"Physics Class" How does the professor explain the closed string?

Narrator: Listen to part of a discussion in a physics class.
Professor Blake:
Okay, you’ll remember that when Einstein was doing his research, uh, the strong and weak forces-they hadn’t been identified yet, but still, he had some questions about the two forces that were generally
accepted at the time-electromagnetism and gravity. You see, Einstein thought that nature, or rather a
theory of nature, a good theory of nature had to be much simpler and, to use his term, more "elegant."
So he spent the next thirty years in an effort to arrive at a... a unified field theory that he assumed...
that.., that would demonstrate how these two forces were really defined by one underlying principle.
    So, today, and that would be about sixty years later; a group of physicists believe that they are close  Q46
to finding that principle in something called the theory of everything.
[Laughter]
    That’s okay. A lot of other equally distinguished physicists are also laughing at this idea. But, anyway,
for the first time in the history of our field, we have, uh, at least, uh, a structure, a framework, with
the potential to explain every fundamental characteristic of the universe. You see, until fairly recently,
we’ve been conceptualizing the particles, that is, the protons, neutrons, electrons, quarks, and everything
else.., we’ve been viewing them as points-very tiny points. But string theory assumes that if we
could really take a look at the particles, and uh, that would have to be with technology that we haven’t
yet discovered, but if we could, then we’d see that the particles aren’t points at all but.., but strings and
these strings are looped back into themselves. Look, think of the strings like a very thin rubber band.  Q47
Oh, and.., and these strings vibrate
Jim:
So everything in the universe is made up of the same thing then? It’s all a combination of... of strings?
Professor Blake:
According to the theory, yes. But of course.., we see differences, and those differences, uh, they’re
accounted for because the vibrations of the strings are different.
Jim: So in physics, you buy into the theory of everything or... or what? Professor Blake:
Well, Jim, the choice isn’t that clear. Um, not at all. There are a lot of scientists in between, and by that
I mean that they see the theory of everything in a more limited way. They think that string theory, and
understand that string theory is incorporated into the theory of everything.., um, that string theory can
explain all of the properties of the forces that cause the particles to interact and influence each other.
Yes, Ellen. Did you have a comment?
Ellen:
Well, a question, really. Wouldn’t it be true that if you understand everything about the... I think you
called it the fundamental characteristics of the universe.., so if you understand that, don’t you understand everything?
Jim:
Wait a minute. So that would mean that we know it all now and there isn’t anything else to discover,
right? Because, uh, everything is physics.., everything is just a reaction between vibrating strings.
Ellen:
I see your point, but you could.., you might look at it as a... as a... starting place to, uh, to build our
knowledge. Dr. Blake, you said that it’d be a structure, didn’t you? So we’d have to fill in a lot of information
but.., we’d have a structure to start with. In my math class we were talking about string theory
because some of the recent advances in mathematics have been possible because of string theory.
Professor Blake:
True enough. And, string theory isn’t finished by any means. It’s evolved from the beginning when we
first started to think about it and, uh, the early models that included both open strings and the closed
strings that I just described to you-the ones that look like a thin rubber band. And there’s a lot of
discussion about vibration or rather various types of vibration. Then there’s the possibility of branes-
b-r-a-n-e-s-which are kind of like closed strings with a membrane over them.
Jim:
But all of this is theoretical, right? Because we don’t have the technology to observe strings-closed or
open-and we certainly can’t verify that there are branes out there.
Ellen:
Sure. But there are some very complex and.., and.., persuasive, uh, mathematical formulas, and
they’re presented in support of the theories. It isn’t like someone’s just dreaming this up without calculations.
Jim:
But I don’t see why we should accept calculations when some of those calculations require us to think
beyond what we can observe.
Professor Blake:
And many physicists would agree with you, Jim. String theory’s unverified. Richard Feynman wrote a
very interesting book, The Character of Physical Law, and to Feynman, to him, the test of any scientific
theory has to be whether the consequences agree with the measurements we take in experiments. Of
course, that assumes that the experiment was performed correctly and, uh, that the calculations were
done without error, but anyway, I think you see the point. Ellen: So you’re saying that string theory requires further developments?  Q48
Professor Blake: What do you think?
Jim:
Well, I tend to be an empirical scientist. I’m a biology major, and I just Want to take something into the  Q49
lab and dissect it,
Professor Blake: Fair enough.
Ellen:
But I’m a physics major and...the idea of a theory of everything appeals to me. I know that we can’t  Q50
observe strings.., yet.., but maybe that’s just a problem with the technology and.., and eventually,
we may be able to observe strings in the laboratory or... or we could find a way to observe strings in a
natural setting and...
Jim: Come on. It’s just conjecture.
Professor Blake:
Well, in fairness, any new theory has to begin as conjecture, but the real question is, can string theory
pass through the developmental stages to a point where it can be verified or rejected. And, uh, these
developments could be in the area of technology like Ellen suggests or perhaps they could be new
methods of performing calculations and, uh, deriving the mathematical predictions. What I’m going to
suggest is that we take a look at the web site that supplements your textbook. There are videos as well
as animations and it includes a really good history of string theory, uh, but that’s not why I want you to
see it. I think the site demonstrates where we need to go from here if we’re going to pursue an ultimate
theory, a... a theory of everything, if you will. And it’s fairly objective so it should provide us with some  Q51
interesting data for both sides of the debate.