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Solid as a Rock

Monday, December 31, 2012 - 05:00 PM

Is reality an ethereal, mathematical poem... or is it made up of solid, physical stuff? In this short, we kick rocks, slap tables, and argue about the nature of the universe with Jim Holt.

It's comforting to think that if you take an object -- a rock, let's say -- and break it down into tinier and tinier more elemental parts, that that's exactly what you end up with: smaller and smaller particles until you reach the smallest. And voila! Those are the building blocks of everything around us.

But as Jim Holt, author of Why Does the World Exist? points out... that's an old worldview that no longer jives with modern-day science. If you start slicing and sleuthing in subatomic particle land -- trying to get to the bottom of what makes matter -- you mostly find empty space. Your hand, your chair, the's all made up of mostly of nothing. So what makes it all take shape?

Robert and Jim go toe-to-toe for a friendly dust-up over whether, at its very base, the universe is made up of solid bits and pieces of stuff...or a cloudy foundation that, more than anything else we can put our fingers on, resembles thoughts and ideas.


Jim Holt


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Comments [66]

Asimov M Gandolf from Orlando FL

This Podcast was very interesting. It made me wonder about what we are and everything around us. When listening to this it made me wonder how everything we are around could be just an equation.

Mar. 29 2015 11:24 AM
Arthur B Kells from Florida

I don't think anything about the world's reason for existing or how it was made can really be discovered. Science can never enable humans to prove or disprove how the world was made, or why it was made, but discussing it can be very interesting. The central nature of the world and everything in is very confusing.

Nov. 03 2014 10:57 PM
Ender J Hayden from Oviedo, FL

I enjoyed this podcast, the subject is very interesting to me. It goes deep into the field of science and concepts. They don't have any guests that are proving any of these items, in order to have a base of their arguments. The format of this podcast isn't anything scientific, it is just a group of people arguing together. Even though the format isn't the greatest, the questions are still interesting to me. If nothing is making us up, there has to be a reason that we don't fall through the floor. Particles stop us, but why do they? This question is only partially answered, and there is no concrete evidence. Although I enjoyed this podcast, there was a lot of data missing from it.

Nov. 01 2014 01:18 PM

As an addendum to my previous comment: I do not intend to belittle the guest nor what he has to say, I simply think the way the matter is presented isn't in a scientific way (the analysis has all of the elements of truth, they're just presented in a poor manner). It sounds to me as if it were trying to reach an end with the information he provides instead of following the stepping stones where they lead.

I would also like to add that, while the Feynman Lectures are an incredible resource and I cherish my copies, they are the result of a class for freshman/sophomore undergraduate students and, while thorough, lack nuance.

It is a very difficult task to try to speak of anything physics has done since the start of the 20th century. I do love how truly difficult it is to explain the reason we don't fall through the floor. It shows the beautiful complexity of all of the interactions in nature, even the simplest, most obvious ones.

"By the way, I'm surprised to learn that only a "small number of physics graduate students" take courses in quantum field theory these days. (It's like hearing that English majors no longer read Shakespeare.) Could this really be true?"

This is true as well by the way. Often the full fledged QFT solution to a problem is unnecessary. Think of it like trying to use some new incredibly powerful supercomputer to solve 1+1.

Nov. 06 2013 05:56 AM

I've been listening to Radiolab for a few months now, mostly on my commute, and I've always enjoyed the way they present scientific ideas without attempting to fully claim an understanding of said ideas, it is a refreshing view of the way I wish all people would approach a field they don't work in. However, this episode upset me a little as a physicist.

While I don't find getting metaphysical about scientific principles to be necessarily a bad thing, I would hope that they are at least being fact checked. This guest, quite simply, doesn't have the full story of what he is talking about. He has some idea, but it is clear that he doesn't have enough experience in the field to make the statements he is trying to make. His understanding of the Pauli Exclusion principle is also quite lacking. I hope people read the comment by "Physical Chemist", because he/she gives a great explanation.

Nov. 06 2013 05:38 AM
Physical Chemist

In reference to the discussion below - "what keeps rocks from passing through each other?" Is it electrostatic forces or quantum mechanics (Heisenburg Uncertainty Principle and Pauli Exclusion Principle)?

The answer depends on what you mean by solids passing through one another. If you mean atoms passing directly THROUGH one another so that at some point they PERFECTLY OVERLAP with each other, occupying the same point in space – this is prohibited by the Pauli Exclusion Principle, end of story. However, if you mean atoms moving BETWEEN each other, like sand falling through the teeth of a comb – this is prevented by enormous electromagnetic forces of repulsion and Heisenburg uncertainty.

The quote from Feynman requires some context. As stated in the last paragraph of page 2-5, his point is to show that electrostatic forces ALONE cannot account for the structure of atoms, and at the bottom of page 2-6 “In order to squash the atoms closer together, the electrons would be CONFINED TO A SMALLER SPACE and, by the uncertainty principle, their momenta would have to be higher on the average, and that means high energy; the resistance to atomic compression is a quantum-mechanical effect and not a classical effect.” The phrase ‘not a classical effect’ is referring to the fact that electrostatic attraction alone would predict that electrons should collapse into the nucleus. ‘Confinement to a smaller space’ is a result of the electrostatic potential that results from squashing electrons together.

The position/momentum/energy of an electron in an atom is a balance between electrostatic potential and quantum mechanics. We can’t describe an atom without considering both. The only reason electrons (-) are found closely surrounding nuclei (+) in the first place is the electrostatic attraction. However, the explanation for why they don’t get too close (confined to a smaller space) is the higher momentum and energy as described by the Heisenburg Uncertainty Principle.

