The REACH radio experiment is trying to catch the faint whisper of hydrogen from the Universe’s infancy, a signal that could reveal how the first stars and galaxies ignited after the Big Bang. This matters because the period known as the Cosmic Dawn and Epoch of Reionisation remains a blank page in cosmic history. We know the Universe went from a nearly empty, dark expanse to one filled with starlight, but not how. The 21-cm radio signal from neutral hydrogen is the only direct probe of that era. Previous attempts, like the contested EDGES detection in 2018, have been plagued by instrument-generated noise that masks the cosmological signal. REACH is a second-generation experiment designed to solve this bottleneck by using a Bayesian data pipeline that jointly models the instrument and the sky, separating the real signal from systematic errors. This is fundamental science. If REACH succeeds in making a confident detection, it will open a direct observational window onto the first billion years of cosmic history. That knowledge could reshape our understanding of galaxy formation and the nature of dark matter. As with past fundamental discoveries in radio astronomy—like the cosmic microwave background or pulsars—a deeper map of the early Universe may eventually underpin new technologies in signal processing or precision timing, but the immediate payoff is a clearer answer to a basic question: how did we get here?
View original technical description
How did the Universe transition from a mostly empty volume after the Big Bang to a complex realm of stars, galaxies and other celestial objects? This unknown process occurred during the so-called Cosmic Dawn and the Epoch-of-Reionziation. 21-cm radio-cosmology is the field of research promising to unlock the secrets of the infant Universe by studying radio signals from the most abundant element in the Universe: hydrogen. I request funding to assemble a research team to focus on the detection and study of the elusive 21-cm signal from atomic hydrogen using the Radio Experiment for the Analysis of Cosmic Hydrogen (REACH) that I conceived and lead. Radio-interferometers have already placed upper limits on the 21-cm power spectra, while it is the single-antenna experiments, measuring the 21-cm signal averaged across all directions in the sky, the ones that are promising even earlier breakthroughs. The EDGES experiment shook the field in 2018 reporting a cosmological signal twice deeper than expected requiring exotic physics to be explained. This has been contested by several groups amid concerns on the data analysis and potential impact of hardware systematic signals, including recent measurements from the SARAS3 experiment incompatible with the EDGES findings. The contamination from instru- ment systematics is the main bottleneck for "1st generation" 21-cm radio telescopes. Aiming to resolve these concerns, a new experimental approach has emerged over the last 5 years giving birth to a 2nd generation of experiments. REACH is a sky-averaged experiment leading this new wave of instruments, where the focus has shifted to a data-driven hardware and algorithm design focusing on the detection and isolation of instrumental systematic signals. To this end REACH uses a fully Bayesian data pipeline to jointly fit instrument models with models of the sky sig- nals. During this project I will lead the team aiming at a first confident detection and study of the sky-averaged 21-cm line.
Plain English summaries and category classifications on this site are generated by AI and may not perfectly reflect the original research.
Is something wrong? Let us know