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OK so, that's how the air ripples work for heat... because of the density of the air.

It makes me wonder, if you had a 10 inch globe of vacuum suspended in air, how different looking thru it would appear vs the air. It seems like you might be able to detect it via sight alone.

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That's what a visible shockwave from an explosion is. Light bending through sharp pressure discontinuities.

https://i.redd.it/jbx7x4a66em21.jpg

https://i.ytimg.com/vi/_31RYF3p42E/maxresdefault.jpg

http://waitbutwhy.com/wp-content/uploads/2014/10/explosion-i...

The vapour cloud which often forms occurs in saturated air as a partial vacuum forms behind the shockwave:

https://frontlinevideos.com/wp-content/uploads/2018/05/massi...

https://media.tenor.com/images/a6572b4115f67f2aeea90c529d598...

Yeah, it'd definitely be visible. I imagine it'd be like looking at an air bubble while underwater, in terms of refraction, except that air doesn't have surface tension so the boundary wouldn't look quite the same.

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