The Greisen-Zatsepin-Kuzmin limit (GZK limit) is a theoretical upper limit on the energy of cosmic rays from distant sources. Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ...

This limit was computed in 1966 by Kenneth Greisen, Vadem Kuzmin and Georgi Zatsepin, based on interactions predicted by special relativity between the cosmic ray and the photons of the cosmic microwave background radiation. They predicted that cosmic rays with energies over the threshold energy of 5×10¹⁹ eV would interact with CMB photons until their energy fell below the threshold. Therefore, extragalactic cosmic rays with energies greater than this threshold energy should never be observed on Earth.-1... Special relativity (SR) or the special theory of relativity is the physical theory published in 1905 by Albert Einstein. ... WMAP image of the CMB anisotropy,Cosmic microwave background radiation(June 2003) The cosmic microwave background radiation (CMB) is a form of electromagnetic radiation that fills the whole of the universe. ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ...

A number of observations have been made by the AGASA experiment that appear to show cosmic rays from distant sources with energies above this limit (whimsically dubbed Oh-My-God particles). The observed existence of these particles is the so-called GZK paradox or cosmic ray paradox. General science-related image. ... The following are some of the unsolved problems in physics. ... WMAP image of the CMB anisotropy,Cosmic microwave background radiation(June 2003) The cosmic microwave background radiation (CMB) is a form of electromagnetic radiation that fills the whole of the universe. ... On the evening of October 15, 1991, an ultra-high energy cosmic particle was observed over Salt Lake City, Utah. ...

These observations appear to contradict the predictions of the theory of special relativity. However, there are a number of possible explanations for these observations that are consistent with special relativity. Firstly, the observations could be due to an instrument error or an incorrect interpretation of the experiment. Secondly, the cosmic rays could have local sources (although it is unclear what these sources could be). Another suggestion involves ultra-high energy weakly interacting particles (for instance neutrinos) which might be created at great distances and later react locally to give rise to the particles observed. The neutrino is an elementary particle. ...

A number of exotic theories have been advanced to explain these observations, of which the most notable is the theory of doubly-special relativity. Doubly-Special Relativity is a new theory of special relativity first postulated in a paper by Giovanni Amelino-Camelia. ...

As of 2003, a number of cosmic ray experiments such as GLAST and the Pierre Auger Observatory are now planned which are intended to confirm or deny the correctness of the earlier observations. 2003 is a common year starting on Wednesday of the Gregorian calendar, and also: The International Year of Freshwater The European Disability Year Events January events January 1 Luíz Inácio Lula Da Silva becomes the 37th President of Brazil. ... The Gamma-ray Large Area Space Telescope, or GLAST, is future space-based gamma-ray telescope, designed to explore the high-energy Universe. ...

External links

• http://www.physics.rutgers.edu/hex/HIRES.html
• http://physicsweb.org/article/world/15/9/3
• http://www.p-ng.si/public/pao/history.php