Archive for May, 2008

What’s the Biggest Number in the World?

Sunday, May 18th, 2008

They go on forever, of course, but one of the entertaining things about mathematics is its habit of defining and naming fabulously large numbers. This can also be useful. The Romans could barely write down the number of citizens in their empire. These days Roman numerals couldn’t write down the number of people on the planet. Not all number systems are created equal.

Millions

The Roman’s could count up to a few million, which turned out to be enough for them. (It is not a coincidence that people never “need” math that hasn’t been invented yet. That’s for essentially the same reason that programmers never need features the programming languages they know don’t have. It’s hard to think things you don’t have language for.)

Googols

Indian place notation made “orders of magnitude” meaningful – every new column increases the size of the largest number by a factor of 10, and that turns out to be plenty for the physical world. There are about 10^80 elementary particles in the universe. And even if we turn out to be missing 99.999999% of the universe, that still doesn’t takes us to 10^90.

Stupid Big

But while the number of “things” is relatively small, the number of relationships between things grows shockingly fast. If there are 20 people at your party there are 171 introductions to make. If you have four tables of five there is a truly ridiculous 11 billion ways of assigning guests to tables.

Does that matter? Sometimes it does. There areĀ  53,644,737,765,488,792,839,237,440,000 different ways to deal a deck of cards to four players. This is a giant number – at one deal per millisecond that’s still about a hundred million times the age of the universe. And yet, if you play cards you care about this number. This is the basis of card odds in Bridge. Sometimes money is at stake.

Stupid Big, But Still Useful

If you think about it, it is extremely odd that such a practically uncountable number could ever have a practical use. This, I think, is one of the distinctive features of mathematics, and one that can either make it seem pointless – why should I care about numbers so big we can never count them? – or almost supernatural.

Here we have tools that let us calculate numbers so large we can’t possibly count to them, and yet we can reason about them, and come to practically important conclusions. We start in reality – 52 cards – we fly off into a fairy land of numbers so big we sometimes need new notations to write them down, and we come back with a discovery that lets us beat the other guy at poker.

Let’s hear it for fairy land.

Who Needs Algebra?

Thursday, May 15th, 2008

One of the biggest questions about mathematical education has to be: Why bother? Anyone teaching math gets lots of practice answering that. It’s a good question.

There are two types of justification, the aesthetic and the practical. The aesthetic case is actually the easy one. Math is one of the least obvious, most complex, profound and uniquely creative things our species has done, right up there with music, painting and dancing. As a liberal art math needs no justification: if you want to understand the glory of what it is to be human then you need to be understand something of these spectacular creations.

But if that was all there was then we certainly wouldn’t be spending all this money teaching math. We had no problem dropping music from the curriculum. (Doubly unfortunate given that music lessons help math scores.) Math is taught for economic reasons: we think the return justifies the expense.

It probably does, but there are many unexamined assumptions here. Consider some justifications for teaching math.

  • it’s useful
  • it’s good for the brain
  • it separates the wheat from the chaff
  • engineers need it, and we need engineers
Usefulness

It’s only useful if you use it, or if being able to use it unlocks some new ability. (Being able to swim enables me to go on the boat, even if I don’t fall in and never have to swim.) But if you never use it, never consider it, are never empowered by it, can never do something only because you have the knowledge, then it is not useful. A lot of the math people are taught is like that.

Good Brains

Any kind of study is good for the brain. Latin and Greek are excellent. Memorizing decks of cards, wine regions of France, the plays of Shakespeare, all good. The brain is a muscle. Use it and make it strong.

That doesn’t explain why mathematics instead of Greek, but there might actually be an answer to this one. I believe that there are useful, brain reshaping ideas in math that none of us is likely to come up with in a single lifetime. Things like the reductio ad absurdum, like proof by induction. The kind of idea some human being comes up with every few hundred years. Things worth sharing. I believe that there are brain rewiring mathematical ideas that most people should be exposed to. But that needs to be proved. And which specific ideas should be prioritized and taught should be determined by something other than habit and inertia.

Math as Gatekeeper

If you need to narrow down the field then math works about as well as height. If you need to eliminate 50% you can choose one type of math and one cut-off score. If you need to eliminate 90% then, hey, let’s require calculus… If the math skills are needed then fair enough, otherwise this is as unfair as discriminating on any other irrelevant criterion. And yes, I’m talking about requiring nurses to know algebra.(this caused a stink) I want nurses to be bright. I’m not sure that requiring algebra measures the kind of smarts that really matter. I might be wrong, but it isn’t obvious. Using math as a proxy for an IQ test is just dishonest, and lazy.

We Need the Eggs

Suppose traditional math education ruined almost everyone’s chances of understanding or enjoying math. And suppose that the only way to train engineers, physicists, quants, etc, was to teach them that way from an early age, before they could even be identified as prospective quants. If that were true then it might well be worth teaching everyone that way. We do need the engineers. (Under the right circumstances even I would swap understanding how the defibrillator works for having a defibrillator.) But this is implausible. Colleges and universities need to be fed numerate students, and the burden imposed on them by the need to supply remedial math classes is considerable, but if the best answer we can come up with is to teach in ways that are known not to work for most people then we need to keep looking.

What To Do?

What is useful and necessary? It depends on personal accident, but there are probably lots of overlaps. This is the kind of thing a rational; research policy would research: what math gets used? What is unknown but of most value? We already spend an unimaginable fortune on math education (This is the good news. Can you imagine how jealous art teachers are right now?), we could spend a few more bucks on measuring needs and results. Every scrap of curriculum needs to earn its place. Historical importance is no more relevant in math than any other historical importance. The speeches of Cicero are of enormous historical importance, but we gave up teaching Latin. Quadratic equations are the Cicero of high school mathematics.

What actually is good for the brain? (This is a special case of ‘usefulness’.) And it’s an empirical question. We ought to be able to answer it and to agree upon the answer.

What do engineers need to learn, and when? In most things we learn what we need to know close to having to use it. That helps with motivation, understanding, and retention. On the other hand musicians, sportsmen and dancers, are generally considered to need an early start. That might also be true for mathematicians. This is an interesting and difficult question, but it’s the right question.

There are real questions here, and issues that should generate research instead of debate. Rather than argue about the facts we should find out what they are.