When you open your fridge, you expect it to be cooler than your kitchen. Similarly, when astronomers look back billions of years into the Universe's history, they expect to find it was hotter than today.

A team of Japanese researchers has just confirmed this prediction with remarkable precision, offering one of the strongest tests yet of our understanding of how the Universe evolved.

Led by doctoral student Tatsuya Kotani and Professor Tomoharu Oka from Keio University, the research team measured the temperature of the cosmic microwave background radiation, which is the faint afterglow of the Big Bang that permeates all of space.

But they didn't measure it as it appears today. Instead, they looked at light that has traveled for seven billion years to reach us, effectively taking the

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