50K walk (training)

Today was my last major training day prior to the FANS 24 hour walk . I took advantage of a free Friday to get in a 50K (31 mile) training walk; my longest since, well, the FANS race last June.

The day started off a bit chilly but warmed up as I went. Still, I wore long sleeves the whole way. I started off at the trail head (ok, it is really a paved bikepath) across the street from the Fon Du Lac building and I walked out to the 1.5 mile sign on the Morton Spur (that is, the length of the trail to the ball field and railroad light then onto the spur) and then back; the out was 1:18 and the back was 1:17 for 2:36 at 11 miles. On this initial leg, I saw tons of rabbits and a woodchuck.

The next leg was to the 1 mile sign (for a bit more than 5 miles each way). I decided to do some 3-2 (3 harder, 2 easier) to freshen things up. I heard someone in the background; it was a woman who was powerwalking and slowly creeping up on me. Very rarely does another walker overtake me.

She finally caught up at the 2 mile mark (13 miles total, 3:03) and said “good morning” as she passed me. She kind of looked like one of those “fitness instructors” and was just pumping her arms away. I smiled and said hi back; she pulled ahead of me by a few yards and my watch beeped; time for another pick up.

As I closed on her she really tried to ramp it up; just pumping away. I should have let it go, but I didn’t want her to get too smug. So I kept my scheduled pick-up and focused on walking techinque; I started to pull ahead.

This time I didn’t slow down for my recovery intervals; she was soon way behind me.

But I noticed that I was at 52:XX just at 4 miles and 1:06 at the next turn around; I didn’t mean to pick it up that much. I was 3:42 at mile 16.

The way back was downhill (you climb about 350 feet on the out leg) and that was a bit slower without Ms. Fitness instructor to push me. Still 1:07 wasn’t a bad return leg and 4:49 is an acceptable 21 mile split.

But then I was tired; the last two out and backs were a more realistic 1:13; I was 6:02 at the marathon mark (46 minutes faster than 5 days ago) and 7:01 at 30 miles for a 7:16 finish.

One scare: I felt some shallow, almost skin pain across the instep of my right foot; it went away when I removed my tape. I must have gone a bit too high up on my tape job.

Science

Physics and Cosmology
Neil Turok talks about the big bang, problems, and models for the universe.

This is a bit of a dense read, but very interesting, especially if you have a mathematics or a physics background.

Here are some highlights (and yes, this is only a small part of the article):

“In recent years, the search for the fundamental laws of nature has forced us to think about the Big Bang much more deeply. According to our best theories — string theory and M theory — all of the details of the laws of physics are actually determined by the structure of the universe; specifically, by the arrangement of tiny, curled-up extra dimensions of space. This is a very beautiful picture: particle physics itself is now just another aspect of cosmology. But if you want to understand why the extra dimensions are arranged as they are, you have to understand the Big Bang because that’s where everything came from.”

NEIL TUROK holds the Chair of Mathematical Physics in the department of applied mathematics and theoretical physics at Cambridge University. He is coauthor, with Paul Steinhardt, of Endless Universe: Beyond the Big Bang.

[...]

But in the 1960’s, when the observational evidence for the Big Bang became very strong, physicists somehow leapt to the conclusion that it must have been the beginning of time. I am not sure why they did so, but perhaps it was due to Fred Hoyle — the main proponent of the rival steady-state theory — who seems to have successfully ridiculed the Big Bang theory by saying it did not make sense because it implied a beginning of time and that sounded nonsensical.

Then the Big Bang was confirmed by observation. And I think everyone just bought Hoyle’s argument and said, oh well, the Big Bang is true, okay, so time must have begun. So we slipped into this way of thinking: that somehow time began and that the process, or event, whereby it began is not describable by physics. That’s very sad. Everything we see around us rests completely on that event, and yet that is the event we can’t describe. That’s basically where things stood in cosmology, and people just worried about other questions for the next 20 years.

And then in the 1980s, there was a merging of particle physics and cosmology, when the theory of inflation was invented. Inflationary theory also didn’t deal with the beginning of the universe, but it took us back further towards it. People said, let’s just assume the universe began, somehow. But, we’re going to assume that when it began, it was full of a weird sort of energy called inflationary energy. This energy is repulsive — its gravitational field is not attractive, like ordinary matter — and the main property of that energy is that it causes the universe to expand, hugely fast. Literally like dynamite, it blows up the universe.

This inflationary theory became very popular. It made some predictions about the universe, and recent observations are very much in line with them. The type of predictions it made are rather simple and qualitative descriptions of certain features of the universe: it’s very smooth and flat on large scales; and it has some density variations, of a very simple character. Inflationary theory predicts that the density variations are like random noise — something like the ripples on the surface of the sea — and fractional variation in the density is roughly the same on all length scales. And these predictions of inflation have been broadly confirmed by observation. So people have become very attracted to inflation and many people think it’s correct. But inflationary theory never really dealt with the beginning of the universe. We just had to assume the universe started out full of inflationary energy. That was never explained.

My own work in this subject started about ten years ago, when I moved to Cambridge from Princeton. There I met Stephen Hawking, who, with James Hartle, developed a theory about how the universe can begin. So I started to work with Stephen, to do calculations to figure out what this theory actually predicted. Unfortunately, we quickly reached the conclusion that the theory predicted an empty universe. Indeed, this is perhaps not so surprising: if you start with nothing, it makes more sense that you’d get an empty universe rather than a full one. I’m being facetious, of course, but when you go through the detailed math, Hawking’s theory seems to predict an empty universe, not a full one.

