A particle-detecting telescope sunk more than a mile beneath the sea off the coast of France has tested a core principle of Einstein's relativity and found no cracks.

The detector, called Oscillation Research with Cosmics in the Abyss (ORCA), detects elusive particles called neutrinos. As a doctoral student, Alba Domi rode onto the Mediterranean aboard one of two boats that helped build the telescope, lowering some of its first detection units to the seafloor about 1.5 miles (2.4 kilometers) below the waves off Toulon, France.

Now, data from those first detection units have been used to test one of the founding rules of Einstein’s relativity: the idea that the laws of nature look the same no matter which way you face or how fast you move.

The team found no sign that this rule, called Lorentz invariance, is broken. But even with a detector only a fraction of its planned size, they set limits that compete with those of far larger and longer-running experiments.

The results were published Wednesday (Nov. 4) in the Journal of Cosmology and Astroparticle Physics.

A crack in space-time?

Physics rests on two successful theories: general relativity, conceived by Albert Einstein more than 100 years ago, and the Standard Model of subatomic physics.

"General relativity describes the universe well on a cosmic scale, and the Standard Model of particle physics describes the microscopic scale; really, the single particles, how they behave," said study co-author Lukas Hennig, a doctoral student in advanced physics at Erlangen-Nürnberg.

Both theories assume Lorentz invariance to be true. But in extreme settings, such as the first moments after the Big Bang, the two theories don't mesh. That has fueled a decades-long hunt for a theory of quantum gravity that unites them. Some candidates, including versions of string theory and loop quantum gravity, suggest that space-time might have a hidden "grain" at the tiniest scales — and that Lorentz invariance, "one of the most basic assumptions we make about our universe, might be violated," Hennig said.

Any such violation would be extremely small. To spot it, physicists would need a probe that could travel long distances and barely interact with anything along the way. Enter the neutrino.

Shape-shifting ghosts

Neutrinos are nearly massless particles that pass through Earth every second and carry zero charge. They barely interact with anything and come in three types: electron, muon and tau neutrinos. As neutrinos travel, they morph from one type into another in a predictable pattern that physicists call neutrino oscillation.

If Lorentz invariance were broken, that oscillation would change, with the effect growing more pronounced the farther the neutrinos traveled. So the team focused on neutrinos created when cosmic rays slam into the atmosphere elsewhere on the globe before traveling up through the planet to the detector. Some of the tested neutrinos crossed the entire 7,900-mile (12,700 km) width of Earth.

ORCA is part of the KM3NeT neutrino telescope. Each of its detection units is anchored to the seabed and holds 18 glass spheres packed with 31 light sensors apiece. When a neutrino collides with a particle in the water, it produces a faint flash of blue light that the sensors catch. The many sensors in each sphere help the team pin down which direction the light came from, Domi said.

Earth itself serves as a filter. The researchers selected only particles traveling upward through the planet, and they were able to weed out the flood of other particles from the atmosphere that would otherwise swamp the signal. "Only the neutrinos can get through," Hennig said.

That setup differs from that of IceCube, the Nobel Prize-winning detector buried in Antarctic ice. "Ice scatters the light more than water, but on the other hand, water absorbs the light more than ice," Domi said, which changes how each team reconstructs a neutrino's energy and path.

Small but mighty

The researchers used 5,828 neutrinos collected over about 17 months between 2020 and 2021. They found that the oscillations matched standard physics. That means if Lorentz violation exists, it must be weaker than the limits the team set.

Those limits matter for theorists. If a model "predicts a Lorentz invariance violation [stronger than the new limits], the data rule it out. In that case, you can be pretty sure that this model is not correct," Hennig said.

The team also set the first direct limits on a kind of violation that would treat muon neutrinos and tau neutrinos differently.

The detector's limits on several key measures are competitive with those from Japan's Super-Kamiokande, which used 12 years of data, and from IceCube, which used two years of data from its full array.

"I'm surprised that we have competitive results with only six detection units," Hennig said. Today, 44 units are in the water, and the collaboration plans to activate 108 by 2030.

The best tests may still lie ahead. Because Lorentz-violating effects grow with distance and energy, neutrinos from distant cosmic sources are "actually the best candidates to do this kind of research," Domi said. The team plans to repeat the search using ORCA's sister detector, ARCA (Astroparticle Research with Cosmics in the Abyss), which sits off the coast of Sicily and is designed to catch those high-energy cosmic travelers.

If space-time does have a grain, those particles may be among the first to feel it.

See how much you know about Albert Einstein with our Albert Einstein quiz!

'> Physicists sank a telescope 1.5 miles under the sea to put Einstein's relativity to the test

The fragment transported hundreds of flowering species and a flourishing collection of other ancient plants north across the prehistoric Tethys Ocean, the research reveals. The findings contradict previous theories that the fragment originated closer to what is now Southeast Asia and that Southeast Asia's tropical forests evolved sometime after the extinction of the dinosaurs around 66 million years ago.

At the time the fragment formed, Australia was connected to Antarctica and India within the ancient supercontinent Gondwana, which the Tethys Ocean separated from another ancient supercontinent, called Laurasia.

After drifting northward for 100 million years, the microplate eventually collided with Southeast Asia, seeding tropical forests that evolved into the lush ecosystems found in this part of the world today, the researchers said.

