The picture in this answer shows a shock traveling into the ground. When it does so it refracts.

For this example pretend that if a lower strength shock went through a higher strength shock, there would be no rarefraction.

So the shock traveling into the ground, (higher density than air) refracts.

If this is the case, why wouldn’t a lower strength shock traveling into a higher strength shock make the lower strength shock refract, as it’s going through a higher density shock?

The definition of refraction is :

the fact or phenomenon of light, radio waves, etc. being deflected in passing obliquely through the interface between one medium and another or through a medium of varying density

So I wouldn’t understand why a lower density shock wouldn’t refract through a higher density shock. (I’m assuming the higher strength shock is higher density).

  • $\begingroup$ Also, if anyone knows of some good resources to learn about this subject, I’d appreciate if you could share! I can’t seem to find any information about this topic besides a little excerpt from Wikipedia. $\endgroup$
    – Wyatt
    Commented Apr 1 at 16:06
  • $\begingroup$ I might recommend: faa.gov/sites/faa.gov/files/regulations_policies/… It's old, but a classic with lots of good information in it. Perhaps this will help satisfy your commendable thirst for knowledge! $\endgroup$ Commented Apr 1 at 16:44

1 Answer 1


Why do you think shock refraction is a thing? Find us citable references that talk about it and give examples and we can discuss it.

The difference in density of air is not enough for it to be considered a different medium. The difference in speed of sound between gas when it has been shocked is already taken care of in the other kinds of shock interaction you have studied.

Instead, by the definition of refraction you provided, it would be limited to air-liquid and air-solid interfaces. Unless you concoct some situation where there is a gas-gas interaction and the two gasses are clearly separate and do not mix.

Shock refraction is a very limited concept. You are trying to apply that word to a much broader range of situations -- or you are asking why it does not apply much more broadly. You may as well be making something up. "Why don't shocks coagulate with other shocks?"

  • $\begingroup$ Ah okay, thanks for your answer. So isn’t the definition of a shock when there is a rapid change in properties? Wouldn’t that be a situation where there is a gas - gas interaction where they don’t mix? (Where the shock doesn’t mix with surrounding air) $\endgroup$
    – Wyatt
    Commented Apr 1 at 17:45
  • 3
    $\begingroup$ The shock is air. The shock is not an object or matter separate from anything else. It is just a location that we identify because properties change quickly. Yes, slip lines create regions where gas 'doesn't mix' -- but that isn't enough to make it a different medium. You're looking for a hornless unicorn -- everybody else just calls that a horse. $\endgroup$ Commented Apr 1 at 18:21

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