http://youtube.com/watch?v=d_urLWPrONI&feature=related

you see the shockwave.. What is that effect??

Can you compress air manually to see that effect, for instance in a glass chamber??

http://youtube.com/watch?v=d_urLWPrONI&feature=related

you see the shockwave.. What is that effect??

Can you compress air manually to see that effect, for instance in a glass chamber??

It's just a change in the density of the air. The exact same thing that causes the shimmering effect on a surface - like a road - that's exposed to the direct heat of sunlight.

Agreed.

The effect is not caused by air being compressed in and of itself, but by there being two areas of different density air in close proximity to one another. Only then can you notice the difference in how light passes through the 2 zones, and see the "effect" of this warping.

If you were to compress the air in glass chamber, all the air in that glass would be of a uniform density, and the light diffraction of the glass itself would almost certainly overpower the effect of the different air densities inside and outside of the container.

Agreed.

The effect is not caused by air being compressed in and of itself, but by there being two areas of different density air in close proximity to one another. Only then can you notice the difference in how light passes through the 2 zones, and see the "effect" of this warping.

If you were to compress the air in glass chamber, all the air in that glass would be of a uniform density, and the light diffraction of the glass itself would almost certainly overpower the effect of the different air densities inside and outside of the container.

Correct, And to be just a bit more specific, the effect occurs precisely at the boundry of the two different air masses - just like it does at the boundry between water and air.

The effect is not caused by air being compressed in and of itself, but by there being two areas of different density air in close proximity to one another. Only then can you notice the difference in how light passes through the 2 zones, and see the "effect" of this warping.In the context of the question you are correct, but small continuous chages in air density do cause refraction. There does not need to be any "boundary" between layers of different density.

For example, as the sun is setting the rays travel long distance thru thin air before reaching you surface level eye at atmospheric pressure. This allows you to see the sun many minutes after it is really below the horizon.

Also as the top part of the sun has its rays bent (lifted up for true straight line) less than the bottom part of the sun, (bottom lifted up more) the image you last see of the sun (setting over any great "flat" region) is very distorted. - As if the sun god were sitting down on it after a hard day of work.

I have looked, but I have never seen it (conditions must be just right), but over water in moist air the green rays may be the last of the sun that is seen. - Called the "green flash."

In the context of the question you are correct, but small continuous chages in air density do cause refraction. There does not need to be any "boundary" between layers of different density.

For example, as the sun is setting the rays travel long distance thru thin air before reaching you surface level eye at atmospheric pressure. This allows you to see the sun many minutes after it is really below the horizon.

Also as the top part of the sun has its rays bent (lifted up for true straight line) less than the bottom part of the sun, (bottom lifted up more) the image you last see of the sun (setting over any great "flat" region) is very distorted. - As if the sun god were sitting down on it after a hard day of work.

I have looked, but I have never seen it (conditions must be just right), but over water in moist air the green rays may be the last of the sun that is seen. - Called the "green flash."

Slightly off-topic, but during many years of trying, I managed to see the "Green Flash" twice off the west coast of Florida. And believe me - it IS instantaneous!!!! A single blink of the eye just about would make one miss it.

See also, Snell's Law: http://en.wikipedia.org/wiki/Snell's_law

You can't create this in a static environment like a pressure or vacuum vessel, because the pressure gradient needed to create the refraction is the result of a dynamic environment, e.g. in the shockwave of an explosion.

The nuclear tests of Operation Crossroads in 1946 show the static overpressure gradient of the explosions quite well. In this case, the cloud of water vapor you see being condensed out of the air is behind the blast front itself. The water is condensing out of the humid tropical air due to a sudden drop of ambient pressure lowering the temperature below the dew point adiabatically. You can see the blast front itself, well ahead of the cloud, indicated by a signature of froth on the ocean's surface:

http://youtube.com/watch?v=eJJGc_FoEGE

Slightly off-topic, but during many years of trying, I managed to see the "Green Flash" twice off the west coast of Florida. And believe me - it IS instantaneous!!!! A single blink of the eye just about would make one miss it.
I've seen the green flash once. It was in the middle of the Mediterranean, back when I was riding around with the Navy. The weather detachment knew conditions conducive to it existed, so they passed the word for anyone who wanted to see it to go topside. It was ten different shades of holy fucking awesome.