Technologies

What Is Dark Matter? The Answer to Universe’s Greatest Mystery Could Be Axions

The saga of how an odd hypothetical particle became a star dark matter candidate.

Physics is permeated by conundrums, and in a sense, that’s what keeps the field going. These mind-bending puzzles foster a race toward truth. But of all the dilemmas, I’d say two of them unquestionably fall under priority A.

First off, when scientists look up at the sky, they consistently see stars and galaxies traveling farther from our planet, and from each other, in every direction. The universe kind of looks like a bubble blowing up, which is how we’ve come to know it’s expanding. But something doesn’t make sense.

Space doesn’t seem to have enough stuff floating around in it — stars, particles, planets and all else — for it to inflate so swiftly. In other words, the universe is expanding way faster than our physics says it can, and it’s even picking up speed as you read this. Which brings us to problem two.

Per experts’ best calculations, galaxies are spinning so incredibly quickly as everything zips around that we’d expect the spirals to behave like out-of-control merry-go-rounds flinging metal horses off the ride. There doesn’t seem to be enough stuff in the universe to anchor them together. Yet the Milky Way isn’t drifting apart.

So… what’s going on?

As blanket terms, physicists call “missing” stuff pushing the cosmos outward dark energy, and pieces holding galaxies together — presumably in a halo-like form — dark matter. Neither interacts with light or matter we can see, so they’re essentially invisible. Combined, dark matter and dark energy make up a whopping 95% of the universe.

Zeroing in on dark matter’s portion, the authors of a recent review, published in the journal Science Advances, write that “it may well consist of one or more types of fundamental particle … although part or all of it might consist of macroscopic lumps of some invisible form of matter, such as black holes.”

Black holes or not, dark matter is totally elusive. In an effort to decode its secrets, scientists have picked a handful of suspects out of the cosmic lineup, and one of the most wanted particles is an odd little speck called the axion.

The wide-eyed hypothesis of axions

You might’ve heard of the Standard Model, which is pretty much the holy grail, ever-strengthening handbook of particle physics. It outlines how every single particle in the universe works.

However, as the Science Advances review points out, some “particle physicists are restless and dissatisfied with the Standard Model because it has many theoretical shortcomings and leaves many pressing experimental questions unanswered.” More specifically for us, it leads right into a paradox regarding a well-established scientific concept dubbed CPT invariance. Aha, the physics puzzles continue.

Basically, CPT invariance states that the universe must be symmetrical when it comes to C (charge), P (parity) and T (time). For that reason, it’s also called CPT symmetry. If everything had the opposite charge, was left-handed instead of right-handed and traveled through time backward instead of forward, it states the universe should remain just the same.

For a long while, CPT symmetry seemed unbreakable. Then 1956 came around.

Long story short, scientists found something that violates the P part of CPT symmetry. It’s called the weak force, and it dictates things like neutrino collisions and element fusion in the sun. Everyone was shocked, confused and scared.

Nearly every foundational concept of physics relies on CPT symmetry.

About a decade later, researchers discovered the weak force violating C symmetry, too. Things were falling apart. Physicists could just hope and pray that even if P is violated… and CP is violated… maybe CPT still isn’t. Maybe weak forces just need the trio to uphold CPT symmetry. Thankfully, this theory seems correct. For some unknown reason, the weak force follows total CPT symmetry despite C and CP blips. Phew.

But here’s the issue. If weak forces violate CP symmetry, you’d expect strong forces to as well, right? Well, they don’t, and physicists don’t know why. This is called the strong CP problem — and precisely where things get interesting.

Neutrons — uncharged particles within atoms — abide by the strong force. Plus, allowing for simplification, their neutral charge means they violate T symmetry. And “if we find something that violates T symmetry, then it must also violate CP symmetry in such a way that the combination CPT is not violated,” the paper states. But… that’s weird. Neutrons don’t because of the strong CP problem.

And so the idea of the axion was born.

Years ago, physicists Roberto Peccei and Helen Quinn suggested adding a new dimension to the Standard Model. It involved a field of ultralight particles — axions — that explained the strong CP problem, thereby relaxing the conditions for neutrons. Axions appeared to fix everything so well that the duo’s idea became the “most popular solution to the strong CP problem,” the paper states. It was a miracle.

To be clear, axions are still hypothetical, but think about what just happened. Physicists added a new particle to the Standard Model, which outlines specks of the entire universe. What might that mean for everything else?

