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

I’ve Seen It With My Own Eyes: The Robots Are Here and Walking Among Us

The «physical AI» boom has created a world of opportunity for robot makers, and they’re not holding back.

It’s been 24 years since CNET first published an article with the headline The robots are coming. It’s a phrase I’ve repeated in my own writing over the years — mostly in jest. But now in 2026, for the first time, I feel confident in declaring that the robots have finally arrived.

I kicked off this year, as I often do, wandering the halls of the Las Vegas Convention Center and its hotel-based outposts on the lookout for the technology set to define the next 12 months. CES has always been a hotbed of activity for robots, but more often than not, a robot that makes a flashy Vegas debut doesn’t go on to have a rich, meaningful career in the wider world.

In fact, as cute as they often are and as fun as they can be to interact with on the show floor, most robots I’ve seen at CES over the years amount to little more than gimmicks. They either come back year after year with no notable improvements or are never seen or heard from again.

In more than a decade of covering the show, I’ve been waiting for a shift to occur. In 2026, I finally witnessed it. From Hyundai unveiling the final product version of the Boston Dynamics Atlas humanoid robot in its press conference to Nvidia CEO Jensen Huang’s focus on «physical AI» during his keynote, a sea change was evident this year in how people were talking about robots.

«We’ve had this dream of having robots everywhere for decades and decades,» Rev Lebaredian, Nvidia’s vice president of Omniverse and simulation told me on the sidelines of the chipmaker’s vast exhibition at the glamorous Fontainebleau Hotel. «It’s been in sci-fi as long as we can remember.»

Throughout the show, I felt like I was watching that sci-fi vision come to life. Everywhere I went, I was stumbling upon robot demos (some of which will be entering the market this year) drawing crowds, like the people lining up outside Hyundai’s booth to see the new Atlas in action.

So what’s changed? Until now, «we didn’t have the technology to create the brain of a robot,» Lebaredian said.

AI has unlocked our ability to apply algorithms to language, and it’s being applied to the physical world, changing everything for robots and those who make them.

The physical AI revolution

What truly makes a robot a robot? Rewind to CES 2017: I spent my time at the show asking every robotics expert that question, sparked by the proliferation of autonomous vehicles, drones and intelligent smart home devices.

This exercise predated the emergence of generative AI and models such as OpenAI’s ChatGPT, but already I could see that by integrating voice assistants into their products, companies were beginning to blur the boundaries of what could be considered robotics.

Not only has the tech evolved since that time, but so has the language we use to talk about it. At CES 2026, the main topic of conversation seemed to be «physical AI.» It’s an umbrella term that can encompass everything from self-driving cars to robots.

«If you have any physical embodiments, where AI is not only used to perceive the environment, but actually to take decisions and actions that interact with the environment around it … then it’s physical AI,» Ahmed Sadek, head of physical AI and vice president of engineering at chipmaker Qualcomm told me.

Autonomous vehicles have been the easiest expression of physical AI to build so far, according to Lebaredian, simply because their main challenge is to dodge objects rather than interact with them. «Avoiding touching things is a lot easier than manipulating things,» he said.

Still, the development of self-driving vehicles has done much of the heavy lifting on the hardware, setting the stage for robot development to accelerate at a rapid pace now that the software required to build a brain is catching up.

For Nvidia, which worked on the new Atlas robot with Boston Dynamics, and Qualcomm, which announced its latest robotics platform at CES, these developments present a huge opportunity.

But that opportunity also extends to start-ups. Featured prominently at the CES 2026 booth of German automotive company Schaeffler was the year-and-a-half-old British company Humanoid, demonstrating the capabilities of its robot HMND 01.

The wheeled robot was built in just seven months Artem Sokolov, Humanoid’s CEO, told me, as we watch it sort car parts with its pincerlike hands. «We built our bipedal one for service and household much faster — in five months,» Sokolov added.

