Archive for the 'Bad Math' category

Speed-Crankery

May 05 2013 Published by under Bad Math, Cantor Crankery

A fun game to play with cranks is: how long does it take for the crank to contradict themselves?

When you're looking at a good example of crankery, it's full of errors. But for this game, it's not enough to just find an error. What we want is for them to say something so wrong that one sentence just totally tears them down and demonstrates that what they're doing makes no sense.

"The color of a clear sky is green" is, most of the time, wrong. If a crank makes some kind of argument based on the alleged fact that the color of a clear daytime sky is green, the argument is wrong. But as a statement, it's not nonsensical. It' just wrong.

On th other hand, "The color of a clear sky is steak frite with bernaise sauce and a nice side of roasted asparagus", well... it's not even wrong. It's just nonsense.

Today's crank is a great example of this. If, that is, it's legit. I'm not sure that this guy is serious. I think this might be someone playing games, pretending to be a crank. But even if it is, it's still fun.

About a week ago, I got en mail titled "I am a Cantor crank" from a guy named Chris Cuellar. The contents were:

...AND I CHALLENGE YOU TO A DUEL!! En garde!

Haha, ok, not exactly. But you really seem to be interested in this stuff. And so am I. But I think I've nailed Cantor for good this time. Not only have I come up with algorithms to count some of these "uncountable" things, but I have also addressed the proofs directly. The diagonalization argument ends up failing spectacularly, and I believe I have a good explanation for why the whole thing ends up being invalid in the first place.

And then I also get to the power set of natural numbers... I really hope my arguments can be followed. The thing I have to emphasize is that I am working on a different system that does NOT roll up cardinality and countability into one thing! As it will turn out, rational numbers are bigger than integers, integers are bigger than natural numbers... but they are ALL countable, nonetheless!

Anyway, I had started a little blog of my own a while ago on these subjects. The first post is here:

http://laymanmath.blogspot.com/2012/09/the-purpose-and-my-introduction.html

Have fun... BWAHAHAHA

So. We've got one paragraph of intro. And then everything crashes and burns in an instant.

"Rational numbers are bigger than integers, integers are bigger than natural numbers, but they are all countable". This is self-evident rubbish. The definition of "countable" say that an infinite set I is countable if, and only if, you can create a one-to-one mapping between the members of I and the natural numbers. The definition of cardinality says that if you can create a one-to-one mapping between two sets, the sets are the same size.

When Mr. Cuellar says that the set of rational numbers is bigger that the set of natural numbers, but that they are still countable... he's saying that there is not a one-to-one mapping between the two sets, but that there is a one-to-one mapping between the two sets.

Look - you don't get to redefine terms, and then pretend that your redefined terms mean the same thing as the original terms.

If you claim to be refuting Cantor's proof that the cardinality of the real numbers is bigger than the cardinality of the natural numbers, then you have to use Cantor's definition of cardinality.

You can change the definition of the size of a set - or, more precisely, you can propose an alternative metric for how to compare the sizes of sets. But any conclusions that you draw about your new metric are conclusions about your new metric - they're not conclusions about Cantor's cardinality. You can define a new notion of set size in which all infinite sets are the same size. It's entirely possible to do that, and to do that in a consistent way. But it will say nothing about Cantor's cardinality. Cantor's proof will still work.

What my correspondant is doing is, basically, what I did above in saying that the color of the sky is steak frites. I'm using terms in a completely inconsistent meaningless way. Steak frites with bernaise sauce isn't a color. And what Mr. Cuellar does is similar: he's using the word "cardinality", but whatever he means by it, it's not what Cantor meant, and it's not what Cantor's proof meant. You can draw whatever conclusions you want from your new definition, but it has no bearing on whether or not Cantor is correct. I don't even need to visit his site: he's demonstrated, in record time, that he has no idea what he's doing.

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The Gravitational Force of Rubbish

May 01 2013 Published by under Bad Math, Bad Physics

Imagine, for just a moment, that you were one a group of scientists that had proven the most important, the most profound, the most utterly amazing scientific discovery of all time. Where would you publish it?

Maybe Nature? Science? Or maybe you'd prefer to go open-access, and go with PLOS ONE? Or more mainstream, and send a press release to the NYT?

Well, in the case of today's crackpots, they bypassed all of those boring journals. They couldn't be bothered with a pompous rag like the Times. No, they went for the really serious press: America Now with Leeza Gibbons.

What did they go to this amazing media outlet to announce? The most amazing scientific discovery of all time: gravity is an illusion! There's no gravity. In fact, not just is there no gravity, but all of that quantum physics stuff? It's utter rubbish. You don't need any of that complicated stuff! No - you need only one thing: the solar wind.

A new theory on the forces that control planetary orbit refutes the 400-year old assumptions currently held by the scientific community. Scientific and engineering experts Gerhard and Kevin Neumaier have established a relationship between solar winds and a quantized order in both the position and velocity of the solar system's planets, and movement at an atomic level, with both governed by the same set of physics.

The observations made bring into question the Big Bang Theory, the concept of black holes, gravitational waves and gravitons. The Neumaiers' paper, More Than Gravity, is available for review at MoreThanGravity.com

Pretty damned impressive, huh? So let's follow their instructions, and go over to their website.

Ever since humankind discovered that the Earth and the planets revolved around the Sun, there was a question about what force was responsible for this. Since the days of Newton, science has held onto the notion that an invisible force, which we have never been able to detect, controls planetary motion. There are complicated theories about black holes that have never been seen, densities of planets that have never been measured, and subatomic particles that have never been detected.

However, it is simpler than all of that and right in front of us. The Sun and the solar wind are the most powerful forces in our solar system. They are physically moving the planets. In fact, the solar wind spins outward in a spiral at over a million miles per hour that controls the velocity and distances that planets revolve around the Sun. The Sun via the solar wind quantizes the orbits of the planets – their position and speed.

The solar wind also leads to the natural log and other phenomenon from the very large scale down to the atomic level. This is clearly a different idea than the current view that has been held for over 400 years. We have been working on this for close 50 years and thanks to satellite explorations of space have data that just was not available when theories long ago were developed. We think that we have many of the pieces but there are certainly many more to be found. We set this up as a web site, rather as some authoritative book so that there would be plenty of opportunity for dialog. The name for this web site, www.MorethanGravity.com was chosen because we believe there is far more to this subject than is commonly understood. Whether you are a scientific expert in your field or just have a general interest in how our solar system works, we appreciate your comments.

See, it's all about the solar wind. There's no such thing as gravity - that's just nonsense. The sun produces the solar wind, which does absolutely everything. The wind comes out of the sun, and spirals out from the sun. That spiral motion has eddies in it an quantized intervals, and that's where the planets are. Amazing, huh?

Remember my mantra: the worst math is no math. This is a beautiful demonstration
of that.

