Faster than 'c' measurements that do not violate relativity theory

AI Thread Summary
Galaxies can emit jets of gas that appear to travel faster than the speed of light, but this does not violate relativity theory. The key point is that the speed of light, denoted as 'c', is a constant in a vacuum, while the jets may be moving through a medium with a different index of refraction. This index can allow for effective speeds greater than 'c' when measured in that medium. The discussion emphasizes that the phenomenon is not a true violation of relativity, as it pertains to the properties of light in various environments. Understanding these concepts is crucial for reconciling observations with established physical laws.
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Homework Statement



Some collections of stars called galaxies release jets of gas. Some of these jets have been measured to travel faster than the speed of light in a vacuum. Explain why relativity theory is not violated.

Homework Equations



This problem requires a qualitative response and no equations are required to answer it.

The Attempt at a Solution



Since according to relativity theory 'c' is a constant, I do not see how it is possible to answer this question. Seemingly this phenomenon does violate relativity theory.
 
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Though I know almost nothing about astro, I'll bet the answer has to do with the jets not actually traveling in a vacuum, and with an index of refraction that changes the speed of light in the index to be faster than the speed of light in a vacuum. That should get you started until an astro person comes along.

v=c/n

so you need n<1
 

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