Scientists find a surprising clue to why the universe’s expansion doesn’t add up
Scientists still lack agreement on how quickly the universe is growing. The mismatch between two well-established ways of estimating its expansion rate is known as the Hubble tension.
One approach uses patterns in the cosmic microwave background, the leftover glow of the Big Bang. Measurements from the Planck Space Telescope point to an expansion rate of about 67 kilometers per second per megaparsec.
A second approach estimates distances to far-off galaxies using Type Ia supernovae, whose brightness can serve as a distance marker. Observations involving the Hubble and James Webb space telescopes produce a higher estimate, around 73.
The gap is considered significant. If both measurement methods are sound, the standard model of cosmology may be missing an important piece.
New research examines whether faint magnetic fields formed soon after the Big Bang could help explain the discrepancy. The idea was first proposed in connection with the mystery of cosmic magnetic fields and may also shed light on physics at extreme energies.
Key points
- Cosmic microwave background data yield an expansion estimate near 67 km/s/Mpc.
- Supernova-based observations indicate a higher rate, around 73 km/s/Mpc.
- Researchers are testing whether ancient magnetic fields could help account for the disagreement.