<ubergeek-mode> Actually, the speed of light *in a vacuum* is the universal constant, invariant regardless of the observer's frame of reference. 'C' is so defined - the speed of light in vacuum. This is now understood to be such a basic constant that in 1983, the meter was defined in terms of the speed of light: "The definition states that the meter is the length of the path traveled by light in vacuum during a time interval of 1/299,792,458 of a second." http://www.mel.nist.gov/div821/museum/timeline.htm Note that when a particle exceed the speed of light *in a given medium*, it gives off cerenkov radiation, analogous to a sonic boom. This is the blue glow you see in the water surrounding nuclear reactors - pretty cool. http://en.wikipedia.org/wiki/Cherenkov_radiation </ubergeek-mode> Rony
_____ From: linux-il-boun...@cs.huji.ac.il [mailto:linux-il-boun...@cs.huji.ac.il] On Behalf Of Shachar Shemesh Sent: Friday, August 28, 2009 1:30 PM To: Gilad Ben-Yossef Cc: Linux-il@cs.huji.ac.il Subject: Re: [OT] Power over radio is it a true thing or just a myth ? Please excuse me for answering a humorous post seriously. Gilad Ben-Yossef wrote: Despite popular belief, the speed of light is only fixed in vacuum and scientists long acknowledged the fact that light may travels in different and lesser speeds when going through different materials, such as air, or water. Again, not precisely accurate. While light will, indeed, travel slower through any material denser than vacuum, this is not what the term "speed of light" refers to. To the best of my knowledge, "speed of light" refers to a basic property of the universe (how fast will any change of any field propagate), and that is the property that goes into the time warping formulas (the famous "c" in Lorentz transformation). Just because light travels through glass at 30% less speed does not mean you have to aim 30% lower if you want to freeze time (unless, and this is something I'm not 100% clear about, YOU are traveling through glass as well). 88 miles per hour, it would seem, is the speed of light as it travels through Hollywood movies. At least that one seems pretty accurate. This also explains why pretty much anything looks different when viewed through the filters of a Holywood movie. The huge refraction coefficient acts like lens, only much more powerful. Shachar -- Shachar Shemesh Lingnu Open Source Consulting Ltd. http://www.lingnu.com
_______________________________________________ Linux-il mailing list Linux-il@cs.huji.ac.il http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
