Scientists from the Paul Scherrer Institute (PSI), conducting a new series of experiments with millions of ultracold neutrons, have determined that the neutral particles do not switch between our universe and a theoretical “mirror universe” containing oppositely charged, identical counterparts of all elementary particles previously proposed by theoretical physicists.

Although the new experiments do not completely disprove the concept of a mirror universe, the experiments do cast doubt on one of the idea’s fundamental principles, making its existence less likely. The team behind the new study said their findings also aid future experiments by eliminating one potential area of inquiry.

Neutrons Are the Perfect Candidate to Test for a Mirror Universe

Although theoretical physicists sometimes propose radical concepts, one such idea proposes a mirror universe where every elemental particle has a “twin.” For example, the authors of the new study explain, there would be mirror protons, mirror electrons, and mirror neutrons. Still, they note, interaction between the particles in our universe and their mirror universe companions is likely to be minimal.

Geza Zsigmond, a researcher at the PSI Center for Neutron and Muon Sciences, said the theory suggests that the two mirror particles “sense each other’s presence” through gravity. Some physicists have even suggested that gravitational interaction with mirror-universe particles could explain dark matter. Unfortunately, experiments designed to hunt for the mirror universe have returned zero positive results.

Bernhard Lauss, leader of the research group for ultracold neutron physics at the PSI Center for Neutron and Muon Sciences, said, “There is no way of proving the existence of mirror particles using gravitational interaction alone.” Fortunately, the theory also offers a second testing possibility.

According to Zsigmond and colleagues, mirror universe particles would interact with our universe either through gravitation or through what they described as a “rare” oscillation of neutrons. This means that neutral particles like a neutron could occasionally disappear from our universe and reappear in the mirror universe. Even more surprisingly, the same theory says that these particles could magically return to our universe as well.

“Based on this hypothesis, neutral particles might oscillate to and fro between our normal matter world and the mirror world,” Lauss said.

The team said that this possibility, combined with new experiments at the Institut Laue-Langevin in France that “rekindled” speculation about the mirror universe, focused their new efforts on this “other” property of mirror universe particles.

Study Finds No Evidence for Neutral Particle Oscillations

After joining up with researchers from ETH Zurich and the Jagiellonian University in Kraków, the PSI team designed a series of experiments that should show if neutrons are zipping back and forth between universes. Zsigmond said that neutrons are ideal to test the concept for two reasons. First, they are neutral particles, and second, the researcher said they have a “strange property” the team hoped to exploit.

“Neutrons appear to have different lifetimes, depending on how this is measured,” Zsigmond explained.

Although several theories have been proposed to explain this discrepancy, the team acknowledged that the varying neutron lifetimes could be caused by some of these neutral particles disappearing from our universe and entering the mirror universe.

First, the team used the high-intensity proton accelerator at PSI to generate the millions of neutrons needed for their experiments. Next, the team slowed the neutrons down, creating what scientists call “ultracold” neutrons.

Next, the researchers trapped the ultracold neutrons in a specially designed non-magnetic stainless steel vacuum chamber. Because the theory suggests that the probability of neutrons jumping between universes is extremely sensitive to magnetic fields, the vacuum chamber was surrounded by magnetic field coils that the researchers could control with the required precision.

Throughout the experimentation phase, the researchers stored 1.5 million ultracold neutrons in the chamber every five minutes. After about 200 seconds, the team would empty the chamber and count how many neutrons remained. The team repeated this process over several months, resulting in the creation, storage, and measurement of approximately 25 billion neutrons.

Lauss said the researchers gradually varied the strength and direction of the magnetic field throughout the process to “scan all the relevant regions in which one might expect oscillations between neutrons and mirror neutrons to occur.” However, Lauss said, “we saw no evidence at all of such oscillations.”

