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Why Can’t the Universe Be Cyclic? Part 4: When a Good Idea Meets Bad Data

(This is Part 4 of a series on whether the universe can be cyclic. Read Part 1, Part 2, and Part 3 first.)

So we left off with a beautiful idea. A universe that always existed, bouncing eternally between higher-dimensional sheets, no singularity, no inflation, entropy neatly reset on every cycle. A genuinely good idea.

Good ideas, unfortunately, are not the same thing as right ideas. And ekpyrotic theory has a list of troubles, starting small and ending with a problem it simply cannot talk its way out of.

Let’s begin with the singularity, the very thing ekpyrotic was supposed to abolish. When the two branes collide, the math describing that instant gets extremely uncomfortable. The theory’s defense is essentially a hopeful one: that the exotic machinery of string theory will smooth everything over at the moment of the bounce and keep the dreaded infinities from rearing up. Maybe it does. But “we’re fairly confident the string math will work out” is a promissory note, not a proof, and an awful lot is riding on it.

Next, that elegant trick with dark energy. Remember that the whole cyclic mechanism hinges on dark energy eventually shutting off, so the branes can stop drifting apart and start falling back together. We have not the faintest evidence that dark energy does any such thing. As far as anyone can actually measure, dark energy is a steady, constant feature of the cosmos with no expiration date printed anywhere on the label. Ekpyrotic theory needs it to quit. The universe has made no such promise.

Then there are the branes themselves. String theory, left to its own devices, has a real appetite for branes. Like zombies, once you allow a couple of them onto the stage, it becomes very hard to stop more from shambling in. Many versions of the ekpyrotic scenario end up populated with whole stacks of branes, which drags the theory straight back into the very multiverse swamp that inflation got bogged down in. The thing it was supposed to do better, it ends up doing about the same.

Now, you can hand-wave your way around all of that. Cross your fingers on the singularity, assume dark energy behaves itself, wave off the extra branes. Cosmologists are nothing if not resourceful. But there is one obstacle no amount of clever hand-waving gets you past, and it happens to be the same standard that crowned inflation in the first place: what we can actually observe.

Inflation, recall, makes a very specific prediction about the seeds of cosmic structure. Not just that the seeds exist, but their detailed statistical properties, the precise mix of large and small ripples sprinkled across the early universe. We can’t watch inflation happen directly, but we can read those seeds straight off the cosmic microwave background, the oldest light in existence and the earliest baby picture of the cosmos we will ever get.

Ekpyrotic theory has to play the same game. You cannot call yourself a serious cosmology without making a prediction for those same statistical properties. So ekpyrotic, too, says something concrete about what the microwave background should look like. And the original version of the theory, worked out in the early 2000s, was off. Not a little off. It was “how did you even find my office to tell me this” off, badly out of step with what we observe. Defenders found ways to patch it, the kind of adjustments a less generous person might call hacks, twisting the model until it produced the right sort of fluctuations.

And here is the killer. Even the patched-up version doesn’t survive.

Ekpyrotic theory was originally tuned to match the rough, blurry measurements of the microwave background that were available back in the early 2000s. It was built and refined to fit the data of its day. Then we launched Planck, a spacecraft devoted to mapping that ancient light in exquisite detail, and it handed us measurements vastly sharper than anything we’d had before. Those measurements lined up beautifully with what inflation predicted. They did not line up with ekpyrotic theory. The sharper our picture of the infant universe became, the worse ekpyrotic looked and the better inflation held up.

There are not many escape routes from a result like that. The theory isn’t dead, exactly. But it is marginalized. Few people work on it now. It carries too much baggage: the math is brutal to wrangle, it doesn’t fully or cleanly deliver on its grand promises, and it stumbles on the one observational test that matters most. It is a good idea. But good ideas are not guaranteed to be right ones. That call belongs to nature, not to us, and nature, so far, has voted against it.

So the theory putters along, with a few stubborn researchers poking at it here and there. Maybe because it is still a genuinely fun idea. Maybe because it might yet bear some unexpected fruit down the line. Stranger things have happened in physics.

But for now, the Big Bang and inflation agree with every observation we can throw at them, and the dream of an eternal, cycling, self-renewing cosmos remains exactly that. A dream.

All the evidence points the same hard direction. This one universe, this single shot, is all we get.

So make the best of it.

