Researchers from Keio University have made the most precise measurement yet of the cosmic microwave background radiation's temperature from seven billion years ago, finding it was approximately 5.13 K, roughly twice today's temperature of 2.7 K. By analysing archived data from the ALMA telescope in Chile, the team confirmed a key prediction of Big Bang model, that the universe cools as it expands, meaning it was hotter in the past. This highly accurate measurement provides strong support for the standard cosmological model and helps scientists better understand the thermal history of our universe.