So if two rocks were to pass through each other (by the nuclei of one moving BETWEEN the nuclei of the other) there would be a huge increase in electrostatic repulsion, resulting in confining the electrons to a smaller space. This electrostatic repulsion is necessary, without it there is no change in the position of the electrons. The confinement would require a huge amount of energy according to the Heisenburg uncertainty principle. So for nuclei moving past each other, the answer is both.

By the way, I am not assigning “cause” in the philosophical sense, just which mathematical model best accounts for the observed phenomena. For further info look up the Hamiltonian operator, which is fundamentally quantum mechanical, yet incorporates electrostatic potential (V).

Oct. 16 2013 03:05 PM
Peter from DC


What confuses me is that when you say that the PE principle "keeps systems of atoms from collapsing" and, "We don't fall through the floor because of the Heisenberg uncertainty principle" it sounds, linguistically, as if you are saying that these principles are causing an effect, rather than describing an effect.

Likewise with the wave function. I hear physicists speak as if this is a real thing in the world, but is it not true that the wave function is merely a descriptive mathematical device - like a map - that we use to make predictions about something in the world? When we speak of the wave function collapsing do we not begin to confuse our map with what it is mapping? Or am I confused? Do physicists really say that there is a wave function out there, interacting with the world like the electromagnetic force?

Likewise with Feynman diagrams. Aren't these merely devices that we use to map the destination, but not the paths, of particles? In other words, do we not make a mistake when working with Feynman diagrams if we think they describe what is actually happening? These tools allow us to say with what probability the particle will end up in a certain location, but despite the method of how this calculation works, the particles do not necessarily get from point A to point B in the way that the diagrams and calculations get there.

Is it not a mistake, when making a calculation, to look too closely at the mechanics of the calculator and confuse it with the thing being calculated?

Sep. 06 2013 04:43 PM
eiaboca from NYC

Oh, the old mind/body dichotomy rears its ugly head YET AGAIN. Even if we are all excitations in a field, or many fields, on the macro level we have stuff. And there's nothing gross or icky or terrible about stuff. The dichotomy is buried so deeply into all of Western thought it's tough to see around it!

I don't think we could have stuff without mind (or in this case, math, fields, laws, etc.), and I don't think we could have mind without stuff. I hope there are some philosophers working on that. I should know, because I'm a philosophy PhD student, but I still don't.

Aug. 29 2013 08:36 PM
One of those NJ engineers from NJ

Like a lot of other commenters, I felt Jim's invocation of HUP and PEP were ill-advised. However, I also thought Jim had a lot of interesting observations that have interesting implication:
1.)Every time scientists learn more about the basic structure of matter, the less the basic matter resembles the objects we interact with in daily life. The nature of matter only grows in complexity with more knowledge.
2.)The more we learn about matter, the more we learn there is less matter in existence (atom-MSG analogy). This may continue ad infintium with a continuing knowledge of subatomic particles, but my own knowledge of these particles is limited.

Mathematical relationships versus stuff is a false dichotomy. Math and stuff have coexisted for hundreds of years. Calculus was invented with "stuff" in mind. Jim's awe of the mathematical relationships is an awe for the consistency and complexity of scientific phenomena. Stuff is our own conception of matter based on our experiences. These concepts don't have to contradict each other. On the topic of stuff, Jim's belief in the non-existence of stuff isn't radically new. It should be noted that Louis de Broglie realized that all particles exhibit properties of waves and vice-versa, a cornerstone of modern physics 87 years ago.

Also, there's nothing wrong with philosophy. No one should have to reject philosophy to impress others. In fact, metaphysics and epistemology are branches of philosophy that lay down the groundwork for scientific observation. I would argue that a good scientist should be at least cognizant of philosophy. Just because one has a knowledge in one field, it shouldn't discredit them from expressing ideas in another field.

May. 13 2013 10:23 PM

I'm late to listening, and therefore to commenting, but I agree with those who are flummoxed by the idea that the EM force is not "responsible" for things falling through other things.

My confusion: I thought electron degeneracy pressure applied to things like white dwarfs or inert helium cores of low mass stars before the helium flash- i.e., densely packed things where the regular rules of temperature and pressure don't apply. I didn't think my hands, for example were held up by degenerate pressure. Or are they? Can someone clarify?

Apr. 22 2013 09:14 PM
Ryn from CA

Hey guys! Think about this possibility: All of matter is composed ONLY of waves and not of "particles," meaning that discrete particles do not exist. If you explore this idea, you may find that the search for the theory of everything becomes moot because there is no longer a discrepancy between quantum mechanics and classical relativity. All matter is composed of waves. What we thought were "particles" were really just the centers of the waves. There are many physicists exploring/testing this theory now. You guys should find them and make a new show about this subject.
(By the way, I second the comment by Matthew - interview some chemists! Disclaimer - I'm a chemist). :) Cheers!

Mar. 25 2013 06:18 PM

After listening to this program right after listening to "Emergence", My first thought is that this program really should do an interview with Rupert Sheldrake.
Then, reading the comments, it seems clear that many here would probably explode in rage and die of heart attacks if Radio Lab were to do so. Too many treat Science as a religion, rather than just an extremely powerful tool.

Mar. 25 2013 01:07 PM

I wonder how the Higgs Boson plays into this? What about Eastern philosophy and the idea of unity of non existence and existence? I'm not so sure I am willing to say that "things" not made up of matter or even space itself,for that matter ;), are discontinuous or separate from those that are. All this goes to ask- what about the limits of our clumsy symbolic communication?

Mar. 17 2013 01:49 AM
Pifie from Argentina

There is a big confusion, both in the podcast and the comments, it is: confusing the map with the terrain.

Science is our map. It's man's way to account for measurements tidily : Y=-a*T^2 is tidier than a graph of the measurement of vertical distances at certain times. BUT the graph is as useful as the function.