Humanoid’s speed can be accounted for by the AI boom plus an influx of talent recruited from top robotics companies, said Sokolov. The company has already signed around 25,000 preorders for HMND 01 and completed pilots with six Fortune 500 companies, he said.

This momentum extends to the next generation of Humanoid’s robots, where Sokolov doesn’t foresee any real bottlenecks. The main factors dictating the pace will be improvements in AI models and making the hardware more reliable and cost effective.

Humanoid hype hits its peak

Humanoid the company might have the rights to the name, but the concept of humanoids is a wider domain.

By the end of last year, the commercialization of humanoid robots had entered an «explosive phase of growth,» with a 508% year-on-year increase in global market revenue to $440 million, according to a report released by IDC this month.

At CES, Qualcomm’s robot demonstration showed how its latest platform could be adapted across different forms, including a robotic arm that could assemble a sandwich. But it was the humanoids at its booth that caused everyone to pull out their phones and start filming.

«Our vision is that if you have any embodiment, any mechatronic system, our platform should be able to transform it to a continuously learning intelligent robot,» said Qualcomm’s Sadek. But, he added, the major benefit of the humanoid form is its «flexibility.»

Some in the robotics world have criticized the focus on humanoids, due to their replication of our own limitations. It’s a notion that Lebaredian disagrees with, pointing out that we’ve designed our world around us and that robots need to be able to operate within it.

«There are many tasks that are dull, dangerous and dirty — they call it the three Ds — that are being done by humans today, that we have labor shortages for and that this technology can potentially go help us with,» he said.

We already have many specialist robots working in factories around the world, Lebaredian added. With their combination of arms, legs and mobility, humanoids are «largely a superset of all of the other kinds of robots» and, as such, are perfect for the more general-purpose work we need help with.

The hype around robots — and humanoids in particular — at CES this year felt intense. Even Boston Dynamics CEO Robert Playter acknowledged this in a Q&A with reporters moments after he unveiled the new Atlas on stage.

But it’s not just hype, Playter insisted, because Boston Dynamics is already demonstrating that they can put thousands of robots in the market. «That is not an indication of a hype cycle, but actually an indication of an emerging industry,» he said.

A huge amount of money is being poured into a rapidly growing number of robotics start-ups. The rate of this investment is a signal that the tech is ready to go, according to Nvidia’s Lebaredian.

«It’s because, fundamentally, the experts, people who understand this stuff, now believe, technically, it’s all possible,» he said. «We’ve switched from a scientific problem of discovery to an engineering problem.»

Robot evolution: From industry to home

From what I observed at the show, this engineering «problem» is one that many companies have already solved. Robots such as Atlas and HMND 01 have crossed the threshold from prototype to factory ready. The question for many of us will be as to when will these robots be ready for our homes.

Playter has openly talked about Boston Dynamics’ ambitions in this regard. He sees Atlas evolving into a home robot — but not yet. Some newer entrants to the robotics market — 1X, Sunday Robotics and Humanoid among them — are keen to get their robots into people’s homes in the next couple of years. Playter cautions against this approach.

«Companies are advertising that they want to go right to the home,» he said. «We think that’s the wrong strategy.»

The reasons he listed are twofold: pricing and safety. Playter echoed a sentiment I’ve heard elsewhere: that the first real use for home humanoid robots will be to carry out care duties for disabled and elderly populations. Perhaps in 20 years, you will have a robot carry you in and out of bed, but relying on one to do so when you’re in a vulnerable state poses «critical safety issue,» he said.

Putting robots in factories first allows people to work closely with them while keeping a safe distance, allowing those safety kinks to be ironed out. The deployment of robots at scale in industrial settings will also lead to mass manufacturing of components that will, at some point, make robots affordable for the rest of us, said Playter (unlike 1X’s $20,000 Neo robot, for example).

Still, he imagines the business model will be «robots as a service,» even when they do first enter our homes. Elder care itself is a big industry with real money being spent that could present Boston Dynamics with a market opportunity as Atlas takes its first steps beyond the factory floor.