Of course... why does the solar wind move in a spiral? Everything we know says that in the absence of a force, things move in a straight line. It can't be spiraling because of gravity, because there is no gravity. So why does it spiral? Our brilliant authors don't bother to say. What makes it spiral, instead of just move straight? Mathematically, spiral motion is very complicated. It requires a centripetal force which is smaller than the force that would produce an orbit. Where's that force in this framework? There isn't any. They just say that that's how the solar wind works, period. There are many possible spirals, with different radial velocities - which one does the solar wind follow according to this, and why? Again, no answer from the authors.

Or... why is the sun producing the solar wind at all? According to those old, stupid theories that this work of brilliance supercedes, the sun produces a solar wind because it's fusing hydrogen atoms into helium. That's happening because gravity is causing the atoms of the sun to be compressed together until they fuse. Without gravity, why is fusion happening at all? And given that it's happening, why does the sun not just explode into a supernova? We know, from direct observation, that the energy produced by fusion creates an outward force. But gravity can't be holding the sun together - so why is the sun there at all? Still, no answers.

They do, eventually, do some math. One of the big "results" of this hypothesis is about the "quantization" of the orbits of planets around the sun. They were able to develop a simple equation which predicts the locations where planets could exist in their "solar wind" system.

Let’s start with the distance between the planets and the Sun. We guessed that if the solar system was like an atom, that planetary distance would be quantized. This is to say that we thought that the planets would have definite positions and that they would be either in the position or it would be empty. In a mathematical sense, this would be represented by a numerical integer ordering (0,1,2,3,…). If the first planet, Mercury was in the 0 orbital, how would the rest of the planets line up? Amazingly well we found.

If we predict the distance from the surface of the Sun to each planet in this quantized approach, the results are astounding. If D equals the mean distance to the surface of the Sun, and d0 as the distance to Mercury, we can describe the relationship that orders the planets mathematically as:

D=d_0 S^n

Each planetary position can be predicted from this equation in a simple calculation as we increase the integer (or planet number) n. S is the solar factor, which equals 1.387. The solar factor is found in the differential rotation of the Sun and the profile of the solar wind which we will discuss later.

Similar to the quantized orbits that exist within an atom, the planetary bodies are either there or not. Mercury is in the zero orbital. The next orbital is missing a planet. The second, third, and fourth orbitals are occupied by Venus, Earth, and Mars respectively. The fifth orbital is missing. The sixth orbital is filled with Ceres. Ceres is described as either the largest of all asteroids or a minor planet (with a diameter a little less than half that of Pluto), depending on who describes it. Ceres was discovered in 1801 as astronomers searched for the missing planets that the Titius-Bode Law predicted would exist.

So. What they found was an exponential equation which products very approximate versions of the size of first 8 planets' orbits, as well as a couple of missing ones.

This is, in its way, interesting. Not because they found anything, but rather because they think that this is somehow profound.

We've got 8 data points (or 9, counting the asteroid belt). More precisely, we have 9 ranges, because all of the orbits are elliptical,but the authors of this junk are producing a single number for the size of the orbits, and they can declare success if their number falls anywherewithin the range from perihelion to aphelion in each of the orbits.

It would be shocking if there weren't any number of simple equations that described exactly the 9 data points of the planet's orbits.

But they couldn't even make that work directly. They only manage to get a partial hit - getting an equation that hits the right points, but which also generates a bunch of misses. There's nothing remotely impressive about that.

From there, they move on to the strawmen. For example, they claim that their "solar wind" hypothesis explains why the planets all orbit in the same direction on the same plane. According to them, if orbits were really gravitational, then planets would orbit in random directions on random planes around the sun. But their theory is better than gravity, because it says why the planets are in the same plane, and why they're all orbiting in the same direction.

The thing is, this is a really stupid argument. Why are the planets in the same plane, orbiting in the same direction? Because the solar system was formed out of a rotating gas cloud. There's a really good, solid, well-supported explanation of why the planets exist, and why they orbit the sun the way they do. Gravity doesn't explain all of it, but gravity is a key piece of it.

What they don't seem to understand is how amazingly powerful the theory of gravity is as a predictive tool. We've sent probes to the outer edges of the solar system. To do that, we didn't just aim a rocket towards Jupiter and fire it off. We've done things like the Cassini probe, where we launched a rocket towards Venus. It used the gravitational field of Venus twice to accelerate it with a double-slingshot maneuver, and send it back towards earth, using the earth's gravity to slingshot it again, to give it the speed it needed to get to Jupiter.

This wasn't a simple thing to do. It required an extremely deep understanding of gravity, with extremely accurate predictions of exactly how gravity behaves.

How do our brilliant authors answer this? By handwaving. The extend of their response is:

Gravitational theory works for things like space travel because it empirically measures the force of a planet, rather than predicting it.

That's a pathetic handwave, and it's not even close to true. The gravitational slingshot is a perfect answer to it. A slingshot doesn't just use some "empirically measured" force of a planet. It's a very precise prediction of what the forces will be at different distances, how that force will vary, and what effects that force will have.

They do a whole lot more handwaving of very much the same order. Pure rubbish.

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Genius Continuum Crackpottery

Mar 21 2013 Published by under Bad Algebra, Bad Logic, Bad Math, Cantor Crankery

There's a lot of mathematical crackpottery out there. Most of it is just pointless and dull. People making the same stupid mistakes over and over again, like the endless repetitions of the same-old supposed refutations of Cantor's diagonalization.

After you eliminate that, you get reams of insanity - stuff which
is simply so incoherent that it doesn't make any sense. This kind of thing is usually word salad - words strung together in ways that don't make sense.

After you eliminate that, sometimes, if you're really lucky, you'll come accross something truly special. Crackpottery as utter genius. Not genius in a good way, like they're an outsider genius who discovered something amazing, but genius in the worst possible way, where someone has created something so bizarre, so overwrought, so utterly ridiculous that it's a masterpiece of insane, delusional foolishness.

Today, we have an example of that: Existics!. This is a body of work by a high school dropout named Gavin Wince with truly immense delusions of grandeur. Pomposity on a truly epic scale!

I'll walk you through just a tiny sample of Mr. Wince's genius. You can go look at his site to get more, and develop a true appreciation for this. He doesn't limit himself to mere mathematics: math, physics, biology, cosmology - you name it, Mr. Wince has mastered it and written about it!

The best of his mathematical crackpottery is something called C3: the Canonized Cardinal Continuum. Mr. Wince has created an algebraic solution to the continuum hypothesis, and along the way, has revolutionized number theory, algebra, calculus, real analysis, and god only knows what else!

Since Mr. Wince believes that he has solved the continuum hypothesis. Let me remind you of what that is:

  1. If you use Cantor's set theory to explore numbers, you get to the uncomfortable result that there are different sizes of infinity.
  2. The smallest infinite cardinal number is called ℵ0,
    and it's the size of the set of natural numbers.
  3. There are cardinal numbers larger than ℵ0. The first
    one larger than ℵ0 is ℵ1.
  4. We know that the set of real numbers is the size of the powerset
    of the natural numbers - 2ℵ0 - is larger than the set of the naturals.
  5. The question that the continuum hypothesis tries to answer is: is the size
    of the set of real numbers equal to ℵ1? That is, is there
    a cardinal number between ℵ0 and |2ℵ0|?