But that map is not the terrain, which could be 'reality'. But you can't even be sure. It's a very simple point, but it seems everyone here is avoiding it.

The other issue is that we know something is true, but not much more than that. We know 'something exists' is true - any thinking person can agree with it, Descartes-wise - , but nothing else I know of has that level of 'trueness', hence, the rest is just supposition.

You shouldn't 'trust' science, based on scientific grounds. You can 'use' it, and study measurements and relations, but that won't make scientific explanation true. Neither does the fact that some person has a PhD in something, and other doesn't : I assume we are all aware that saying something is truer because a person with an entitlement said it is a logical fallacy.

TL;DR version: Truth is not a scientific issue, but a philosophical one.

Mar. 07 2013 10:52 AM
carolyn from SF Ca

I second the comments by Paul Dille. Holt makes the classic mistake of getting a bit too philosophical about subatomic physics. And his understanding of quantum mechanics is rudimentary at best. His definition of a field is the most flawed I've ever heard.

Feb. 09 2013 03:09 PM
Adam from Minneapolis

I really liked this podcast since it seemed to address the same concepts the Buddha was trying to discuss 2500 years ago when contemplating the nature or reality and emptiness. I'm definitely no scholar on Buddhism or physics, but it seemed to me they are trying to tackle the same question just from a slightly different angle and with a different vocabulary. Interestingly, they both came to similar conclusions about the illusory nature of reality. just my two cents.

Jan. 28 2013 08:41 PM
Michael mark Anthony from Hohenwald Tennessee

You may want to read my newly released book that proves the existence if God using pure science and mathematics.

Jan. 28 2013 05:34 PM
Physicist from Finland

I just listened to this episode, and as several of the people commenting below, I was surprised that Jim Holt was allowed to so easily discard electromagnetic forces as a cause for why we can clap, why we do not fall through the earth etc.

Reading Jim's last comment in this conversation, I have the impression that Jim has misunderstood the Feynman passage he quoted: "the resistance to atomic compression is a quantum-mechanical effect and not a classical effect." Atomic compression. Quantum mechanics is needed to explain why you can not compress the atom, why it is the size that it is. Quantum mechanics is needed to explain why solids are stable, why our hands can exist at all. But to explain why they repel when we bang them together, we must consider electromagnetic forces - like Krulwich said. The Feynman passage does not contradict this at all.

My background: I have a PhD in physics. My field of research is however not in the domain of quantum physics, so my knowledge about this comes from basic university courses and a general interest.

Jan. 26 2013 07:27 AM
Bruce Davenport from Cramlington, Northumberland, Uk

Well... this one got me thinking... I'm struggling with the image of it being maths all they way down and keep getting stuck on the thought that there must be something that sustains the maths or that precedes the maths...?

Jan. 24 2013 03:32 PM
No ideas are necessary for the laws of physics to work. Physics existed before living things, and thus before ideas.

Jan. 21 2013 07:25 PM
Matthew from Kansas

Can anyone pick out the piano music that starts playing in the background at about 11:30 in? I would love to know the name of it.

Jan. 18 2013 05:25 PM
Aaron from Sydney

They were saying that the stuff of atoms flickers in and out of "existence" and it's exact location at any point is unknown. And from that suggesting we are made up of mostly "nothing". This is all emotional interpretation of loaded scientific terms! Like why is the field effects of something we find difficult to visualise less real than the imagined spheres of protons and electrons? This is all more about poor human visualisation of physics than the physics itself.

For instance if it's impossible to pin down a particle to a specific time and place, within some area then why not imagine it occupies all of it?

At least they didn't talk about that bloody cat! :)

Jan. 14 2013 07:04 PM

This stunk of idealism ontology masquerading as science. Quite a few leaps of logic have to be made to get to this point. All in all, it felt more like it was rabid abuse of the ideas.

I like the boundary thought provoking stuff, but this felt a little bit too much like mental-wankery.

Also I don't know why that one guy is bashing Krulwich. I thought he was keeping things pretty grounded.

Jan. 13 2013 04:17 PM

To Jad:

Please interview chemists. These physics guys seem to get confused about certain concepts that fall outside of their discipline. Luckily there is a whole other science devoted to just such questions call chemistry. I implore you to interview some chemists. Thanks.

Jan. 12 2013 06:24 PM

I have a quick question:
how can i download the whole episode? Because, right now i can only download 15 mins of it

Jan. 12 2013 01:55 PM

I enjoyed the episode. Those that get offended by the ideas brought forth in this episode need to 1) remember that radiolab has always been about thought provocation (and not necessarily giving the correct answer) and 2) the biggest obstacle to learning is pre-disposed beliefs in models.

Jan. 12 2013 10:23 AM

I was excited initially to listen to this episode but found it not very thought-provoking (and now I wonder if this in fact intentional).

Jim's musings seemed quasi-religious and as others have pointed out also factually suspect - the end goal being to arrive at an 'answer' for everything which just seems inappropriate for how the discussion and the episode was advertised.

Jan. 11 2013 05:15 PM
Chad Koppes from Rochester, NY

Jeesh, calm down folks.

What is wrong with thinking through different ways of perceiving and experiencing reality? Maybe you agree or disagree or have different arguments you would like to explore in relation to the topic - that's great!

What's scary is that the hyper-materialists sound so threatened by what is essentially an interesting Platonic argument that they sound a lot like certain religious extremists. "Radiolab! I'm disappointed! Don't perpetuate (or even help people think about!) arguments that I don't agree with!!"

The bottom line is that it's fun to think about - it's OK to disagree (I do!) but let's not disparage Radiolab for introducing a topic that might undermine your religious....errr..scientific commitments.

