String Theory Cribsheet

By Sean Carroll | April 18, 2007 12:13 pm

String Theory Cribsheet SEED has come out with it’s latest Cribsheet, this one on String Theory. The Cribsheets are very handy one-page summaries of some fascinating science issue. The latest one is pretty good; it only refers glancingly to the anthropic principle, which is a much more accurate view of the state of discussion about string theory than one would get by reading blogs. Clifford was apparently a consultant. You can see it in gif or as a pdf.

Previous Cribsheets include:

  1. Stem Cells
  2. Climate Change
  3. Avian Flu
  4. Hybrid Cars
  5. Nuclear Power
  6. Hurricanes
  7. Extinction
  8. The Elements

With the latest one, we seem finally to have escaped the tyrrany of the mesoscopic. I predict that the next one will involve cosmology or astrophysics. Unless they are going to count The Elements, whose origin does after all take place in the sky. Perhaps some day we will get quantum mechanics.

  • Thomas

    Just checked the one one climate change: “Clouds are made up of concentrated greenhouse gas”. Who writes this stuff anyway?

  • Sean

    People who know what a greenhouse gas is?

  • BG

    What’s wrong with that statement? They explain below (previously, if you read by number) that water vapor is a greenhouse gas. Which is perfectly true; in some ways it’s more effective than CO2.

  • wolfgang

    The Hydrogen atom looks a bit funny on this string theory cribsheet.
    It seems to have 4 electrons and an extra nucleon…

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  • Peter Woit

    “The Issue: Is It Real?”

    “…string theory’s rich diversity makes it difficult to derive any clear predictions”

    I guess that’s one way of saying it is an ugly mess that can’t predict anything.

    “particle physics experiments being performed with collisions of very heavy ions at Brookhaven National Laboratory… could connect string theory with reality.”

    Not mentioning that the “string theory” in question that may or may not get connected to reality at BNL is a different one than the one described in the rest of the document might accidentally mislead some readers. Of course I’m sure no one intends that to happen.

    I’m all in favor of promoting public understanding of science, but how about, as far as physics goes, keeping things like “The Elements” and “String Theory” separate? Why not explain to people some of the beautiful science that we actually have evidence for, like the Standard Model, instead of giving them slick sales jobs about highly speculative ideas that aren’t working out very well?

  • John Faughnan

    Nice stuff, but GIF is an odd choice as a display format. It’s not 1994 any more! Let’s get them to switch to PNG.

  • John Faughnan

    BTW, they show the proton as 10**-14m. I thought the electron was about 10**-13 to 10**-14m, so the proton should be maybe 10**-10m. Of course I’m more likely wrong …

  • B

    I really like it, it is very to the point and accurate. But the illustrations I find extremely poor. Esp. the one with the Calabi Yau’s. Not only does it look ugly, it also doesn’t become clear at all why these … heaps? … are in this lattice like shape. Also, I wonder who was responsible for choosing the pink in the large figure, it doesn’t go with the red from the headings. And the M-theory figure… maybe someone can explain me what was wrong with the star-shaped one? The one they used seems to indicate ‘the five known formulations’ are themselves large areas, and it also suggests some kind of 5-fold symmetry.

  • Roman

    I think I’ve seen the first direct manifestation of string related effect – the string image at the “scale” illustration has expanding or pulsating center (look at pdf version and not directly at the “string” center but close by). Now explain this! (or do I need a drink)

  • Neil B.

    I can see the usefulness of “strings” for building up and explaining particles. However, as for “space-time” the realm of action for the particles, I think that not enough attention is paid to consistency of classical field theory applied to different dimensions. That seems to be a passé pastime, but there are things which do not really work out consistently when the number of large space dimensions is not three. (I mean physical issues of conservation, propagation, etc; not as per unstable orbits or distorted waves making life impossible or difficult.) The “why” for space seems to work from the top down, not the ground up. Somehow the two have to be consistent with each other, of course.

  • Ben L

    Jonh, #8,

    I think the proton is more like 10**-15m. Atoms are about 10**-10m. Electrons have no size at all, at least as far as we are able to tell. I believe current limits are at least around 10**-17m, although I could be way off on that one.

  • Lab Lemming

    Sean, the “elements” crib isa basically cosmology in disguise. Half the sheet is about the big bang, and the other half is about stars, cramming in fusion and S,R process nucleasynthesis without actually mentioning them by name or discribing how they differ.

    According to the chart of elemental abundances, No elements heavier than tin exist, and fluorine has been relabeled as sodium.

    There is absolutely no mention of chemistry whatsoever.

  • Thomas

    Sean and BG, yes water vapor is a greenhouse gas, but clouds are not made of water vapor but of water droplets. Liquid water. Clouds affect the climate by *reflecting* visible as well as infrared light, not by absorbing IR as a greenhouse gas would. I suppose in some way you can call a liquid a concentrated gas, but it is misleading in this case.

  • BG

    Thomas: to say clouds are made of water droplets is as much of an oversimplification as to say that they’re water vapor. Clouds are a complicated equilibrium between condensing water droplets (or even ice crystals) and air that is saturated with water vapor. The actual lifetime of a droplet isn’t terribly long; they re-evaporate as they fall through the cloud.

    Clouds reflect visible light and maybe some near IR, but they definitely do not reflect all IR wavelengths the way they do optical. The details depend on cloud composition. I’m sure you know that clouds have a very complicated effect on climate modeling; they’re probably one of the biggest sources of uncertainty, and volumes have been written about them.

    Anyway, given the rather ridiculous task of simplifying a huge research area down to one page, statements like “Clouds are made up of concentrated greenhouse gas” are probably unavoidable.

  • Khurram

    SEED is a great magazine. Although, when I first started reading it, I was a little taken aback. I was not used to seeing scientists glorified in this way before. It makes us seem hip and trendy. I still do not know how I feel about this but as long as they keep up the good writing, it’s OK.

  • Hektor Bim

    The sentence about “string theory’s rich diversity” is quite strange. What diversity are they talking about – is there Latino string theory? Rich diversity seems like exactly what you don’t want in a theory. What you want is clarity and simplicity, which leads to a diverse array of predictions. It’s precisely in the range of diverse predictions that string theory is not diverse at all.

  • Thomas

    BG, clear sky can also be saturated with water vapor. What makes a cloud a cloud is the water that has condensed to water or ice. The lifetime of the individual droplets may be interesting if you want to explore the dynamics further but doesn’t change the basic fact that clouds do not consist of water vapor. No matter how far you want to simplify the science that is simply a lousy description.

    Wikipedia, for example, starts its article as:
    “A cloud is a visible mass of condensed droplets or frozen crystals suspended in the atmosphere above the surface of the Earth or another planetary body. “

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  • slinkybender

    I freind described the problem with string theory is that different people will come to different conclusions given the same set of data because it’s realy more of a belief system than a true science.

  • Doug

    The depicted sinusoidal strings [in 2D?] are probably helical strings in 3D.

    This likehood seems to be well explained at this wevsite:

    Copyright 1998 All Rights Reserved C. Langton,
    Complex representation of Fourier series
    [Euler’s identity: -1 = e^{iPI}] = e^{jwt} = cos wt + i sin wt (1)
    Figure 3 — e^(jwt) plotted in three dimensions is a helix
    In Figure 3 cos wt is plotted on the Real axis and sin wt is plotted on the Imaginary axis. The function looks like a helix moving forward in time to the right. The X-Z and the Y-Z projections, if plotted, would be the sine and cosine functions.

  • Don

    Link to the large version seems broken :(


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About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] .


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