After the correct comments, this question is not here to compare gravity's and EM's long range forces' energetics and amplitudes to microscopic scattering amplitudes of such forces as weak and strong. I am basically trying to figure out if there is any observable effect in everyday life of the weak force. From the answers it is obvious that the weak force can be attractive or repulsive too. I am just trying to figure out if there is an observable effect of this (for the weak force) that we can see somehow in everyday life. Maybe not obvious, maybe we see it, experience it every day, we just do not know (that it is because of the weak force) it until it is explained in detail (like the strong force).

Maybe my question can be asked as simply as, 1. can the weak force pull/push (attr/rep) particles? 2. does it push/pull (attr/repl) particles in everyday life observable or is it just a rare thing, like decay? Does it hold something (particles) together or keep something apart in the everyday matter that we live in/around?

I have read these questions:

Weak force: attractive or repulsive?

Do strong and weak interactions have classical force fields as their limits?

Has the weak force ever been measured as a force?

As it is currently known,

  1. EM force is mediated by virtual photons, and can either be attractive or repulsive, and in everyday life it is easily observable, just hold a magnet. You can see the same thing with electricity. Then there is the covalent bond that makes molecules out of atoms. It is observable too, that the EM force is stronger on the short distance then gravity

  2. gravity, just let something go, and you see it is always attractive, there are obviously observable effects in everyday life, and it is observable that gravity on the short distance is weaker then the EM force or the strong force

  3. even the strong force, that keeps quarks confined, inside a nucleon, a neutron or proton, and the residual strong force that keeps neutrons and protons inside a nucleus, has an observable effect in everyday life, since without it, nuclei would not exist, they would fall apart. It is attractive on certain distances (between 0.8 fm and 2.5 fm), but it becomes repulsive at short distances (less then 0.7 fm), and that makes sure neutrons and protons do not get too close. This effect, though not commonly known, is responsible in part for giving material volume. It is observable too, that the strong force is stronger then gravity and EM on the short scale.

But what about the weak force? I know it can be repulsive or attractive, see here:

Weak force: attractive or repulsive?


For weak isospin, there are two isospin charges (or flavors), up and down, and their associated anti-charges, anti-up and anti-down.

up repels up (anti-up repels anti-up)
down repels down (anti-down repels anti-down)
up attracts down (anti-up attracts anti-down)
up attracts anti-up (down attracts anti-down)
up repels anti-down (down repels anti-up)

For weak hypercharge, there is just one type of charge and its associated anti-charge.

hypercharge repels hypercharge (anti-hypercharge repels anti-hypercharge)
hypercharge attracts anti-hypercharge

Note that electric charge is a certain mixture of weak isospin and weak hypercharge.

OK, so I know that the weak force can be either attractive or repulsive. But the answers say too, that the weak or strong force does not have a classical field theory. Still, the strong force does have observable (in everyday life) attractive or repulsive effects.


  1. But what about the weak force, are there any effects that are in everyday life observable where the weak force is attractive or repulsive?
  • $\begingroup$ You may be conflating/mushing two issues: the long range of classical-limit forces such as gravity and EM, in sharp contrast to short range ones such as EW and strong; and the energetics of their amplitudes, presenting as attractive/repulsive in their long range forms, but hardly meaningful in microscopic scattering amplitudes. Would you narrow or limit your question to avoid false implicit dichotomies? $\endgroup$ – Cosmas Zachos Apr 12 '19 at 16:17
  • $\begingroup$ @CosmasZachos thank you I will edit. $\endgroup$ – Árpád Szendrei Apr 12 '19 at 16:22
  • $\begingroup$ The tortured attraction/repulsion aside is dealt with here, and should probably be removed from the fire. $\endgroup$ – Cosmas Zachos Apr 12 '19 at 16:23
  • $\begingroup$ @CosmasZachos you are right. maybe my question can be asked as simply as, 1. can the weak force pull/push (attr/rep) particles? 2. does it push/pull (attr/repl) particles in everyday life observable or is it just a rare thing, like decay? Does it hold something together or keep something apart in the everyday matter that we live in/around? $\endgroup$ – Árpád Szendrei Apr 12 '19 at 16:32
  • 1
    $\begingroup$ I understand that you are asking about attractive/repulsive forces, but, as far as macroscopic effects in general, beta decay is definitely the main one. The proton-proton fusion that powers stars would be impossible without beta decay; most light radioisotopes decay this way; PET scans use it; its an important part of the decay chains of heavy elements; the s-process and r-process that make elements beyond nickel are differentiated by when beta decay is allowed to happen; neutron stars fuse protons and electrons into neutrons via electron capture more the further down you go. $\endgroup$ – H. H. Jul 28 '20 at 7:32

In everyday life? Like in your kitchen? No. Or if yes, totally not in the way that you're thinking.

