Tag Archives: forces

Has a New Force of Nature Been Discovered?

There have been dramatic articles in the news media suggesting that a Nobel Prize has essentially already been awarded for the amazing discovery of a “fifth force.” I thought I’d better throw some cold water on that fire; it’s fine for it to smoulder, but we shouldn’t let it overheat.

There could certainly be as-yet unknown forces waiting to be discovered — dozens of them, perhaps.   So far, there are four well-studied forces: gravity, electricity/magnetism, the strong nuclear force, and the weak nuclear force.  Moreover, scientists are already fully confident there is a fifth force, predicted but not yet measured, that is generated by the Higgs field. So the current story would really be about a sixth force.

Roughly speaking, any new force comes with at least one new particle.  That’s because

  • every force arises from a type of field (for instance, the electric force comes from the electromagnetic field, and the predicted Higgs force comes from the Higgs field)
  • and ripples in that type of field are a type of particle (for instance, a minimal ripple in the electromagnetic field is a photon — a particle of light — and a minimal ripple in the Higgs field is the particle known as the Higgs boson.)

The current excitement, such as it is, arises because someone claims to have evidence for a new particle, whose properties would imply a previously unknown force exists in nature.  The force itself has not been looked for, much less discovered.

The new particle, if it really exists, would have a rest mass about 34 times larger than that of an electron — about 1/50th of a proton’s rest mass. In technical terms that means its E=mc² energy is about 17 million electron volts (MeV), and that’s why physicists are referring to it as the X17.  But the question is whether the two experiments that find evidence for it are correct. Continue reading

What is the “Strength” of a Force?

Particle physicists, cataloging the fundamental forces of nature, have named two of them the strong nuclear force and the weak nuclear force. [A force is simply any phenomenon that pushes or pulls on objects.] More generally they talk about strong and weak forces, speaking of electromagnetism as rather weak and gravity as extremely weak.  What do the words “strong” and “weak” mean here?  Don’t electric forces become strong at short distances? Isn’t gravity a pretty strong force, given that it makes it hard to lift a bar of gold?

Well, these words don’t mean what you think.  Yes, the electric force between two electrons becomes stronger (in absolute terms) as you bring them closer together; the force grows as one over the square of the distance between them.  Yet physicists, when speaking their own language to each other, will view this behavior as what is expected of a typical force, and so will say that “electromagnetism’s strength is unchanging with distance — and it is rather weak at all distances.

And the strength of gravity between the Earth and a bar of gold isn’t relevant either; physicists are interested in the strength of forces between individual elementary (or at least small) particles, not between large objects containing enormous numbers of particles.

Clearly there is a language difference here… as is often the case with words in English and words in Physics-ese.  It requires translation.  So I have now written an article explaining the language of “strong” and “weak” forces used by particle physicists, describing how it works, why it is useful, and what it teaches us about the known forces: gravity, electromagnetism, the strong nuclear force, the weak nuclear force, and the (still unobserved but surely present) Higgs force. Continue reading