"The rich tropical rainforest flora of [Southeast Asia] is not endemic but owes much of its biota to the great southern land, Gondwana," study co-author Byron Lamont, a distinguished professor emeritus in Curtin University's School of Molecular and Life Sciences in Australia, told Live Science in an email.

But the collision with Southeast Asia was far from smooth, Lamont said. The fragment, which is known as the West Burma Block (WBB) or the Burma terrane due to its location in western Myanmar, wasn't the only piece of crust crossing the Tethys Ocean around 100 million years ago. The Indian subcontinent was also moving north, and it was doing so at a relatively rapid speed of 4 inches (10 centimeters) per year.

Around 80 million years ago, the Indian Plate bumped into the WBB, altering the fragment's orientation. The Indian Plate continued to shove the WBB until they both collided with Asia. The Indian Plate then slid beneath the Eurasian Plate to form the Himalayas, and the WBB ground to a halt to the west of present-day Myanmar, where it created a deep valley between mountain ranges about 35 million years ago, Lamont explained.

Both the Indian Plate and the WBB "took some time to stop," he said.

From the time the WBB broke off from Gondwana until its collision with Southeast Asia starting 50 million years ago, the microplate spent tens of millions of years hovering near the equator, where it was humid and hot like it is today. This climate and the fragment's isolation provided a refuge where ancient plant lineages could survive and diversify, Lamont said.

For the study, Lamont and his colleagues examined more than 3,000 plant fossils from Myanmar that were preserved in amber around 100 million years ago. The fossils included flowers, leaves, fruits and seeds. They belonged to at least 392 types of flowering plants and a vast array of conifers, ferns, mosses, cycads and liverworts that reached Southeast Asia by floating on the WBB.

Amber has been mined from the north end of the WBB valley for at least a century, Lamont said. "Its beautiful fossils, preserved in 3D, have long attracted interest for their novelty value alone and there has been much commercial interest in them, especially from Chinese traders," he noted.

Some of the study's co-authors acquired chunks of amber from traders at least a decade ago, and they have been studying these pieces ever since. Advice was often required from experts at other institutions around the world, which is how Lamont got involved in the study, he said.

The findings, published Oct. 27 in the journal Nature Ecology & Evolution, reveal the deep evolutionary roots of the tropical forests that grow in Southeast Asia today. The WBB didn't strip Australia of its ancient flora, because the descendants of many plants found in the 100 million-year-old amber still exist in the country's Northeast, which is hot and humid, Lamont said.

It's hard to say what kinds of animals arrived in Southeast Asia via the WBB, because only creatures small enough to be preserved in amber are represented in this fossil assemblage.

"The animals present in the amber are small insects, such as ants and mosquitoes," Lamont said. "Typical Australian vertebrates, such as marsupials, emus and nectar-feeding birds, arrived from South America in Australia over 100 million years later [after the WBB split off], and of course they would not have got caught in the resin even if they had been around."

Rainforest quiz: Can you sort Earth's largest rainforests from biggest to smallest?

'> A tiny chunk of Australia seeded Southeast Asia's tropical forests 50 million years ago, plant fossils preserved in amber reveal Swift telescope has reached the conclusion of its nearly 22-year mission, burning up in Earth's atmosphere after studying some of the universe's most powerful and mysterious events.

According to NASA, the spacecraft reentered the atmosphere at "7:39 a.m. EST Wednesday over the North Sumatra region of Indonesia, at approximately 3.4 degrees north latitude and 98.6 degrees east longitude." NASA expected most of the telescope's structure to burn up during its passage through Earth's atmosphere, estimating a 1-in-2,100 chance of any surviving debris falling over a populated area. No damage or injuries have been reported.

Weighing approximately 3,200 pounds (1,450 kilograms), the Neil Gehrels Swift Observatory was initially designed for a two-year mission, but it far exceeded expectations. Over two decades, Swift became an important tool in the study of gamma-ray bursts, supernovas, black holes and other cosmic phenomena.

Exceeding expectations

Launched in November 2004, Swift was designed to detect gamma-ray bursts, powerful explosions that occur throughout the universe. Its three onboard telescopes let scientists observe cosmic events across different wavelengths, including ultraviolet, optical and X-ray light. The telescope could swivel to focus on different sky targets in a matter of minutes, allowing it to rapidly follow up on sudden events like supernova explosions.

NASA estimates that Swift's scientific observations have contributed to approximately 7,000 research papers, leaving behind an extensive collection that scientists can continue studying for years.

Why did Swift's mission end?

Swift's return was driven by atmospheric drag, which eventually slowed the spacecraft and caused its orbit to decay. Increased solar activity intensified the drag, thus accelerating the space telescope's descent toward Earth.

Earlier this year, NASA explored an ambitious rescue mission to extend Swift's operational life. In August 2026, a privately developed robotic spacecraft built by Katalyst Space Technologies was intended to rendezvous with Swift and boost it into a higher orbit. However, the mission failed after launching, leaving the observatory on its path toward reentry.

NASA officially ended Swift's scientific operations on Oct. 20 after its declining altitude made observations too difficult. For NASA and the broader astronomy community, Swift's story is a reminder that even missions designed to last just a few years can fundamentally change our understanding of our universe.

'> Swift has fallen: NASA's 22-year-old space telescope burns up over Sumatra