Why Does the Speed of Light Remain Constant When Moving in an Airplane?

sirissa
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We know that light propagates in a constant speed c, but what if we are moving in an air plane and then turning on the light, why the speed of light remains constant?...
Thank u.
 
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Velocities don't "add" the same way in relativity as they do in classical physics.

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/einvel.html

In the equation on the page above, let u' = c (velocity of the light with respect to the airplane) and see what you get for u (velocity of the light with respect to the ground).
 
The real answer is "because that's what experiment tells us". Everything else is derived from that.
 

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