helenofjoy wrote:
I forgot to mention: point the knife away from your face!

 Lazy8 wrote:  This made my face hurt.

 oldslabsides wrote:
Yes. Shockwaves are a finite thickness, and what you see is the light bending as it passes thru the shockwave. From the side the light passes thru more of the shockwave along the leading surface of the shock than is does behind the leading surface on its way to you, so you see it in profile.

Here's a way to think about it that might help: hold an imaginary half of a pumpkin in your hand with the guts all scooped out. It's a pretty much a uniform thickness. Now imagine you have a long pumpkin-carving knife you can poke thru the pumpkin, and poke it thru near the open end of the pumpkin, all the way across.

It goes thru nearly perpendicular to the outer surface, which penetrates nearly the minimum amount of pumpkin possible while still getting thru both sides. Now poke it thru sideways across the bottom of the pumpkin. Since it goes thru the wall at a shallower angle it goes thru more pumpkin on its way out the other side. Poke it thru low enough and its whole trip thru will be inside the wall of the pumpkin. A ray of light taking that path will see the maximum amount of distortion from the differential index of refraction of the shock wave—not because it spent more time in the different index, but because it had farther to go before its path straightened out again when it reached undisturbed air on the other side.

So rays of light along the leading surface of the shock will appear to show it in cross-section.

 ptooey wrote: 
I bet this makes a wave, too

 

 NoEnzLefttoSplit wrote: 
We're a little short on brass instruments, actually.  I've got 2 guitars, a drum set, a piano, and a harmonica (oh, and I'm expecting a ukulele on Thursday .)  The kids have an accordion and a cello. 

 ptooey wrote: 

Yeah, but what about the trombone?

 ScottFromWyoming wrote: 
Yeah, I've got a couple of old scientific surplus catalogs sitting at the house.  I'll check into what they've got.  It really doesn't look all that tough.

 ptooey wrote: 
I thought that might be trouble
 
$250 is the price for new. Talk to someone there about what you need: a mirror out of a trashed telescope, it can have some scratches, I doubt that will matter much. 

 ptooey wrote: 

 ScottFromWyoming wrote: 
Dammit.  Dammit, dammit, dammit. 

*heads off to e-bay*

Edit:  $250 for an 8" mirror.  Ahh.  Nope.

 oldslabsides wrote: 
The depth of field is so shallow that it essentially is showing you just a cross-section of the half-a-bubble wave. Nearer to or further from the lens is out of focus so it doesn't show up.

Edit: well I was on the right track crack.

Schleiren photography note the link from there to Collimated light

A do-it-yourself guide to Schlieren photography 

 oldslabsides wrote: 

i think its because the wave will travel slower as it propagates out to the sides, kind of like waves turning the corner at the beach, presuming you have a beach with corners, that is..

 oldslabsides wrote: 

But I see the edge. Don't you?
just rattling your cage...

 oldviolin wrote: 
yes, but the contact lens has an edge in addition to its convex side...

who said anythin' about hatin'? 

 oldviolin wrote: 
or the shock wave from an explosion, wherever you view from it's still dome shaped (in ideal conditions).

 oldslabsides wrote: 

look at a contact lens from the side...any side, and it's the same. The shock wave is basicallythe same convex shape. maybe...
stop hatin' on peoples horn bones will ya?

now wait a minute...

What if this were filmed from above the trombone?  Or from beneath; would the "shockwave" still be in the shape of an arc?  Something about the perspective here just doesn't seem real to me. 

 aflanigan wrote: 

Ah, but if we were based on right-handed amino acids would we have built merry-go-rounds that turn the other way?

 oldslabsides wrote: 

Because they are better at grabbing the brass ring on the merry-go-round, of course!

so, why all the right-handed people?