VISIBLE sonic boom
 

Like someone else mentioned recently, I feel a little awkward starting a new thread on IOTD, but this was just TOO cool!

A VISIBLE sonic boom:

http://antwrp.gsfc.nasa.gov/apod/ima...plane_navy.jpg

higher resolution image available here

Explanation: Many people have heard a sonic boom, but few have seen one. When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane. When this shock wave passes, a listener hears all at once the sound emitted over a longer period: a sonic boom. As a plane accelerates to just break the sound barrier, however, an unusual cloud might form. The origin of this cloud is still debated. A leading theory is that a drop in air pressure at the plane described by the Prandtl-Glauert Singularity occurs so that moist air condenses there to form water droplets. Above, an F/A-18 Hornet was photographed just as it broke the sound barrier. Large meteors and the space shuttle frequently produce audible sonic booms before they are slowed below sound speed by the Earth's atmosphere.

I saw this image lately, and I read that it wasn't actually a sonic boom. It *was* something created by the sheer speed of the plane, but not actually a sonic boom. I'll try and find more information and edit it into this post when I do. Anyone else is encouraged to respond with more...

Clarification: No doubt that a sonic boom will be occuring in this picture, but the cloud is *not* a sonic boom.

and just FYI, sonic booms are *loud*. They sound like big explosions. I've heard a few - my proximity to DC means I heard some last Tuesday (apparently that's how the carbomb theory started too - fighter jets were taking off and making sonic booms, and people thought they were carbombs), as well as one time back up in Maryland when a fighter jet (I'm guessing) went zipping by as I was working on my roof.

MORE clarification: I'm retarded today, and my brain isn't working. Every time I read this, I find something else I want to say. FYI again, a sonic boom occurs when the sound gets to your ear. It's not a thing really, it's just a phenomenon of sound. Sound == vibration, remember. I'm sure we could find more on it. And I just did. Check out

http://www.physlink.com/ae53.cfm

I love Google.

Well, I think you're clearly right on that point -- sonic booms, by definition, are not visible, they're audable.

But this effect apparently occurs only at, or very close to, the speed of sound, so it's the "visual counterpart" of a sonic boom. I suppose the phrase "Visible sonic boom" just appealed to me. :)

Yah, but I was really interested in it when I read it like a week ago, and it's bugging the hell out of me 'cause I can't remember what it actually is/is caused by, and I can't find the source of information either. :)

Ah! I just found a little more information including an mpeg, where you can see the effect in motion.

I also found a technical explination at this site.

man. that video is really really really cool. and the explanation is much like the one i read. thanks.

i'm glad i was a dork and said what i said, so that you said what you said, so that i said what i said, so that you found that, and now i'm happy :)

also - i think you and i have too much free time at work.

--dave

Re: VISIBLE sonic boom
 

This picture (like the one from the DMSP satellite of US lights at night) are all over offices in Defense plants. This effect has been seen before, but occurs rarely. It is as difficult to photograph as Tornados since it appears to involve limited temperatures, humidity, and the acceleration of the plane.

Watch the wings on your commerical airliner. Sometimes the air rolling off the end of the wing creates the same 'vapor' leaving a trail in the sky.

As for sonic booms: we were laying on the beach when the ground felt to vibrate. Earthquake? We thought so. It turns out the Concorde was remaining supersonic too long causing a vibration that many attributed to an earthquake. The boom would only read shore during certain weather conditions. The solution was to drop out of super sonce flight farther from the US coast.