Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

HIGHLIGHTS OF 2019

The expansion of the Universe is faster than expected

Nature Reviews Physics volume 2, pages 10–12 (2020)Cite this article

Subjects

This article has been updated

The present rate of the expansion of our Universe, the Hubble constant, can be predicted from the cosmological model using measurements of the early Universe, or more directly measured from the late Universe. But as these measurements improved, a surprising disagreement between the two appeared. In 2019, a number of independent measurements of the late Universe using different methods and data provided consistent results, making the discrepancy with the early Universe predictions increasingly hard to ignore.

Key advances

  • The local or late Universe measurement of the Hubble constant improved from 10% uncertainty 20 years ago to less than 2% by 2019.

  • In 2019, multiple independent teams presented measurements with different methods and different calibrations to produce consistent results.

  • These late Universe estimations disagree at 4\(\sigma \) to 6\(\sigma \) with predictions made from the cosmic microwave background in conjunction with the standard cosmological model, a disagreement that is hard to explain or ignore.

The goal of modern cosmology is to explain the evolution of the Universe from its inception to the present time using our limited understanding of its composition and physical laws. This is even harder than it sounds! The first difficulty materialized in 1929 when initial estimates of the present expansion rate — known as the Hubble constant or H0 — rewound to the Big Bang singularity implied that the Universe was younger than the age estimated for the Earth and Sun. In retrospect, both figures were well off the mark, but there has been tremendous progress in the meantime. The measurement of H0 improved from 10% uncertainty at the start of the 2000s to less than 2% by 2019. In the past few years, reduced uncertainties from both the cosmic microwave background (CMB) — the afterglow of the Big Bang — and local Universe measurements have revealed an underlying discrepancy that is growing harder to ignore.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Get just this article for as long as you need it

$39.95

Learn more

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Disagreement between the Hubble constant prediction from the cosmological model using measurements of the early Universe and the more direct measurements from the late Universe.

Change history

  • 10 January 2020

    The Competing interest statement is added as it was missing from the previous version.

References

  1. Riess, A. G. et al. Large Magellanic Cloud Cepheid standards provide a 1% foundation for the determination of the Hubble constant and stronger evidence for physics beyond ΛCDM. Astrophys. J. 876, 85 (2019).

    Article  ADS  Google Scholar 

  2. Pietrzyn´ski, G. et al. A distance to the Large Magellanic Cloud that is precise to one per cent. Nature 567, 200–203 (2019).

    Article  ADS  Google Scholar 

  3. Reid, M. J., Pesce, D. W. & Riess A. G. An improved distance to NGC 4258 and its implications for the Hubble constant. Astrophys. J. Lett. 886, L27 (2019).

    Article  ADS  Google Scholar 

  4. Wong K. C. et al. H0LiCOW XIII. A 2.4% measurement of H0 from lensed quasars: 5.3σ tension between early and late-Universe probes. Preprint at: https://arxiv.org/abs/1907.04869 (2019).

  5. Shajib, A. J. et al. STRIDES: A 3.9 per cent measurement of the Hubble constant from the strong lens system DES J0408-5354. Preprint at: https://arxiv.org/pdf/1910.06306 (2019).

  6. Freedman, W. L. et al. The Carnegie-Chicago Hubble Program. VIII. An independent determination of the Hubble constant based on the tip of the red giant branch. Astrophys. J. 882, 34 (2019).

    Article  ADS  Google Scholar 

  7. Yuan, W. et al. Consistent calibration of the tip of the red giant branch in the Large Magellanic Cloud on the Hubble Space Telescope photometric system and a re-determination of the Hubble constant. https://10.3847/1538-4357/ab4bc9 (2019).

  8. Huang, C. D. et al. Hubble Space Telescope observations of Mira variables in the type Ia supernova host NGC 1559: an alternative candle to measure the Hubble constant. Astrophys. J. in the press.

  9. Verde, L., Treu, T. & Riess, A. G. Tensions between the early and the late Universe. Nat. Astron. 3, 891–895 (2019).

    Article  ADS  Google Scholar 

  10. Knox, L & Millea, M. The Hubble hunter’s guide. Preprint at: https://arxiv.org/abs/1908.03663 (2019).

  11. Wu, H. Y. & Huterer, D. Sample variance in the local measurements of the Hubble constant. Mon. Not. R. Astron. Soc. 471, 4946–4955 (2017).

    Article  ADS  Google Scholar 

  12. Kenworthy, W. D., Scolnic, D. & Riess, A. G. The local perspective on the Hubble tension: local structure does not impact measurement of the Hubble constant. https://10.3847/1538-4357/ab0ebf (2019).

Download references

Author information

Authors and Affiliations

  1. Department of Physics & Astronomy, Johns Hopkins University, Baltimore, MD, USA

    Adam G. Riess

Authors
  1. Adam G. Riess
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Adam G. Riess.

Ethics declarations

Competing interests

The author declares no competing interests.

Supplementary information

Rights and permissions

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Riess, A.G. The expansion of the Universe is faster than expected. Nat Rev Phys 2, 10–12 (2020). https://doi.org/10.1038/s42254-019-0137-0

Download citation

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s42254-019-0137-0

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing