Is it okay to go on to chapter 4?

Hardly anyone has written anything about Chapter 3, so it may be too soon to move on to Chapter 4, but I really like it.

It's quite long and involved, so perhaps there will be many posts about Chapter 4 and we'll discuss it long enough to let everyone catch up.

The first thing I liked about Chapter 4 is the poetic language. The undeserved miracle of mathematics, the light scattering off sheets of metal, the dance of subatomic particles, the Ionian Enchantment, the emotional consequences of having our alarm clock vaporized by an alien laser -- what a lovely chapter!

I also like spacetime. It seems to me to fix a lot of the things about space and time individually that make us dizzy. And, while I was a bit dismayed to see the Aging Twin again, I thought they did a good job at presenting the paradox in a slightly newer and more interesting way.

What did you guys like in Chapter 4?

The Aged Twin

In one of the Science of the Discworld books (I'm too lazy to go check) the authors joke that it is required by the union of science writers that they mention Schroedinger's cat and the twin who flies off on a rocket ship and comes back to find his twin back home all aged and decrepit.

In another book on physics (again, I'm too lazy to get the reference unless someone asks for it), the author has exhausted all sorts of thought experiments and goes on to say that there is "a real example": the aged twin.

In what sense, I want to ask the guy, is that "real"? It has never happened that someone has traveled off at the speed of light and come back all rested-looking. I have always found it very irritating that physicists can take something completely imaginary like this and think of it as observable data.

I was therefore really happy to read about the muons. I had not heard of this experiment before, and -- since I've always accepted relativity on faith -- I'm really happy that technology has advanced to the point at which it is possible to have measurable, observable confirmation of the theory.

I'm still sort of irritated by Figure 2, though. I read this chapter while giving an exam and found that on the way home everything I looked at had arrows and little letters on it. Do you know what I mean? You look at a building and there's the hypoteneuse of the triangle formed by the wall and the ground, in imaginary dotted lines. I figure this must happen to other people sometimes, not just to me, because I see it in movies sometimes.

But Figure 2 means nothing to me at all.

So this was my favorite part of chapter 3 -- the opportunity to get rid of the Aged Twin.

What was your favorite part?

An Interlude for Philosophy of Science

Wired Magazine has an article this month about a philosophy of science guy who followed top scientists around to see what they did with surprising data. Data, that is, that contradicts their hypotheses.

They throw it out.

Our book has talked quite a bit about the importance of experimental confirmation of mathematical conclusions about physics, and it is written by guys willing to push the envelope. Yet, in discussing the idea that Einstein was able to do his paradigm-changing work because he was an outsider (a suggestion made in the Wired article), they caution us that loonies like to use that idea to justify their looniness.

Scientists faced with surprising data, the Wired article says, assume that they've made a mistake and toss the data even though following it up might lead to bold new ideas. They look for problems with the method, errors in their calculations, and bugs in the software. The authors posit that this is because we humans just have a hard time giving up the stuff we believe is true, even in the face of new information.

I think our discussions here show that, at least a little bit. Faced with not-terribly-new ideas from 20th century physics which clash with our direct experience of the world, we're having a bit of a hard time with the cognitive dissonance the clash engenders.

Math and the Ether

There were two things I really liked in chapter 2.

First, the ether. I remember the ether from my Philosophy of Science class; I've always been fond of it. The physicists of the 19th century assumed that, just as sound moves through things like air or water, light must also move through something. They called that something "the ether" and worked diligently to find some evidence of its existence. Chapter 2 describes some of that painstaking work, and reveals that no evidence could be found.

Our prof asked us what this meant, and we said it meant that the ether didn't exist. He corrected us: you can't prove that something doesn't exist, he said, but it did prove that it didn't matter. If something has no observable effects, then it doesn't matter whether it exists or not.