«I spent a lot of money … with my mom in specialty care the last few years,» he said. «Having robots that can preserve autonomy and dignity at home, I think people will actually spend money — maybe $20K a year.»

The first «care» robots are more likely to be companion robots. This year at the CES, Tombot announced that its robotic labrador, Jennie, who first charmed me back at the show in 2020, is finally ready to go on sale. It served as yet another signal to me that the robots are ready to lead lives beyond the convention center walls.

Unlike in previous years, I left Vegas confident that I’ll be seeing more of this year’s cohort of CES robots in the future. Maybe not in my home just yet, but it’s time to prepare for a world in which robots will increasingly walk among us.

Technologies

Today’s Wordle Hints, Answer and Help for Jan. 29, #1685

Here are hints and the answer for today’s Wordle for Jan. 29, No. 1,685.

Looking for the most recent Wordle answer? Click here for today’s Wordle hints, as well as our daily answers and hints for The New York Times Mini Crossword, Connections, Connections: Sports Edition and Strands puzzles.

Today’s Wordle puzzle was a tough one for me. I never seem to guess three of the letters in this word. If you need a new starter word, check out our list of which letters show up the most in English words. If you need hints and the answer, read on.

Today’s Wordle hints

Before we show you today’s Wordle answer, we’ll give you some hints. If you don’t want a spoiler, look away now.

Wordle hint No. 1: Repeats

Today’s Wordle answer has no repeated letters.

Wordle hint No. 2: Vowels

Today’s Wordle answer has one vowel and one sometimes vowel.

Wordle hint No. 3: First letter

Today’s Wordle answer begins with F.

Wordle hint No. 4: Last letter

Today’s Wordle answer ends with Y.

Wordle hint No. 5: Meaning

Today’s Wordle answer can refer to a pastry that breaks apart easily.

TODAY’S WORDLE ANSWER

Today’s Wordle answer is FLAKY.

Yesterday’s Wordle answer

Yesterday’s Wordle answer, Jan. 28, No. 1684 was CRUEL.

Recent Wordle answers

Jan. 24, No. 1680: CLIFF

Jan. 25, No. 1681: STRUT

Jan. 26, No. 1682: FREAK

Jan. 27, No. 1683: DUSKY

Don’t miss any of our unbiased tech content and lab-based reviews. Add CNET as a preferred Google source.

Technologies

Today’s NYT Strands Hints, Answers and Help for Jan. 29 #697

Here are hints and answers for the NYT Strands puzzle for Jan. 29, No. 697.

Looking for the most recent Strands answer? Click here for our daily Strands hints, as well as our daily answers and hints for The New York Times Mini Crossword, Wordle, Connections and Connections: Sports Edition puzzles.

Today’s NYT Strands puzzle is a bit of a puzzler until you realize the theme. Some of the answers are difficult to unscramble, so if you need hints and answers, read on.

I go into depth about the rules for Strands in this story.

If you’re looking for today’s Wordle, Connections and Mini Crossword answers, you can visit CNET’s NYT puzzle hints page.

Read more: NYT Connections Turns 1: These Are the 5 Toughest Puzzles So Far

Hint for today’s Strands puzzle

Today’s Strands theme is: Talk of the town.

If that doesn’t help you, here’s a clue: What a legend.

Clue words to unlock in-game hints

Your goal is to find hidden words that fit the puzzle’s theme. If you’re stuck, find any words you can. Every time you find three words of four letters or more, Strands will reveal one of the theme words. These are the words I used to get those hints but any words of four or more letters that you find will work:

ROIL, CLAIM, RARE, HELP, PEAR, PEARS, MORE, COIN, SPEAR, SPEARS

Answers for today’s Strands puzzle

These are the answers that tie into the theme. The goal of the puzzle is to find them all, including the spangram, a theme word that reaches from one side of the puzzle to the other. When you have all of them (I originally thought there were always eight but learned that the number can vary), every letter on the board will be used. Here are the nonspangram answers: