Skip to main content

Thank you for visiting 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.

Why unify?


Unified gauge theories (such as SU(5)) of particle interactions are built on the colour SU(3) and SU(2) × U(1) gauge theories which apparently describe strong and weak and electromagnetic interactions at distances as small as 10−16 cm. In this article the classical reasons for going beyond SU(3) × SU(2) × U(1) to a fully unified theory such as SU(5) are reviewed, and a new reason formulated. A class of imaginary worlds similar to our own is considered and it is shown that unification is possible only in ours. This suggests that the low-energy interactions are unique in that they are constructed to make unification possible.

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

Access options

Rent or buy this article

Get just this article for as long as you need it


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


  1. De Rújula, A. et al. Phys. Rev. D12, 147 (1975).

    Article  Google Scholar 

  2. Mulvey, J. Nature 278, 403–409 (1979).

    Article  ADS  CAS  Google Scholar 

  3. Marciano, W. & Pagels, H. Nature 79, 479–483 (1979).

    Article  ADS  Google Scholar 

  4. Georgi, H. & Glashow, S. L. Phys. Rev. Lett. 32, 236 (1974).

    Article  Google Scholar 

  5. Georgi, H., Quinn, H. R. & Weinberg, S. Phys. Rev. Lett. 33, 451 (1974).

    Article  ADS  CAS  Google Scholar 

  6. Bouchiat, C., Iliopoulos, J. & Meyer, Ph. Phys. Lett. 38B, 519 (1972).

    Article  Google Scholar 

  7. Gross, D. & Jackiw, Phys. Rev. D6, 477 (1972).

    Article  ADS  Google Scholar 

  8. Pati, J. C. & Salam, A. Phys. Rev. D8, 1240 (1973).

    ADS  CAS  Google Scholar 

  9. Coleman, S. in New Phenomena in Subnuclear Physics (ed. Zichichi, A.) 297 (Plenum New York, 1977).

    Book  Google Scholar 

  10. Pati, J. C. & Salam, A. Phys. Rev. Lett. 31, 661 (1973).

    Article  ADS  Google Scholar 

  11. Pati, J. C. & Salam, A. Phys. Rev. D10, 275 (1974).

    ADS  CAS  Google Scholar 

  12. Nanopoulos, D. V. & Weinberg, S. Phys. Rev. D20, 2484 (1979).

    ADS  CAS  Google Scholar 

  13. Marshak, M., Winn, D., Steinberg, R. & Sulak, L. First Workshop on Grand Unification, (eds Frampton, P. H., Glashow, S. L. & Yildiz, A.) (Math Science Press, Brooklin, 1980).

    Google Scholar 

Download references

Author information

Authors and Affiliations


Rights and permissions

Reprints and Permissions

About this article

Cite this article

Georgi, H. Why unify?. Nature 288, 649–651 (1980).

Download citation

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


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