Jan. 10 2013 12:19 PM
Shanta Kamath from Eugene, OR.

Well, I'm just glad that I don't have to think everything into a coherent set of relationships with everything else around it on an ongoing basis because I simply could not manage it. We would all be in trouble if I had to do it. I noticed at some point (I've forgotten the experience, actually, but other babies do it in infancy, I'm told) that things don't go away when I stop seeing them and thinking about them. This may be because other people or parts of Consciousness are still seeing them and thinking about them, but from what I observe of how far I can trust others with their apparent choices, I doubt they are taking care of this, either. It seems to work without any help, existence, and for that, I am thankful.

Jan. 10 2013 12:08 PM

I loved the episode, personally. It did a nice job of pushing boundaries and presenting new ideas. I felt the point was not to prove or disprove anything, but rather to expand a thought. Science is increasingly leading us to a reality that is not at all what we think it is. "What if..." is what this episode did for me, and I like that question a lot.

Jan. 10 2013 12:08 PM

Like some previous posters I am afraid that Jad is in trouble. He never should have gotten himself involved with Krulwich, who is long-known as an anti-science government shill. Jad's recent silence speaks volumes, but I hope that he can make it out of this situation okay. With Jonah Lehrer gone and credible scientists unwilling to speak to Radiolab, it's too late for the show to return to the earlier days of fun-but-safe questions like 'what is laughter?' but hopefully Jad will make it out of this situation safely and start a new career somewhere else.

Jan. 09 2013 07:54 PM
Martin Fencl from Madison, WI

I could not digest what Jim said. Just like Paul Dille, Tim, and Physics Grad and probably others could not. I wrote my own harangue about how and why the direct, the immediate cause stopping our clapping hands from penetrating each other are, high-school-obviously, the intermolecular - i.e. electromagnetic - forces of the chemical bonds holding the atoms, ions and molecules of our hands together. Then I rewrote it, then again, and again. Revising my initial response, I came to see how and why it could be the way Jim says. Maybe Jim is thinking what I am now but did not express himself clearly enough in that respect (inviting the strong resistance).

I'd like to ask you, Jim, can you please describe how is the penetration of the hands happening in your mind that it makes you point at Pauli's exclusion and Heisenberg's uncertainty principles (rather than the electromagnetic forces of the chemical bonds) as the explanation for why our clapping hands do not go through each other like two clouds?

Jan. 09 2013 07:27 PM
Jim Gonzales from Omaha

When I heard the comment that was something like "it looks like its going to be math and structure all the way down" I couldn't help but think about the lady who thought the earth sat atop a giant turtle and when asked what the turtle was standing on she said something like "you're very clever but its turtles all the way down".

Jan. 08 2013 11:36 AM
Joel Dueck from Minneapolis, Minnesota

I personally enjoyed this episode. As a postmodernist, I'm even delighted with the criticism it's getting. I am writing a serial ebook about Everything, structured around the headings in Roget's 1852 Thesaurus, and I felt that this episode validated my chapters on Substantiality and Insubstantiality.

Jan. 07 2013 11:23 AM
Burk from CA

Hi, Radiolab- I was disappointed at the load of Platonic trash you unleashed on this episode. The guest kept saying the particles are "nothing but math". And that is a classically mystical and platonic way of looking at things. It is also completely wrong. We are dealing with *things* every day, all the time. Indeed all information also has to be embodied in *things*, which you learn from information theory. No things, no information. And math does not exist outside our very physical heads either. Tehre is no god our thre furiously doing math to make the universe come out "right". It is our *tool* for encapsulating complicated phenomena. When it works, great... but often phenomena are very complex and can not be condensed into math. Like, say, evolution. Does that mean they don't exist?

This whole inversion of "everything is a computer" or something similar is very attractive to certain temperaments, but has no solid(!) argument behind it. And this show shouldn't promote such amateurish philosophy. Best wishes!

Jan. 05 2013 05:18 PM
Please Jad

Why has this happened to Radiolab? Is Jad asleep at the wheel? You guys know better than jump on this bandwagon of anti-scientific nihilism. We've always known that physical properties can be described by mathematics. We've always known that science is a dangerous profession and those with an interst in hiding the truth havs a habit of killing men of science.

All that has changed is that now billions of dollars in government funding are going into convincing the masses that science is over and nothing is real, while they ravage a populace that increasingly thinks it doesn't matter because it's all fake anyway. Jad, whatever they're doing to you, please consider that fighting this might be a cause worth dying for.

Jan. 05 2013 06:38 AM

This episode was very interesting and obviously had some kind of success since it inspired a debate like the one on this forum.

Here's my two cents. I am sitting on a chair. There is a force pulling me down (in this case gravity). The EMF between the charged particles in my atoms and those of the chair resists the gravitational force and I remain sitting. It does not end there however. The reaction of the EMF on the electrons attempts to move the electrons closer to their nuclei. Here I am referring to the component of the EMF resulting from the repulsion of the electrons in my atoms by those of the chair. This force is in addition to the force of attraction between the nuclei and their electrons. Everyone here has conceded that it is the result of the PEP and HUP that atoms don't collapse on themselves due to this force of attraction. Therefore everyone, some unwittingly, has conceded that the PEP and HUP also prevent the additional repulsive EMF between the electrons in my body and those of the chair from collapsing the atoms.

I would say that the quantum effects are the more fundamental reason why I don't fall through the chair.

Jan. 05 2013 03:35 AM
Tim (not the other Tim) from Madison, WI

I remember sitting in Advanced Quantum Mechanics during my last semester of college day dreaming about what some of the tangible effects of the mathematics that my professor was barreling through was. I would always think about how to try to explain to people who weren't one of the six of us in the class room about how quantum mechanics can legitimately influence your idea of what is real, but I've never been able to do so without losing sounding half-baked. Now I can just send them a link to this clip and say, "listen to this, then we can talk." Thank you Jim and RadioLab.

