When the biggest numbers don’t add up

Astronomers using the Hubble Space Telescope have made their most precise measurement yet for the expansion rate of the Universe.

It comes out at 74.03km/second per megaparsec (a megaparsec is 3.26 million light-years). Or put another way – the expansion increases by 74.03km/s for every 3.26 million light-years we look further out into space.

The problem is that’s 9% faster than expected. The BBC Today programme’s Justin Webb asked Nobel laureate Adam Riess of the Space Telescope Science Institute and Johns Hopkins University, US, why the discrepancy mattered.