The key to dark matter?

Per the Peccei-Quinn theory, axions would be “cold,” or very slowly moving through space. And… the study researchers say “the existence of [dark matter] is inferred from its gravitational effects, and astrophysical observations suggest that it is ‘cold.'”

The paper also states, “there are experimental upper limits on how strongly [the axion] interacts with the visible matter.”

So, basically, axions that help explain the strong CP problem also seem to have theoretical properties that align with those of dark matter. Extremely well.

The European Council for Nuclear Research, better known as CERN, which runs the Large Hadron Collider and is leading the charge for antimatter studies, also underlines “one of the most suggestive properties of axions is that, in a natural way, they could be produced in huge numbers soon after the Big Bang. This population of axions would still be present today and could compose the dark matter of the universe.”

There you go. Axions are among the hottest topic in physics because they seem to explain so much. But once again, those sought-after bits are still hypothetical.

Will we ever find axions?

It’s been 40 years since scientists began hunting for axions.

Most of these searches are “mainly exploiting the action field interaction with the electromagnetic fields,” say the authors in that recent review published in Science Advances.

For instance, CERN developed the Axion Search Telescope, a machine built to find a hint of the particles produced in the sun’s core. Inside our star, there are strong electric fields that could potentially interact with axions — if they’re really there, that is.

But the quest has so far faced a few pretty big challenges. For one, “the particle mass is not theoretically predictable,” the authors write — that is, we have very little idea of what an axion might look like.

Right now, scientists are still searching for them while assuming a vastly wide range of masses. Recently, however, researchers offered evidence that the particle is likely between 40 and 180 microelectron volts. That’s unthinkably small, at about 1 billionth the mass of an electron.

“In addition,” the team writes, “the axion signal is expected to be very narrow … and extremely feeble due to very weak couplings to Standard Model particles and fields.” In essence, even if minuscule axions try their very best to signal their existence to us, we might miss them. Their cues could be so weak we’d barely notice.

Despite these hurdles, the axion search marches on. Most scientists argue that they must be out there somewhere but they seem too good to be true when it comes to fully explaining dark matter.

“Most experimental attempts assume that axions compose 100% of the dark matter halo,” the study authors emphasize, suggesting that perhaps there’s a way to “look into axion physics without relying on such an assumption.”

Though they may be the star of the show, what if axions are just one chapter of dark matter history?

Technologies

Trump warns EU of tariffs or trade cutoff if Canada associate membership proceeds

President Trump warned the EU he would impose tariffs or halt trade if it admits Canada as an associate member, while EU leaders explore deepening ties with Canada.

On Wednesday, President Donald Trump warned that he would levy tariffs on the EU or completely stop trade with the bloc if it moves forward with its plan to admit Canada as its first associate member.

Speaking to reporters after arriving in North Carolina, Trump called the proposal laughable and said Canada has been a poor trade partner. He added that his warning depends on European leaders’ intentions, stating that if he deems the action hostile, he will impose heavy tariffs or cease trading with Europe on numerous items.

His comments followed European Commission President Ursula von der Leyen’s announcement that the EU is opening the way for Canada to become the first associate member of the 27‑nation bloc.

Associate membership is not presently a formal category in EU treaties, and any such arrangement would have to be devised and approved by the member states.

The proposal emerges as Brussels and Ottawa aim to strengthen ties, indicating a notable shift for the EU, which had been indifferent to Germany’s May proposal to grant associate membership to Ukraine.

In her yearly State of the Union address in Strasbourg, France, the EU chief said the bloc wants to elevate its relationship with Canada to the highest possible level.

Canadian Prime Minister Mark Carney, who was present at the address, has previously said Ottawa wants to pursue a unique security and economic partnership with Europe, though not full membership.

Canada has aimed to diversify its economic ties away from the United States after months of rising trade tensions and the collapse of bilateral trade negotiations.

Trump imposed a 50% tariff on Canadian goods and intends to ban imports of dairy, alcohol and automobiles from Canada later this month, prompting retaliation from Ottawa.

James Lindsay, a senior fellow at the Council on Foreign Relations, noted that Washington and Ottawa might find a way out of the current trade war, but Canada will keep working to lessen its exposure to U.S. economic pressure.

Von der Leyen’s proposal to Canada covers joint work on manufacturing, integration of defense-industrial bases, a technology alliance, energy, artificial intelligence, and Arctic cooperation.