The other thing I liked in this chapter was the discussion of the place of math in physics. I've always had some trouble with the idea that having the math come out right proves something about the universe. I particularly have trouble with the idea that having the math come out wrong allows us to posit random stuff (multiple universes, for example) to make the math come out right, and then behave as though it must actually exist in reality.

Isn't that sort of like deciding that the existence of an extra chair at the table proves that there must actually be another dinner guest?

Where Are We?

Before we leave chapter 1 (have we all got our books now?) I'd like for us to talk a bit more about the question of location.

We've talked about motion and the fact that "Who moved?" is an impossible question when everything is moving in different ways. Rosie said that made her feel like she was falling down the rabbit hole, which made a lot of sense to me.

In the book, the authors also talk about the idea of being able to plot things out on a grid. We can start with the longitude and latitude of the earth, a system which works very well, and extend it out infinitely into space. That, then, can be the box in which things move around. If we do this, then even if things are moving around, we can still say where they are.

I think this is the image we grew up with, in which we can say that Mars will be visible in the evening sky to the west, just above the horizon, or that the Big Dipper shows us true North and stuff like that. We recognize that we're moving, but we carry our imaginary grid around with us, and say where things are in relation to ourselves.

Once we give up the idea that "in relation to ourselves" is an adequate position to take, then we have to give up the idea that things really are in a particular place. If there isn't any unmoving spot at which to anchor the grid, then the grid itself becomes meaningless, and we can no longer say that something occupies a location.

I read an explanation of relativity once that talked about loud music in the park. For people, who can get up and move away easily to a place where the sound is quieter, it makes perfect sense to think of the volume as relative to your location (your location relative to the source of the sound, that is). We have no trouble with the concept of sound that is louder when you're closer to the source and softer when you move away.

But for a snail, which couldn't leave the area before the end of the music, it would seem preposterous to talk about loudness being relative.

So I guess that's why we have to think about outer space before we can grasp the idea of space and motion being relative in any useful way.

Space and Time

In this first chapter our authors set out to prove to us that there is no such thing as absolute motion. Meaning, of course, that all things are moving so there is no single stationary thing with which we may prove we have moved. Using the Law of Non-contradiction they also sort of address the issue of absolute time, though in nowhere near the detail used when dealing with space and motion.

As I mentioned before, I have a lot of trouble coming to terms with the idea of an unending void, yet I found that I have no trouble whatsoever with the idea that everything is orbiting around something else with no clear center at all. It is possible that this is just an idea to which I have become accustomed thanks to so many hours of public education, but in truth it seems reasonable.

Rational, even.

That leads me, then, to this question: If all motion is relative, then what aspect (if any) can be considered absolute? Distance? Speed? Though is speed specifically a relationship between time and distance... keeping in mind that time is apparently relative, as well?

While we wait for our books to arrive...

The introduction to the book asks us to think about space and time. It suggests that we might think of space as limitless vistas punctuated by planets, or golden ships with people named "Buzz."

I was sort of taken aback by that. I don't think "outer space" when I hear the word "space" in the context of physics. Do you? I think as much of the space between the molecules of an apparently solid surface as I do of the space between planets.

As for time, I don't really believe in it. Someone said, "Time is God's way of making sure everything doesn't happen at once." Or Nature's way, if you prefer anthropomorphism to deism. But that makes sense to me. I think we define movement or change or things like that in terms of time because it's measurable and tidy that way.

Like dividing writing up into paragraphs. It's right and proper and even natural to do so, but it's still a convention. Thoughts don't actually occur in paragraph form.

So these are my random thoughts about time and space. I don't think I've given anything away or gone ahead for those of you who are still waiting for the arrival of your books, but I think it would be interesting to know your current idea of time and space. Then we can see whether our ideas about these things change as we read.

Write in the comments, if you like, or ask Rosie to invite you in as an author so you can write on this page if you prefer. I'm really looking forward to hearing (or seeing) everyone's thoughts.

Why Does E=mc2 (and why should we care?)