Special Relativity at Action in the Universe

  • G. Ghisellini


Nature succeeds in accelerating extended and massive objects to relativistic velocities. Jets in active galactic nuclei and in galactic superluminal sources and gamma-ray burst fireballs have bulk Lorentz factors from a few to several hundreds. A variety of effects then arises, such as the beaming of the radiation produced, light aberration, time contraction and the Doppler frequency shift. I will emphasize that special relativity applied to real (i.e., extended) observed objects inevitably must take into account the fact that any piece of information is carried by photons. Being created in different parts of the source, they travel different paths to reach the observer, depending on the viewing angle. The object is seen rotated, not contracted, and at small viewing angles time intervals are observed shorter than intrinsic ones.


Special Relativity Active Galactic Nucleus Travel Path Bulk Motion Radiation Energy Density 
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© Springer-Verlag Italia 2000

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  • G. Ghisellini

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