How Heavy Can a Particle of Light Be? Scientists Just Figured It Out

how heavy can a particle of light be? scientists just figured it out

We have a new upper limit for the mass of light.

According to measurements of pulsing stars scattered throughout the Milky Way and mystery radio signals from other galaxies, a particle of light – called a photon – can be no heavier than 9.52 × 10-46 kilograms.

It's a tiny limit, but finding that light has any mass at all would significantly impact how we interpret the Universe around us, and our understanding of physics.

Photons, typically, are described as massless particles. These discrete quantities of energy zip through space-time at a constant speed, unable to accelerate or slow down in a vacuum. This constant velocity implies masslessness, and there isn't evidence to the contrary.

However, we don't know for absolute certainty that photons are massless.

A non-zero mass would have profound implications. It would contradict Einstein's special relativity, and Maxwell's electromagnetic theory, probably leading to new physics, and possibly answering some giant questions about the Universe (although raising many more in the process).

If a photon did have mass, it would need to be extremely small to not have major effects on the way the Universe appeared, which means that we just don't have the tools to measure it directly.

But we can take indirect measurements that will give us an upper limit for this hypothetical mass, and this is exactly what a group of astronomers did.

A team from Sichuan University of Science & Engineering, the Chinese Academy of Sciences, and Nanjing University analyzed data collected by the Parkes Pulsar Timing Array and data on fast radio bursts from a number of sources to determine how massive light can possibly be.

A pulsar timing array is an array of radio telescope antennas to monitor neutron stars that send out pulsing beams of electromagnetic radiation on extremely precise millisecond pulsars. Fast radio bursts are extremely powerful bursts of light of unknown origin that are detected across vast intergalactic gulfs of space.

The property the researchers examined is known as the dispersion measure, one of the key attributes of pulsars and fast radio bursts. It refers to how much a tightly pulsed beam of radio light is scattered by the free electrons between us and the light source.

If photons have mass, their propagation through non-vacuum space populated by plasma would be affected both by the mass and the free electrons in the plasma. This would lead to a delay time proportional to the mass of the photon.

A pulsar timing array looks for delays in the timing of pulsar pulses relative to each other. Particularly within the ultrawide bandwidth, the dispersion effects can be minimized, allowing the researchers to calculate how much delay could be contributed by the hypothetical photon mass.

Meanwhile, dedispersing the signals from fast radio bursts can also reveal a delay proportional to the photon mass.

By carefully studying this data, the team was able to derive their upper limit of 9.52 × 10-46 kilograms (or, in equivalent energy, 5.34 × 10-10 electron volts c-2). Note that this doesn't mean that the photon has mass; it just means that we have a new boundary wherein the mass could fall, if it existed.

"This is the first time," the authors write, "that the interaction between a nonzero photon mass and the plasma medium has been taken into account and calculated as the photon propagates through the plasma medium."

It's not very much lower than a measurement published in 2023, but it is a refinement. This means that scientists investigating the effects of a hypothetical photon mass have a more precise range in which to operate.

The study also demonstrates, the astronomers say, the need for highly precise radio telescopes. We're not likely to be able to weigh a photon anytime soon, but obtaining consistently higher-quality data will allow us to narrow the measurement down further, and with it its potential effects on the Universe around us.

The research has been published in The Astrophysical Journal.

OTHER NEWS

18 minutes ago

Russia takes revenge on Japan with Toyota boss ban

18 minutes ago

Archive: Flyers' 'New Era of Orange' Began In Earnest With Teardown Process

18 minutes ago

Report: Jets offered Haason Reddick extension before trade

18 minutes ago

Trump campaign says it's 'well-positioned to prosecute the case' against Kamala Harris

18 minutes ago

Gutherson’s role locked in for rest of 2024

18 minutes ago

Brush fire sparks along Saanich's Pat Bay Highway

18 minutes ago

Donald Trump Heads to North Carolina Under Pressure

18 minutes ago

Big Lots store closures 2024: Full list of shops shutting amid financial woes

18 minutes ago

Hillary Clinton says Harris can beat Trump despite ‘sexism’ in politics

18 minutes ago

Laziness has become the new British disease

18 minutes ago

Two Russian and two Chinese bombers are intercepted off Alaskan coast

18 minutes ago

Millions are given common painkillers that 'may make them MORE ill'

18 minutes ago

What is ‘rejection therapy’? The latest TikTok trend pushes people to combat social anxiety

18 minutes ago

Japan's Honda to close China plant, halt production at another factory

19 minutes ago

Video: Alabama pastor tells congregation how he wrestled gun off his 'murderer' grandson minutes after mom and four children were massacred at home - and reveals a shocking family secret

19 minutes ago

In this Uganda region, most women report domestic violence. Signed pledges are being used to end it

19 minutes ago

Kate Beckinsale, Emma Roberts and Camilla Cabello wear long black dresses for Summer Gala

19 minutes ago

Cher announces release date for forthcoming two-part memoir

19 minutes ago

Steelers' Najee Harris confirms he wants to stay in Pittsburgh despite disappointment over contract situation

19 minutes ago

Senator Professor Warren Has Big Plans to Restore the Chevron Deference

19 minutes ago

Francisco Lindor joins elite MLB group in Mets' rout of Yankees

19 minutes ago

Ireland 7s secure place in Olympic quarter-finals after hammering Japan

19 minutes ago

Lower your carbon calories with these flavourful vegan recipes

19 minutes ago

Top 10 African countries with the lowest fuel prices in July 2024

19 minutes ago

LIV Golf star Jon Rahm has choice words for golf and Olympics critics

19 minutes ago

India is on alert after a fresh outbreak of the deadly Nipah virus. Here’s what you need to know

19 minutes ago

Video: Australian singer Firerose makes a huge move following split from Billy Ray Cyrus - after shocking audio of him verbally abusing her in expletive-ridden rant emerges

19 minutes ago

Video: Kourtney Kardashian's rarely-seen son Mason makes shock return to reality TV amid secret family heartbreak

19 minutes ago

Video: Kim Kardashian CENSORS the name of ex boyfriend she DUMPED after he questioned her lifestyle choices... and fan theories go wild

19 minutes ago

North Korea trash balloons disrupt flights in Seoul, cause rooftop fire

19 minutes ago

Cordlife subsidiaries in Hong Kong, Malaysia obtain re-accreditations

19 minutes ago

Learner driver, supervisor penalised for lead-footed freeway run

19 minutes ago

Taylor Decker "hopeful" about receiving an extension from Lions

19 minutes ago

Call for AFL to fix ‘messy process’

19 minutes ago

Eiffel Tower stadium wows Olympic beach volleyball players: 'I got goosebumps'

19 minutes ago

Chariots of Fire review – hugely enjoyable production that’s not just running on the spot

19 minutes ago

Japan's population falls for a 15th year with record low births and record high deaths

19 minutes ago

Are these dogs good for owners with allergies? Hypoallergenic dog breeds

19 minutes ago

How to get rid of slugs

19 minutes ago

Judge rules health legislation unconstitutional in ‘major blow to NHI idea’