Theoretical physicists Valerio Faraoni and Massimiliano Rinaldi published a pre-print paper on arXiv suggesting that black holes expand along with the universe, challenging the long-held assumption that gravitationally bound objects are entirely immune to cosmic expansion. This theoretical development arrives as observatories like the James Webb Space Telescope detect supermassive black holes in infant galaxies that defy standard astrophysical growth limits.
How Cosmological Expansion Affects Black Holes
For more than a century, physicists have modeled black holes using the Schwarzschild solution. This mathematical framework treats a black hole as an isolated, motionless object sitting inside an infinite, empty void that never changes. According to Faraoni and Rinaldi, that static condition does not reflect reality. Previous work by the pair showed that substituting a realistic expanding background into the static model creates a physically impossible naked singularity where the math fails.
To resolve this mathematical dilemma, the researchers tracked the apparent horizon—the boundary where gravity becomes so strong that light cannot escape. By building mathematical models of black holes formed in the early universe, they found that the only viable physical outcome occurs when the black hole becomes comoving with the cosmos. In short, the boundary expands at the exact same pace as the surrounding universe.
Did you know? The James Webb Space Telescope has pushed our view back to the dawn of the universe, uncovering supermassive black holes nestled inside infant galaxies that textbooks say should not be able to support them.
Solving the Early Universe Mass Mystery
Observations from the James Webb Space Telescope have consistently surprised astrophysicists by locating supermassive black holes just a few hundred million years after the Big Bang. Standard astrophysics textbooks rely on the Eddington limit, a physical speed limit governing how fast gas can fall into a black hole. Based on this limit, the early universe simply was not old enough for these objects to swallow enough gas to reach their observed sizes.
The new theory proposed by Faraoni and Rinaldi offers an alternative solution. If black holes expand alongside the universe, their massive size inside infant galaxies does not depend solely on swallowing gas at the Eddington limit. Instead, the expansion of the universe itself drives their growth, explaining an otherwise unexplainable cosmological puzzle.
Implications for Gravitational Wave Detectors
Modern-day gravitational wave observatories, including LIGO and Virgo, have recorded black hole collisions involving masses sitting squarely inside an upper mass gap. Stellar evolution models indicate that standard stars cannot create black holes of these specific sizes. If black holes continue to expand with the universe over time, researchers gain a viable mechanism for how these out-of-place masses can form and merge.
This cosmic expansion does not affect everyday life on Earth. Electromagnetic and gravitational forces tightly hold human biology and planetary structures together at scales far stronger than cosmic expansion. Even so, extreme gravitational wells like black holes cannot entirely shield themselves from the overarching stretching of space itself.
Pro Tip: Watch for upcoming data releases from the James Webb Space Telescope and gravitational wave detectors. Researchers expect these observatories to yield the empirical evidence needed to test whether black holes truly expand with the cosmos.
Frequently Asked Questions
Do black holes grow by absorbing matter?
Yes, black holes grow by accreting surrounding gas and dust, but theoretical models by Valerio Faraoni and Massimiliano Rinaldi suggest they may also expand directly with the background expansion of the universe.
Why do early universe supermassive black holes puzzle scientists?
According to data from the James Webb Space Telescope, supermassive black holes existed hundreds of millions of years after the Big Bang, which exceeds the growth rate permitted by the Eddington limit.
Does cosmic expansion tear apart solar systems or black holes?
No. Gravitationally bound systems like solar systems and local galaxies are held together by forces much stronger than cosmic expansion, though theoretical physics suggests black hole horizons themselves may still scale with the universe.
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