The Dark Energy Spectroscopic Instrument (DESI) Mission: Results and Future Directions for a 3D Map of the Universe
The effect was first tentatively reported in April last year, but the latest results — presented on 19 March by the Dark Energy Spectroscopic Instrument (DESI) collaboration at a meeting of the American Physical Society in Anaheim, California — are based on three years’ worth of data-taking, versus one year for the results announced in 2024.
Catherine Heymans is an astronomer at the University of Edinburgh, UK, and the Astronomer Royal for Scotland.
At Kitt Peak National Observatory, the DESI Telescope is located. It uses 5,000 robotic arms to point optical fibres at selected points where galaxies or quasars are located within its field of view. The fibres then deliver light to sensitive spectrographs that measure how much each object is redshifted — meaning the degree to which its light waves were stretched by the expansion of space on their way to Earth. Researchers can estimate an object’s distance using its redshift, to produce a 3D map of the Universe’s expansion history.
In that map, researchers then look at the density of galaxies to identify variations that are left over from sound waves called baryon acoustic oscillations (BAOs), which existed before stars began to form. The largest known features of the current Universe are the variations, which started at 150 kiloparsecs and have now grown by a factor of 1000 to 150 megaparsecs.
A small human hair tinier than a light emitting diode: evidence of Aboriginal reburial of the Mungo Lady
In the past five years alone, around 9,000 satellites were launched into Earth orbit, taking the total from just over 2,000 to 11,000. Musk’s company, SpaceX, runs the Starlink system and more than 7,000 of them belong to it. The spacecraft play a crucial role in connecting people around the world, but their soaring numbers are giving astronomers a headache by creating streaks in images and interfering with observations. The focus now is damage control. Astronomers are working with satellite companies to build a centralized tracking system, develop technologies that can de-streak their images and re-direct signals that can overwhelm radio telescopes.
There is a court case in Australia regarding the fate of human remains taken from Lake Mungo in the 1960s and 1970s. TheMungo Lady is an example of one of the oldest-known cremations, as well as the earliest human skeletons ever found. The history of First Nations people is represented by the bones of the aboriginal Australian people who were part of the same area, and how science sometimes disrespects their rights by treating their ancestors as scientific material. Scientists and members of the Aboriginal Australian communities are not on the same page about whether the reburying of the remains was the right decision.
Physicists have created the tiniest light-emitting diode (LED) displays ever. The image above was shown on a monochromatic display with pixels less than 100 micrometres across, about the width of a human hair. The team made an even tinier LED if that was small enough. The pixels in this teensy display were just 90 nanometres wide — about the size of a virus, and too small to be resolved even by the most powerful optical microscopes. (Nature | 3 min read)
Artificial Intelligence and Artificial Immune Cells: A Microsatellite to Send Quantum Keys to South Africa & China
Within 4 years, artificial intelligence (AI) systems could outpace human computer programmers on long tasks that take months, and which they’ve so far lagged on. Since 2019, the ‘task-completion time horizon’ — a metric devised to track how long programmers take to complete tasks that AI can complete with a 50% success rate — has doubled roughly every seven months. By the year 2029, that suggests tasks that take humans about a month will be mastered by artificial intelligence. Joshua, a management professor, says that uncertainties about how Artificial Intelligence will be used do not mean these kinds of extrapolations are always useful.
A study in mice showed that the skin immune cells create their own bandages to protect themselves from infections after an injury. Researchers found that white blood cells called neutrophils form a ring of protein-rich ‘goo’ around areas where the skin has been breached to trap pathogens. Neutrophils are known as the first responders to sites of infection and injury, killing pathogens by ingesting them or releasing toxins. This study reveals that after the initial attack, a second wave of neutrophils is deployed to form the sticky barrier.
Researchers have broken the record for quantum communication by sending an encryption key nearly 13,000 kilometres from China to South Africa via a ‘microsatellite’. Laser light came from a roof in Beijing and then came from the University of South Africa. The images shown are one of China’s Great Wall and part of the campus in South Africa. The feat, known as quantum key distribution, is a step towards being able to beam ultra-secure messages through space between any two locations on Earth, however far apart.