Learn how viruses lingering in sewage can enter bodies of water, posing a public health risk that may be on the rise as climate change brings more rain.
This episode of the Physics World Weekly podcast features Ileana Silvestre Patallo, a medical physicist at the UK’s National Physical Laboratory, and Ruth McLauchlan, consultant radiotherapy physicist at Imperial College Healthcare NHS Trust.
In a wide-ranging conversation with Physics World’s Tami Freeman, Patallo and McLauchlan explain how ionizing radiation such as X-rays and proton beams interact with our bodies and how radiation is being used to treat diseases including cancer.
This episode was created in collaboration with IPEM, the Institute of Physics and Engineering in Medicine. IPEM owns the journal Physics in Medicine & Biology.
Europe’s investment in HydRON, a multi-orbit optical data relay network, signals a pivotal shift in how data is moved across Earth and beyond. The program aims to transform satellite connectivity, […]
Helium deep with the Earth could bond with iron to form stable compounds – according to experiments done by scientists in Japan and Taiwan. The work was done by Haruki Takezawa and Kei Hirose at the University of Tokyo and colleagues, who suggest that Earth’s core could host a vast reservoir of primordial helium-3 – reshaping our understanding of the planet’s interior.
Noble gases including helium are normally chemically inert. But under extreme pressures, heavier members of the group (including xenon and krypton) can form a variety of compounds with other elements. To date, however, less is known about compounds containing helium – the lightest noble gas.
Beyond the synthesis of disodium helide (Na2He) in 2016, and a handful of molecules in which helium forms weak van der Waals bonds with other atoms, the existence of other helium compounds has remained purely theoretical.
As a result, the conventional view is that any primordial helium-3 present when our planet first formed would have quickly diffused through Earth’s interior, before escaping into the atmosphere and then into space.
Tantalizing clues
However, there are tantalizing clues that helium compounds could exist in some volcanic rocks on Earth’s surface. These rocks contain unusually high isotopic ratios of helium-3 to helium-4. “Unlike helium-4, which is produced through radioactivity, helium-3 is primordial and not produced in planetary interiors,” explains Hirose. “Based on volcanic rock measurements, helium-3 is known to be enriched in hot magma, which originally derives from hot plumes coming from deep within Earth’s mantle.” The mantle is the region between Earth’s core and crust.
The fact that the isotope can still be found in rock and magma suggests that it must have somehow become trapped in the Earth. “This argument suggests that helium-3 was incorporated into the iron-rich core during Earth’s formation, some of which leaked from the core to the mantle,” Hirose explains.
It could be that the extreme pressures present in Earth’s iron-rich core enabled primordial helium-3 to bond with iron to form stable molecular lattices. To date, however, this possibility has never been explored experimentally.
Now, Takezawa, Hirose and colleagues have triggered reactions between iron and helium within a laser-heated diamond-anvil cell. Such cells crush small samples to extreme pressures – in this case as high as 54 GPa. While this is less than the pressure in the core (about 350 GPa), the reactions created molecular lattices of iron and helium. These structures remained stable even when the diamond-anvil’s extreme pressure was released.
To determine the molecular structures of the compounds, the researchers did X-ray diffraction experiments at Japan’s SPring-8 synchrotron. The team also used secondary ion mass spectrometry to determine the concentration of helium within their samples.
Synchrotron and mass spectrometer
“We also performed first-principles calculations to support experimental findings,” Hirose adds. “Our calculations also revealed a dynamically stable crystal structure, supporting our experimental findings.” Altogether, this combination of experiments and calculations showed that the reaction could form two distinct lattices (face-centred cubic and distorted hexagonal close packed), each with differing ratios of iron to helium atoms.
These results suggest that similar reactions between helium and iron may have occurred within Earth’s core shortly after its formation, trapping much of the primordial helium-3 in the material that coalesced to form Earth. This would have created a vast reservoir of helium in the core, which is gradually making its way to the surface.
However, further experiments are needed to confirm this thesis. “For the next step, we need to see the partitioning of helium between iron in the core and silicate in the mantle under high temperatures and pressures,” Hirose explains.
Observing this partitioning would help rule out the lingering possibility that unbonded helium-3 could be more abundant than expected within the mantle – where it could be trapped by some other mechanism. Either way, further studies would improve our understanding of Earth’s interior composition – and could even tell us more about the gases present when the solar system formed.
While Starlink’s broadband contract wins often grab the spotlight, a panel of multi-orbit operators at the Satellite Conference here highlighted how they are also gaining significant traction with enterprise and government customers.
HELSINKI — China is expanding its presence and capabilities in the strategically vital geostationary belt, raising security concerns due to unpredictable satellite movements, according to experts. Participants in a panel […]
The loss of a solid rocket motor nozzle on the second flight of United Launch Alliance’s Vulcan Centaur last October was caused by a manufacturing defect.
Two months into Donald Trump’s second presidency and many parts of US science – across government, academia, and industry – continue to be hit hard by the new administration’s policies. Science-related government agencies are seeing budgets and staff cut, especially in programmes linked to climate change and diversity, equity and inclusion (DEI). Elon Musk’s Department of Government Efficiency (DOGE) is also causing havoc as it seeks to slash spending.