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JWST May Be Missing Water Hidden Deep Within Mini-Neptune Worlds

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Sub-Neptune exoplanets, exoplanets that are slightly smaller than Neptune, have been designated as the most common type of planet in the Milky Way Galaxy based on their vast discovery numbers, totaling almost 3,300 out of the more than 6,300 confirmed exoplanets to date. Despite these numbers, the characteristics of sub-Neptunes remain relatively unknown. This is primarily due to our own solar system not having its own sub-Neptune to use as an analog, along with their atmospheres being thick and hazy. As a result, this makes telescopic observations, even from powerful instruments like NASA’s James Webb Space Telescope, extremely difficult.

Now, a team of researchers from the United States and Canada and led by the University of Chicago (UChicago) might be one step closer to better understanding the compositions of sub-Neptunes, which they discuss in a recent study published in The Astrophysical Journal. For the study, the team used a series of computer models to simulate the atmospheric and interior composition of TOI-270 d, which is a sub-Neptune discovered in 2019 and located about 73 light-years away. Its radius and mass are about two times and 4.2 times of Earth, respectively, and it takes about 11.4 days to orbit its red dwarf star, which is smaller and cooler than our Sun. TOI-270 d and its sister planets, TOI-270 b and TOI-270 c, all orbit within the interior of their star’s habitable zone.

JWST had previously identified the existence of carbon dioxide, methane, and hydrogen within TOI-270 d’s atmosphere, which this combination indicates the presence of water. However, the exact state of the water remains unknown, meaning scientists don’t know if the water is a solid, a liquid, or a gas, along with the conditions that enable water and hydrogen to mix or separate.

In the end, the researchers found that a combination of temperature and the water-hydrogen ratio play a role in determining the mixing and separating of water and hydrogen. Specifically, TOI-270 d has a larger amount of water than hydrogen and combined with its warmer temperatures of 537 degrees Celsius (1,000 degrees Fahrenheit) could result in the water sinking beneath the hydrogen atmosphere, with the former shielding the lower-level water from observations, even from JWST. Essentially, sub-Neptunes could possess more water than scientists had previously estimated, and this challenges longstanding hypotheses that sub-Neptunes had well-mixed interiors instead of separated interiors as proposed by this study.

“It’s very possible these planets are hiding much more water than their atmospheres let on,” said Dr. Caroline Piaulet-Ghorayeb, who is a postdoctoral researcher at UChicago and lead author of the study. “It’s an interesting question, both because water is so important for life as we know it, and because it signals we have to interpret the data coming in from new, powerful telescopes in a more nuanced way to really know what’s going on.”

Some examples of “new, powerful telescopes” that Dr. Piaulet-Ghorayeb could be alluding to include several NASA, European Space Agency (ESA), and European Southern Observatory (ESO) planned telescopes. Most notably, NASA’s Nancy Grace Roman Space Telescope is slated to launch on August 30, 2026, and whose primary mission will include using a coronagraph to directly image exoplanets. An example of a ground-based telescope that could contribute to exoplanet atmospheric science is the ESO’s Extremely Large Telescope (ELT), which is currently under active construction and is slated to begin scientific operations around December 2030.

What new insights into sub-Neptunes and their deep, watery atmospheres will researchers make in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!

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ICE shootings protested in Pasadena on National Day of Action

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Approximately 50 demonstrators gathered Saturday morning in Pasadena as part of a national action to honor lives lost during immigration enforcement operations and in detention centers during the Trump administration.

They wore fliers around their necks, hung with yellow thread, bearing the smiling faces and names of some of the 75 people who have died since January 2025.

“Killed by ICE” was printed above a photo of each person, including local resident Roberto Carlos Montoya Valdez, a 52-year-old killed while trying to flee immigration agents who descended on a Home Depot in Monrovia last year.

The Los Angeles residents, part of the San Gabriel Foothills Indivisible group, carried American flags and held signs that read “No ICE No War” and “Stop ICE Murders.”

“Good morning, Pasadena,” Betsy Hanger, an organizer with the group, boomed into a megaphone as she walked through an intersection. “Honk for democracy. Honk if you want ICE off our streets now.”

A chorus of horns sounded as drivers signaled their support.

Organizer Andra Clarke held a banner in each hand that read “Neighbors Say ICE Out.” The sign around her neck carried the name and photo of Francisco Gaspar-Andrés, a 48-year-old who died in a Texas detention center in December.

Clarke, 61, said the group has been gathering at the intersection of Colorado Boulevard and Fair Oaks Avenue every Saturday since March. Last weekend, they celebrated civil rights activist John Lewis.

