Here's What Needs to be Explained

By Sean Carroll | November 15, 2010 7:57 am

The results from this weekend’s question are in: “What is the one concept in science that you really think should be explained better to a wide audience?” I tried to collate the answers from Twitter and Facebook as well as here, at least up to the point where my patience evaporated. Answers below the fold, grouped into three categories: big concepts, specific ideas, and meta issues.

Scott Aaronson wrote, “The skill of sharpening a question to the point where it could actually have an answer.” Which is a skill I should probably try to develop myself, as the question I asked was amenable to different interpretations. Many people answered “evolution,” but as Ed Yong pointed out on Twitter, evolution is actually explained quite well in many places. So when we ask what needs to be explained better, there are at least two issues at work: what we actually do a bad job at explaining, and what doesn’t succeed at penetrating out into the public consciousness. In contrast with evolution, for example, I would say that quantum mechanics is explained in many places, but very rarely is it explained well.

The winner by a wide margin was the meta issue of “the scientific method.” Which raises another question: do we agree on what the scientific method is? I suspect not. But I am completely on board with the idea that “how science works” is not explained very well, and possibly a higher priority than any particular scientific concept.

Others that did well: evolution, statistics, certainty/uncertainty, entropy, quantum mechanics, time, and gravity. I cannot refrain from pointing out that these last four were all addressed at some length in From Eternity to Here. Which makes me think that what people are really saying is, “more folks should read Sean’s book.” Only 40 more shopping days ’till Xmas…

Also of note is that there wasn’t actually a great deal of consensus; the list of concepts that came up is quite long. Clearly we need to do a better job of explaining.

Here are the answers:


  • Evolution (IIIIIIIIII)
  • Entropy/Second Law (IIIIII)
  • Quantum mechanics (IIII)
  • Time (IIII)
  • Gravity (IIII)
  • Genetics (III)
  • Supply and demand
  • Energy
  • Climate change
  • Math
  • Cognition
  • Complexity
  • Emergence
  • Quantum field theory


  • Renormalization (III)
  • Scale of the universe (III)
  • F***ing magnets (III)
  • Curvature of spacetime (II)
  • Deep time (II)
  • Particle/wave duality (II)
  • Gyroscopes
  • Cancer biology
  • Wave equation
  • The Big Bang
  • Entanglement
  • Deformation and torsion
  • Radiation
  • Force-carrying particles
  • Toddler psychology
  • Superposition
  • The holographic principle
  • Seasons
  • The double-slit experiment
  • Decoherence
  • String theory
  • Cognitive biases
  • Duck sex
  • Cognitive illusions
  • Expansion of space
  • Goedel’s incompleteness theorem
  • Comparative advantage
  • Spin 1/2
  • Computational equivalence
  • Laws of thermodynamics
  • Principle of least action
  • Fusion energy
  • Weak interactions
  • Price equation
  • Black body radiation
  • Comparative advantage
  • Effective field theory
  • Chirality
  • Bell’s theorem
  • Gears
  • Climate vs. weather
  • Arrow of time
  • Conservation of energy
  • Free will
  • Tides
  • Membrane theory
  • Particle accelerators
  • Speed of light
  • Exponents


  • The scientific method (IIIIIIIIIIIIII)
  • Statistics (IIIIIIII)
  • Certainty/uncertainty (IIIIII)
  • Falsifiability/testability (II)
  • Time scales
  • Comparing tiny numbers
  • Scientists
  • Occam’s razor
  • Theory
  • Confidence intervals
  • Evidence vs. anecdotes
  • Experimentation
  • Peer review
  • Basic research
  • Null results
  • Science doesn’t prove things
CATEGORIZED UNDER: Science and Society
  • Mirik Smit

    Great list, sir!

    Some topics are super interesting but don’t enter into public mind or practical application (yet) such as entanglement, so those seem low priority for general educative appeal.

    Others aren’t in the public mind but VERY relevant, like entropy and evolutionary biology that are being understood less and less. Time may just be too abstract as a concept to foster any understanding for. It still being there if you don’t understand, us not knowing what to do with it anyways, and all. :-)

    Understanding of scientific method or the scientific theory are great ones, didn’t think of that.

    Cool stuff!

