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Space

It’s official – we don’t know how fast the universe is expanding

The Hubble constant describes how fast the universe is expanding, but our measurements won’t line up, which may mean our standard model of the universe is wrong

By Leah Crane

20 January 2022

Figure 4. Pseudo-color images of all Cepheid-bearing galaxies analyzed in this work.

Images taken by the Hubble Space Telescope of galaxies looked at in the study

ESA

The expansion of the universe is accelerating, but we don’t know how quickly. With new observations, this issue has only got more severe, and now some astronomers are saying that it is officially a real problem – not one caused by uncertainties in the measurements.

There are two main ways we measure the Hubble constant, which describes the expansion of the universe. The first is to examine the cosmic microwave background – a relic of the …

Article amended on 24 January 2022

We clarified that 5 sigma refers to the difference between the two ways of measuring the Hubble constant.

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