Experiments “Set the Standard” For the Foreseeable Future

When discussing the significance of their findings, the PSI-led team said the lack of evidence of mirror universe oscillation by ultracold neutrons suggests a very high probability that such mirror universe neutral particle roundtrips “can be ruled out.” They also note that failing to find evidence of a mirror universe still resulted in benefits for particle physics by eliminating an area of inquiry.

“By restricting the scope for certain speculations, we are showing researchers in theoretical physics that they need to explore new avenues,” Zsigmond explained. “Physics needs that kind of impetus if it is to continue to evolve.”

Moving forward, the team said that “substantial improvements” to their experiments would require a much more elaborate setup. Until then, they said their experiment and its results are “the best of its kind in the world and will set the standard for the foreseeable future.”

The study “New High-Sensitivity Search for Neutron to Mirror-Neutron Oscillations at the PSI Ultracold Neutron Source” was published in Physical Review Letters.

Christopher Plain is a Science Fiction and Fantasy novelist and has spent the last six years as Associate News Editor and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him at christopher@thedebrief.org

New computer models of Venus’s surface features, including ridges likely caused by volcanic activity, have determined that the second rock from the Sun remains geologically active to this day.

The ETH Zurich research team behind the new Venusian models, which suggest that Venus may still have active volcanoes, said their findings could help planned NASA and ESA missions select the most promising targets. The new models could also help in the search for rocky planets outside of our Solar System, including those that may support life.

Venus Previously Considered Geologically Dormant for Over 100 Million Years

Venus has long fascinated planetary scientists due to its similarities. For example, the planet’s mass and circumference make it roughly 95% the same size as Earth overall. However, although Venus’ elliptical orbit brings it closer to Earth than any other planet in the Solar System, its extreme surface temperatures and toxic atmosphere make it inhospitable to life as we know it.

Ground and space observations have detected rift valleys on Venus’s surface, which the research team notes indicate tectonic activity. Some can measure up to 10,000 kilometers and resemble the longest ridges on Earth. Although the timing of Venus’ rift formations remains uncertain, the team said most scientists have typically considered the planet to be geologically dormant. Some estimates have put their formation more than 100 million years ago.

Curious if data captured by space and ground-based observatories could provide enough information to answer the timing question, a research team from ETH led by Taras Gerya, a Professor of Geodynamics at the Department of Earth and Planetary Sciences, decided to plug that data into computer models. According to their results, the reports of Venus’ demise may have been greatly exaggerated. 

Models Reveal Planet Likely Supports Active Volcanoes

Working under Professor Gerya’s supervision, Master’s candidate and lead author of the paper detailing the team’s work, Xi Yang, and colleagues employed computer models to simulate the planet’s rifts in high-resolution and 3D. The team said these models allowed them to “accurately replicate these rift structures” in a level of detail never achieved. The data also allowed them to perform simulations to best determine how they originally formed.

Critically, the team notes that earlier attempts to model Venus’ tectonic history and potential ongoing activity had been mostly two-dimensional. Yang’s team also said those earlier models had relied on “simplified material assumptions” that his team was able to expand upon.

After completion, the models yielded several compelling results. First, they indicated that the broad ridges geologists call ‘rift flanks’ form along the edges of rift valleys at a time when the rifts are still “geologically young.” Specifically, the team’s models suggested that these flanks formed when Venus was still either actively moving or had only recently stopped moving.

A closer look at the simulations also suggested that these geological rifts open over a much shorter time scale than previously assumed, with an estimated rate between 3 and 10 centimeters per year. The models also indicated that rift flanks tend to flatten very quickly once the movement ends.

“The older the rift system, the less steep and narrow its flanks,” they explained.

A comparison to erosion patterns on Earth also supported a more recent time frame for the rift flank formations spotted on the Venusian surface from the Magellan probe during its 1990s mission. The team said that these formations and their models suggest that “Venus remains an active planet with a more dynamic interior than had been previously believed.”

“Venus remains geologically “alive” and even hosts active volcanoes,” they explained.

