Research claims that all observables in nature can be measured by a single constant.

A group of Brazilian researchers has published an innovative proposal that resolves a decades-old debate among theoretical physicists: how many fundamental constants are needed to describe the observable universe? “Fundamental constants” here refer to the basic standards necessary to measure anything.

This research will be published in the scientific journal Scientific Reports.

This group argues that the number of fundamental constants depends on the type of spacetime for which the theory is formulated. And in relativistic spacetime, this number can be reduced to a single constant used to define the basis of time. The study is an original contribution to the controversy sparked by a famous paper by Michael Duff, Lev Okun, and Gabriele Veneziano published in the Journal of High Energy Physics in 2002.

The whole story began ten years ago, in the summer of 1992, when three scientists met on the cafeteria terrace of CERN, the European Organization for Nuclear Research. In an informal conversation, they realized that they could not agree on the number of fundamental constants.

“In the summer of 2001, we returned to the subject and found that our opinions still differed. We therefore decided to explain our position,” the three wrote in their paper. It is written in the summary.

In short, Okun stated that three basic units are needed to measure all physical quantities: the meter (length), the kilogram (mass), and the second (time). In other words, he reaffirmed the so-called MKS system (M for meters, K for kilograms, S for seconds), which was later incorporated into the International System of Units (SI). Veneziano argued that the two units of time and length are sufficient in certain contexts. Duff was vague, saying the number of constants could change depending on the theory in question.

Explaining the new paper, Matsas said, “The goal is to find the most fundamental description of physics possible. The questions posed by Okun, Duff, and Veneziano are by no means trivial. Physics As academics, we are faced with the need to understand the nature of physics.” The minimum number of criteria needed to measure everything. ”

The Brazilian researchers argue that the number of fundamental constants depends on the space-time in which the physical quantity is considered. They analyze two types of spacetime. One is Galileo, whose classical mechanics was founded by Isaac Newton (1642-1727). And relativity forms the basis of Albert Einstein’s (1879-1955) general theory of relativity.

There are several relativistic spacestimes that correspond to different solutions of Einstein’s equations. The simplest of these is Minkowski spacetime, named after the German-born Jewish-Lithuanian mathematician Hermann Minkowski (1864-1909). It is a spacetime that is empty (absent of particles and everything else), homogeneous (all points have the same properties), and isotropic (all spatial directions are equal). For simplicity, the article in question uses Minkowski spacetime. However, the authors point out that their conclusions can be generalized to any relativistic spacetime.

“In Galilean spacetime, we need a ruler and a clock to measure all the physical variables. But in relativistic spacetime, a clock is sufficient. “One unit is enough.” High-precision clocks, such as the atomic clocks used today, can meet any measurement need,” says Matsas.

As can be seen from the previous sentence, even in Galilean spacetime a simplification of the fundamental quantities is already possible, omitting the mass.

“Historically, a kilogram was defined as the mass of one liter of pure water at a particular pressure and temperature, based on standardization efforts adopted during the French Revolution (1789-1799). It’s very useful to have mass. It’s standard, but from a fundamental point of view, it’s not necessary,” Vanzella says. “The mass of an object is given by the acceleration attracted to the particle when it is at a certain distance from the mass.”

In its current version, the International System of Units (SI) has seven basic units: meter (length), second (time), kilogram (mass), kelvin (temperature), ampere (current), and candela (light intensity). Use units. and moles (number of molecules or atoms).

“But these units are only basic because they serve a practical purpose. For example, if someone needs to buy a light bulb, the number of candelas is the amount of light that that light bulb needs to provide. However, it has been known for a long time how much light intensity these units should provide. Mostly the speed of light (c) and Planck’s constant (h) ” says Matsas.

According to the criterion used by Duff, Okun, and Veneziano, the number of fundamental constants is related to the minimum number of independent standards needed to represent all physical quantities. Again, in Galileo’s spacetime, all observable objects can be expressed in units of time and space, typically “seconds” and “meters.” In relativistic space-time, any observable object can be expressed in units of time, or “seconds.”

And the definition of a “second” is now based on a constant of nature, the energy difference between two specific levels of the cesium-133 electron layer. One second (1s) corresponds to the time of 9,192,631,770 oscillations of the radiation emitted when an electron passes between two states of cesium-133.

“Any artifact that can regularly count 9,192,631,770 vibrations of this radiation measures one second and can be considered an honest clock,” Matsas explains.

In other words, in relativistic space-time (the space-time in which we are thought to be living in the study in question), all physical quantities can be measured in seconds, the unit of time. While time is variable because it is always changing, a “second” is defined by a constant associated with a particular energy level in the electron layer of a cesium-133 atom.

“The judgment whether something observable is a constant of nature or not is absolute, because it is pronounced by an honest clock. For the very concept of space and time to make sense, that clock must exist. But the choice of which ‘fundamental constants’ are used, and defining them, is a social and historical construction that depends on convenience,” Vanzella comments. .

George Matsas and Vicente Pleitez of the Institute of Theoretical Physics of the State University of São Paulo (IFT-UNESP) and Alberto Saa of the Institute of Mathematics, Statistics and Scientific Computing of the State University of Campinas participated in this research ( IMECC -UNICAMP), Daniel Vanzella Paulo of the San Carlos Institute of Physics, University of San Carlos (IFSC-USP).