WHEN Joseph Conlon was an undergraduate in the early 2000s, he avoided popular science accounts of string theory because he wanted to engage with it on a technical level, without preconceptions. It was a few years after the “second string theory revolution”, when theoretical physicists felt they might be about to crack open the deepest workings of reality, perhaps even deliver a theory of everything. As he explored the maths, Conlon was captivated.

String theory famously suggests that everything is made up of one-dimensional strings (see “String theory: A primer”, below), and also predicts a huge array of possible universes – some 10⁵⁰⁰, for those taking notes. Whatever you think about that, it is fair to say that string theory hasn’t generated the testable predictions that many were hoping for. Today, it has a reputation for being untestable, maybe even unscientific. One arch string theory critic dubbed it “not even wrong”.

But for Conlon, now a physicist at the University of Oxford, the thrill never faded. String theory remains a potential route to uniting the incompatible ways we think about gravity and the quantum world, he argues, to create a unified theory of quantum gravity. He also claims that his field has been unfairly maligned, and that its detractors are applying double standards. He even insists that string theory does make predictions that we could conceivably probe with upcoming astronomical observations.

Here, Conlon tells New Scientist about the enduring joys of string theory, why it is too early to write it off, and why we might need to revise our conception of what makes a useful scientific idea.

…

An experimental aircraft commissioned by NASA will fly over major US cities at faster than the speed of sound. The purpose of the X-59 plane is to gather evidence that will determine if supersonic commercial aviation over land should be legalised.

Aircraft create a wake of shock waves once they pass the speed of sound. This “sonic boom” is so loud it can startle humans and animals and even shatter windows and set off car alarms. When flying at an altitude of 15,000 metres, the now-retired Concorde would…

Physicists are close to performing the most accurate tests of Einstein’s ideas about gravity ever undertaken. Their first-of-its-kind experiment involves using two kinds of extremely cold atoms aboard the International Space Station (ISS).

A key principle of Einstein’s theory, and one that researchers have been testing for decades, is the equivalence principle. This states that all objects fall with the same acceleration when gravity is the only force acting on them.

One of the most sensitive tests of the principle so far undertaken relied on putting very cold rubidium atoms into freefall at a special facility in California; another sensitive test involved exploring the effects of gravity on materials of precisely measured mass that were launched into space on a satellite.

Naceur Gaaloul at the Leibniz University Hannover in Germany and his colleagues have now built an experiment that combines elements of both of these earlier tests by using ultracold atoms in space.

They used the Cold Atoms Laboratory (CAL) on the ISS, which was launched in 2018 and built to examine quantum effects that atoms undergo in a noticeable way only when they are extremely cold and when gravity is extremely low. Within CAL, atoms are confined to a chip and made very cold by being pushed, pulled, and hit by magnetic forces and lasers.

At temperatures only billionths of a degree above absolute zero, quantum effects make these atoms behave like a collection of overlapping “matter waves” rather than distinct particles. In the new experiment, the researchers cooled potassium and rubidium atoms on the same chip and then manipulated them in a way that effectively turned the chip into two separate devices called interferometers.

Interferometers measure acceleration based on patterns made inside them by clashing matter waves. The ISS is always in freefall – it is always accelerating due to gravity – so if the two interferometers recorded different acceleration values, the equivalence principle would be broken.

While the team have now successfully made the two interferometers in the CAL, they need to optimise the two devices further before they can use them to fully test the equivalence principle.

“The equivalence principle is the bedrock of our understanding of gravity, but these experiments could go beyond just testing general relativity. There could be new particles which are not included in the Standard Model that manifest as breaking this principle,” says Timothy Kovachy at Northwestern University in Illinois. He says that the accuracy of atom-based interferometers increases the longer the atoms are in freefall, and since there are time constraints on how long such freefall can be maintained on Earth, reaching extreme precision requires going to space.

And doing so is a growing and competitive field says Gaaloul. In 2017, he was part of a team sponsored by the German Space Agency, or DLR, which achieved atom interferometry using ultracold rubidium atoms – but not potassium atoms – aboard a research rocket. The DLR team will launch another rocket in the coming months, this time with both potassium and rubidium atoms on board.

The CAL experiments are expected to yield results that are hundreds of times more accurate than those obtained with satellite-based tests, and hundreds of thousands of times more accurate than the results of Earth-based experiments, but Gaaloul says that ultimately it will be necessary to go beyond the ISS as well. “Because of the vibrations from astronauts biking and other things that are going on, the ISS is not perfect for precision experiments,” he says. “But here we will make sure of techniques for equivalence principle tests which will ultimately happen on a dedicated satellite.”