So we tried to think of various ways in which this problem might be cured, but everything we did to improve that result — to make the prediction more realistic&mdashspoils the beauty of the theory. Theoretical physics is really a wonderful subject because it’s a discipline where crime does not pay in the long run. You can fake it for awhile, you can introduce fixes and little gadgets which make your theory work, but in the long run, if its no good, it’ll fall apart. We know enough about the universe and the laws of nature, and how it all fits together, that it is extremely difficult to make a fully consistent theory. And when you start to cheat, you start to violate special symmetries which are, in fact, the key to the consistency of the whole structure. If those symmetries fall apart, and then the whole theory falls apart. Hawking’s theory is still an ongoing subject of research, and people are still working on it and trying to fix it, but I decided, after four or five years, that the approach wasn’t working. It’s very, very hard to make a universe begin and be full of inflationary energy. We needed to try something radically different.

[....]

Something I’m especially excited about right now is that we have been working on the finer mathematical details of what happens at the Bang itself. We’ve made some very good progress in understanding the singularity, where, according to Einstein’s theory, everything becomes infinite; where all of space shrinks to a point, so the density of radiation and matter go to infinity, and Einstein’s equations fall apart.

Our new work is based on a very beautiful discovery made in string theory about ten years ago, with a very technical name. It’s called the Anti-De Sitter Conformal Field Theory correspondence. I won’t attempt to explain that, but basically it’s a very beautiful geometrical idea, which says that if I’ve got a region of space and time, which might be very large, then in some situations I can imagine this universe surrounded by what we call a boundary — which is basically a box enclosing the region we are interested in. About ten years ago, it was shown that even though the interior of this container is described by gravity, with all of the difficulties that brings&mdashlike the formation of black holes and the various paradoxes they cause — all of that stuff going on inside the box can be described by a theory that lives on the walls of the box surrounding the interior. That’s the correspondence. A gravitational theory corresponds to another theory which has no gravity, and which doesn’t have any of those gravitational paradoxes. What we’ve been doing recently is using this framework to study what happens at a cosmic singularity which develops in time, within the container. We study the singularity indirectly, by studying what happens on the surface of the box surrounding the universe. When we do this, we find that if the universe collapses to make a singularity, it can bounce, and the universe can come back out of the bounce. As it passes through the singularity, the universe becomes full of radiation–very much like what happens in the colliding brane model — and density variations are created.

This is very new work, but once it is completed I think it will go a long way towards convincing people that the Big Bang, or events like it, are actually describable mathematically. The model we’re studying is not physically realistic, because it’s a universe with four large dimensions of space. It turns out that’s the easiest case to do, for rather technical reasons. Of course, the real universe has only three large dimensions of space, but we’re settling for a four-dimensional model for the moment, because the math is easier. Qualitatively, what this study is revealing is that you can study singularities in gravity and make sense of them. I think that’s very exciting and I think we’re on a very interesting track. I hope we will really understand how singularities form in gravity, how the universe evolves through them, and how those singularities go away.

I suspect that will be the explanation of the Big Bang — that the Big Bang was the formation of a singularity in the universe. I think by understanding it we’ll be better able to understand how the laws of physics we currently see were actually set in place: why there is electro-magnetism, the strong force, the weak force, and so on. All of these things are a consequence of the structure of the universe, on small scales, and that structure was set at the Big Bang. It’s a very challenging field, but I’m very happy we’re actually making progress.

[...]

The current problem which is dominating theoretical physics — wrongly, I believe, because I think people ought to be studying the singularity and the Big Bang since that’s clearly where everything came from, but most people are just avoiding that problem — is the fact that the laws of physics we see, according to string theory, are a result of the specific configuration of the extra dimensions of space. So you have three ordinary dimensions, that we’re aware of, and then there are supposed to be six more dimensions in string theory, which are curled up in a tiny little ball. At every point in our world there would be another six dimensions, but twisted up in a tiny little knot. And the problem is that there is a huge number of ways of twisting up these extra dimensions. Probably, there are an infinite number of ways. Roughly speaking, you can wrap them up by wrapping branes and other objects around them, twisting them up like a handkerchief with lots of bits of string and elastic bands wound around.

This caused many people to pull their hair out. String theory was supposed to be a unique theory and to predict one set of laws of physics, but the theory allows for many different types of universes with the extra dimensions twisted up in different ways. Which one do we live in? What some people have been doing, because they assume the universe simply starts after the Bang at some time, is just throwing a dice. They say, okay, well it could be twisted up in this way, or that way, or the other way, and we have no way of judging which one is more likely than the other, so we’ll assume it’s random. As a result, they can’t predict anything. Because they don’t have a theory of the Big Bang, they don’t have a theory of why those dimensions ended up the way they are. They call this the landscape; there’s a landscape of possible universes, and they accept that they have no theory of why we should live at any particular place in the landscape. So what do they do?

Well, they say, maybe we need the anthropic principle. The anthropic principle says, the universe is the way it is because if it was any different, we wouldn’t be here. The idea is that there’s this big landscape with lots of universes in it, but the only one which can allow us to exist is the one with exactly the laws of physics that we see. It sounds like a flaky argument&mdashand it is. It’s a very flaky argument. Because it doesn’t predict anything. It’s a classic example of postdiction: its just saying, oh well, it has to be this way, because otherwise we wouldn’t be here talking about it. There are many other logical flaws in the argument which I could point to, but the basic point is that this argument doesn’t really get you anywhere. Its not predictive and it isn’t testable. The anthropic principle, as it’s currently being used, isn’t really leading to any progress in the subject. Even worse than that, it is discouraging people from tackling the important questions, like the fact that string theory, as it is currently understood, is incomplete and needs to be extended to deal with the Big Bang. That’s just such an obvious point, but at the moment surprisingly few people seem to appreciate it.