William Gilbert, the British physicist and physician who experimentally verified the magnetic nature of our planet, contemplated with the ubiquity of magnetism.
A recent paper, authored by a pair of French and Canadian researchers, brought forward a hypothesis that echoes with Gilbert's idea: our entire universe could have been in a cosmic scale network of magnetic fields during its infancy. And what's more intriguing, this primordial presence of magnetism could be the key to resolve a major problem in astrophysics - Hubble tension.
In the mid-20th century, American astronomer Edwin Hubble famously concluded that our universe is expanding universe, based on his observation of our nearby galaxies are receding at a rate proportional to their distance from Earth.
These days physicists are deploying many advanced methods, including measuring minuscule ripples in the cosmic microwave background (CMB) and localized distance between faraway pulsating stars, to attempt an accurate estimate of the rate of the expansion. To their surprise, these observations revealed a small, yet mathematically irreconcilable difference between measured values, presenting a conundrum called the Hubble tension.
In the current publication, the cosmology duo argued that this problem could be mitigated through establishing weak magnetic fields in the early universe. As we know, a magnetic field is the product of the flow of electrically charged particles. And before the recombination era, a time roughly 370,000 years after the Big Bang, unbound, free-flowing electrons and protons were everywhere, providing the perfect backdrop for omnipresent magnetism.
Scientists theorized that once the initial separate fields were formed, they coalesced and became more prominent in size and strength, eventually forming a vast network that can cover the entire universe. These fields pushed and pulled the charged particles, causing "baryon inhomogeneities", in other words, uneven distribution of common matters.
The Hubble tension arises from the expansion rate discrepancy, obtained through measurements on historical and contemporary cosmic markers. The proposed primordial magnetic network could potentially explain why the expansion was slower in the early universe than currently.
The authors hope that their work could bring the primordial magnetism into the attention of the cosmology community. They are confident that by defining some of measurable parameters according to their new theory, future observation-based studies can help prove (or disprove) this intriguing idea.
This paper is available through the pre-print servicer arXiv.
Want to learn more about the omnipresence of magnetism? Check out this video from NASA.
Magnetism - Defending Our Planet, Defining The Cosmos (NASA Multimedia Science)
Source: Quanta Magazine
