Australia: The Land Where Time Began

A biography of the Australian continent 

Light Speed and the speed variation Arising from the Effects of Quantum Gravity

Lorentz invariance, the postulate that all observers measure exactly the same speed of light in a vacuum, independent of the energy of the photons, is a cornerstone of Einstein’s special relativity. Though it is assumed by special relativity there is no fundamental length-scale that is associated with such invariance, there is a fundamental scale, the Planck scale, I_Planck ≈ 1.62 x 10^-33 cm or E_Planck = M_Planckc² ≈ 1.22 x 10¹⁹ GeV, at which it is expected that quantum effects will affect strongly the nature of spacetime. There is great interest in the idea, which has yet to be validated, that Lorentz invariance might break near the Planck scale. A possible variation of the photon speed with energy is a key test of such violation (Wheeler & Ford, 1998; Amelino-Carmelia et al., 1998; Mattingly, 2005; Kostelecky & Mewes, 2008; Amelino-Carmelia et al. & Smolin, 2009; Jacobson, Liberati & Mattingly, 2006; Amelino-Carmelia, 2008). When accumulated over cosmological light-travel times, even a tiny variation of photon speed may be revealed by observed sharp features in γ-ray burst (GRB) light-curves (Amelino-Carmelia et al., 2008). In this paper Abdo et al. report the detection of emission up to ~31 GeV from the distant and short GRB 090510. According to Abdo et al. they found no evidence for the violation of the Lorentz invariance, and have placed a lower limit of I_Planck/1.2 on the length scale of the effect. They suggest their results disfavour quantum-gravity theories (Mattingly, 2005; Jacobsen, Liberati & Mattingly, 2006; Amelino-Carmelia, 2008) in which light speed is linearly altered by the quantum nature of spacetime on a very small scale.

Sources & Further reading

Abdo, A. A., M. Ackermann, M. Ajello, K. Asano, W. B. Atwood, M. Axelsson, L. Baldini, J. Ballet, G. Barbiellini, M. G. Baring, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, P. N. Bhat, E. Bissaldi, E. D. Bloom, E. Bonamente, J. Bonnell, A. W. Borgland, A. Bouvier, J. Bregeon, A. Brez, M. S. Briggs, M. Brigida, P. Bruel, J. M. Burgess, T. H. Burnett, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, J. M. Casandjian, C. Cecchi, O. Celik, V. Chaplin, E. Charles, C. C. Cheung, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, L. R. Cominsky, V. Connaughton, J. Conrad, S. Cutini, C. D. Dermer, A. de Angelis, F. de Palma, S. W. Digel, B. L. Dingus, E. do Couto e Silva, P. S. Drell, R. Dubois, D. Dumora, C. Farnier, C. Favuzzi, S. J. Fegan, J. Finke, G. Fishman, W. B. Focke, L. Foschini, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Gehrels, S. Germani, L. Gibby, B. Giebels, N. Giglietto, F. Giordano, T. Glanzman, G. Godfrey, J. Granot, J. Greiner, I. A. Grenier, M. H. Grondin, J. E. Grove, D. Grupe, L. Guillemot, S. Guiriec, Y. Hanabata, A. K. Harding, M. Hayashida, E. Hays, E. A. Hoversten, R. E. Hughes, G. Johannesson, A. S. Johnson, R. P. Johnson, W. N. Johnson, T. Kamae, H. Katagiri, J. Kataoka, N. Kawai, M. Kerr, R. M. Kippen, J. Knodlseder, D. Kocevski, C. Kouveliotou, F. Kuehn, M. Kuss, J. Lande, L. Latronico, M. Lemoine-Goumard, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, G. M. Madejski, A. Makeev, M. N. Mazziotta, S. McBreen, J. E. McEnery, S. McGlynn, P. Meszaros, C. Meurer, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, C. Monte, M. E. Monzani, E. Moretti, A. Morselli, I. V. Moskalenko, S. Murgia, T. Nakamori, P. L. Nolan, J. P. Norris, E. Nuss, M. Ohno, T. Ohsugi, N. Omodei, E. Orlando, J. F. Ormes, M. Ozaki, W. S. Paciesas, D. Paneque, J. H. Panetta, D. Parent, V. Pelassa, M. Pepe, M. Pesce-Rollins, V. Petrosian, F. Piron, T. A. Porter, R. Preece, S. Raino, E. Ramirez-Ruiz, R. Rando, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, T. Reposeur, S. Ritz, L. S. Rochester, A. Y. Rodriguez, M. Roth, F. Ryde, H. F. W. Sadrozinski, D. Sanchez, A. Sander, P. M. Saz Parkinson, J. D. Scargle, T. L. Schalk, C. Sgro, E. J. Siskind, D. A. Smith, P. D. Smith, G. Spandre, P. Spinelli, M. Stamatikos, F. W. Stecker, M. S. Strickman, D. J. Suson, H. Tajima, H. Takahashi, T. Takahashi, T. Tanaka, J. B. Thayer, J. G. Thayer, D. J. Thompson, L. Tibaldo, K. Toma, D. F. Torres, G. Tosti, E. Troja, Y. Uchiyama, T. Uehara, T. L. Usher, A. J. van der Horst, V. Vasileiou, N. Vilchez, V. Vitale, A. von Kienlin, A. P. Waite, P. Wang, C. Wilson-Hodge, B. L. Winer, K. S. Wood, X. F. Wu, R. Yamazaki, T. Ylinen and M. Ziegler (2009). "A limit on the variation of the speed of light arising from quantum gravity effects." Nature 462(7271): 331-334.