A new study on the expansion of the Universe may have revealed a missing piece in our understanding of the physics of the cosmos.


It found that an earlier study announced in June 2016 on the Hubble Constant, which is a measurement of the rate of expansion of the Universe, was correct.

But, it also found disagreement with a different measurement of the Hubble Constant made by the ESA Planck satellite.

Because Planck measured the Hubble Constant by observing the cosmic microwave background, which is the radiation left over from the Big Bang, this suggests there is a missing piece in our understanding of the physics of the Universe.

The study used gravitational lensing to observe distant quasars, which are galaxies with incredibly bright cores.

Gravitational lensing is based on Einstein’s general theory of relativity and uses the effect on space-time of nearby massive cosmic structures to magnify light from distant objects.

In this case, light from distant quasars was bent round massive galaxies lying between the quasars and Earth.

Galaxies, however, do not create perfect spherical distortions in the fabric of space, and the galaxies and quasars are not perfectly aligned, meaning the light from each quasar followed different paths of slightly different lengths.

This created multiple images of the same quasar as seen from Earth.

And, because the brightness of quasars changes, the astronomers who carried out the study were able to see each quasar flicker at a different time, depending on which path of light was being observed.

Such delays in the paths taken by the light are directly related to the Hubble Constant, and so measuring the delays meant the team were able to calculate the Hubble Constant.

A video explaining the technique of gravitational lensing, used by astronomers to observe distant objects in space.
Credit: ESA/Hubble, NASA

Using this method, the team were able to confirm the findings of last year’s study on the Hubble Constant, but found it different from the measurement made by Planck.

This, the study’s authors say, suggests a misunderstanding in our knowledge of the Universe.

“The expansion rate of the Universe is now starting to be measured in different ways with such high precision that actual discrepancies may possibly point towards new physics beyond our current knowledge of the Universe,” says Sherry Suyu, lead author of the study.


“The Hubble Constant is crucial for modern astronomy as it can help to confirm or refute whether our picture of the Universe - composed of dark energy, dark matter and normal matter - is actually correct, or if we are missing something fundamental.”

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Iain Todd BBC Sky at Night Magazine
Iain ToddScience journalist

Iain Todd is BBC Sky at Night Magazine's Content Editor. He fell in love with the night sky when he caught his first glimpse of Orion, aged 10.