Why The Higgs Field is Nothing Like Molasses, Soup, or a Crowd

The idea that a field could be responsible for the masses of particles (specifically the masses of photon-like [“spin-one”] particles) was proposed in several papers in 1964. They included one by Peter Higgs, one by Robert Brout and Francois Englert, and one, slightly later but independent, by Gerald Guralnik, C. Richard Hagen, and Tom Kibble. This general idea was then incorporated into a specific theory of the real world’s particles; this was accomplished in 1967-1968 in two papers, one written by Steven Weinberg and one by Abdus Salam. The bare bones of this “Standard Model of Particle Physics” was finally confirmed experimentally in 2012.

How precisely can mass come from a field? There’s a short answer to this question, invented a couple of decades ago. It’s the kind of answer that serves if time is short and attention spans are limited; it is intended to sound plausible, even though the person delivering the “explanation” knows that it is wrong. In my recent book, I called this type of little lie, a compromise that physicists sometimes have to make between giving no answer and giving a correct but long answer, a “phib” — a physics fib. Phibs are usually harmless, as long as people don’t take them seriously. But the Higgs field’s phib is particularly problematic.

The Higgs Phib

The Higgs phib comes in various forms. Here’s a particularly short one:

There’s this substance, like a soup, that fills the universe; that’s the Higgs field. As objects move through it, the soup slows them down, and that’s how they get mass.

Some variants replace the soup with other thick substances, or even imagine the field as though it were a crowd of people.

How bad is this phib, really? Well, here’s the problem with it. This phib violates several basic laws of physics. These include foundational laws that have had a profound impact on human culture and are the first ones taught in any physics class. It also badly misrepresents what a field is and what it can do. As a result, taking the phib seriously makes it literally impossible to understand the universe, or even daily human experience, in a coherent way. It’s a pedagogical step backwards, not forwards.

What’s Wrong With The Higgs Phib

So here are my seven favorite reasons to put a flashing red warning sign next to any presentation of the Higgs phib.

1. Against The Principle of Relativity

The phib brazenly violates the principle of relativity — both Galileo’s original version and Einstein’s updates to it. That principle, the oldest law of physics that has never been revised, says that if your motion is steady and you are in a closed room, no experiment can tell you your speed, your direction of motion, or even whether you are in motion at all. The phib directly contradicts this principle. It claims that

• if an object moves, the Higgs field affects it by slowing it down, while
• if it doesn’t move, the Higgs field does nothing to it.

But if that were true, the action of the Higgs field could easily allow you to distinguish steady motion from being stationary, and the principle of relativity would be false.

2. Against Newton’s First Law of Motion

The phib violates Newton’s first law of motion — that an object in motion not acted on by any force will remain in steady motion. If the Higgs field slowed things down, it could only do so, according to this law, by exerting a force.

But Newton, in predicting the motions of the planets, assumed that the only force acting on the planets was that of gravity. If the Higgs field exerted an additional force on the planets simply because they have mass (or because it was giving them mass), Newton’s methods for predicting planetary motions would have failed.

Worse, the slowing from the Higgs field would have acted like friction over billions of years, and would by now have caused the Earth to slow down and spiral into the Sun.

3. Against Newton’s Second Law of Motion

The phib also violates Newton’s second law of motion, by completely misrepresenting what mass is. It makes it seem as though mass makes motion difficult, or at least has something to do with inhibiting motion. But this is wrong.

As Newton’s second law states, mass is something that inhibits changes in motion. It does not inhibit motion, or cause things to slow down, or arise from things being slowed down. Mass is the property that makes it hard both to speed something up and to slow it down. It makes it harder to throw a lead ball compared to a plastic one, and it also makes the lead ball harder to catch bare-handed than a plastic one. It also makes it difficult to change something’s direction.

To say this another way, Newton’s second law F=ma says that to make a change in an object’s motion (an acceleration a) requires a force (F); the larger the object’s mass (m), the larger the required force must be. Notice that it does not have anything to say about an object’s motion (its velocity v).

To suggest that mass has to do with motion, and not with change in motion, is to suggest that Newton’s law should be F=mv — which, in fact, many pre-Newtonian physicists once believed. Let’s not let a phib throw us back to the misguided science of the Middle Ages!

