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GeorgeDishman
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[This thread was split from https://www.physicsforums.com/threa...wave-travelling-together.878450/#post-5518001 as it's an interesting topic in its own right]
That's actually an important point, in the core of neutron stars, the speed of sound increases with the density and provides a limit on the maximum mass. If the speed of sound exceeded the speed of light, there would be frames in which effects preceded causes, thus causality would be violated. That region is shown for example on this plot of various Equations of State as the "Causality Limit".
http://www3.mpifr-bonn.mpg.de/staff/pfreire/images/Graph-R-M-with-pulsars.png
Dale said:.. if the speed of sound in a medium were equal to the speed of light in that same medium (I suspect that is not true for any medium) then they would go at the same speed.
That's actually an important point, in the core of neutron stars, the speed of sound increases with the density and provides a limit on the maximum mass. If the speed of sound exceeded the speed of light, there would be frames in which effects preceded causes, thus causality would be violated. That region is shown for example on this plot of various Equations of State as the "Causality Limit".
http://www3.mpifr-bonn.mpg.de/staff/pfreire/images/Graph-R-M-with-pulsars.png
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