[1] EoR stands for epoch of reionization, a time in cosmic history when neutral atomic hydrogen gas became ionised due to ultraviolet light from the first stars.

The experiment has two low-band instruments, each of which has a dipole antenna pointed to the zenith and observing a single polarisation.

[3][4] In March 2018, the collaboration published a paper in Nature announcing the discovery of a broad absorption profile centered at a frequency of

The signal is possibly due to ultraviolet light from the first stars in the Universe altering the emission of the 21cm line by lowering the temperature of the hydrogen relative to the cosmic microwave background (the mechanism is Wouthuysen–Field coupling).

A "more exotic scenario," encouraged by the unexpected strength of the absorption, is that the signal is due to interactions between dark matter and baryons.

[2][5] In 2021, Melia reported that the deeper absorption is compatible with the alternative Friedmann–Lemaître–Robertson–Walker (FLRW) cosmology known as the Rh = ct universe.