In mid-February, DOGE fired more than 300 employees at the National Nuclear Safety Administration, which is part of the US Department of Energy, many of whom were responsible for reassembling nuclear warheads at the Pantex plant in Texas. A day later, the agency was forced to rescind all but 28 of the sackings amid concerns that their absence could jeopardise national security.
A judge has also reinstated workers who were laid off at the National Science Foundation (NSF) as well as at the Centers for Disease Control and Prevention. The judge said the government’s Office of Personnel Management, which sacked the staff, did not have the authority to do so. However, the NSF rehiring applies mainly to military veterans and staff with disabilities, with the overall workforce down by about 140 people – or roughly 10%.
The NSF has also announced a reduction, the size of which is unknown, in its Research Experiences for Undergraduates programme. Over the last 38 years, the initiative has given thousands of college students – many with backgrounds that are underrepresented in science – the opportunity to carry out original research at institutions during the summer holidays. NSF staff are also reviewing thousands of grants containing such words as “women” and “diversity”.
NASA, meanwhile, is to shut its office of technology, policy and strategy, along with its chief-scientist office, and the DEI and accessibility branch of its diversity and equal opportunity office. “I know this news is difficult and may affect us all differently,” admitted acting administrator Janet Petro in an all-staff e-mail. Affecting about 20 staff, the move is on top of plans to reduce NASA’s overall workforce. Reports also suggest that NASA’s science budget could be slashed by as much as 50%.
Hundreds of “probationary employees” have also been sacked by the National Oceanic and Atmospheric Administration (NOAA), which provides weather forecasts that are vital for farmers and people in areas threatened by tornadoes and hurricanes. “If there were to be large staffing reductions at NOAA there will be people who die in extreme weather events and weather-related disasters who would not have otherwise,” warns climate scientist Daniel Swain from the University of California, Los Angeles.
Climate concerns
In his first cabinet meeting on 26 February, Trump suggested that officials “use scalpels” when trimming their departments’ spending and personnel – rather than Musk’s figurative chainsaw. But bosses at the Environmental Protection Agency (EPA) still plan to cut its budget by about two-thirds. “[W]e fear that such cuts would render the agency incapable of protecting Americans from grave threats in our air, water, and land,” wrote former EPA administrators William Reilly, Christine Todd Whitman and Gina McCarthy in the New York Times.
The White House’s attack on climate science goes beyond just the EPA. In January, the US Department of Agriculture removed almost all data on climate change from its website. The action resulted in a lawsuit in March from the Northeast Organic Farming Association of New York and two non-profit organizations – the Natural Resources Defense Council and the Environmental Working Group. They say that the removal hinders research and “agricultural decisions”.
The Trump administration has also barred NASA’s now former chief scientist Katherine Calvin and members of the State Department from travelling to China for a planning meeting of the Intergovernmental Panel on Climate Change. Meanwhile, in a speech to African energy ministers in Washington on 7 March, US energy secretary Chris Wright claimed that coal has “transformed our world and made it better”, adding that climate change, while real, is not on his list of the world’s top 10 problems. “We’ve had years of Western countries shamelessly saying ‘don’t develop coal’,” he said. “That’s just nonsense.”
At the National Institutes of Health (NIH), staff are being told to cancel hundreds of research grants that involve DEI and transgender issues. The Trump administration also wants to cut the allowance for indirect costs of NIH’s and other agencies’ research grants to 15% of research contracts, although a district court judge has put that move on hold pending further legal arguments. On 8 March, the Trump administration also threatened to cancel $400m in funding to Columbia purportedly due to its failure to tackle anti-semitism on the campus.
A Trump policy of removing “undocumented aliens” continues to alarm universities that have overseas students. Some institutions have already advised overseas students against travelling abroad during holidays, in case immigration officers do not let them back in when they return. Others warn that their international students should carry their immigration documents with them at all times. Universities have also started to rein in spending with Harvard and the Massachusetts Institute of Technology, for example, implementing a hiring freeze.
Falling behind
Amid the turmoil, the US scientific community is beginning to fight back. Individual scientists have supported court cases that have overturned sackings at government agencies, while a letter to Congress signed by the Union of Concerned Scientists and 48 scientific societies asserts that the administration has “already caused significant harm to American science”. On 7 March, more than 30 US cities also hosted “Stand Up for Science” rallies attended by thousands of demonstrators.
Elsewhere, a group of government, academic and industry leaders – known collectively as Vision for American Science and Technology – has released a report warning that the US could fall behind China and other competitors in science and technology. Entitled Unleashing American Potential, it calls for increased public and private investment in science to maintain US leadership. “The more dollars we put in from the feds, the more investment comes in from industry, and we get job growth, we get economic success, and we get national security out of it,” notes Sudip Parikh, chief executive of the American Association for the Advancement of Science, who was involved in the report.
Marcia McNutt, president of the National Academy of Sciences, meanwhile, has called on the community to continue to highlight the benefit of science. “We need to underscore the fact that stable federal funding of research is the main mode by which radical new discoveries have come to light – discoveries that have enabled the age of quantum computing and AI and new materials science,” she said. “These are areas that I am sure are very important to this administration as well.”
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