The continuum hypothesis was "solved" in 1963. In 1940, Gödel showed that you couldn't disprove the continuum hypothesis using ZFC. In 1963,
another mathematician named Paul Cohen, showed that it couldn't be proven using ZFC. So - a hypothesis which is about set theory can be neither proven nor disproven using set theory. It's independent of the axioms of set theory. You can choose to take the continuum hypothesis as an axiom, or you can choose to take the negation of the continuum hypothesis as an axiom: either choice is consistent and valid!

It's not a happy solution. But it's solved in the sense that we've got a solid proof that you can't prove it's true, and another solid proof that you can't prove it's false. That means that given ZFC set theory as a basis, there is no proof either way that doesn't set it as an axiom.

But... Mr. Wince knows better.

The set of errors that Wince makes is really astonishing. This is really seriously epic crackpottery.

He makes it through one page without saying anything egregious. But then he makes up for it on page 2, by making multiple errors.

First, he pulls an Escultura:

x1 = 1/21 = 1/2 = 0.5

x2 = 1/21 + 1/22 = 1/2 + 1/4 = 0.75

x3 = 1/21 + 1/22 + 1/23 = 1/2 + 1/4 + 1/8 = 0.875

...

At the end or limit of the infinite sequence, the final term of the sequence is 1.0

...

In this example we can see that as the number of finite sums of the sequence approaches the limit infinity, the last term of the sequence equals one.

xn = 1.0

If we are going to assume that the last term of the sequence equals one, it can be deduced that, prior to the last term in the sequence, some finite sum in the series occurs where:

xn-1 = 0.999…

xn-1 = 1/21 + 1/22 + 1/23 + 1/24 + … + 1/2n-1 = 0.999…

Therefore, at the limit, the last term of the series of the last term of the sequence would be the term, which, when added to the sum 0.999… equals 1.0.

There is no such thing as the last term of an infinite sequence. Even if there were, the number 0.999.... is exactly the same as 1. It's a notational artifact, not a distinct number.

But this is the least of his errors. For example, the first paragraph on the next page:

The set of all countable numbers, or natural numbers, is a subset of the continuum. Since the set of all natural numbers is a subset of the continuum, it is reasonable to assume that the set of all natural numbers is less in degree of infinity than the set containing the continuum.

We didn't need to go through the difficult of Cantor's diagonalization! We could have just blindly asserted that it's obvious!

or actually... The fact that there are multiple degrees of infinity is anything but obvious. I don't know anyone who wasn't surprised the first time they saw Cantor's proof. It's a really strange idea that there's something bigger than infinity.

Moving on... the real heart of his stuff is built around some extremely strange notions about infinite and infinitessimal values.

Before we even look at what he says, there's an important error here
which is worth mentioning. What Mr. Wince is trying to do is talk about the
continuum hypothesis. The continuum hypothesis is a question about the cardinality of the set of real numbers and the set of natural numbers.
Neither infinites nor infinitessimals are part of either set.

Infinite values come into play in Cantor's work: the cardinality of the natural numbers and the cardinality of the reals are clearly infinite cardinal numbers. But ℵ0, the smallest infinite cardinal, is not a member of either set.

Infinitessimals are fascinating. You can reconstruct differential and integral calculus without using limits by building in terms of infinitessimals. There's some great stuff in surreal numbers playing with infinitessimals. But infinitessimals are not real numbers. You can't reason about them as if they were members of the set of real numbers, because they aren't.

Many of his mistakes are based on this idea.

For example, he's got a very strange idea that infinites and infinitessimals don't have fixed values, but that their values cover a range. The way that he gets to that idea is by asserting the existence
of infinity as a specific, numeric value, and then using it in algebraic manipulations, like taking the "infinityth root" of a real number.

For example, on his way to "proving" that infinitessimals have this range property that he calls "perambulation", he defines a value that he calls κ:

\sqrt[\infty]{\infty} = 1 + \kappa

In terms of the theory of numbers, this is nonsense. There is no such thing as an infinityth root. You can define an Nth root, where N is a real number, just like you can define an Nth power - exponents and roots are mirror images of the same concept. But roots and exponents aren't defined for infinity, because infinity isn't a number. There is no infinityth root.

You could, if you really wanted to, come up with a definition of exponents that that allowed you to define an infinityth root. But it wouldn't be very interesting. If you followed the usual pattern for these things, it would be a limit: \sqrt[\infty]{x} \lim_{n\rightarrow\infty} \sqrt[n]{x}. That's clearly 1. Not 1 plus something: just exactly 1.

But Mr. Cringe doesn't let himself be limited by silly notions of consistency. No, he defines things his own way, and runs with it. As a result, he gets a notion that he calls perambulation. How?

Take the definition of κ:

\sqrt[\infty]{\infty} = 1 + \kappa

Now, you can, obviously, raise both sides to the power of infinity:

\infty = (1 + \kappa)^{\infty}

Now, you can substitute ℵ0 for \infty. (Why? Don't ask why. You just can.) Then you can factor it. His factoring makes no rational sense, so I won't even try to explain it. But he concludes that:

  • Factored and simplified one way, you end up with (κ+1)ℵ = 1 + x, where x is some infinitessimal number larger than κ. (Why? Why the heck not?)
  • Factored and simplified another way, you end up with (κ+1)ℵ = ℵ
  • If you take the mean of of all of the possible factorings and reductions, you get a third result, that (κ+1)ℵ = 2.

He goes on, and on, and on like this. From perambulation to perambulating reciprocals, to subambulation, to ambulation. Then un-ordinals, un-sets... this is really an absolute masterwork of utter insane crackpottery.

Do download it and take a look. It's a masterpiece.

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Pi-day randomness

Mar 14 2013 Published by under Bad Math

One of my twitter friends was complaining about something that's apparently making the rounds of Facebook for π-day. It annoyed me sufficiently to be worth ranting about a little bit.

Why isn't π rational if π=circumference/diameter, and both measurements are plainly finite?

There's a couple of different ways of interpreting this question.

The stupidest way of interpreting it is that the author didn't have any clue of what an irrational number is. An irrational number is a number which cannot be written as a ratio of two integers. Another way of saying essentially the same thing is that there's no way to create a finite representation of an irrational number. I've seen people get this wrong before, where they confuse not having a finite representation with not being finite.

π doesn't have a finite representation. But it's very clearly finite - it's less that 3 1/4, which is obviously not infinite. Anyone who can look at π, and be confused about whether or not it's finite is... well... there's no nice way to say this. If you think that π isn't finite, you're an idiot.

