DrSzin
14-Dec-04, 21:03
Wow, what a great photo! I'm referring to this pic (http://www.caithness.org/fpb/december2004/photogallery/photos.htm?0?7) on today's front page.
It may look like a tornado but I'm pretty sure George Brims is right. It's almost certainly the condensation trail of an aircraft. It appears to be vertical simply because the plane is flying (almost) directly away from the photographer's position, and it's fatter at the top because the condensed water vapour has had more time to diffuse away from where it was emitted by the aircraft's engines. As George suggests, the contrail is likely yellower than the "natural" cloud because it's higher in the sky.
This page (http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html) provides an explanation of why sunlight scattered from air near the horizon is mainly red, whilst light scattered from high in the sky is mainly blue -- as illustrated by the pic at the top. (This is the simplest explanation I could find that's more or less technically correct.)
The suggestion is that the yellow light reflected by the contrail lies between red & blue, but it's closer to red because the trail is still quite close to the horizon, at least in an angular sense. I suspect there's more to the yellow brightness than that, but let's take one thing at a time :)
There's a pic of a similar trail here (http://tordach.org/jpg/BadSoden20040616_0320.jpg), but it's not nearly as colourful.
It may look like a tornado but I'm pretty sure George Brims is right. It's almost certainly the condensation trail of an aircraft. It appears to be vertical simply because the plane is flying (almost) directly away from the photographer's position, and it's fatter at the top because the condensed water vapour has had more time to diffuse away from where it was emitted by the aircraft's engines. As George suggests, the contrail is likely yellower than the "natural" cloud because it's higher in the sky.
This page (http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html) provides an explanation of why sunlight scattered from air near the horizon is mainly red, whilst light scattered from high in the sky is mainly blue -- as illustrated by the pic at the top. (This is the simplest explanation I could find that's more or less technically correct.)
The suggestion is that the yellow light reflected by the contrail lies between red & blue, but it's closer to red because the trail is still quite close to the horizon, at least in an angular sense. I suspect there's more to the yellow brightness than that, but let's take one thing at a time :)
There's a pic of a similar trail here (http://tordach.org/jpg/BadSoden20040616_0320.jpg), but it's not nearly as colourful.