Jan. 04 2013 11:30 PM
Scott McGregor from Silicon Valley, CA

I loved this episode -- except how it ended -- where I felt you really failed to close the loop, leaving the audience with a proposition that blurs rather than clarify the difference between the map (our explanation of what the world is) and the territory (what the world is, including stuff not on the map). You also didn't close the loop back to the anthropomorphic principle you have discussed in other episodes.

I was disappointed that you didn't close those loops because you have dealt with related phenomena more completely and incisively in some of your other episodes. I hope you will revisit this issue in a future episode and complete both loops.

For instance, in your earlier episodes on colors, you talked about how the human perceptual system limits our experience of different colors, and that some birds, butterfies and shrimps have different limitations and can thus experience and differentiate colors in a way we cannot. You did an exceptional job of helping your listeners get a notion about what that different perceptual experience would be like using the analogy of more polyphonic voices. But while this helps use "get" the difference conceptually, it didn't give anyone in the audience the ability to start seeing like a 5-chromat or a 15-chromat simply because they now could conceive what that would be like.

In short, the perceptual models we build in our brains are "inherently incomplete" because the are necessarily limited to what our perceptual systems can register. Luckily, the information we are missing is generally not life-threatening -- unless we are a Manta Shrimp.

In your recent episode, Solid as a Rock, you ask if the world might *really* be thought, mathematics or ethereal "stuff" at the bottom. I wish you had gone the next step and draw the logical parallel between how limitations of our perceptual systems limit what we can perceive, that so too does our cognitive system wiring limit what we can conceive of. Thus, science may be telling us more about how we are limited to think about reality in certain ways.

Saying that the real world might just be ethereal mathematics because that is the model we have found that most accurately predicts how the results of some physical experiment is mistaking our best map/model, which is surely incomplete, for the territory/phenomenon being observed, which surely has many aspects we don't have senses to perceive or the ability for our brain to model.

In short -- all concepts are false (or at very least incomplete).They are at best crude approximations which capture enough to be useful in practice most of the time. However, while they are false or incomplete, they are often useful in predicting the future. And the ability to better predict the future has survival value. What we are missing may not have much survival value, but that doesn't mean it isn't there.

Jan. 04 2013 05:23 PM

Although I understand the ideas underlying this broadcast, I disagree with the PEP vs Coulomb detail. Jim, saying "its true because the highly decorated Nobel Prize-winning scientist says so" does not substantiate the claim.

Jan. 04 2013 09:26 AM

I dislike the idea of surrounding the idea of "mathematical objects" as somehow being etherial and mystical. The truth is that when Jim Holt refers to such objects what he really means is that we know some of the rules for how this "thing" or "structure" behaves. "Hard little balls bouncing around" is just a different set of rules, one that we happen to be familiar with. So better than "etherial" would be simply "unfamiliar" or "beyond our everyday experience."

Jan. 04 2013 06:03 AM
Jim Holt

To Paul:

All I can do is to implore you, yet again, to read very carefully the Feynman passage I quoted below. That is why I took the trouble to type it out. Focus on these words of Feynman's: "the resistance to atomic compression is a quantum-mechanical effect and not a classical effect." Electrostatic forces, governed by Coulomb's law, are a classical effect. Feynman is explicitly denying that they are responsible for our failure to fall through the floor. He is explicitly denying what you claim to be the case. Let me say that again: He is explicitly denying that, as you insist, EMF is "the most DIRECT reason" we do not fall through the floor. If you will not accept the judgment of Richard Feynman, a Nobel laureate and one of the greatest figures of modern physics, then I'm afraid I have nothing left to convince you with.

Jan. 03 2013 09:32 PM
Paul Dille from Nanchang, Jiangxi, PRC

The original criticism of your comments was not, that the PEP and HUP are not responsible for the structure of atoms. Every commenter on this thread has conceded that point. The problem is that you deny the EMF's role in the whole process of "not falling through the floor". Now I'm not sure if Radiolab cut you off or edited you out, but to exclude the EMF as a contributing factor to "not falling through the floor" and in such a "matter-of -fact" way is not acceptable. I never said the EMF was the "sole" reason either, but it is the most DIRECT reason. I could argue that without the Strong Nuclear Force quarks and protons wouldn't "come together" therefore with out IT there would be no atoms, therefore it is also has a hand in "not falling through the floor". Most things in nature can be connected with a long enough chain. Yes without the rules of the PEP and HUP matter would collapse. It gives the atom it's "shelliness" or it's "hardness". When two solids try to pass through each other the EMF given off by all the atoms with their "shelliness" repels the other atoms by transferring photons back and forth. Of course, the Grad Student's explanation is much more eloquent, concise, and trusted.

I have not been offended by any of your comments. I enjoy a good row. I also appreciate your willingness to discuss with the listeners. But I feel like you have been misleading the listeners. I know a bit about science. I am not a scientist, but I tend to trust scientists over others when discussing topics in which those scientists are experts. Nothing you say rings the same way a Physicist would say it. The only other explanation I can think of, and definitely could be the case, is if those physicists are dumbing down the information for the public. But public figure physicists like Greene, Cox, Krauss, Weinberg, and the like, don't shy away from other abstract concepts. It would seem strange for them to mislead us in the field in which they are experts.

I am afraid that is all I have to offer the conversation. I would love to hear more expert physicists opinion on these matters, however I feel Grad Students comments have more than satisfied my need for technical information.

Jan. 03 2013 07:57 PM
Eric from Grand Rapids, MI

I'd like to hear an entire episode devoted to this topic. It sort of blew my mind.