The other way of interpreting this statement is less stupid: it's a question of measurement. If you have a circular object in real life, then you can measure the circumference and the diameter, and do the division on the measurements. The measurements have finite precision. So how can the ratio of two measurements with finite precision be irrational?

The answer is, they can't. But perfect circles don't exist in the real world. Many mathematical concepts don't exist in the real world. In the real world, there's no such thing as a mathematical point, no such thing as a perfect line, no such thing as perfectly parallel lines.

π isn't a measured quantity. It's a theoretical quantity, which can be computed analytically from the theoretical properties derived from the abstract properties of an ideal, perfect circle.

No "circle" in the real world has a perfect ratio of π between its circumference and its diameter. But the theoretical circle does.

The facebook comments on this get much worse than the original question. One in particular really depressed me.

Just because the measurements are finite doesn't mean they're rational.
Pi is possibly rational, we just haven't figured out where it ends.

Gah, no!

We know an awful lot about π. And we know, with absolute, 100% perfect certainty that π never ends.

We can define π precisely as a series, and that series makes it abundantly clear that it never ends.

\pi = \frac{4}{1} - \frac{4}{3} + \frac{4}{5} - \frac{4}{7} + \frac{4}{9} ...

That series goes on forever. π can't ever end, because that series never ends.

Just for fun, here's a little snippet of Python code that you can play with. You can see how, up to the limits of your computer's floating point representation, that a series computation of π keeps on going, changing with each additional iteration. 

def pi(numiter):
  val = 3.0
  sign = 1
  for i in range(numiter):
    term = ((i+1)*2) * ((i+1)*2 + 1) * ((i+1) *2 + 2)
    val = val + sign*4.0/term
    sign = sign * -1
  return val
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New Dimensions of Crackpottery

Feb 26 2013 Published by under Bad Physics

I have, in the past, ranted about how people abuse the word "dimension", but it's been a long time. One of my followers on twitter sent me a link to a remarkable piece of crackpottery which is a great example of how people simply do not understand what dimensions are.

There are several ways of defining "dimension" mathematically, but they all come back to one basic concept. A dimension an abstract concept of a direction. We can use the number of dimensions in a space as a way of measuring properties of that space, but those properties all come back to the concept of direction. A dimension is neither a place nor a state of being: it is a direction.

Imagine that you're sitting in an abstract space. You're at one point. There's another point that I want you to go to. In order to uniquely identify your destination, how many directions do I need to mention?

If the space is a line, you only need one: I need to tell you the distance. There's only one possible direction that you can go, so all I need to tell you is how far. Since you only need one direction, the line is one-dimensional.

If the line is a plane, then I need to tell you two things. I could do that by saying "go right three steps then up 4 steps", or I could say "turn 53 degrees clockwise, and then walk forward 5 steps." But there's no way I can tell you how to get to your destination with less than two directions. You need two directions, so the plane is two dimensional.

If the space is the interior of a cube, then you'll need three directions, which means that the cube is three dimensional.

On to the crackpottery!

E=mc2 represents a translation across dimensions, from energy to matter.

No, it does not. Energy and matter are not dimensions. e=mc^2 is a statement about the fundamental relation between energy and matter, not a statement about dimensions. Our universe could be 2 dimensional, 3 dimensional, 4 dimensional, or 22 dimensional: relativity would still mean the same thing, and it's not a statement about a "translation across dimensions".

Energy can travel at the speed of light, and as Special Relativity tells us, from the perspective of light speed it takes no time to travel any distance. In this way, energy is not bound by time and space the way matter is. Therefore, it is in a way five-dimensional, or beyond time.

Bzzt, no.

Energy does not travel. Light travels, and light can transmit energy, but light isn't energy. Or, from another perspective, light is energy: but so is everything else. Matter and energy are the same thing.

From the perspective of light speed time most certainly does pass, and it does take plenty of time to travel a distance. Light takes roughly 6 minutes to get from the sun to the earth. What our intrepid author is trying to talk about here is the idea of time dilation. Time dilation describes the behavior of particles with mass when they move at high speeds. As a massive particle moves faster and approaches the speed of light, the mass of the particle increases, and the particle's experience of time slows. If you could accelerate a massive particle to the speed of light, its mass would become infinite, and time would stop for the particle. "If" is the key word there: it can't. It would require an infinite amount of energy to accelerate it to the speed of light.

But light has no mass. Relativity describes a strange property of the universe, which is hard to wrap your head around. Light always moves at the same speed, no matter your perspective. Take two spacecraft in outer space, which are completely stationary relative to each other. Shine a laser from one, and measure how long it takes for the light to get to the other. How fast is it going? Roughly 186,000 miles/second. Now, start one ship moving away from the other at half the speed of light. Repeat the experiment. One ship is moving away from the other at a speed of 93,000 miles/second. From the perspective of the moving ship, how fast is the light moving away from it towards the other ship? 186,000 miles/second. From the perspective of the stationary ship, how fast is the laser light approaching it? 186,000 miles/second.

It's not that there's some magic thing about light that makes it move while time stops for it. Light is massless, so it can move at the speed of light. Time dilation doesn't apply because it has no mass.

But even if that weren't the case, that's got nothing to do with dimensionality. Dimensionality is a direction: what does this rubbish have to do with the different directions that light can move in? Absolutely nothing: the way he's using the word "dimension" has nothing to do with what dimensions mean.

All “objects” or instances of matter are time-bound; they change, or die, or dissolve, or evaporate. Because they are subject to time, objects can be called four-dimensional.

Nope.

Everything in our universe is subject to time, because time is one of the dimensions in our universe. Time is a direction that we move. We don't have direct control over it - but it's still a direction. When and where did I write this blog post compared to where I am when you're reading it? The only way you can specify that is by saying how far my position has changed in four directions: 3 spatial directions, and time. Time is a dimension, and everything in our universe needs to consider it, because you can't specify anything in our universe without all four dimensions.

The enormous energy that can be released from a tiny object (as in an atomic bomb) demonstrates the role dimensions play in constructing reality.

No: the enormous energy that can be released from a tiny object demonstrates the fact that a small quantity of matter is equivalent to a large quantity of energy. As you'd expect if you look at that original equation: e=mc^2. A gram of mass - something the size of a paperclip - is equivalent to about 25 million kilowatt-hours of energy - or more than the total yearly energy use of 1,200 average americans. That's damned impressive and profound, without needing to draw in any mangled notions of dimensions or magical dimensional powers.

Higher dimensions are mind-blowingly powerful; even infinitely so. Such power is so expansive that it can’t have form, definition, or identity, like a ball of uranium or a human being, without finding expression in lower dimensions. The limitations of time and space allow infinite power to do something other than constantly annihilate itself.

Do I even need to respond to this?

Einstein’s equation E=mc2 bridges the fourth and the fifth dimensions, expressed as matter and energy. Imagine a discovery that bridges expressions of the fifth and sixth dimensions, such as energy and consciousness. Consciousness has the five-dimensional qualities of energy, but it can’t be “spent” in the way energy can because it doesn’t change form the way energy does. Therefore, it’s limitless.