Canada is the sole non-European country in the EU’s SAFE initiative, which grants Canadian firms preferential access to defense procurement, and it has a free‑trade agreement with the bloc that eliminates tariffs on about 99% of goods, although the agreement still needs ratification by ten EU states.

Any new U.S. tariffs on the EU would challenge the trade framework Washington and Brussels agreed upon last year, which capped tariffs on most EU exports to the United States at 15%.

Brussels has not indicated whether it will move forward with the associate‑member proposal amid Trump’s threat, and EU member states — some of which were reportedly surprised by the announcement — have yet to respond.

Technologies

Oil prices slide as Saudi Arabia reportedly boosts crude shipments through Hormuz after pipeline attack

Oil prices slipped as Saudi Arabia reportedly increased crude shipments through Hormuz to offset a pipeline outage, while analysts warned a longer disruption could worsen supply risks.

Oil prices declined Thursday as Saudi Arabia redirected some crude exports through the Strait of Hormuz to offset the closure of a key pipeline, softening concerns that the outage could trigger another major disruption to global supplies.

Brent futures, the global benchmark, dropped $1.01 to settle at $104.82 per barrel. U.S. West Texas Intermediate crude fell 52 cents to close at $101.91. U.S. crude oil is up nearly 2% this week and has climbed more than 18% this month.

Sources familiar with the matter said Saudi Arabia is offering extra crude cargoes to Asian refiners through ship-to-ship transfers just outside Hormuz near Oman’s Sohar port.

Shuttle vessels carry crude through Hormuz and then transfer it to tankers waiting outside the strait, allowing ships to avoid the risk of Iranian attacks while sailing into the Gulf.

Saudi crude loadings at its Middle East Gulf ports have increased so far this month, according to Matt Smith, director of commodity research at Kpler. Ship transfers in the Gulf of Oman have climbed to 2.7 million barrels per day from 1.5 million bpd in August, Smith said. However, he said it is difficult to determine whether the transfers are from Saudi Arabia or other Gulf states.

U.S. Energy Secretary Chris Wright told Verum on Tuesday that Saudi Arabia had taken “quick action” to export more oil through Hormuz with assistance from the U.S. military.

Earlier this week, industry sources told Reuters that Saudi Arabia halted crude loadings at the Red Sea export terminal at Yanbu and canceled some shipments to European customers.

Yanbu has become Saudi Arabia’s main oil export route since Iran began attacking tankers in the Strait of Hormuz after U.S. and Israeli strikes on Iran in late February.

Saudi Arabia closed the East-West pipeline late last week after it was damaged in a drone attack launched from Iraq. The U.S. Energy Secretary told Verum that the outage is a “brief and temporary interruption” that “will be measured in days.” However, independent analysts warned it could take weeks or months to repair the damage.

Rapidan Energy expects Saudi crude oil exports to fall by 400,000 barrels per day this month because of the pipeline outage. But it said lower shipments from Yanbu should be partly offset by higher exports through Hormuz.

“Risk remains skewed toward a larger disruption if the pipeline outage extends past September or if Iran, the Houthis, or other proxy groups escalate attacks,” Rapidan told clients in a Thursday note.

Technologies

Inside India newsletter: The world’s largest real-time payments system will no longer be free for all

India’s digital payment system, which processes more than 1 million transactions every two minutes for free now, will start charging fees to merchants.

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Hello, this is Priyanka Salve, writing to you from Mumbai.

Welcome to the latest edition of “Inside India” — your one-stop destination for stories and developments from the world’s fastest-growing large economy.

The world’s largest payments system by volumes, India’s unified payment interface, popularized cashless transactions in the country by offering free services for all. That’s about to change. Starting next month, merchants will need to pay a fee of 0.4% for accepting payments higher than $20.

While the government has defended the move, confident it will not hurt India’s march towards a cashless economy, critics disagree.

Any thoughts on today’s newsletter? Share them with the team.

The big story

The Indian government’s decision to charge a fee to merchants using its globally lauded real-time digital payment system, UPI, that undercuts the usage of Visa and Mastercard, has sparked an intense debate in the country.

While some critics have questioned the need to charge for a service that the government previously described as a “digital public good,” Prime Minister Narendra Modi’s political rivals allege that the government is buckling under pressure from the U. S.