Jan. 03 2013 04:24 PM
Jim Holt

P.S. to the physics graduate student.

Perhaps the simplest way to resolve our disagreement is to observe that we are in effect asking two different questions.

I ask: why are solids solid (as opposed to mutually permeable)?

You ask: why are solid solid (as opposed to liquids and gasses)?

These are both good questions. Some people just happen to find the first one more profound (and its answer more counter-intuitive).

Thanks again to everyone for having the patience to listen to this podcast and the intellectual passion to register such interesting comments.

Jan. 03 2013 01:29 PM
Jim Holt

To the physics graduate student:

As a scientific realist, I believe that neutron stars are perfectly good macroscopic objects. But let's stick to shoes and floors, as you suggest. Here is Richard Feynman ("Lectures on Physics: Quantum Mechanics," vol. III, p. 2-6):

"So we now understand why we do not fall through the floor. As we walk, our shoes with their masses of atoms push against the floor with Its mass of atoms. In order to squash the atoms closer together, the electrons would be confined to a smaller space and, by the uncertainty principle, their momenta would have to be higher on the average, and that means high energy; the resistance to atomic compression is a quantum-mechanical effect and not a classical effect. Classically, we would expect that if we were to draw all the electrons and protons closer together, the energy would be reduced still further, and the best arrangement of positive and negative charges in classical physics is all on top of each other. This was well known in classical physics and was a puzzle because of the existence of the atom. Of course, the early scientists invented some ways out of the trouble--but never mind, we have the right way out, now!"

By the way, I'm surprised to learn that only a "small number of physics graduate students" take courses in quantum field theory these days. (It's like hearing that English majors no longer read Shakespeare.) Could this really be true? Quantum field theory is the basis for all of theoretic physics.

Jan. 03 2013 01:05 PM
A Physics Grad Student from LA

I would like to caution those who are discussing against using credentials and names as weapons.

I would also like to remind Jim that the inspiration for discussion was in his explanation of ORDINARY MATTER. That is matter like us and the floor.... or literally rocks ! Exotic things which physics is at this point in time most incapable of adequately describing such as neutron stars and black holes would only serve to confound discussion of the objects which were originally discussed. These things are exotic and hard to understand precisely because they are force our current theories of physics into scales which they do not make sense. Explaining why black holes are how they are and how neutron stars are how they are will not help in understanding why the floor holds us up.

Before saying anything about the implications of the citation Jim has given (J. Math. Phys. 8, 1538 (1967)) I would like to point out that the author manifestly used electrostatic interactions in the model. What he did not force in the model is the 'Columbic' interaction. That is the precise 1/r^2 nature of the force. Electrical interaction are required however their precise nature is not forced in the author's model.

Additionally all the the paper proves is that the existence of matter requires the exclusion principle ! The paper proves that for matter to remain uncollapsed the exclusion principle is needed. I did not disagree with Jim on this point. However, matter can come in many forms. The paper in no way addresses the nature of solids whereby the position of the atoms are fixed making their macroscopic behavior substantially different than say liquids. It is built right into the model for those who care to view equation (1).

My main point, that I will here reemphasize, is that the fixed relative position of the atoms in solids is due to electrostatic forces. And that when two solids refuse to go through each other it is because the atoms have found an energetically favorable arrangement in their solid static arrangement.

I would also like to point out, upon re-listening to the segment, that only a small number of physics graduate student's take quantum field theory. It is by no means a required course for all physics students and is additionally the successful marriage of special relativity and quantum mechanics which are not theories that we should consider when describing rocks. Certainly for black holes , but that is an entirely different type of matter for that matter.

Jan. 03 2013 12:33 PM
Jim Holt

To Paul:

First, I am not a philosopher. My only graduate degree is in mathematics.

Second, Steven Weinberg has read my book, and he does not think I have misrepresented his ideas (unless he is too polite to tell me, which is always, I suppose, a possibility).

Third, if you do not think quantum principles are germane to the macro-world, then how do you explain the difference between a neutron star and a black hole? And have you heard of something called "quantum cosmology" (which is what Hawking does)?

I am familiar with Feynman's strictures on philosophy, which do not, I think, represent him at his best. As the philosopher of physics Tim Maudlin has recently shown, Feynman's own analysis of the "twin paradox" is invalid.

Thank again for your comments, and sorry to be a bit terse in replying.

Jan. 03 2013 11:48 AM
Paul Dille from Nanchang, Jiangxi, PRC


I am not an expert on Physics, and I appreciate Grad Student's weight on the issue. But, every physicist I have read or listened to, think it very irresponsible to apply Quantum rules to the macroscopic world. I watched your Charlie Rose interview as well and it seems like you do not have a firm grasp of what science is, what it does, and what it tells us. It's key principle is not simplicity. That is a Liberal Arts undergrad student's idea of what science is. I feel like you totally misrepresented Krauss and Weinberg and spun their arguments/ideas only in a way to strengthen yours (Straw man).

I managed to peek at a little snippet of The Feynman Lectures vol III 2-6. Did you read the "warning" he gives to Philosophers hijacking ideas from the Quantum world?

Jan. 03 2013 11:31 AM
Jim Holt

To the physics grad student from L.A.:

You are incorrect in saying that electrostatic repulsion is responsible for the mutual impermeability of solids. Here is the reference you want: Freeman J. Dyson and A Lenard: Stability of Matter, Parts I and II, (J. Math. Phys., 8, 423-434 (1967).

If you doubt that quantum-mechanical effects (like the Pauli exclusion principle) are central to the understanding of how macroscopic object behave, then how do you explain the difference between, say, a neutron star and a black hole? It is quantum degeneracy pressure (a consequence of Pauli) that keeps the former from collapsing into the latter.