Topics:

Almost everyone in the US with a mobile phone, radio or TV can expect to hear and see an alert message from the US government as part of a nationwide test – but there is no need for alarm or tinfoil hats.

The nationwide test of the Wireless Emergency Alerts system on 4 October will cause people’s mobile phones to vibrate and emit an audio tone, each action repeating twice, along with displaying a text message in either English or Spanish. The testing period is scheduled to start at 2:20 PM Eastern Time and to continue for 30 minutes.

The messages will read: “THIS IS A TEST of the National Wireless Emergency Alert System. No action is needed.”

Simultaneously, the US government plans to conduct a nationwide test of the separate Emergency Alert System that will broadcast similar one-minute messages through radio and TV.

Who is doing this test and why?
The US Federal Emergency Management Agency (FEMA) and Federal Communications Commission (FCC) are responsible for managing both systems and holding the national tests.

Real alerts are typically issued by local and state government officials, along with other federal agencies such as the National Weather Service, during actual emergencies. Most are local messages sent to specific counties or neighbourhoods and include warnings of imminent threats such as extreme weather or active shooters, less urgent public safety messages, and AMBER Alerts in child abduction cases.

“The national test is best thought of as a system-wide test,” says Elizabeth Ellcessor at the University of Virginia. “If the system works for this, it should also work for the smaller, more local, ordinary uses.”

In the rarest emergencies, the system could send out a national alert issued by the president or by the head of FEMA.

How often do these tests take place?
This is only the third nationwide test of the Wireless Emergency Alerts system. Previous tests on mobile phones took place in 2018 and 2021, and additional tests are planned every few years in accordance with federal law.

Both earlier national tests attracted groundless conspiracy theories – and many people reported not understanding the different types of phone alerts or their uses after the nationwide test in 2021.

By comparison, Ellcessor describes the local alerts sent to phones for actual emergencies as typically not provoking any outcry “because people are more familiar with them and do see benefits firsthand”. Real phone alerts in the US have already been issued more than 84,000 times since the system first launched in 2012.

The US government might consider holding “an annual national or local testing day” so that people become familiar with the system through more frequent tests, says Hamilton Bean at the University of Colorado Denver. He points out that Canada already holds tests of its national Alert Ready system twice every year – and he recommends that the US make more effort to educate people about its own system.

Can I opt out of getting the test message?
There is no official opt-out option for the national tests of the Wireless Emergency Alerts system on mobile phones. However, phones will not receive the test alert message if they are turned off or put in “aeroplane mode” for the duration of the test.

People may also fail to receive the message if they are beyond the range of cell tower signals during that time or are not using compatible phones. Some older mobile devices may also fail to display the text alert during a phone call.

Survivors of domestic violence who rely on hidden phones should consider turning off their devices for the duration of the national test, according to the National Network to End Domestic Violence, a non-profit organisation based in Washington DC.

Topics:

When researchers claimed recently that they had created a material that perfectly conducts electricity – a superconductor – and that it does so at room temperature and pressure, many people were understandably sceptical. Such a finding would be transformative to many areas of science and technology. Now, labs around the world have kicked into action in a race to create and test the new material, called LK-99, to see if it really is what its creators claim.

Superconductors could radically increase the efficiency of many technologies, including …

A navigation system based on high-energy particles created by cosmic rays has been successfully tested underground for the first time. The technology could one day be used to guide underground and underwater robots, and even aid search and rescue efforts in collapsed mines or buildings.

Existing navigation tools like GPS use radio waves to triangulate a position, but these signals tend to be absorbed or reflected by water or thick rock. “That’s why it’s difficult to use GPS in indoor or underground environments,” says Hiroyuki Tanaka at the University of Tokyo, Japan.

To get around this problem, researchers have turned to particles called muons, which are created when cosmic rays collide with particles in Earth’s atmosphere and can pass through water and rock unaffected. For example, the US Navy has investigated using a muometric position system, or MuPS, that utilises the properties of muons to navigate underground and underwater.

Now, Tanaka and his colleagues have developed a wireless version of the technology, dubbed the muometric wireless navigation system (MuWNS).

In the first real-world test of MuWNS, researchers placed four reference detectors on a building’s sixth floor, while someone walked with a receiver detector around the basement. Similar to how a GPS works, the system calculated the location of the person in the basement using the time taken for the muons to pass between the reference detectors and the receiver detector in the basement, as well as their angle.

The team found that MuWNS could track the person in the basement with an accuracy of between 2 to 25 metres, which is comparable to GPS. That is enough to make the system useful for providing navigation to vehicles in tunnels or perhaps one day to find survivors in rubble after earthquakes or cyclones, says Tanaka.