Planned NASA & ESA Missions Could Confirm Models

When discussing the implications of their work, Professor Gerya said the findings “help us to better assess the tectonic activity on Venus.” The team noted that their models could also guide future missions by pinpointing potentially active regions worthy of closer examination.

The ETH team said their study also has planetary formation implications, particularly for rocky planets like Venus and Earth. Such data could prove valuable in the search for rocky exoplanets, including the type that may host life.

Moving forward, the study authors noted that NASA and the European Space Agency (ESA) are actively preparing “multiple missions” to explore Venus in further detail. ETH geophysics professors Paul Tackley and Gerya, and their team of collaborators, are already participating in ESA’s EnVision mission.

The work includes developing instruments for the orbiter to analyze the surface in greater detail. Scheduled for launch in the early 2030s, the team said that EnVision will explore the planet more thoroughly than previous efforts “from its core to its upper atmosphere.”

The study “Recent active rifting on Venus revealed by wide rift flank uplifts” was published in Nature Geoscience.

Christopher Plain is a Science Fiction and Fantasy novelist and has spent the last six years as Associate News Editor and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him at christopher@thedebrief.org.

Food waste may become a powerful climate tool thanks to tiny reusable beads that capture carbon directly from the air. Keeping global warming below 1.5°C over the long term will require more than major cuts in greenhouse gas emissions. According to climate scenarios outlined in the latest Assessment Report from the Intergovernmental Panel on Climate [...]

Scientists from ETH Zurich in Switzerland have announced a series of successful experiments involving the repair of injured spinal cords in zebrafish and mice after being injected with magnetically controlled microrobots containing pluripotent stem cells.

According to a statement announcing the ETH team’s work, both the zebrafish and mice injected with the microrobots showed improved movement and normalized exploratory behavior within just a few days after treatment.

Although the initial studies were confined to lab animals, the team hopes their magnetically controlled microrobot approach to the precision delivery of pluripotent stem cells could eventually be adapted for humans with spinal cord injuries.

Spinal Cord Repair Microrobots Treat Nerve Cells That Resist Regeneration

Unlike some cells in the human body, nerve cells within the spinal cord rarely regenerate on their own. If the spinal cord is injured, scarring can further reduce the ability of the nerve fibers within the cord to regrow. For people living with spinal cord injuries, this scenario can offer a bleak prognosis for recovery.

In recent decades, scientists have turned to the natural regenerative properties of pluripotent stem cells. Although the use of stem cells was initially controversial due to the need to extract neonatal stem cells, scientists ultimately learned to convert ordinary stem cells into pluripotent stem cells capable of becoming any cell type in the human body.

The most promising approach involves implanting stem cells at the site of the injury and then using electrical stimulation to promote the growth of new cells. However, according to the ETH team behind the new approach, the current method has several drawbacks.

First, stimulating the cells requires the use of implanted electrodes. Second, the team notes that after transplantation, many of the stem cells “do not always survive or integrate properly into the existing tissue.”

To improve healing and increase the chance of restoring spinal cord nerve cell function, they said their new approach combines therapeutic stem cells with magnetoelectric nanoparticles and uses magnetic fields to guide them to the “precise site of an injury” and “stimulate the stem cells to accelerate repair.”

NPCbots Combine Stem Cells and Magnetically Controlled Nanoparticles

To construct their magnetically guided spinal cord repairing robot, the team built what they termed a “biohybrid microrobot.”

First, the team creates pluripotent stem cells from adult cells by genetically manipulating them in the lab. The result is what researchers call an “induced” pluripotent stem cell (iPS). According to the study authors, these newly pluripotent iPS cells are used to derive living neural progenitor cells (NPCs), meaning “they have the potential to differentiate into various types of nervous system cells.”

Next, the team creates customized magnetic nanoparticles consisting of two layers. The inner layer responds to the “commands” from the magnetic fields used to control them, and an outer layer that converts this response into an electrical signal.