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  • Tevong

    I think it would be nice to see more blogs actually explaining physics rather than *about* physics. 99% of blog posts and pretty much every popular physics article talk about what physicists do, what they’re discovering, what they think about, what they eat, why physics is important etc.. But rarely is anything actually explained in an honest way. “quantum mechanics says this” and “Einstein says that” don’t qualify as explanations. Instead of saying “light is an electromagnetic wave” and expecting people to take your word for it, how about giving a qualitative picture of maxwell’s equations and how the interplay between the induced magnetic and electric fields propagates out in free space. After all faraday did all his work without mathematical training! I guess it’s pretty tough to explain quantum mechanics without maths, but Feynman did a good job in QED so it must be possible.

    I think this contributes to the popular perception that science is just an alternative explanation for things. We don’t expect the layman to think things through for himself, but to just accept what science has discovered as gospel.

    (btw ethan’s blog starts with a bang is a nice example of explanations of how we really know things, like the distance to the stars or the age of the universe. Sean’s post about the quantum zeno effect and non-destructive measurements was also one of the coolest things I’ve read here!)

  • JMW

    And there’s the table of contents for your next book.

  • Droid Boy

    Awsome. So you could say the answer is: It needs more and better explaining.
    Thats absolutely what i would agree about.

    In Germany there is a professor of physics (harals lesch) explaining pretty complicated stuff in verry small steps to people who have no clue about what he is actually speaking about. But he makles it possible to understand, as he uses their language and tries to go with them step by step.

    In my opinion its all about a question of rhethorics, which means that the target group defines how you explain something.
    This is probably as difficult as physics itself and there is a reason why there are people doing nothing else than explaining and communicating for a lifetime.

    I agree on what Tewvong says, more explaining in blogs would be much apreciated too. But this is hard stuff, as blogs tend to be short, and there is nothing as difficult as to explain something complex in verry few sentences.
    But this i see as another chance of giving blogs a reputation.

    Droid Boy

  • ChuckWhite

    I see the term “Theory” is on the list, but feel this should be given a MUCH higher priority.

    Unfortunately, in today’s hyper-political climate, the science-debunkers invariably fall back on the claim that, “It’s not necessarily true – it’s only a ‘Theory'”. Sure, that’s true, but those same science-debunkers don’t realize the difference between a theory in science and the statement, “My theory is that the Flying Spaghetti Monster created the universe.”

    … well, maybe that’s a bad example. After all, maybe the FSM DID create the universe [grin]

  • Aaron Sheldon

    Counter-Factual Argumentation. Not only is it completely absent from public discourse, but most scientist are ill equipped at this important form of reasoning.

    Terence Tao has an excellent series of posts of mathematical and logical examples of counter-factual reasoning It should almost not need mentioning that this form of argument is at the heart of the scientific method

  • Non-Believer

    I voted for Quantam Mechanics, but my original thought was scientific method. I decided it was not a concept as much as a process. I’m glad others voted for it. Its such an important thing that needs to be understood. If people understood it better, they would be less likely to jump to the most unlikely conclusions or have unrealistic expectations from initial findings in some experiment. (read media headlines that extrapolate ridiculous ideas from experiments.)

    Is this a list you plan to do something with?

  • spyder

    Well, here is a new/50 million year old story that seems to involve many of the above components yet hasn’t garnered the just-due diligence of explaining the import of the science involved. The casual reporting of the birth of a black hole seems particularly important i might be led to think.

  • Josh Rosenau

    I’d skip “the scientific method” as there is not one unitary “scientific method.” I prefer talking about scientific processes, and I would urge people to lean heavily on as an awesome source of material on how to teach about the nature of science. It’s an NSF funded project based on peer-reviewed research on education.

  • Matt B.

    I wasn’t reading over the weekend, or I might have suggested “enumeration of favorable circumstances”. It could replace one of the 2 appearances of “comparative advantage” in the Specific list.

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  • Charon

    I prefer the pure, romantically idealized version of duck sex:

  • Low Math, Meekly Interacting

    To put in a plug for emergence: Heck, I’d settle for an adequate definition.

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  • Torbjörn Larsson, OM

    The winner by a wide margin was the meta issue of “the scientific method.” Which raises another question: do we agree on what the scientific method is?

    Quite right. Most of the meta issues (statistics, certainty, scientists, testing, …) can be folded into the larger issue.

    @ Josh Rosenau:

    I prefer talking about scientific processes, and I would urge people to lean heavily on […] as an awesome source of material on how to teach about the nature of science. It’s an NSF funded project based on peer-reviewed research on education.