And now we move from crackpottery to mysticism. Einstein's mass-energy equation doesn't bridge dimensions, and dimensionality has nothing do with mass-energy equivalence. And now our crackpot friend suddenly throws in another claim, that consciousness is the sixth dimension? Or consciousness is the bridge between the fifth and sixth dimensions? It's hard to figure out just what he's saying here, except for the fact that it's got nothing to do with actual dimensions.

Is there a sixth dimension? Who knows? According to some modern theories, our universe actually has many more than the 4 dimensions that we directly experience. There could be 6 or 10 or 20 dimensions. But if there are, those dimensions are just other directions that things can move. They're not abstract concepts like "consciousness".

And of course, this is also remarkably sloppy logic:

  1. Consciousness has the 5-dimensional qualities of energy
  2. Consciousness can't be spent.
  3. Consciousness can't change form.
  4. Therefore consciousness is unlimited.

The first three statements are just blind assertions, given without evidence or argument. The fourth is presented as a conclusion drawn from the first three - but it's a non-sequitur. There's no real way to conclude the last statement given the first three. Even if you give him all the rope in the world, and accept those three statements as axioms - it's still garbage.

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The Intellectual Gravity of Brilliant Baseball Players

Feb 21 2013 Published by under Bad Math, Bad Physics

Some of my friends at work are baseball fans. I totally don't get baseball - to me, it's about as interesting as watching paint dry. But thankfully, some of my friends disagree, which is how I found this lovely little bit of crackpottery.

You see, there's a (former?) baseball player named Jose Canseco, who's been plastering twitter with his deep thoughts about science.

At first glance, this is funny, but not particularly interesting. I mean, it's a classic example of my mantra: the worst math is no math.

The core of this argument is pseudo-mathematical. The dumbass wants to make the argument that under current gravity, it wouldn't be possible for things the size of the dinosaurs to move around. The problem with this argument is that there's no problem! Things the size of dinosaurs could move about in current gravity with absolutely no difficult. If you actually do the math, it's fine.

If dinosaurs had the anatomy of human beings, then it's true that if you scaled them up, they wouldn't be able to walk. But they didn't. They had anatomical structures that were quite different from ours in order to support their massive size. For example, here's a bone from quetzlcoatlus:

Media,111639,en See the massive knob sticking out to the left? That's a muscle attachement point. That gave the muscles much greater torque than ours have, which they needed. (Yes, I know that Quetzalcoatlus wwasn't really a dinosaur, but it is one of the kinds of animals that Canseco was talking about, and it was easy to find a really clear image.)

Most animal joints are, essentially, lever systems. Muscles attach to two different bones, which are connected by a hinge. The muscle attachement points stick out relative to the joint. When the muscles contract, that creates a torque which rotate the bones around the joint.

The lever is one of the most fundamental machines in the universe. It operates by the principal of torque. Our regular daily experiences show that levers act in a way that magnifies our efforts. I can't walk up to a car and lift it. But with a lever, I can. Muscle attachment points are levers. Take another look at that bone picture: what you're seeing is a massive level to magnify the efforts of the muscles. That's all that a large animal needed to be able to move around in earths gravity.

This isn't just speculation - this is stuff that's been modeled in great detail. And it's stuff that can be observed in modern day animals. Look at the skeleton of an elephant, and compare it to the skeleton of a dog. The gross structure is very similar - they are both quadripedal mammals. But if you look at the bones, the muscle attachment points in the elephants skeleton have much larger projections, to give the muscles greater torque. Likewise, compare the skeleton of an american robin with the skeleton of a mute swan: the swan (which has a maximum recorded wingspan of 8 feet!) has much larger projections on the attachment points for its muscles. If you just scaled a robin from its 12 inch wingspan to the 8 feet wingspan of a swan, it wouldn't be able to walk, much less fly! But the larger bird's anatomy is different in order to support its size - and it can and does fly with those 8 foot wings!

That means that on the basic argument for needing different gravity, Canseco fails miserably.

Canseco's argument for how gravity allegedly changed is even worse.

What he claims is that at the time when the continental land masses were joined together as the pangea supercontinent, the earths core moved to counterbalance the weight of the continents. Since the earths core was, after this shift, farther from the surface, the gravity at the surface would be smaller.

This is an amusingly ridiculous idea. It's even worse that Ted Holden and his reduced-felt-gravity because of the electromagnetic green saturn-star.

First, the earths core isn't some lump of stuff that can putter around. The earth is a solid ball of material. It's not like a ball of powdered chalk with a solid lump of uranium at the center. The core can't move.

Even if it could, Canseco is wrong. Canseco is playing with two different schemes of how gravity works. We can approximate the behavior of gravity on earth by assuming that the earth is a point: for most purposes, gravity behaves almost as if the entire mass of the earth was concentrated at the earths center of mass. Canseco is using this idea when he moves the "core" further from the surface. He's using the idea that the core (which surrounds the center of mass in the real world) is the center of mass. So if the core moves, and the center of mass moves with it, then the point-approximation of gravity will change because the distance from the center of mass has increased.

But: the reason that he claims the core moved is because it was responding to the combined landmasses on the surface clumping together as pangea. That argument is based on the idea that the core had to move to balance the continents. In that case, the center of gravity wouldn't be any different - if the core could move to counterbalance the continents, it would move just enough to keep the center of gravity where it was - so if you were using the point approximation of gravity, it would be unaffected by the shift.

He's combining incompatible assumptions. To justify moving the earths core, he's *not* using a point-model of gravity. He's assuming that the mass of the earths core and the mass of the continents are different. When he wants to talk about the effect of gravity of an animal on the surface, he wants to treat the full mass of the earth as a point source - and he wants that point source to be located at the core.

It doesn't work that way.

The thing that I find most interesting about this particular bit of crackpottery isn't really about this particular bit of crackpottery, but about the family of crackpottery that it belongs to.

People are fascinated by the giant creatures that used to live on the earth. Intuitively, because we don't see giant animals in the world around us, there's a natural tendency to ask "Why?". And being the pattern-seekers that we are, we intuitively believe that there must be a reason why the animals back then were huge, but the animals today aren't. It can't just be random chance. So people keep coming up with reasons. Like:

  1. Neal Adams: who argues that the earth is constantly growing larger, and that gravity is an illusion caused by that growth. One of the reasons, according to his "theory", for why we know that gravity is just an illusion, is because the dinosaurs supposedly couldn't walk in current gravity.
  2. Ted Holden and the Neo-Velikovskians: who argue that the solar system is drastically different today than it used to be. According to Holden, Saturn used to be a "hyperintelligent green electromagnetic start", and the earth used to be tide-locked in orbit around it. As a result, the felt effect of gravity was weaker.
  3. Stephen Hurrell, who argues similarly to Neal Adams that the earth is growing. Hurrell doesn't dispute the existence of gravity the way that Adams does, but similarly argues that dinosaurs couldn't walk in present day gravity, and resorts to an expanding earth to explain how gravity could have been weaker.
  4. Ramin Amir Mardfar: who claims that the earth's mass has been continually increasing because meteors add mass to the earth.
  5. Gunther Bildmeyer, who argues that gravity is really an electromagnetic effect, and so the known fluctuations in the earths magnetic fields change gravity. According to him, the dinosaurs could only exist because of the state of the magnetic field at the time, which reduced gravity.