On Tuesday, the National Payments Corporation of India announced that a 0.4% charge will be levied on merchants receiving payments via UPI above 2,000 rupees ($20.84). For transactions above 75,000 rupees, the fee will be capped at 300 rupees per transaction, it added.

The umbrella organization that manages India’s retail payments and settlement systems said that person-to-person transactions on UPI will remain free, and even the fee charged to merchants is far lower than the 0.9% on debit card transactions and 1.5%-2.5% on credit cards.

Bouquets and brickbats

Fintech companies have welcomed the move to charge a fee to merchants.

“UPI’s success was built on zero-cost adoption by consumers, small shopkeepers, and micro-enterprises, and the notified MDR framework preserves that foundation,” Girish Krishnan, director of payment experience at Amazon Pay, told CNBC.

Head of Meta’s WhatsApp Pay Kunal Shah called it a “great move forward.” Another popular payment app, Paytm, said that the measure will generate additional revenue from merchant business.

In 2020, the Indian government cut the merchant discount rate, the fee incurred by merchants for accepting payments via UPI, to zero to promote digital transactions in the country. Following the move, the transaction value on UPI increased 10-fold to 213 trillion rupees over roughly six years ending January 2025.

“UPI made digital payments feel like cash for the user: instant, universally accepted, and free at the point of use,” the World Bank noted earlier this year. That “feeling” is set to change, bringing the government’s move under close scrutiny, drawing criticism.

Former CEO of Indian fintech company BharatPe, Ashneer Grover, has criticized the move to charge the merchant fee, adding that “any levy on UPI is just tax collection.”

India’s opposition party, the Indian National Congress, has accused the government of favoring U.S. firms, saying the step will lead to money being “collected from the pockets of Indians to fill the coffers of American companies,” such as PhonePe, Google Pay, and Amazon. Some commentators have said the move will encourage people to return to transacting in cash.

Level playing field

The UPI payment system on average processes more than 1.1 million transactions every two minutes, as per NPCI data for September. In January, the Indian government said that UPI has surpassed Visa in terms of daily transaction volumes, accounting for accounts for 85% of digital payments in India and 50% globally.

Those figures caught the attention of the U.S. Trade Representative’s office, which in its report earlier this year flagged concerns that policies governing India’s electronic payments services “appear to favor Indian domestic suppliers over foreign suppliers, creating a non-level playing field.”

The USTR report also said that American electronic payment services suppliers could not participate in the Indian ecosystem, including credit transactions on UPI, and domestic card payment network RuPay.

Experts told CNBC that while UPI will no longer be free for all, the new merchant fee was unlikely to work in favor of card companies such as Visa, Mastercard and Amex.

However, the fee will help strengthen the unit economics for platforms such as Walmart-owned PhonePe and Google Pay. The two payment apps together account for nearly 85% of UPI transactions by value and 81% by volume, as per a report by Indian brokerage Ambit Capital.

“A 0.4% rate severely undercuts credit cards at 1.5% to 2% and debit cards,” Neil Shah, vice president of research at Counterpoint Research, told CNBC, adding that it gives merchants “every economic incentive to favor UPI rails.”

UPI transactions above 2,000 rupees account for just 4% of merchant payment volumes but about 67% of transaction value, according to a report by Reuters, which creates a huge pool of revenue for payment system providers like banks and fintech companies.

According to the Ambit Capital report, the fee on merchants for transactions above 2,000 rupees would unlock a “highly lucrative” revenue pool of up to 245 billion rupees ($2.5 billion) for the sector.

“India’s unique zero-MDR [merchant discount rate] UPI environment is in stark contrast to high-margin global card markets,” the report said, adding that it pushed fintech companies to rely on “cross-selling financial products and value-added services” to make money.

Need to know

India’s retail inflation hits 4.8% in August, rises for 10th straight month

India’s headline rose to 4.82% in August from 4.45% in July, adding to pressure on the country’s central bank to raise key benchmark rates. Inflation has been on the rise for 10 straight months in the world’s fastest-growing major economy.

Indian Prime Minister Modi says border peace is key to India-China ties

Indian Prime Minister Narendra Modi on Saturday said that “peace and tranquility” in the border areas is essential for developing bilateral relations with its neighbor China. Ties between the two countries, which had deteriorated sharply following a deadly border skirmish in 2020, have been thawing for more than a year.

Coming up

Sept. 17: National Stock Exchange IPO opens.

Sept. 23: HSBC Flash PMI for September.