“It is intriguing to see muons being used in a prototype positioning system which claims quite a high accuracy,” says Stephen Blundell at the University of Oxford. “This new technique could find applications in certain specialised environments.”

Topics:

IBM’s Eagle quantum computer completed a calculation that stumped the conventional supercomputer it was pitted against.

Quantum computers have sparked excitement for a few decades, but researchers haven’t built one that universally outperforms all conventional computers. This is partly because all existing quantum computers are “noisy” – their results are corrupted by errors, in the same way that sound can get lost in a crackly recording.

Now, Abhinav Kandala at IBM and his colleagues have shown that even a noisy quantum computer can be more accurate in its calculations than a conventional machine.

They compared the performance of IBM’s Eagle quantum computer, which contains 127 quantum bits, or qubits, with that of a supercomputer at the Lawrence Berkeley National Laboratory in California. Both were tasked with calculating the most likely behaviour of a collection of particles, such as atoms with spin, arranged in a grid and interacting with each other.

The difficulty of this problem increases with the number of particles. For up to a certain number of particles, researchers can solve the relevant equations on a computer exactly. Supercomputers and approximation methods can handle the calculations when larger number of particles are involved, but eventually computations become so complex that conventional computing fails. The IBM researchers wanted to test Eagle together with a set of methods they developed for mitigating the effects of noise in each of these cases.

When the supercomputer could complete the calculations, the results of the two methods were in agreement. But when the complexity was increased beyond a certain point, the supercomputer failed, while Eagle was still able to deliver a solution. Even though there was no way to test if Eagle’s result was correct, Kandala says good agreement with established calculations up to that point gave his team confidence that the quantum computer had passed the test.

The IBM team does not claim to have achieved quantum supremacy, which would mean proving that Eagle’s performance is impossible to match for any conventional computer and algorithm. They didn’t test the quantum computer against every existing conventional approach. Kandala says this was not their goal as he expects classical computing methods to continue to improve, but he and his colleagues wanted to test the usefulness of the quantum processors available now.

He says that the methods they used for these calculations could be adapted to a broader set of problems such as calculating the behaviour of materials or molecules that are of interest in biophysics and chemistry.

Xavier Waintal at CEA Grenoble in France says demonstrating that a quantum computer is truly useful beyond an experiment designed specifically to show computational power is a tall order. He says that Eagle’s hardware performance is impressive and is an important milestone, but he is sceptical of how much utility researchers can get from the demonstrated ability.

“Demonstrating that a device is doing something that absolutely cannot be simulated on a classical computer is notoriously difficult. You would have to prove it for every existing technique as well as every conceivable technique that doesn’t even exist yet,” says Mark Howard at the University of Galway in Ireland. But the competition between quantum and classical computers has historically improved how researchers use both, he says.

IBM’s team is already looking to repeat its experiment for more complicated calculations and with larger, and therefore potentially more powerful, quantum computers. The hope is that with further development, quantum computers could assist in creating new materials for batteries or fertilisers, or new compounds for medicines.

“We know classical computing is not going anywhere, but we are excited about getting utility out of our quantum computers. We now have a good tool with over 100 qubits, and the more we use it the better we will get at making it even more useful,” says IBM’s Katie Pizzolato.

Topics:

• quantum computing/
• quantum physics

AI-generated advertisements proved generally indistinguishable from human-made ads in a competition described as the first ad Turing test.

The competition was inspired by the original Turing test, which challenges how well machines can mimic humans in conversation. In this case, a panel of 17 marketing experts achieved just 57 per cent accuracy in correctly identifying three ads primarily made using generative AIs and seven ads made by marketing students. The results were announced at the inaugural BrXnd Conference on marketing and AI in New York City …

A clever use of capital letters could be an easy way to flummox artificial intelligences like ChatGPT, letting people distinguish them from humans in conversation.

The idea is reminiscent of the Turing test, first proposed by computer scientist Alan Turing in 1950. He said that an AI would be considered truly intelligent once we couldn’t distinguish its answers from a human’s. But now that large language models (LLMs) like ChatGPT can sound convincingly human, Hong Wang at the University of …

People can only tell apart artificial intelligences from humans around 60 per cent of the time, according to a test taken by more than 1.5 million people. The results raise questions about whether the new generation of AIs should have to identify themselves in conversation, say researchers.

Computer scientist Alan Turing first proposed a test for machine intelligence in 1950. In its original form, a person talks via text with both another person and a machine and has to guess which is which — if …