There are many others. All of them grasping at straws, trying to explain something that doesn't need explaining, if only they'd bother to do the damned math, and see that all it takes is a relatively small anatomical change.

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Euler's Equation Crackpottery

Feb 18 2013 Published by under Bad Math, Bad Physics

One of my twitter followers sent me an interesting piece of crackpottery. I debated whether to do anything with it. The thing about crackpottery is that it really needs to have some content. Total incoherence isn't amusing. This bit is, frankly, right on the line.

Euler's Equation and the Reality of Nature.

a) Euler's Equation as a mathematical reality.

Euler's identity is "the gold standard for mathematical beauty'.
Euler's identity is "the most famous formula in all mathematics".
‘ . . . this equation is the mathematical analogue of Leonardo
da Vinci’s Mona Lisa painting or Michelangelo’s statue of David’
‘It is God’s equation’, ‘our jewel ‘, ‘ It is a mathematical icon’.
. . . . etc.

b) Euler's Equation as a physical reality.

"it is absolutely paradoxical; we cannot understand it,
and we don't know what it means, . . . . .’
‘ Euler's Equation reaches down into the very depths of existence’
‘ Is Euler's Equation about fundamental matters?’
‘It would be nice to understand Euler's Identity as a physical process
using physics.‘
‘ Is it possible to unite Euler's Identity with physics, quantum physics ?’

My aim is to understand the reality of nature.

Can Euler's equation explain me something about reality?

To give the answer to this. question I need to bind Euler's equation with an object – particle. Can it be math- point or string- particle or triangle-particle? No, Euler's formula has quantity (pi) which says me that the particle must be only a circle .

Now I want to understand the behavior of circle - particle and therefore I need to use spatial relativity and quantum theories. These two theories say me that the reason of circle – particle’s movement is its own inner impulse (h) or (h*=h/2pi).

a) Using its own inner impulse (h) circle - particle moves ( as a wheel) in a straight line with constant speed c = 1. We call such particle - ‘photon’. From Earth – gravity point of view this speed is maximally. From Vacuum point of view this speed is minimally. In this movement quantum of light behave as a corpuscular (no charge).

b) Using its own inner impulse / intrinsic angular momentum ( h* = h / 2pi ) circle - particle rotates around its axis. In such movement particle has charge, produce electric waves ( waves property of particle) and its speed ( frequency) is : c.

1. We call such particle - ‘ electron’ and its energy is: E=h*f.

In this way I can understand the reality of nature.

==.

Best wishes.

Israel Sadovnik Socratus.

Euler's equation says that e^{i\pi} + 1 = 0. It's an amazingly profound equation. The way that it draws together fundamental concepts is beautiful and surprising.

But it's not nearly as mysterious as our loonie-toon makes it out to be. The natural logarithm-base is deeply embedded in the structure of numbers, and we've known that, and we've known how it works for a long time. What Euler did was show the relationship between e and the fundamental rotation group of the complex numbers. There are a couple of ways of restating the definition of that make the meaning of that relationship clearer.

For example:

e^z = lim_{n\rightarrow \infty}(1 + \frac{z}{n})^n

That's an alternative definition of what e is. If we use that, and we plug i\pi into it, we get:

e^{i\pi} = lim_{n \rightarrow \infty}(1+\frac{i\pi}{n})^n

If you work out that limit, it's -1. Also, if you take values of N, and plot (1 + \frac{i\pi}{n})^1, (1+\frac{i\pi}{n})^2, (1 + \frac{i\pi}{n})^3, and (1 + \frac{i\pi}{n})^4, ... on the complex plane, as N gets larger, the resulting curve gets closer and closer to a semicircle.

An equivalent way of seeing it is that exponents of e^i are rotations in the complex number plane. The reason that e^{i\pi} = -1 is because if you take the complex number (1 + 0i), and rotate it by \pi radians, you get -1: 1(e^{i\pi}) = -1.

That's what Euler's equation means. It's amazing and beautiful, but it's not all that difficult to understand. It's not mysterious in the sense that our crackpot friend thinks it is.

But what really sets me off is the idea that it must have some meaning in physics. That's silly. It doesn't matter what the physical laws of the universe are: the values of \pi and e will not change. It's like trying to say that there must be something special about our universe that makes 1 + 1 = 2 - or, conversely, that the fact that 1+1=2 means something special about the universe we live in. These things are facts of numbers, which are independent of physical reality. Create a universe with different values for all of the fundamental constants - e and π will be exactly the same. Create a universe with less matter - e and π will still be the same. Create a universe with no matter, a universe with different kinds of matter, a universe with 300 forces instead of the four that we see - and e and π won't change.

What things like e and π, and their relationship via Euler's equation tell us is that there's a fundamental relationship between numbers and shapes on a two-dimensional plane which does not and cannot really exist in the world we live in.

Beyond that, what he's saying is utter rubbish. For example:

These two theories say me that the reason of circle – particle’s movement is its own inner impulse (h) or (h*=h/2pi). Using its own inner impulse (h) circle - particle moves ( as a wheel) in a straight line with constant speed c = 1. We call such particle - ‘photon’. From Earth – gravity point of view this speed is maximally. From Vacuum point of view this speed is minimally. In this movement quantum of light behave as a corpuscular (no charge).

This is utterly meaningless. It's a jumble of words that pretends to be meaningful and mathematical, when in fact it's just a string of syllables strung together nonsensical ways.

There's a lot that we know about how photons behave. There's also a lot that we don't know about photons. This word salad tells us exactly nothing about photons. In the classic phrase, it's not even wrong: what it says doesn't have enough meaning to be wrong. What is the "inner impulse" of a photon according to this crackpot? We can't know: the term isn't defined. We are pretty certain that a photon is not a wheel rolling along. Is that what the crank is saying? We can't be sure. And that's the problem with this kind of crankery.

As I always say: the very worst math is no math. This is a perfect example. He starts with a beautiful mathematical fact. He uses it to jump to a completely non-mathematical conclusion. But he writes a couple of mathematical symbols, to pretend that he's using math.

