.
Region II is the bag.
Region I is where the ship is.
Region IV is the warp bubble
Now, warp drives are cool of themselves, but what I really want to talk about is the device that distorts space so the inside of the bag is bigger than the outside of the bag.  This is sometimes called a "van den Brocek bubble", or, somewhat more appropriately, a Bag of Holding.

We've gone from warp drives to the bag of holding, and we're not even done yet.  We're going all the way to Narnia.

Thursday, August 1, 2013

The Bottomless Starbucks Gift Card and Quantum Immortality

I have recently acquired an item of rare wonder and power.  An artifact of legend, forged in a mythical age.  I am now the owner of the Bottomless Starbucks Gift Card.

From Piled Higher and Deeper
How this enchanted relic came in to my possession is common enough.  Believe it or not, it was given to my mother (a middle school teacher) as an end-of-semester present.  She, seeing no need to for it, did bequeath it unto me.  And I, a grad student in physics, have found very much need for some extra coffee money.

I've gone through a number of these re-gifted Starbucks cards from my mom, almost all of which were for $5.  They got me about two uses, then I'd switch to the next.  I seriously carried four or five of them around, gradually burning through them.  But the Bottomless Card... that's the last one I came to.

I have no idea how much money is on it, or was on it.  I go up to the counter, order whatever I want, show them the card, they swipe it, and there's always still enough money left for next time.

There is an interpretation of Quantum Mechanics that is called Everett's Many-Worlds Hypothesis.  This is often misunderstood and abused by science fiction authors, and philosophers as implying something stronger than it actually does -- the actual existence of parallel universes with alternative versions of ourselves (like in His Dark Materials).  This isn't quite what it means; it's more like every quantum measurement, rather than resulting in a collapse of the wave function, actually results in the further entanglement of the observer with one of the terms in the superposition.  The parts of the universal wave function describing us continue to exist but now in a superposition, one with every possibility of the measurement.  It's kind of the same thing, but not really.
From Asbtruse Goose

Everett's is a popular interpretation and appears frequently cited in "popular science" articles and books.  It is not the strict implication of quantum mechanics, nor is it anything more than a philosophical framework built around quantum mechanics, but it's there and cited a lot.  Most of the appeal is the fantasticality of it; alternative universes, Narnia, cool!  There's also some physicists who prefer it for philosophical reasons; for instance, Everett's hypothesis would recover a deterministic universe, which was believed to be broken by quantum measurement.  Actually, Frank Tipler -- physicist, transhumanist, many-worldsist, and all around weird dude --  proposed an experiment to test Everett's based on the convergence of quantum interference patterns, to see if "probability" were in fact "leaking" to another universe.  I have no idea why no one has done this experiment yet, but he's put it out there.

Tipler's experiment is slightly more sane than another proposal: Quantum Immortality.

Quantum Immortality is - roughly - proposed to work in the following way.  You have a quantum gun; whether it fires a bullet when you pull the trigger is tied to some quantum mechanical superposition, so there is always a chance it won't fire.  In the Everett interpretation, each time you do this, your wave function splits in to two "worlds": one where the gun fires, the other where it doesn't.  The experiment calls for you to point the gun at your head and pull the trigger.  In Everett's interpretation, each time you do this, your wave function splits in to "dead" and "alive" parts; therefore, even if you do this 10,000 times, there still exists some version of you in some "universe" that is still alive.  Therefore, if you pull the trigger 10,000 times and live, you can conclude that you live in the "world" where you're still alive.

Here's an illustration from Super Mario World, where Mario keeps splitting and one Mario copy always survives:


The Quantum Immortality experiment doesn't require that you point the gun at your head.  It basically just states that if you keep making a quantum observation and keep getting the same result, then it makes more sense to assume you live in a universe that is a segment of a multiverse than that you just keep getting lucky.  You could even do this experiment with...

... a Starbucks Gift Card.

I have no idea how much money is on the card.  Each time I swipe it, I make an observation of whether or not there is sufficient money for my purchase.  There always is.  Always.  It's been weeks, and I still have enough money.  I've even started ordering fancy-fru-fru drinks and it keeps working.  It always works.

So now you can see how it works.  So long as I don't directly observe the exact amount of money on the card, there is no exact amount of money on the card!  Between "No Money" and "Yes Money", I also happen to live in the universe where the Card always splits to the "Yes Money" side of things.  Always.

And that is how I came upon the key to eternal coffee, and the strange mysteries that went to forging its powers.

[P.S. I'm not going to bother explaining every thing wrong with the Quantum Immortality proposal, nor my wonky application of it to an inherently non-quantum event.  Suffice it to say, almost none of it is scientifically rigorous, and Everett's interpretation is pretty dumb, even if it makes for fun science fiction.]

Tuesday, March 19, 2013

The Width of Narnia

As is revealed in Voyage of the Dawn Treader, the world of Narnia is a flat earth.  Characters can literally fall of the edge of the world.

I started wondering, at one point, how thick is that edge?

Characters from our world report no differences in the gravity (or whatever) on Narnia; they don't feel any greater or lesser weight walking around.  Arguably, if Narnia had a lower gravity, then the Pevensies might have had, at least, an easier time crossing through the snow.  And contrariwise, if Narnia had a much higher gravity, then the adventure would have mostly been about aching knee joints.

