Atlas V's Sonic Boom Made Visible By Sundog

Ross-Shire Geek writes "Atlas V lifted off on Feb 11 from Kennedy. As it goes supersonic through a sundog (aka parhelion) you can see (video link) wonderful visible ripples of the shock wave in the sky."

Comments

Wow

[cntThnkofAname]

There is something incredibly belittling about trying to comprehend the vastness that vehicles like that help us explore.

Re:Wow

[Solandri]

So I guess the normal compression wave by a sonic boom is not enough to alter the way light goes through it (think flickering air when looking across a heated highway), but these ice crystals do the trick. Right?

No, the compression wave always alters the way light travels through it. It's just that normally there's no light going straight through the wave to you, or if there is it's uniform in color and brightness (i.e. blue sky) so altering the direction of the light slightly doesn't produce a visible change.

My guess would be that the sundog by its very nature means sunlight is at the proper angle at that location to be reflected back to you. A compression wave at this location alters the angle of sunlight being reflected off ice crystals . So the large variability in brightness as a function of small changes in angle makes the ripples visible. Kinda like if someone were trying to signal you with a mirror. If you're seeing blue sky reflected in the mirror, shaking the mirror still yields blue sky so you don't notice any change. But if you're seeing the sun reflected in the mirror, shaking the mirror makes it alternately reflect sunlight and blue sky, causing a strobing effect which is easily visible.

How incredibly appropriate.

[Jane Q. Public]

Very appropriate, it seems to me, that a rocket carrying the Solar Dynamics Observatory should make pretty with a sundog.