Astronomy
Probing the Epoch of Reionization with 21-cm Observations
Quick fact
The 21-cm line of neutral hydrogen is so faint that its signal from the Epoch of Reionization is less than 0.01% of the background noise, yet it is being hunted by a global network of radio telescopes.
Why this is interesting
You've heard of the cosmic microwave background, but what about the 'cosmic dawn'? How can we see the very first stars and galaxies, when light from them is too faint to detect directly?