Further, when the Pevensies stay in Narnia as kings and queens, they eat the food there, and this does not make them sick.  The food they eat they report as tasting equivalent to earth food.  When they grow up, they marry dryads and naiads and other mythological things and have children.  Weird as this is, it all proves pretty much conclusively that Narnia is made of the same kind of "stuff" as Earth; this is important.

So we know three things.  We know Narnia has the same overall downward-pulling force as Earth's gravity, we know that Narnia is made of the same kind of stuff as Earth, and we know that Narnia is a flat earth with a literal edge that you could fall off.

This is enough to calculate, to a very good approximation, how thick Narnia is.

Tuesday, January 1, 2013

Why Travel to Hyperspace Would Instantly Kill You

So, I've wondered a lot about a way to construct a "system of magic" (as often appear in modern fantasy works) from a collection of physical laws.  And until I got carried up in classes last semester, that was one of my main focuses of attention.

I was thinking that, in an alternative universe, there's no reason why they should have the same number of spatial dimensions as us.  So why not four, or five, or ten?

Because if you traveled to four-dimensional space, then you would find your skin insufficient to contain all of the air, blood, half-digested food, and maybe even internal organs that now find an extra degree of freedom within which to diffuse.

Five and higher dimensions makes it worse; the many things inside of you that keep you alive would disperse and splatter even faster.

So far I have discovered that to have any sort of meaningful adventure in a parallel universe, it must have the same number of spatial dimensions as we do (namely 3), it must have at least one time-like dimension, the electromagnetic interaction must exist and must recognize and interact with your electrons and protons.  Gravity would be nice, and I don't know enough about weak and strong interactions to know if they would be necessary.
http://abstrusegoose.com/457

There are most likely other limitations and dangers in such fantastic travel that have not yet come to mind.

In short, the inter-universe questing of children from our universe can never be to any world truly alien from our own.  Which is very sad.

Friday, August 3, 2012

On Reading "His Dark Materials"


I originally wrote this February, 2011 on a different blog, but decided to repost it here.

Lyra and Iorek
This week I read the entire His Dark Materials series.  I started with Golden Compass idly at about ten last Sunday just to give me something non-work-related to do before I went to bed.  I finished the Amber Spyglass yesterday evening sometime.  I put aside work and school and sleep (I slept in my office one night to get more reading time) and to some extent eating as I read through the series.

It's a really, really good book.

Friday, July 20, 2012

From The Magicians

I recently read The Magicians by Lev Grossman.  The story is sort of a commentary/deconstruction of childhood fantasy novels, especially Harry Potter and Narnia.  I suppose I have more I could say about it, but I was really struck by this quote:

Penny chose Oslo -- not even New Oslo, just Oslo, as if they thought they came up with it first -- for its total lack of anything that might distract him.  He arrived in mid-September and had no trouble renting a small farmhouse on the outskirts of town on a one-lane rural route.  His landlord was a retired schoolteacher who handed him the keys and then fled to his winter in South Carolina.  Penny's nearest neighbors on either side were a congregationless one-shack Pentecostal church and an out-of-session summer camp for disturbed children.  It was perfect.  He had found his Walden.

He had everything he needed: silence; solitude; a U-haul trailer packed with an enviable library of magical codices, monographs, chapbooks, reference books, ad broadsheets.  He had a sturdy desk, a well-lit room, and a window with an unscenic view of an unmown backyard that offered no particular temptation to gaze out at it.  He had a manageable, intriguingly dangerous research project that showed every sign of maturing into a genuinely interesting line if inquiry.  He was in heaven.

But one afternoon a few weeks after he arrived, as he sat at his desk, his watery blue eyes trailing over words of consummate power written centuries ago with a pen made out of a hippogriff feather, Penny found his mind wandering.  His large, usually lineless brow crinkled.  Something was sapping his powers of concentration.  Wa he under attack, maybe by a rival researcher?  Who would dare!  He rubbed his eyes and shook his head and focused harder.  But his attention continued to drift.

It turned out Penny had discovered in himself a weakness, a flaw he never would have suspected himself of in a thousand years, an age to which, with a few careful modifications that he would look into wen he had the time, he had every intention of living.  The flaw was this: he was lonely.

The idea was outrageous.  It was humiliating.  He, Penny, was a stone-cold loner, a depserado.  He was the Han Solo of Oslo.  He knew and loved this about himself.

This describes me almost perfectly.  Sometimes I want cloister myself off and just read and study and solve problems, free from the oppressive burdens of human interactions... but I just can't.  I can go with very little human interaction, but very little still isn't none.  And it has been interesting to learn of my own possession of the weakness of needing human interaction.

Monday, June 18, 2012

To Stand on Charn

Since C.S. Lewis showed us a world on the other side of a wardrobe (and perhaps before), fantasy and science-fiction stories have abounded with this idea of traveling to parallel universes and experiencing strange new worlds.  It's almost iconic: awkward teenager struggling in school and with bullies, gets sucked in to an alternate magical world, meets fascinating elves and confronts evil, and finds confidence to face real-world issues on his or her return.

Typical example

So here's my question: how do they interact with matter in the alternate universe?