    Of course you would, it is an accommodationist religious site:

    “Science doesn’t draw conclusions about supernatural explanations
    Do gods exist? Do supernatural entities intervene in human affairs? These questions may be important, but science won’t help you answer them. Questions that deal with supernatural explanations are, by definition, beyond the realm of nature — and hence, also beyond the realm of what can be studied by science. For many, such questions are matters of personal faith and spirituality.”

    Do you really expect Sean Carroll to be aboard with blatant theology like that? We know that science rejects many supernatural claims like the existence of 3 day old zombies of some cults, the making of wine from water of others, or that the world need to be created by outside influence by yet others.

    In fact, it isn’t very difficult to see that science production of natural hypotheses amassed enough tested and codependent hypotheses around 1970-1980 (IIRC, it was some time since I crunched the numbers) to make a binomial test for materialism theory, monism of nature, that rejects dualism of any kind.

    If that is the case, if we can reject supernaturalism dualism on the basis of observation, there is no foundation for making the claim that it is “by definition” beyond science. And of course the long standing tradition of science revealing parapsychology, tooth fairies and other supernatural claims as false tell us likewise.

    Such a “beyond science” claim has no basis in science, indeed “by definition”; it is purely dogmatic theological storytelling, while observation and theory on the other hand is an open-ended process. NSF, as a federal US agency that should hold up US constitution of separation between science and religion, should know better than to make religious claims on science. In fact, if you are in any way involved in education and/or science as I remember being the case, you should too.

  • Torbjörn Larsson, OM

    “NSF, as a federal US agency that should hold up US constitution of separation between science and religion”.

    I wish; meanwhile, they should hold up US constitution of separation between *state* and religion.

  • Charlie C

    Sean, what is the next step?

  • Dunc

    “I would say that quantum mechanics is explained in many places, but very rarely is it explained well.”

    Is it even possible to explain quantum mechanics well?

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  • RM

    I think most of the topics listed under Meta ought to be be explained as aspects of the the scientific method.

    So long as many people think a theory is “just an idea”, a lot can be gained from explaining the scientific method. It should be part of the curriculum of basic education.

  • Robert Huang, Canada

    Earth was the center of the observed universe until Nicolaus Copernicus, Johannes Kepler and Galileo Gallei proved it was not the case. Certainly, neither is the Sun as we know it today. However, the Homo sapiens centric model as you have stated at the conclusion of your book, From Eternity to Here, is still the common belief as in the geocentric days.
    Although Homo sapiens does have the appearance of the most effective communication ability (it cannot be said that other living things do not have superior form since we do not understand and able to communicate with them), other living things have proven that they can have apparently superior sensory functions. With this observation, I trust there is more than what we can “see”.
    Since our vision is determined by the existence of “photon” with finite speed, my question is how can we rely what we can see, such as red shift, the distance galaxies and other observable things, in theorizing on things that we cannot see? In other words, can we trust what we see?
    Since photons take time to enable our vision, we can only see the “past”. However, we can infer the existence of a “present “. After all, Sun does rise and set with a regular pattern. Better yet, with the reference frame of a blind person without the corruption of learning about time, he can tell the seeing the existence of a “present”. Does this reference frame proves the co-existence of future with past and present in the space time continuum except it is not visible to the seeing?

  • Robert Huang, Canada

    In addition to the seeing part, has anybody done calculations as to how fast an object travels that eyes cannot see, distance limitation as well as the reaction time of the brain vs the relative volcity?

  • Ray

    Most ‘mysteries’ are amenable to further research and discovery, at least in theory. I do, however, wonder if Consciousness isn’t the biggest unanswered question. With the idea in mind that a well-formulated question is a large part of the answer, I suspect we need a new way of looking at the question. I haven’t seen a definition of consciousness that is completely satisfying. Looked at philosophically or mechanically, nobody seems to be able to define it in a useful way.

  • Robert Huang, Canada

    Regarding “consciousness”, I am reading “The origin of consciousness in the break down of the bicameral mind” by Julian Jaynes. 1/4 way through. Interesting. Will find out what the “word” really represents. It is very dificult to match the meaning of words since the neurons in each person’s head conditioned differently, especially, the big words.

  • Vladimir Kalitvianski

    I found an simple explanation why renormalizations “work”. See

  • Vladimir Kalitvianski

    I found a simple explanation why renormalizations “work”. See

    Roughly, renormalizations (subtractions) remove wrong contributions of self-action from the total interaction Hamiltonian. This understanding opens, I think, a healthy way of constructing theories without UV and IR divergences.


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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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