'The reason sound can't travel through a vacuum is that sound needs a medium (solid, liquid or gas with real vibrating molecules) and not because it is a longitudinal wave' How does this make sense as there are particles in space which can vibrate. Light waves travel through space hence they reach earth and they also use vibration of particle to transport energy. It seems like these two ideas are contracting themselves. Maybe the thing I don't understand is why longitudinal waves such as sound have to travel through a media.
Electromagnetic waves are produced by oscillating charged particles but they do not need other particles to propagate. Indeed electromagnetic waves are solutions of the Maxwell equations with no sources, i.e. in the vacuum.
On the other hand, mechanical waves need an elastic medium to propagate, regardless of being transverse, longitudinal or mixed waves.
Regarding the particles present in deep space which could propagate sound, I suggest you to read this post.
Longitudinal electromagnetic waves do not exist in vacuum because the Divergence of E, and B are zero. The consequence of this is that the k-vector, propagation direction, is orthogonal to E and B.
protected by Qmechanic♦ Jul 21 '17 at 12:10
Thank you for your interest in this question.
Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).
Would you like to answer one of these unanswered questions instead?