This Saturday, though, their focus was aimed at ICE.

“Now 75 people have died at the hands of ICE,” Clarke said. “We were originally told, ‘Oh they’re going to go after the criminals, the people who are the worst of the worst.’ That’s a lie; that is not what’s happening.

“They’re targeting communities, they’re targeting people of color. It’s fascism. … Anybody who cares about humanity should care about what’s happening.”

Clarke said it hit her hard when she learned of the two recent deaths at the hands of ICE.

The event was also a vigil honoring 52-year-old Lorenzo Salgado Araujo, who was killed by an ICE agent in Houston on July 7 while driving his construction crew to a job site, and Johan Sebastian Guerrero, 25, who was fatally shot by an ICE officer in Maine during a traffic stop earlier this month.

“It’s like, again? It just doesn’t end. It feels like it never ends — the evil.”

Shortly before noon, Clarke used a megaphone to read aloud the names of the dozens who have died. After each name read, Hanger struck a singing bowl, the vibrations sounding out in the corner where they stood. At times, she read “unidentified man” or “four unidentified women.”

Next to them was a poster board with a photo of Daphy Michel, a 31-year-old woman found unresponsive at a bus shelter in Pittsburgh after ICE released her “into cold winter conditions and no care for mental health episodes or notice to relatives.”

“Let’s take a moment of silence for all those who were taken,” Clarke said, bowing her head.

Among those gathered to listen was Leticia Lopez, a 65-year-old South Pasadena resident whose voice trembled as she talked about the impact of hearing about another arrest or death tied to enforcement operations.

“It gets me to the core,” she said, striking her chest. “It’s not getting any better, it’s getting worse. I just feel like I need to do something.”

Lopez, who wore a shirt that read “Immigrants are not criminals but the president is,” said her mother and grandmother were forcefully repatriated from Arizona to Mexico.

Her mother, who was raised in Mexico, later met her father there. He moved to the U.S. in the 1950s as a bracero. Hearing the stories of today, she said, “triggers everything that they went through.”

“When I see it happening, it’s a generational trauma that I feel,” she said. Lopez said people around her are carrying passports and documents in public to prove they’re citizens.

“Because they’re afraid they might be profiled, picked up, kidnapped by ICE. When my son goes out, I worry,” she said of her 28-year-old.

Later that afternoon, about four miles away outside of Home Depot in Pasadena, organizers staked in the ground dozens of white crosses that bore photos of the dead — the majority of them men. Attendees of the vigil laid flowers at the crosses in a makeshift cemetery.

“Shot dead by ICE,” read one with a photo of Keith Porter Jr., who was killed by an off duty ICE officer in California.

Several of them contained details of how the deaths unfolded. A man killed after a tractor trailer struck him as he fled an ICE raid in Florida. A Cuban immigrant who died in a detention center (his death was later ruled a homicide). A Mexican national who fell 30 feet to his death during a raid in California.

Among the photos on crosses were Renee Good and Alex Pretti.

“Are we going to wait until 70 more die to do something?” asked Marlom Portillo, an educator with the National Day Laborer Organizing Network, as he staked more crosses into the ground.

“What they want us to do is forget them,” Portillo added. “We will never get tired of denouncing this atrocity.”

“There are more people who died than there are people here protesting,” Kathleen Vallee, a Monrovia resident, observed to her friend. “And that says a lot about us.”

Vallee said when she attended the “No Kings” protest, it was “jam-packed.” Only a dozen people had gathered around 20 minutes into the vigil.

“It turns my stomach,” Vallee said, hands clasped. “This just seems to be seeping up from the sewer into our democracy and that motivates me.”

As the small crowd assembled, demonstrators carried signs that read “Every person is sacred,” “we keep us safe” and “neighbors say ICE out.” One woman carried a handmade sign that read: “Who will they come for next?”

Sheri Lochner, a 64-year-old Monrovia resident, is part of East Pasadena Community Defense Corner, a small group that “provides support and a sense of community” for day laborers.

Lochner said she watched as immigrant agents took six or seven men at an Oct. 1 ICE raid at the Monrovia Home Depot.

“So un-American,” Lochner said, as she scanned the rows of crosses. “This isn’t right.”

She added that her mom, who voted for Trump the first time, agreed with her.

“I speak up, I will not be silent,” she added.

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Inside the Rushed Effort to Get Trump His New Air Force One

A New York Times investigation found that President Trump’s push to speed delivery of the aircraft led to ballooning costs and trade-offs in safety features.