We have been told that nothing can travel faster than light, but in fact, most of the Universe has traveled away from us at superluminal speeds since time began, and in order to understand how that happens, we will need a brief introduction to cosmology and the relativistic Friedmann model for a radially expanding universe.
REFERENCES
1.
Jack
Higbie
, “Radial photon paths in a cosmic model: A student exercise,”
Am. J. Phys.
51
, 1102
(Dec. 1983
).© 2013 American Association of Physics Teachers.
2013
American Association of Physics Teachers
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