4. Not a Universal Mass-Giver

The phib implies that the Higgs field gives mass to all objects with mass, causing all of them to slow down. After all, if there were a universal “soup” found everywhere, then every object would encounter it. If it were true that the Higgs field acted on all objects in the same way — “universally”, similar to gravity, which pulls on all objects — then every object in our world would get its mass from the Higgs field.

But in fact, the Higgs field only generates the masses of the known elementary particles. More complex particles such as protons and neutrons — and therefore the atoms, molecules, humans and planets that contain them — get most of their mass in another way. The phib, therefore, can’t be right about how the Higgs field does its job.

5. Not Like a Substance

As is true of all fields, the Higgs field is not like a substance, in contrast to soup, molasses, or a crowd. It has no density or materiality, as soup would have. Instead, the Higgs field (like any field!) is more like a property of a substance.

As an analogue, consider air pressure (which is itself an example of an ordinary field.) Air is a substance; it is made of molecules, and has density and weight. But air’s pressure is not a thing; it is a property of air, , and is not itself a substance. Pressure has no density or weight, and is not made from anything. It just tells you what the molecules of air are doing.

The Higgs field is much more like air pressure than it is like air itself. It simply is not a substance, despite what the phib suggests.

6. Not Filling the Universe

The Higgs field does not “fill” the universe any more than pressure fills the atmosphere. Pressure is found throughout the atmosphere, yes, but it is not what makes the atmosphere full. Air is what constitutes the atmosphere, and is the only thing that can be said, in any sense, to fill it.

While a substance could indeed make the universe more full than it would otherwise be, a field of the universe is not a substance. Like the magnetic field or any other cosmic field, the Higgs field exists everywhere — but the universe would be just as empty (and just as full) if the Higgs field did not exist.

7. Not Merely By Its Presence

Finally, the phib doesn’t mention the thing that makes the Higgs field special, and that actually allows it to affect the masses of particles. This is not merely that it is present everywhere across the universe, but that it is, in a sense, “on.” To give you a sense of what this might mean, consider the wind.

On a day with a steady breeze, we can all feel the wind. But even when the wind is calm, physicists would say that the wind exists, though it is inactive. In the language I’m using here, I would say that the wind is something that can always be measured — it always exists — but

• on a calm day it is “off” or “zero”, while
• on a day with a steady breeze, it is “on” or “non-zero”.

In other words, the wind is always present, whether it is calm or steady; it can always be measured.

In rough analogy, the Higgs field, though switched on in our universe, might in principle have been off. A switched-off Higgs field would not give mass to anything. The Higgs field affects the masses of elementary particles in our universe only because, in addition to being present, it is on. (Physicists would say it has a “non-zero average value” or a “non-zero vacuum expectation value”)

Why is it on? Great question. From the theoretical point of view, it could have been either on or off, and we don’t know why the universe arranged for the former.

Beyond the Higgs Phib

I don’t think we can really view a phib with so many issues as an acceptable pseudo-explanation. It causes more problems and confusions than it resolves.

But I wish it were as easy to replace the Higgs phib as it is to criticize it. No equally short story can do the job. If such a brief tale were easy to imagine, someone would have invented it by now.

Some years ago, I found a way to explain how the Higgs field works that is non-technical and yet correct — one that I would be happy to present to my professional physics colleagues without apology or embarrassment. (In fact, I did just that in my recent talks at the physics departments at Vanderbilt and Irvine.) Although I tried delivering it to non-experts in an hour-long talk, I found that it just doesn’t fit. But it did fit quite well in a course for non-experts, in which I had several hours to lay out the basics of particle physics before addressing the Higgs field’s role.

That experience motivated me to write a book that contains this explanation. It isn’t brief, and it’s not a light read — the universe is subtle, and I didn’t want to water the explanation down. But it does deliver what it promises. It first carefully explains what “elementary particles” and fields really are [here’s more about fields] and what it means for such a “particle” to have mass. Then it gives the explanation of the Higgs field’s effects — to the extent we understand them. (Readers of the book are welcome to ask me questions about its content; I am collecting Q&A and providing additional resources for readers on this part of the website.)

A somewhat more technical explanation of how the Higgs field works is given elsewhere on this website: check out this series of pages followed by this second series, with additional technical information available in this third series. These pages do not constitute a light read either! But if you are comfortable with first-year university math and physics, you should be able to follow them. Ask questions as need be.

Between the book, the above-mentioned series of webpages, and my answers to your questions, I hope that most readers who want to know more about the Higgs field can find the explanation that best fits their interests and background.