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2nd of March 2022
In Search of the Cosmic Dawn
by Singh et al.
The "cosmic dawn" occurred when the first stars formed, roughly 100 million years after the Big Bang. Detecting radio waves from this period of the Universe's history is extremely challenging, as they are drowned out by radio waves from within, and beyond, our Galaxy, human technology, and the detectors themselves. In 2018, the Experiment to Detect the Global EoR (Epoch of Reionization) Signature (EDGES) reported the presence of a feature in the radio spectrum obtained with their detector at the Murchison Radio-Astronomy Observatory that resembled the signature of the Cosmic Dawn. The so-called Sagan standard states that "extraordinary claims require extraordinary evidence," and the EDGES result has inspired a number of efforts to duplicate the result. The latest was reported in Nature Astronomy this week. The team from India, Canada, and Australia made observations with the Shaped Antenna Measurement of the Background Radio Spectrum 3 (SARAS 3) radiometer on a lake in India, and found no evidence of the spectral feature seen in the EDGES data. Scientific progress is often two steps forward and one step back, and sometimes one step forwards and two steps back! Further searches for evidence of the Cosmic Dawn are underway, and the SKA-Low telescope will enable far more sensitive searches to be made later this decade. The image above shows the monocone SARAS3 antenna. (Image credit: Singh et al. preprint.)

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