A tiny UK-developed satellite, roughly the size of a small carry-on suitcase, could help answer one of the biggest questions in cosmology: What happened during the roughly 150 million years of the cosmic dark ages, before the universe's first stars appeared?

An international team of scientists led by the University of Cambridge will use the far side of the moon as a "shield" so the satellite—called CosmoCube—can block out all the noise from Earth and listen for a faint whisper from the very early universe.

This whisper, known as the 21-centimeter line, is a signal emitted by hydrogen atoms in the period between the afterglow of the Big Bang and cosmic dawn, when nuclear fusion lit up the first stars. No one has directly observed this era before.

Detecting this signal from more than 13.5 billion years ago is extremely difficult with Earth-based telescopes because Earth's ionosphere blocks the right frequencies, and interference from FM radio, satellites and telecommunications drowns it out.

However, the moon provides a natural shield. As CosmoCube orbits the far side of the moon, it will be shielded from all the noise from Earth for roughly 40 minutes of each 2-hour orbit. Over an expected 2-year mission, it will build up 1,000 hours of data on one of the last unexplored periods of the universe, helping us understand how the universe transitioned from dark and nearly empty to the complexity we see today.