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Scientists from Brazil are challenging the traditional view of universal constants, proposing that only one constant—time itself—is needed to measure relativistic spacetime.The research team argued for a paradigm shift, suggesting that establishing the exact spacetime being studied stabilizes the number of constants required for physical observations.Their paper explained that once physicists standardize variables for studying particular spacetimes, time remains the only fundamental constant needed.
According to the Standard Model of particle physics, there are 26 universal constants—physical quantities that always remain the same throughout our universe. These universal constants include the speed of light in a vacuum, Newton’s gravitational constant, Planck’s constant (the scale at which quantum effects begin), and the masses of the fundamental particles, along with a few others. But not all constants are the same. Most are dimensionless—pure numbers with no units. For example, since the masses of fundamental particles are usually expressed as ratios relative to a fundamental scale, such as the Planck mass, they are considered dimensionless. On the other hand, a few of the universal constants, such as the speed of light, are typically considered “dimensionful” because they are expressed in units. But just how many dimensionful universal constants are there—two, three, or even none? This question has long been a matter of debate among physicists.
Now, a team of scientists from Brazil has suggested that we only need one constant, or standard, to measure our own relativistic spacetime. This claim is controversial, as physicists have publicly argued for decades about the best way to marry “local” spacetime with the broader theory of relativity introduced by Albert Einstein and elaborated on in the following century-plus. In the work, the researchers suggest that the only constant value we need is the one most bystanders think of as variable: time itself. More importantly, time will tell if this contrary-sounding claim can hold up to scientific rigor around the world.
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This research was published in the journal Nature Scientific Reports by four coauthors, all of whom are colleagues at the Institute for Theoretical Physics at São Paulo State University in Brazil. In the paper, they explain that they’re suggesting we change the way we think about the question of constants, rather than introducing any kind of novel or confusing new answers. “[B]y having spacetime as the starting point,” the scientists wrote, “[…] it is shown that the same units fixed by the apparatuses used to construct the spacetimes are enough to express all observables of the physical laws defined over them. As a result, the number of fundamental constants equals one in relativistic spacetimes.”
In other words, since the world’s many physicists are doing work in different types of spacetimes, it might make sense to start any sorting or potential arguing by establishing the exact spacetimes being used. This, in turn, stabilizes the number of constants required, because they’re part of the work that physicists have done in even starting to examine that spacetime.
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There are many types of spacetime within physics, the same way there are infinite dimensions in math. Some spacetimes are linked with real-life scenarios within our universe, while others are thought exercises used to help physicists break through to new ideas or understandings.
So, once physicists stabilize the variables they need to begin to study a particular type of spacetime, just one question remains: time. The standardized measurement of time and the invention of clocks made much of modern life possible—including public transit, manufacturing, global sports, and even navigation—but our own time has little bearing on time elsewhere in the galaxy. After all, we’re bombarded with starlight that is billions of years old.
The 2017 primer Little Book of Time puts it this way: “The concept of relativistic spacetime is fundamental to the structure of modern physics. The measurement of time is no longer absolute, but is, according to special relativity theory, path-dependent.” In 2026, we may find it more fruitful to compare with others on the same path, and take time off the list.
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Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She’s also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, math of everyday things, and the philosophy of it all.