If you insist on thinking of the fundamental interactions in terms of attraction and repulsion, one way to do that is to describe them all in terms of the Yukawa potential energy,

$$ U = \pm \alpha \frac{\hbar c}{r} e^{-r/r_0} $$

where the sign comes from the relative signs of the charges involved and distinguishes attractive from repulsive potentials, the coupling constant $\alpha$ is determined experimentally, and the range parameter

$$ r_0 = \frac{\hbar c}{mc^2} $$

depends on the mass $m$ of the field which mediates the interaction. For gravitation, electromagnetism, and the QCD color force, the this field (graviton, photon, gluon) is massless, so those forces in principle have infinite range. However, in the strong case, the coupling constant $\alpha$ is so large that multi-gluon exchanges are more important than single-gluon exchanges. This strong coupling means that color charges effectively can't be separated from each other, which is known as "color confinement." At low energies and long distances, the effective strong interaction is mediated by a spectrum of massive meson fields, whose own Yukawa potentials conspire to give the nuclei the structure that they have. An attractive force, mediated by pions, acts between nucleons that are separated by a few femtometers, but a repulsive force mediated by heavier mesons makes it expensive for nucleons to approach each other closer than about one femtometer.

For the weak interaction, the charged- and neutral-current bosons both have masses of nearly $100\,\mathrm{GeV}/c^2$. That's three orders of magnitude larger than the pion mass $140\,\mathrm{MeV}/c^2$, which is what mostly defines the size of a nucleon. So in order for nucleons to feel any attraction or repulsion due to the weak force, they would have be substantially "overlapping" in a way that's forbidden by the hard-core repulsion of the residual strong force. The effects of the strong force are much larger than the effects of the weak force --- partially because the coupling constants are different, but partially because the strong force prevents particles from approaching each other close enough that the weak force can affect them very much directly.

This same feature that makes the weak force mostly-irrelevant in nuclei (and more so in electromagnetically-bound systems, where the length scales are longer than in nuclei, and even more so in the even-larger gravitationally-bound systems) also makes the weak interaction harder to measure. In fact, measurements of the weak interaction would be impossible in strongly-interacting systems if the strong and weak interactions had the same set of symmetries, and we would be limited to patiently waiting for weak decays. However, we can take advantage the fact that the weak interaction is the only one of the fundamental forces which changes under mirror reflection.

If there's a way that the weak interaction affects life in your kitchen, it's because the weak interaction is parity-violating and the other fundamental interactions aren't. The Vester-Ulbricht hypothesis suggests a way that parity violation may have been important historically. But it's a much more subtle situation than "X is attracted to Y," because in contests of attraction and repulsion the weak interaction always loses to electromagnetism and the strong force.


The Fermi constant $G_F$ characterizing the weak interactions is half the square of $10^{-18}$m, hence a much shorter characteristic distance than the size of nuclei, or any composite particle.

That is why the weak interactions can help with microscopic decay and species mutation properties of particles, but can hardly amount to collective, coherent, macroscopic effects.

N.B. Aside. The strong force is not that different, in this respect: Even though its range is about a thousand times longer that that of the weak interactions, of the order of fermis, it too has no everyday-life macroscopic consequences not inherent in nuclear structure.


I would disagree with point three partially. It is true they hold nuclei together however you cannot say that it is a daily phenomena. On the same grounds you could speak about Beta decay for the weak force, but I would still not count them as daily life effects. Additionally, volume is not a property associated to the strong force. In terms of scales the EM force produced is the most relevant at daily scales in that respect. In other words the fact that you don't go through matter and it occupies a volume is mainly electromagnetic.

So all in all, the best argument I can give you has to do with the gauge bosons involved. You can classify forces into two, long-raged and short-ranged. The first ones fall off polynomially with distance while the latter falls off exponentially with distance. This has to do with the mass of the gauge boson that communicates such a force. Gravity, electromagnetism and the strong nuclear force are mediated by gravitons, photons and gluons respectively, all of which are massless and correspond to long-ranged forces. While the weak force is mediated by $W^{\pm},Z$ which are massive and therefore leads to it having a range proportional to $e^{-1/m_{Z,W^{\pm}}}$ which explains the difference in orders of magnitude in distance at which it is relevant.


If there were no weak interaction, the isotopic composition of many elements would be dramatically different: there would be much more atoms with more neutrons. I am sure that would affect our everyday life, but cannot provide more details right now.

An example of use of weak interaction in everyday life (although you may disagree) is positron-emission tomography (https://en.wikipedia.org/wiki/Positron_emission_tomography)


Everyday life? Maybe if you are a graduate student and live in the lab.

This comes from the Feynman Lectures, 52-2. Feynman is talking about symmetry and how to describe left and right to a martian. We cannot show an example. We have to use words.

Using a very strong magnet at a very low temperature, it turns out that a certain isotope of cobalt, which disintegrates by emitting an electron, is magnetic, and if the temperature is low enough that the thermal oscillations do not jiggle the atomic magnets about too much, they line up in the magnetic field. So the cobalt atoms will all line up in this strong field. They then disintegrate, emitting an electron, and it was discovered that when the atoms were lined up in a field whose B vector points upward, most of the electrons were emitted in a downward direction.

In short, we can tell a Martian where to put the heart: we say, “Listen, build yourself a magnet, and put the coils in, and put the current on, and then take some cobalt and lower the temperature. Arrange the experiment so the electrons go from the foot to the head, then the direction in which the current goes through the coils is the direction that goes in on what we call the right and comes out on the left.” So it is possible to define right and left, now, by doing an experiment of this kind.]1

Here is more on the CP and CPT symettries behind this. Time reversal and CPT symmetry (III)


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