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Back to an old topic: Bad Vaccine Math

Jan 25 2013 Published by under Bad Math, Bad Probability, Bad Statistics

The very first Good Math/Bad Math post ever was about an idiotic bit of antivaccine rubbish. I haven't dealt with antivaccine stuff much since then, because the bulk of the antivaccine idiocy has nothing to do with math. But the other day, a reader sent me a really interesting link from what my friend Orac calls a "wretched hive of scum and quackery", naturalnews.com, in which they try to argue that the whooping cough vaccine is an epic failure:

(NaturalNews) The utter failure of the whooping cough (pertussis) vaccine to provide any real protection against disease is once again on display for the world to see, as yet another major outbreak of the condition has spread primarily throughout the vaccinated community. As it turns out, 90 percent of those affected by an ongoing whooping cough epidemic that was officially declared in the state of Vermont on December 13, 2012, were vaccinated against the condition -- and some of these were vaccinated two or more times in accordance with official government recommendations.

As reported by the Burlington Free Press, at least 522 cases of whooping cough were confirmed by Vermont authorities last month, which was about 10 times the normal amount from previous years. Since that time, nearly 100 more cases have been confirmed, bringing the official total as of January 15, 2013, to 612 cases. The majority of those affected, according to Vermont state epidemiologist Patsy Kelso, are in the 10-14-year-old age group, and 90 percent of those confirmed have already been vaccinated one or more times for pertussis.

Even so, Kelso and others are still urging both adults and children to get a free pertussis shot at one of the free clinics set up throughout the state, insisting that both the vaccine and the Tdap booster for adults "are 80 to 90 percent effective." Clearly this is not the case, as evidenced by the fact that those most affected in the outbreak have already been vaccinated, but officials are apparently hoping that the public is too naive or disengaged to notice this glaring disparity between what is being said and what is actually occurring.

It continues in that vein. The gist of the argument is:

  1. We say everyone needs to be vaccinated, which will protect them from getting the whooping cough.
  2. The whooping cough vaccine is, allagedly, 80 to 90% effective.
  3. 90% of the people who caught whooping cough were properly vaccinated.
  4. Therefore the vaccine can't possibly work.

What they want you to do is look at that 80 to 90 percent effective rate, and see that only 10-20% of vaccinated people should be succeptible to the whooping cough, and compare that 10-20% to the 90% of actual infected people that were vaccinated. 20% (the upper bound of the succeptible portion of vaccinated people according to the quoted statistic) is clearly much smaller than 90% - therefore it's obvious that the vaccine doesn't work.

Of course, this is rubbish. It's a classic apple to orange-grove comparison. You're comparing percentages, when those percentages are measuring different groups - groups with wildly difference sizes.

Take a pool of 1000 people, and suppose that 95% are properly vaccinated (the current DTAP vaccination rate in the US is around 95%). That gives you 950 vaccinated people and 50 unvaccinated people who are unvaccinated.

In the vaccinated pool, let's assume that the vaccine was fully effective on 90% of them (that's the highest estimate of effectiveness, which will result in the lowest number of succeptible vaccinated - aka the best possible scenario for the anti-vaxers). That gives us 95 vaccinated people who are succeptible to the whooping cough.

There's the root of the problem. Using numbers that are ridiculously friendly to the anti-vaxers, we've still got a population of twice as many succeptible vaccinated people as unvaccinated. so we'd expect, right out of the box, that better than 2/3rds of the cases of whooping cough would be among the vaccinated people.

In reality, the numbers are much worse for the antivax case. The percentage of people who were ever vaccinated is around 95%, because you need the vaccination to go to school. But that's just the childhood dose. DTAP is a vaccination that needs to be periodically boosted or the immunity wanes. And the percentage of people who've had boosters is extremely low. Among adolescents, according to the CDC, only a bit more than half have had DTAP boosters; among adults, less that 10% have had a booster within the last 5 years.

What's your succeptibility if you've gone more than 5 years without vaccination? Somewhere 40% of people who didn't have boosters in the last five years are succeptible.

So let's just play with those numbers a bit. Assume, for simplicity, than 50% of the people are adults, and 50% children, and assume that all of the children are fully up-to-date on the vaccine. Then you've got 10% of the children (10% of 475), 10% of the adults that are up-to-date (10% of 10% of 475), and 40% of the adults that aren't up-to-date (40% of 90% of 475) is the succeptible population. That works out to 266 succeptible people among the vaccinated, which is 85%: so you'd expect 85% of the actual cases of whooping cough to be among people who'd been vaccinated. Suddenly, the antivaxers case doesn't look so good, does it?

Consider, for a moment, what you'd expect among a non-vaccinated population. Pertussis is highly contagious. If someone in your household has pertussis, and you're succeptible, you've got a better than 90% chance of catching it. It's that contagious. Routine exposure - not sharing a household, but going to work, to the store, etc., with people who are infected still gives you about a 50% chance of infection if you're succeptible.

In the state of Vermont, where NaturalNews is claiming that the evidence shows that the vaccine doesn't work, how many cases of Pertussis have they seen? Around 600, out of a state population of 600,000 - an infection rate of one tenth of one percent. 0.1 percent, from a virulently contagious disease.

That's the highest level of Pertussis that we've seen in the US in a long time. But at the same time, it's really a very low number for something so contagious. To compare for a moment: there's been a huge outbreak of Norovirus in the UK this year. Overall, more than one million people have caught it so far this winter, out of a total population of 62 million, for a rate of about 1.6% or sixteen times the rate of infection of pertussis.

Why is the rate of infection with this virulently contagious disease so different from the rate of infection with that other virulently contagious disease? Vaccines are a big part of it.

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Vortex Garbage

Jan 22 2013 Published by under Bad Physics

A reader who saw my earlier post on the Vortex math talk at a TEDx conference sent me a link to an absolutely dreadful video that features some more crackpottery about the magic of vortices.

It says:

The old heliocentric model of our solar system,
planets rotating around the sun, is not only boring,
but also incorrect.

Our solar system moves through space at 70,000km/hr.
Now picture this instead:

(Image of the sun with a rocket/comet trail propelling
it through space, with the planets swirling around it.)

The sun is like a comet, dragging the planets in its wake.
Can you say "vortex"?

The science of this is terrible. The sun is not a rocket. It does not propel itself through space. It does not have a tail. It does not leave a significant "wake". (There is interstellar material, and the sun moving through it does perturb it, but it's not a wake: the interstellar material is orbiting the galactic center just like the sun. Gravitational effects do cause pertubations, but it's not like a boat moving through still water, producing a wake.) Even if you stretch the definition of "wake", the sun certainly does not leave a wake large enough to "drag" the planets. In fact, if you actually look at the solar system, the plane the ecliptic - the plane where the planets orbit the sun - is at a roughly 60 degree angle to the galactic ecliptic. If planetary orbits were a drag effect, then you would expect the orbits to be perpendicular to the galactic ecliptic. But they aren't.

If you look at it mathematically, it's even worse. The video claims to be making a distinction between the "old heliocentric" model of the solar system, and their new "vortex" model. But in fact, mathematically, they're exactly the same thing. Look at it from a heliocentric point of view, and you've got the heliocentric model. Look at the exact same system from point that's not moving relative to galactic center, and you get the vortex. They're the same thing. The only difference is how you look at it.

