There’s a mystery behind the calculations of the universe’s expansion rate: a difference in numbers depending on what we’re measuring. The latest observations from the James Webb Space Telescope have made it possible to refine the calculations, but the disparity remains.
This is called the “Hubble voltage” and is the difference between the observed cosmic expansion and what it should be – a measurement called the Hubble constant (named after the 1920s astronomer Edwin Hubble). Basically, the expansion is faster than models allow based on what we know about the Big Bang. Put simply, this means that the equations are missing something fundamental and the new telescope’s observations don’t even suggest we’re close to a solution. Several theoretical physics texts in recent years have concluded that there would be no simple solution.
For cosmology, this is nothing less than its most important controversy: a controversy that concerns the composition of the universe, which is only 5% ordinary matter, compared to 27% “dark matter” and 68% dark energy. If we don’t know what the latter two are made of, we can at least deduce that it is the gravity of dark matter that gives galaxies their structure, and that it is the pressure exerted by dark energy (a type of repulsive gravitational force). , which determines the acceleration of the universe. This repulsive force would have gradually gained the upper hand in the evolution of the cosmos, which explains the fact that the expansion is accelerating.
But if this model helps explain why the expansion is accelerating – a discovery that is itself barely 25 years old – it does not allow us to go much further: what is this speed and how high will the acceleration be indefinitely stop? The fact that we don’t know what dark energy is doesn’t help understanding either, and the fact that some physicists are talking about how dark energy could represent a “new physics” means that consensus is a long time coming could leave. .
Since the moment acceleration was discovered a quarter of a century ago, astronomers have attempted various measurements, whether in our cosmic “suburbs” – the nearest galaxies – or as far away as could be observed. Basically, the new James-Webb observations confirm that the “real” acceleration is 8% faster than the “theoretical” acceleration.
There are still proponents of the theory that this is all a problem due to the limitations of our observations: in other words, this difference is a “fata morgana.” They have fewer arguments as the observations in question become more precise, but they have no reason to give up, at least until we find out whether there is actually a “new physics” hidden in dark energy.