What’s the Smallest Particle in the Universe?

What is the smallest particle in the universe?

By Gayoung Lee Edited by Lee Billings

Forget the turtles; For all practical purposes, they are really particles all along.

Whether as protons and neutrons who help form chemical elements, the photons that we perceive as light or even the electrons flows that feed our smartphones, the subatomic particles constitute essentially everything that we will live. Ironically, however, because they are so tiny, the particles underlying our daily reality tend to escape our opinion and our understanding.

Consider the apparently simple question of their size, the very thing that makes them so foreign. We are generally taught to imagine all particles as tiny colorful spheres, as if they were solid things that we could put a rule alongside to determine their dimensions as we would have for any other physical object in the world. But the subatomic particles do not look like that at all. And while for the greatest particles, there are ways to measure the “size” in a very general sense, for those who are smaller and ostensibly more “fundamental”, the concept of size itself is so slippery that it becomes almost meaningless.

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However, if Google requests are a guide, people want to really know “what is the smallest particle in the universe?” It doesn’t matter that the best question could be “is there a moment to ask?”

First things first

“There are a lot of meanings for” small “,” explains Janet Conrad, particle physicist at the Massachusetts Institute of Technology. “Like, I could say that a cotton ball is` small ” because it is very light. Or I could say that a small metal ball is `small ” because its radius is very small, but it would weigh much more than the cotton ball.”

The Conrad point is that there is a categorical difference between a particle which is “the smallest” in mass and a particle of “the smallest” diameter. There is also another important categorical difference to take into account the functional distinction between two classes of different particles: farms, or “matter” particles such as protons or electrons that make up everything in the universe, and bosons, or “carriers” particles such as photons that provide strengths between fermions.

And most fundamentally, there is the question of so -called fundamental particles, which are separated from those apparently non -fundamental. Whether it is a fermion or a boson, physicists consider a “fundamental” particle if it cannot be more decomposed with a technology currently available. In this sense, certain relatively known particles, such as protons, are not fundamental particles; If you hit a proton with a certain strength, it will burst into quarks, which are considered fundamental.

So, in terms of physical size, you would probably think that fundamental particles would be “smaller” than non -fundamental. But this is where things become really difficult, explains Juan Pedro Ochoa-Ricoux, particle physicist at the University of California in Irvine. According to the standard model of particles physics, which incorporates all the particles and forces known in addition to gravity to make ridiculously precise physical predictions, all the fundamental particles Have no size. In other words, asking if one is larger or smaller than another is an absurd question, similar to wondering what is north of “up” or trying to divide by zero.

Dimension chance?

“”[Fundamental particles] are Euclidian points, “says Ochoa-Ricoux.” They are not even one-dimensional. We consider them as [zero-dimensional] points [that] do not have a determined position. And therefore, rather than thinking of electrons like small balls that go around an atomic nucleus, in reality, we should consider them as a cloud [of probabilities]. “”

All fundamental particles seem to be in this way, showing no signs of deeper internal structure, adds Conrad. “We continue to test to see if there is a spatial extent associated with them,” she says, “but we see no evidence that there is something inside these particles.”

Physicists like to circumvent this uncertainty, known as Ochoa-Ricoux, by making reverse calculations using the famous equation of Albert Einstein E = MC²which quantifies the equivalence between energy and mass. More specifically, these calculations generally involve the VOLT electron (EV), an energy unit for which 1 EV represents the load of an electron. The use of the Einstein equation to convert this mass value reveals that the electron actually weighs approximately 0.51 mega-electrons per speed at the light square (0.51 mev / c²)-that is to say about 9.109 × 10^–31 kilogram. In comparison, the “lightest” quark, the Quark up, is more than four times heavier, weighing approximately 2.14 MEV / C².

As small as these values ​​are, they are still much greater than “zero”, which is the mass deduced for certain other particles. These so-called mass-free particles are undoubtedly the best candidates for the “smaller”.

A question, many answers

Strictly speaking of bosons or force transport particles, the clear winner of competition for the “smaller particle of the universe” would be the photon without mass. (Gluons – Bosons that bind together – are also considered to be without mass but are much more difficult to study because they are generally trapped inside protons and neutrons.) If we speak of climbs, the particles which are the constituent elements of matter – a reasonable supposition for the smallest particle of the universe would be neutrino. It is a “assumption” because we do not really know the exact mass of a neutrino for some, although we are sure that it is not zero. To put the mass of neutrino in perspective, it probably weighs approximately 0.45 EV / C²– Less than a millionth the mass of an electron!

But again, as Ochoaa-Ricoux and Conrad independently point out, it is only an approach that experts tend to use when considering the size of a particle. As with many types of scientific survey, the answer you get depends intimately on how you ask exactly the question.