Chapter 8

The final chapter of the book has some interesting points. It goes over the warping of spacetime (gravity, you see, is not so much a force as it is like putting something heavy on a mattress so that things go down toward the heavy thing when they think they're going straight) and the experimental and experiential evidence for relativity.

I like the fact that there is direct evidence for it.

There is a also a section in which we imagine multiple tiny physicists in tiny individual elevators, which might make a nice allover pattern for quilting cotton or something.

We are then reminded (or informed, if we didn't already know it) that quantum theory and the theory of relativity don't work together. They both seem to be right, to the extent that we can determine their rightness, but they can't both be right at the same time.

Job security for physicists.

The authors also point out -- or, I hope, remind us -- that we only get the new knowledge that allows us to have new technology (like lasers, GPS, and the internet) when we allow people freedom to think about stuff that doesn't necessarily have an obvious and immediate usefulness. And when we also educate people in ways that encourage such thought.

I found this an enjoyable and satisfying book. How about you?

Chapter 7

Chapter 7 is primarily about the Master Equation, which contains hidden within it, largely just because of symmetry, all the important things in the whole universe!

I've read the explanation several times, and have to confess that I haven't been able to get really excited about the Master Equation. I understand how cool it is that this equation explains everything, but a) I don't find myself convinced that it really does, and b) I'm just not feeling it.

No, the thing about chapter 7 that really seemed exciting to me is the fact that the sun is a very inefficient source of energy.

This totally amazes me. I think of the sun as a fantastic source of energy, probably the best, but it's not well designed at all.

Or -- and this is the thing that occupied my thoughts most -- perhaps efficiency is not the point of the universe.

I guess the reason that this came to my mind so strongly is that when I read chapter 7, a couple of weeks ago, I was also working on a biology lesson for Artsedge. The original author of the lesson stated baldly that reproduction is the most important process for living organisms. From a biological perspective, this is true.

And yet, think how little of what we humans do is actually effective in terms of reproductive success! Survival, of course, and work and caring for our families -- all these things contribute to our overall reproductive success. But think of all the time we waste on video games, and music, and gourmet cooking, and yoga, and reading about physics...

We're highly inefficient living organisms. And yet we are arguably more interesting and impressive than the mayfly, just as the sun is arguably more impressive than a light bulb.

I'm not the only one who could post...

I'm just the one who gives in first and does it.

So, how cool is chapter 6? I admired the slippery way in which the authors went from the philosophically intense issue of how and whether we should respond to all mass and energy by saying, "Ooh! That could run my X Box 360!" to the fascinating world of white dwarfs and black holes.

Not new to me, all that stuff about stars, but I confess that I have always previously skipped the math. Inspired by Darin's habit of doing the sums when he sees them in the book, I actually read the calculations, so I learned new things.

What did the rest of you like about Chapter 6? and do you want to have a bit of civilized debate about whether harnessing as much power as possible is necessary or wise?

There's a wonderful book about the Manhattan project called Brighter Than a Thousand Suns which says that it was that project that ended the option, for scientists, of saying "We're just learning stuff. We're innocent of what gets done with what we discover." The split between science (beautiful, pure, and clean) and technology (worldly, greedy, profit-centered) is gone, now.

What do you think?

So... Chapter 5

Here's my synopsis of Chapter 5. I'm still hoping that someone will help me out:

1. Everything travels through spacetime at speed c, which is to say at the speed of light. However, light travels only in space, not in time. Everything else does some of its traveling in time. Therefore, we don't get from place to place as fast as light does. In fact, we move so slowly (that is, we use so much of our share of c on traveling in time) that our experience of spacetime is quite different from light's experience -- or what light's experience would be if it were sentient.

2. We can think of distances between two points in space (Fayetteville and Shreveport) or two points in time (5:00 and 6:00). We can also think about two points in spacetime (waking up in bed and breakfast at the kitchen table). If the distance needs to have a direction, then we can think of it as an arrow, or a vector (studiously ignoring mosquitoes as disease vectors). Depending on what's important, we can describe distances in spacetime by as many as three numbers: length, height, width, and passage of time.

3. The spacetime distance between two points is always the same, mathematically speaking; it can be distributed differently, though. So if we consider the spacetime between my great-grandfather at Ellis Island and me, there's the distance in miles between us of 1314.68 or so; then he was at sea level so I'm higher; I don't know how width could be measured; and then there's the time difference of a century. Presumably, there could have been a great burst of light at Ellis Island at just that moment that the ship arrived from Antwerp and the spacetime between that and me now would be identical to the spacetime between Robert Allen Haden and me -- but it would be taken up entirely by space and not by time.

I have no idea what #3 would mean. "So much," as the authors say, "for vectors."

4. Billiard balls colliding will take off with the same amount of energy with which they collided, but in opposite directions -- except for friction, which spoils this story, so we leave it out. All the energy used in any undertaking is conserved: it doesn't get used up or anything. It's still there, just as the water we're now drinking is the same water the dinosaurs drank. Energy can be stored and used and moved around, but it doesn't diminish.

5. This hooks up with the idea of all the movement through spacetime adding up to c. But it's better because it makes a nicer equation with y.


What am I missing?

Having Trouble with Chapter 5

Knowing that some of the crowd were skiing in Colorado... in Ohio where apparently they have no computers... lazing around eating the remaining Christmas cookies.... I didn't want to forge ahead for fear of leaving anyone behind.

Now that Janet has brought up her concerns about global warming in Chapter 6, though, I feel justified in asking for help with Chapter 5.

I began to feel a little lost right at the point where the observer in the bed has the spacetime distance vector pointing up his time axis. It sounds uncomfortable, and figure 9 isn't helping.

I may be having trouble with vectors. I keep thinking about mosquitoes being vectors for malaria, and then there's the giant arrow to Manchester (I'm thinking of it in electric blue plastic)... Then they bring in hyperbolae and I'm lost.

Why can't we have momentum in time? It seems to me that momentum unavoidably exists in time as well as space. Why do these guys imagine that things are interesting or boring based on stuff like length? Have they actually begun rambling madly, or am I just missing the point?

Your assistance will be greatly appreciated.

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?