According to Professor Salvador Pané i Vidal of the Multi-Scale Robotics Lab at ETH Zurich, each tiny robot has a reservoir near the center “where we trap the cells.” The professor said the best way to accomplish this is to inject the nanoparticles into a solution with the NPC, “and wait for the two components to bind.”

After 30 minutes, the process is complete, and the team is left with a batch of nanobots, each around 6 micrometers in size. Since the new robots combine a magnetic bot and a reservoir of NPCs, the team named them ‘NPCbots.’

In preparatory cellular experiments, the researchers used hundreds of thousands of NPCbots. However, several million were required for animal trials.

Zebrafish and Mice Regain Movement After Injections

To test the efficacy of their new NPCbots, the ETH team injected millions of them into the spinal cord of zebrafish larvae with spinal cord injuries. To improve the chances of nerve regeneration, the NPCbots were injected directly into the site of the injury.

After injecting the microrobots, the injury site was subjected to electromagnetic fields. Although the repair was not immediately evident, the team noted that after three days, the zebrafish with the injured spinal cords “exhibited nearly normal swimming and exploratory behaviour.”

Next, the team injected millions of NPCbots into mice with completely separated spinal cords. According to the team, the results were “very promising.”

“After 28 days, the animals’ nerve cells had reconnected at the site of the injury,” they explained.

The team said further observation of the treated mice revealed “increasingly normal movement patterns,” including improvements in gait, stride length, and coordination. The ETH team also noted that the mice’s exploratory behavior “improved significantly.”

When discussing the mouse experiments, the team described the result as “particularly significant” because zebrafish spinal cords regenerate, whereas mouse spinal cords do not. They also noted that the treatment was “well tolerated by the animals,” with no reported immune reactions or adverse effects.

Minimally Invasive and More Precise Treatments with Microbots

Unlike science fiction movies, where tiny robots repair tissue mechanically, the research team said that the stem cells carried by the NPCbots are exposed to electrical stimulation, “greatly enhancing their differentiation after transplantation.” This means the nanoparticles convert the electric signals from the EM field into electrical impulses, stimulating healing.

Unlike more complicated stem cell procedures that use implanted electrodes and cables, the team said they only needed to apply external magnetic fields around the spinal cord injury site. The team said this simplification was “crucial,” since the spinal cord is considered extremely sensitive. They also note that the ability to manipulate the frequency and field strength of magnetic fields, combined with their ability to penetrate deeply into tissue, makes the entire process safe and easy to control.

“Microrobotic guidance makes the treatment more precise and minimally invasive,” Hao explained.

After the NPC bots have delivered and stimulated the stem cells, the team said they “essentially dissolve” within the tissue. Because the bots contain a barium titanate coating, the researchers also believe that they will be “stable and minimally reactive” with surrounding tissue. Still, they concede that “further studies will determine whether and how the particles are degraded or excreted over the long term.”

Expanding NPCbot Therapies to Increase the Effectiveness of Other Targeted Therapies

Although the team described the animal trials of their NPCbots as “promising,” they noted that further research is needed before the process can be attempted on human patients with spinal cord injuries. For example, Hao noted that in addition to ‘clinical aspects’ that require more exploration, the team needs to start by determining which magnetic fields “work best in humans” and determining the “optimal stimulation duration” for human NPCs. Nevertheless, the team noted, they are “already considering further applications.”

“The reproducible and scalable production of microrobots using our lab-on-a-chip system demonstrates that the platform’s application potential extends beyond basic research,” Professor Vidal explained.

Some potential biomedical applications mentioned by the RETH team include cardiology, oncology, wound healing, “and other targeted therapies,” adding that their process could make such treatments “safer, more controllable and more effective.”

The study “Magnetoelectric Microrobots for Spinal Cord Injury Regeneration” was published in Nature Materials. 

Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.