Thanks for your other comments, which were shrewd and enlightening.

Jan. 03 2013 11:13 AM
A Physics Grad Student from LA, CA

I would have to agree with those who are complaining that it was wrong of Jim Holt to correct Robert as to why solids are solids.

While it is very much true that the reason that ATOMS have a finite volume and exist is because of quantum mechanical effects:the exclusion principle and uncertainty relationships, it is not true that these effects are the sole reason that SOLIDS exist and have the properties that they do. Or that is it proper to think about quantum mechanics when trying to describe the behavior of macroscopic objects.

Electrical forces are responsible for matter condensing and collectively repelling one another. One has to simply ponder why there are separate phases of matter... Why, given that the atoms in solids, liquids and gases are identical are their properties so different ? Once one has explained why atoms come in different forms (which is a quantum mechanical effect) , explaining why they form these distinct phases (at least those that are naturally occurring) is a much more classical question-a question which is most directly answered by considering the electrical (and thus chemical) properties of atoms. They are also questions of different length scales which distinct theories exist.

The reason that we do not fall through the floor while liquids and gases will happily pass through each other is because the atoms in solids are have found an energetically favorably arrangement together in the form of a solid matter. When two solids are brought in close proximity to each other it is the electrical repulsion both against the other object AND BETWEEN THE OTHER ATOMS WITHIN THE OBJECT which keep things in place and prevent the two solids from passing through each other. In the case of liquids or gases, this electrical repulsion exists but the atoms simply scatter off each other. It is because atoms in a solid have each other that they can stay put and collectively repel this other solid. This is the fundamental difference between phases of matter.

To sum up it is certainly true that to understand why atoms exist quantum mechanics is central, but to understand why solids exist it is not. For a complete discussion going from vacuum to solids Jim is right to say that we quantum mechanics is key but wrong to say that electrical forces are not as well. The fundamental mode of modern physics is to understand which theory at which scale most correctly describes the phenomena we see. This is a subtle subject and it was wrong of Jim to dismiss Robert and reduce his explanation so quickly and matter-of-factly.

I very much enjoy listening to radiolab, but have always thought that they let guests get too fast and loose when talking about physics among other things ! I am willing to bet that we will soon here from one of their more trusted sources

Jan. 03 2013 10:58 AM
Jim Holt

P.S. to Paul:

I hate to resort to quoting Wikipedia, but here is a statement that might clarify the matter for you (in the entry under "electron degeneracy pressure," which stems from the Pauli exclusion principle):

"Freeman Dyson showed that the imperviousness of solid matter is due to quantum degeneracy pressure rather than electrostatic repulsion as had been previously assumed.[1]"

The reference to Dyson's paper is contained in the article. Dyson's analysis had a forerunner in the great Paul Ehrenfest.

Jan. 03 2013 10:46 AM
Nenad Bach from Croton on Hudson, NY

Loved the show. Since I was 10 or 11 I am puzzled with the question why do electrons circle, vibrate around the atom. If we can figure it out why, we would know a lot, probably even the answer to whether this is Solid as a Dream or Rock? Are dreams, thoughts solid as a rock? Regards to Jad. Loved the sound of the show. Is sound solid?

Jan. 03 2013 10:21 AM
Jim Holt

To Paul:
I didn't mean to attack your view. I merely pointed out that it is at variance with the analysis of Richard Feynman, Freeman Dyson, Paul Ehrenfest, and other physicists. (Do take a look at Feynman vol. III, among other references.)

If electrostatic forces were all that mattered, wouldn't the electrons in an atom just love to be pushed into the positively charged nucleus when other electrons crowded in on them? And isn't it odd how two electrons can happily inhabit the very same orbit as long as they have opposite spins?

I do think you are on to something when you question how laws of nature enter into explanations of how the world is. But that, as I said before, is another conversation.

Thanks for your observations.

Jan. 03 2013 10:20 AM
Paul Dille from Nanchang, Jiangxi, PRC

Either my point is not coming out clearly enough or you are misrepresenting my position to make it easier to attack. The most DIRECT reason why two hands do not pass through each other has nothing to do with "incompressability of atoms". You say that without the PEP and HUP, matter collapses. Okay so I will grant you that they give us, what we consider, "solid" matter. But once you get "solid" matter, the REASON why you don't fall through the floor is because of electromagnetism. Take it up with physicists, not me.

I admit I am unfamiliar with your metaphysical views and I will now probably buy your book to find out. But it is a harder sell on your metaphysical views when your physical views, which they are based upon, are wrong. It also doesn't bode well for your position if your only defenses are logical fallacies (Straw man, red herrings)

Is this journalism? Robert correctly asserted the reason why matter doesn't pass though other matter. His guest gave him a smug, "no". The answer is OBVIOUSLY not, "no". At the very least it should of been a "Yes, and" or "Yes, but". To claim the EMF is not responsible for our ability to push and pull things or to stand up, is embarrassing. If I were the Radiolab producers, I would find a physicist on their rolodex and give them a call. This is an edited program with much thought going into the production of each episode. Why these ideas were given a free pass is beyond my comprehension, but Radiolab just might have Jumped the Shark.

I know this is very informal, but....Brian Cox....Physicist....and his credentials speak for themselves if you give him a google.

Jan. 03 2013 09:39 AM
JIm Holt

To Paul:
Your claim that the incompressibility of matter is due to electromagnetic effects is explicitly denied by Richard Feynman in the reference that I gave.

As to which physical laws are the most fundamental--say, Coulomb's law versus the Heisenberg uncertainty principle--that's another conversation. Just what a law of nature really amounts to is a vexed issue in the philosophy of science.

