Little is known about what was happening shortly after the Big Bang, but researchers now hope to shed new light on the matter by taking advantage of the far side of the Moon. Scientists plan to put a suitcase-sized satellite into orbit around the Moon, using the data it collects as it passes by the far side to search for a radio frequency signal emitted by neutral hydrogen atoms in the early universe. More specifically, the satellite, dubbed CosmoCube, will search for what is known as the 21cm line. Crucially, the older the signal, the more its wavelength has been stretched or redshifted to longer wavelengths, providing a way to track its strength over time relative to the cosmic microwave background radiation. “The main thing we track by looking at this signal is what the physical temperature of the gas is during the early universe,” said Professor Eloy de Lera Acedo, lead author from the University of Cambridge’s Cavendish Laboratory. With the 21cm signal acting a bit like a thermometer, the team hopes to study events from the beginning of the so-called “dark ages,” about 380,000 years after the Big Bang, through the cosmic dawn, when the first stars and galaxies emerged, to the end of what is known as the epoch of reionization, about a billion years after the Big Bang. “The temperature of the gas is affected by what is happening in the universe at that time,” said de Lera Acedo. In addition, he noted that the amplitude and shape of the 21 cm signal were expected to be influenced by dark matter, which would offer experts a way to investigate the nature of this mysterious component of the universe. A representative model of the CosmoCube being tested. The 21 cm line is the radio frequency signal emitted by neutral hydrogen atoms in the early universe. Photograph: RAL Digital Creative Services/STFC/UKRI Researchers have tried to detect the 21cm line before, but it is difficult to do so using ground-based instruments. Not only is the signal weak, but man-made technology (from FM radios to air communications) can cause interference. Writing in the journal Nature Astronomy, de Lera Acedo and his colleagues said other challenges included perturbations created by Earth’s ionosphere. While experts at the Edges radio telescope (Experiment to Detect the Global EoR Signature) in Australia claim to have found the 21cm line, doubts have been raised about the results. The team behind the CosmoCube mission, which is expected to last two years, said taking observations from the far side of the Moon should avoid many of the challenges they face. “The total cost is estimated at just under £50 million and the launch date we hope will be within five years,” de Lera Acedo said, adding that the UK Space Agency had already awarded CosmoCube more than £2 million of funding. Phil Bull, professor of cosmology at the Jodrell Bank Center for Astrophysics, who is not involved in the project, welcomed the mission. “CosmoCube measurements will help us understand the main ingredients of our cosmic origins: the processes that led to the formation of the first stars and galaxies, and illuminated the Universe after a period called the cosmic dark age,” he said. But, Bull noted, CosmoCube wasn’t the only mission to try to make these measurements, and others may get there first. “More disturbingly, other planned lunar missions could bring with them exactly the kind of human-generated radio noise the mission is trying to escape,” he said, “making this a race against time.” Join us on September 3 for a live recording of The Guardian’s Science Weekly podcast with Black Box host Michael Safi at Kings Place in London. Buy your ticket here.
