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Faster-than-light
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===Light spots and shadows=== If a laser beam is swept across a distant object, the spot of laser light can seem to move across the object at a speed greater than ''c''.<ref name="Gibbs"/> Similarly, a shadow projected onto a distant object seems to move across the object faster than ''c''.<ref name="Gibbs"> {{cite web |last=Gibbs |first=P. |year=1997 |url=http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html |title=Is Faster-Than-Light Travel or Communication Possible? |work=The Original Usenet Physics FAQ |access-date=20 August 2008 }}</ref> In neither case does the light travel from the source to the object faster than ''c'', nor does any information travel faster than light. No object is moving in these examples. For comparison, consider water squirting out of a garden hose as it is swung side to side: water does not instantly follow the direction of the hose.<ref name="Gibbs"/><ref> {{cite book |last1=Salmon |first1=W. C. |year=2006 |title=Four Decades of Scientific Explanation |url=https://books.google.com/books?id=FHqOXCd06e8C&pg=PA107 |publisher=[[University of Pittsburgh Press]] |isbn=978-0-8229-5926-7 |page=107 }}</ref><ref> {{cite book |last1=Steane |first1=A. |year=2012 |title=The Wonderful World of Relativity: A Precise Guide for the General Reader |url=https://books.google.com/books?id=4m14K1PpJwMC&pg=PA180 |page=180 |publisher=[[Oxford University Press]] |isbn=978-0-19-969461-7 }}</ref>
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