And that's just the start of the rubbish. Once they get past their description of their "vortex" model, they go right into the woo. Vortex is life! Vortex is sprirituality! Oy.

If you follow their link to their website, it gets even sillier, and you can start to see just how utterly clueless the author of this actually is:

(In reference to a NASA image showing the interstellar "wind" and the heliopause)

Think about this for a minute. In this diagram it seems the Solar System travel to the left. When the Earth is also traveling to the left (for half a year) it must go faster than the Sun. Then in the second half of the year, it travels in a “relative opposite direction” so it must go slower than the Sun. Then, after completing one orbit, it must increase speed to overtake the Sun in half a year. And this would go for all the planets. Just like any point you draw on a frisbee will not have a constant speed, neither will any planet.

See, it's a problem that the planets aren't moving at a constant speed. They speed up and slow down! Oh, the horror! The explanation is that they're caught by the sun's wake! So they speed up when they get dragged, until they pass the sun (how does being dragged by the sun ever make them faster than the sun? Who knows!), and then they're not being dragged anymore, so they slow down.

This is ignorance of physics and of the entire concept of frame of reference and symmetry that is absolutely epic.

There's quite a bit more nonsense, but that's all I can stomach this evening. Feel free to point out more in the comments!

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Types Gone Wild! SKI at Compile-Time

Jan 21 2013 Published by under Bad Software, lambda calculus

Over the weekend, a couple of my Foursquare coworkers and I were chatting on twitter, and one of my smartest coworkers, a great guy named Jorge Ortiz, pointed out that type inference in Scala (the language we use at Foursquare, and also pretty much my favorite language) is Turing complete.

Somehow, I hadn't seen this before, and it absolutely blew my mind. So I asked Jorge for a link to the proof. The link he sent me is a really beautiful blog post. It doesn't just prove that Scala type inference is Turing complete, but it does it in a remarkably beautiful way.

Before I get to the proof, what does this mean?

A system is Turing complete when it can perform any possible computation that could be performed on any other computing device. The Turing machine is, obviously, Turing complete. So is lambda calculus, the Minsky machine, the Brainfuck computing model, and the Scala programming language itself.

If type inference is Turing complete, then that means that you can write a Scala program where, in order to type-check the program, the compiler has to run an arbitrary program to completion. It means that there are, at least theoretically, Scala programs where the compiler will take forever - literally forever - to determine whether or not a given program contains a type error. Needless to say, I consider this to be a bad thing. Personally, I'd really prefer to see the type system be less flexible. In fact, I'd go so far as to say that this is a fundamental error in the design of Scala, and a big strike against it as a language. Having a type-checking system which isn't guaranteed to terminate is bad.

But let's put that aside: Scala is pretty entrenched in the community that uses it, and they've accepted this as a tradeoff. How did the blog author, Michael Dürig, prove that Scala type checking is Turing complete? By showing how to implement a variant of lambda calculus called SKI combinator calculus entirely with types.

SKI calculus is seriously cool. We know that lambda calculus is Turing complete. It turns out that for any lambda calculus expression, there's a way rewriting it without any variables, and without any lambdas at all, using three canonical master functions. If you've got those three, then you can write anything, anything at all. The three are called S, K, and I.

  • The S combinator is: S x y z = x z (y z).
  • The K combinator is: K x y = x.
  • The I combinator is: I x = x.

They come from intuitionistic logic, where they're fundamental axioms that describe how intuitionistic implication works. K is the rule A \Rightarrow (B \Rightarrow A); S is the rule (A \Rightarrow (B \Rightarrow C)) \Rightarrow ((A \Rightarrow B) \Rightarrow C); and I is (A \Rightarrow A).

Given any lambda calculus expression, you can rewrite it as a chain of SKIs. (If you're interested in seeing how, please just ask in the comments; if enough people are interested, I'll write it up.) What the author of the post id is show how to implement the S, K, and I combinators in Scala types. 

trait Term {
  type ap[x <: Term] <: Term
  type eval <: Term
}

He's created a type Term, which is the supertype of any computable fragment written in this type-SKI. Since everything is a function, all terms have to have two methods: one of them is a one-parameter "function" which applies the term to a parameter, and the second is a "function" which simplifies the term into canonical form.

He implements the S, K, and I combinators as traits that extend Term. We'll start with the simplest one, the I combinator.

trait I extends Term {
  type ap[x <: Term] = I1[x]
  type eval = I
}

trait I1[x <: Term] extends Term {
  type ap[y <: Term] = eval#ap[y]
  type eval = x#eval
}

I needs to take a parameter, so its apply type-function takes a parameter x, and returns a new type I1[x] which has the parameter encoded into it. Evaluating I1[x] does exactly what you'd want from the I combinator with its parameter - it returns it.

The apply "method" of I1 looks strange. What you have to remember is that in lambda calculus (and in the SKI combinator calculus), everything is a function - so even after evaluating I.ap[x] to some other type, it's still a type function. So it still needs to be applicable. Applying it is exactly the same thing as applying its parameter.

So if have any type A, if you write something like var a : I.ap[A].eval, the type of a will evaluate to A. If you apply I.ap[A].ap[Z], it's equivalent to taking the result of evaluating I.ap[A], giving you A, and then applying that to Z.

The K combinator is much more interesting:

// The K combinator
trait K extends Term {
  type ap[x <: Term] = K1[x]
  type eval = K
}

trait K1[x <: Term] extends Term {
  type ap[y <: Term] = K2[x, y]
  type eval = K1[x]
}

trait K2[x <: Term, y <: Term] extends Term {
  type ap[z <: Term] = eval#ap[z]
  type eval = x#eval
}

It's written in curried form, so it's a type trait K, which returns a type trait K1, which takes a parameter and returns a type trait K2.

The implementation is a whole lot trickier, but it's the same basic mechanics. Applying K.ap[X] gives you K1[X]. Applying that to Y with K1[X].ap[Y] gives you K2[K, Y]. Evaluating that gives you X.

The S combinator is more of the same.

// The S combinator
trait S extends Term {
  type ap[x <: Term] = S1[x]
  type eval = S
}

trait S1[x <: Term] extends Term {
  type ap[y <: Term] = S2[x, y]
  type eval = S1[x]
}

trait S2[x <: Term, y <: Term] extends Term {
  type ap[z <: Term] = S3[x, y, z]
  type eval = S2[x, y]
}

trait S3[x <: Term, y <: Term, z <: Term] extends Term {
  type ap[v <: Term] = eval#ap[v]
  type eval = x#ap[z]#ap[y#ap[z]]#eval
}

Michid then goes on to show examples of how to use these beasts. He implements equality testing, and then shows how to test if different type-expressions evaluate to the same thing. And all of this happens at compile time. If the equality test fails, then it's a type error at compile time!

It's a brilliant little proof. Even if you can't read Scala syntax, and you don't really understand Scala type inference, as long as you know SKI, you can look at the equality comparisons, and see how it works in SKI. It's really beautiful.

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