And then there were five

摘要

The ground is shifting under our feet. Fundamental properties of the Universe are changing, and physicists can't explain how or why. Now researchers say an as yet undiscovered fifth force could be behind these mysterious changes. Physicists combine supposedly unchanging physical properties, such as the speed of light and an electron's charge, into a number called the "fine structure constant" that describes how our Universe hangs together. But in 1999, astronomers analysing 10-billion-year-old light from distant quasars got a shock when they found that it was different from what we'd expect to see today.