Fallstreak Holes and Subsuns
Professor Bohren in his second response declined to speculate on the O’Hare event, but offered some interesting scientific insights into cloud holes and other alleged “UFO” related phenomena:
It is very difficult for me to speculate on something for which there are
no good observations. It is not uncommon for me to get a query from
someone saying that they saw a light in the sky: What was it? When I
press for details I rarely get them. This then gets distorted into
"Scientist baffled by inexplicable phenomenon." There is a distinction
between inexplicable and unexplained, but, unfortunately, not often
made…
As I noted, holes in clouds, even spectacular ones, are not mysterious.
And by holes in clouds I do not mean just breaks in clouds on partly
cloud days.
Fallstreak holes really get your attention because the holes can appear
to have been cut out with a cookie cutter. Every so often Weatherwise
magazine (and Weather, the British equivalent) will publish a spectacular
photograph of a fallstreak hole.
Use Google to search on fallstreak holes. The first entry I got was a
collection of great photos, assembled by Australians, of fallstreak holes
all over the world. Now I am not saying that what was observed is a
fallstreak hole, only that strange holes in clouds are not the work of
extraterrials.
The folks who use the term Unidentified Flying Object are, in a sense,
already biased. How the hell do they know that the "object" (which in
fact may be an image) is in fact "flying"? Suppose that a searchlight
illuminates the base of clouds, the result being a moving white spot. Is
this a flying object? I don't think so. It is a moving patch of
illuminated cloud brighter than adjacent cloud. But it is neither an
object nor is it flying. I'll give you another example. I have seen many
subsuns from airplanes. They are elliptical bright spots. As the plane
moves the subsun moves with it. Is the subsun flying? Is it an object?
Neither. It is a slightly distorted image of the sun reflected by falling
ice crystals that are oriented. And yet the subsun is probably the most
common "unidentified flying object." My colleague Alistair Fraser told me
that he once saw a book about flying saucers in a shop window. On the
cover of was a photo of one of these saucers. Alistair said that it was a
beautiful photo of a subsun.
It is easy to see why subsuns are mistaken for flying saucers. They are
bright, elliptical, and no matter how fast the plane flies the "saucer"
keeps up. Wow! The mystery vanishes when you realize that what you are
seeing is fundamentally no different from what you would see if you were
walking along the edge of a fairly still lake with the sun low in the
sky. You would see the reflected image of the sun, and as you moved the
image would move. Run fast and the image will keep up with you. This is
exactly what happens in the atmosphere. The mirrors are just thousands of
tiny ice crystals.
Craig Bohren
Professor Bohren in his second response declined to speculate on the O’Hare event, but offered some interesting scientific insights into cloud holes and other alleged “UFO” related phenomena:
It is very difficult for me to speculate on something for which there are
no good observations. It is not uncommon for me to get a query from
someone saying that they saw a light in the sky: What was it? When I
press for details I rarely get them. This then gets distorted into
"Scientist baffled by inexplicable phenomenon." There is a distinction
between inexplicable and unexplained, but, unfortunately, not often
made…
As I noted, holes in clouds, even spectacular ones, are not mysterious.
And by holes in clouds I do not mean just breaks in clouds on partly
cloud days.
Fallstreak holes really get your attention because the holes can appear
to have been cut out with a cookie cutter. Every so often Weatherwise
magazine (and Weather, the British equivalent) will publish a spectacular
photograph of a fallstreak hole.
Use Google to search on fallstreak holes. The first entry I got was a
collection of great photos, assembled by Australians, of fallstreak holes
all over the world. Now I am not saying that what was observed is a
fallstreak hole, only that strange holes in clouds are not the work of
extraterrials.
The folks who use the term Unidentified Flying Object are, in a sense,
already biased. How the hell do they know that the "object" (which in
fact may be an image) is in fact "flying"? Suppose that a searchlight
illuminates the base of clouds, the result being a moving white spot. Is
this a flying object? I don't think so. It is a moving patch of
illuminated cloud brighter than adjacent cloud. But it is neither an
object nor is it flying. I'll give you another example. I have seen many
subsuns from airplanes. They are elliptical bright spots. As the plane
moves the subsun moves with it. Is the subsun flying? Is it an object?
Neither. It is a slightly distorted image of the sun reflected by falling
ice crystals that are oriented. And yet the subsun is probably the most
common "unidentified flying object." My colleague Alistair Fraser told me
that he once saw a book about flying saucers in a shop window. On the
cover of was a photo of one of these saucers. Alistair said that it was a
beautiful photo of a subsun.
It is easy to see why subsuns are mistaken for flying saucers. They are
bright, elliptical, and no matter how fast the plane flies the "saucer"
keeps up. Wow! The mystery vanishes when you realize that what you are
seeing is fundamentally no different from what you would see if you were
walking along the edge of a fairly still lake with the sun low in the
sky. You would see the reflected image of the sun, and as you moved the
image would move. Run fast and the image will keep up with you. This is
exactly what happens in the atmosphere. The mirrors are just thousands of
tiny ice crystals.
Craig Bohren