Jan. 03 2013 07:55 AM
Paul Dille from Nanchang, Jiangxi, PRC

Okay. The HUP and the PEP are not "responsible" for anything. They are ideas and equations which explain certain traits of the Universe. Traits of the Universe which just happen to be the way they are; and if the Universe did not have those traits we would live in a different Universe. For example, a Universe in which electrons would not "orbit" the nucleus of an atom, and all "stuff" would collapse into a single point. Not our Universe. Without these traits, there would be no galaxies, stars, planets, organisms, chemistry, molecules, or atoms. The PEP and HUP aren't responsible for "your hands not passing through each other", they let us know why the Universe allows hands to exist in the first place

So, now that we have a Universe which has the right traits and rules of chemistry to produce "stuff" as we know it, what "prohibits" my hands from passing through each other is the Electromagnetic Force. As Richard Feynman and every other PHYSICIST I have read, will attest. As electrons approach each other, photons are exchanged between them, which produces an Electromagnetic Field and acts as the repellent force between objects. It is true that the HUP and the PEP are involved with the structure and chemistry of atoms, but to imply they are the reason "we don't fall through the Earth" would be equal to saying, The Big Bang and all the laws of the Universe are the reason "we don't fall through the Earth".

So when Robert thought the EMF was the reason his hands did not pass through each other, the reply with "No that's false" should have been met with incredulity and skepticism. For Radiolab to air the comment and leave it unchallenged was irresponsible and needs to be retracted.

Jan. 03 2013 06:15 AM
Jim Holt

No, Michael, but after watching the relevant youtube clip I shall certainly start doing so. JIM Holt! Anything to escape this dungeon on nonentity-hood.

Thank you for your learned comment.

Jan. 02 2013 12:11 PM

This may seem somewhat less intelligent than all the other comments. But, to anyone who has seen "Arrested Development", do you ever say "JIM HOLT" just as Steve Holt said his name in the show? Just a small thought that's probably never going to get a response and was never fully on topic.

Jan. 02 2013 11:20 AM
Jim Holt

So the general idea is that the Heisenberg principle keeps individual atoms from collapsing, and the Pauli principle keeps systems of atoms from collapsing (although it is defeated by the extreme pressures that lead to the formation of black holes). The role of the Pauli principle in guaranteeing the stability of matter was established in detail by Freeman Dyson and a collaborator in a paper published in the 1960s (although it had been conjectured long before that).

Thanks again for taking the trouble to listen to my somewhat desultory rant.

Jan. 02 2013 08:55 AM


Many thanks, both for your quick response and for teaching me a little something! It appears that the Pauli Exclusion Principle *is* an integral part of keeping two solids from passing through one another. I hadn't considered the topic thoroughly enough and forgot that under the influence of the EMF alone atoms would immediately compress to a single point in space. To be fair though, although the PEP and HUP are the underlying *causes*, the EMF is still the *medium* (if I understand correctly).

I really wish they had aired that section of the interview.

By the way, in addition to the Feynman lectures, I thought this link contained a nice explanation:

Jan. 01 2013 07:43 PM
Jim Holt

This too might help. It's my response to the question of a radiolab producer.

Producer: Couldn’t you say at the scale of two hands clapping that it really is mostly an electric force thing?

Me: No, because the same electrical force would tend to bring the electrons in an atom toward the nucleus until they sat right on top of it. Poof! A little neutral object that has an infinitesimal volume compared to the original atom. And there would be no electical forces to keep these neutral objects apart. Poof! Matter collapses.
We don't fall through the floor because of the Heisenberg uncertainty principle, not because of classical electrical forces. Squashing the empty space out of atoms means confining the electons to a smaller volume--which, by HUP, means higher momenta and hence more energy. As Richard Feynman put it, "the resistance to atomic compression is a quantum-mechanical effect and not a classical effect."

Jan. 01 2013 06:01 PM
Jim Holt

This is for Tim.
See Feynman's Lectures on Physics, vol. III, pp. 2-5, 2-6, wherein Feynman attributes the incompressibility of atoms to the Heisenberg uncertainty principle.

Jan. 01 2013 05:55 PM

Having studied physics as an undergraduate, I was extremely surprised to hear the Pauli Exclusion Principle quoted as the reason your left hand cannot pass through your right hand. I have always heard it explained that this is caused by the electromagnetic force, as Robert initially asserted. Indeed, after a cursory search of the interwebs, I found a Feynman video reaffirming my understanding:

Could you either quote the recent research that has exposed the Pauli Exclusion Principle as the dominant repulsive mechanism between most solids or run some sort of retraction correcting the error? It may seem like a small thing, but these things are very hard to comprehend to begin with, and spreading misinformation makes explaining these phenomena infinitely more difficult.

Jan. 01 2013 05:39 PM
Paul Dille from Nanchang, Jiangxi, PRC

I think it is a good rule of thumb for journalists to do a little more digging when presenting a piece like this. Robert had it right when he explained why his hand does not go through the table. Jim Holt is a philosopher. Ask a well respected physicist (Brian Greene would work) to make sure the philosopher isn't spewing "sciencey" sounding terms around to make some existential point that isn't rooted in reality. Every time this man spoke i let out a sigh. It is not right to let "New Age" Metaphysicians proselytize his beliefs(especially when he puts them up on a scientific pedestal.) At least check REAL experts first, or put a counter argument out there.

Jan. 01 2013 02:24 AM

Science! I enjoyed this short. I've been loving the most recent episodes, and after this one, I'd love to hear, say, an episode entirely dedicated to string theory. Get my boy Brian Greene in studio and hash it out. (I don't think there's been any Radiolab episode/segment on string theory, but I might be wrong.)

Dec. 31 2012 10:59 PM

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