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More Sightings

[Note added February 7, 2001: I had links on this page to the work of John Bro, whose photos are discussed. Those links no longer work, so I have removed them. I cannot say I am terribly sad that someone who promulgates silliness is no longer on the web. Still, if you search on his name you'll find other pages which refer to his work.]

(May 7, 1997)
Some television programs are worse than others when it comes to Bad Astronomy and Bad Science. Loyal readers know I am no great fan of the Sci Fi Channel's tabloid television show Sightings. The slogan of the show, advertised during their commercials, is "We present the facts, and let you decide for yourself." But do they? Maybe you should decide for yourself.

The edition aired on Sunday, April 13 1997, had a segment called "Solar Obliteration". The obvious sensationalist title immediately perked my ears up. The segment was about a man who claims he has a new way to videotape UFOs. Someday I will write up my feelings about UFOs, but for now let's just say that most reports leave me pretty skeptical. This one was certainly no exception. The man, named John Bro, found that when he placed his video camera just in the shadow of an awning or building edge and started taping, the tape would reveal dozens of small white objects moving quickly across the field of view in all different directions. He calls the technique "solar obliteration" because it just barely blocks the view of the Sun's disk, letting the camera peer into the sky very close to the Sun without being completely washed out by the brightness of the actual solar disk.

The Sightings crew reproduced his technique on the show, and also saw these mysterious objects. Calling them "UFO's", both Bro and Sightings quickly dismiss the idea that they are seeing simple debris like cottonseed or lint fluff. The evidence from his own tapes indicated to me that the objects are indeed nearby bits of fluff, but there is no need to make qualitative judgments when it is actually pretty easy to make quantitative ones.

I sent the email message below to the address listed on the Sightings web page. In it I describe how to test this technique in an easy, straightforward and above all mathematical way. I sent this email two weeks ago as I write this and have yet to receive a response. When/if I do receive one, I will post it here in its entirety. Oddly, the Sightings web pages had a synopsis of the April 13 show with a description of the "solar obliteration" technique before I sent the letter, but now I cannot find it anywhere at their site. Conspiracy theories, anyone? ;-)

Here is the letter I sent to the people at "Sightings":
Oops! In the letter, I said something that turns out not to be true. It's not a big deal; it's something I did not know when I wrote the letter. I'll explain after the letter below.

Dear Sirs:

I watched your Sunday, April 13th edition of "Sightings" with some interest. I was particularly engaged by the story "Solar Obliteration".

I suppose I should start off by saying I am what you would categorize as a skeptic. I am extremely doubtful that there was anything unusual going on in the video clips you showed, and I have a suggestion to you for a way of proving it.

I am a scientist by training, and so I have some experience with interpreting images. Although the video clips were shown quickly, it appeared to me that some of the objects in the images were in focus, while some were out of focus. This immediately suggests that the objects were close to the camera, rather than very far away. If they were all far away, they would all have been in focus. The seemingly randomized trajectories were also indicative of objects blowing in the wind. Since the photographer, Jon Blo [sic; I misspelled it], was near the eave of a building one would expect there to be turbulent air movement.

It is possible to get the distance to these objects. We have objects of unknown size and distance flying in a camera's field of view. We can determine a lower limit of the distance to these objects by using a second camera and a technique that astronomers call parallax. The method is relatively simple: stand at a given position (call it "A") and observe a distant object, marking its location against a background. Now move to a second position ("B") and reobserve the object, again noting its position. If it is not too far away, it will have appeared to have shifted position. Closer objects appear to shift more; this is why nearby trees seem to fly by when you are driving a car, but distant trees appear to pass you more slowly. If the distance from "A" to "B" is known, the distance to the object can be calculated using simple trigonometry.

Since you have the proper equipment, I urge you to try the following experiment: set up two cameras some known distance apart (say, two or three meters). Start taping, and make sure you have some sort of time signal going; you could program a computer to beep every second, and have someone clearly announce every five seconds. Or you could use a timing radio, which I believe can be found at Radio Shack. They tune to a radio broadcast which gives off beeps at one second intervals, and announces every minute. Once you've set that up, simply point the cameras in a parallel direction and start taping.

If the objects are very far away compared to the distance between the two cameras, they will appear in both cameras at the same time and in the same part of the field of view (FOV). If however, the objects are close by, you might see a particular object in the left hand side of one camera's FOV but in the right hand side of the other's. If the objects are very close, like a meter or two away, you might only see a given one in one camera and not the other. The timing announcements will make it possible to directly compare one camera's FOV at any instant to the other's.

Again, I urge you to try this and air the results. Your motto is "We present the facts, and let you decide for yourself". This is an excellent opportunity to stand behind that phrase.

If you don't object, I would like to post this message to you and any other correspondence on my web page, and possibly also post them to some USENET groups.

Thank you for your time,

Phil Plait

P.S. Jon Bro made a factually incorrect statement in the program. He said that by blocking the surface of the Sun, we can see the corona. That is not true; the sky around the Sun is still very bright, thousands of times brighter than the corona. If he were right, we could all make eclipses any time we want simply by holding a disc up against the Sun! That might work out in space where there is no air to scatter sunlight, but here on the Earth we have to wait for the Moon to do it for us, so that the sunlight is blocked before it gets into the Earth's atmosphere.

DISCLAIMER: I speak for no one but myself. No organization I work for now or with which I have ever been associated bears any responsibility for anything I write.

As I said above, I made a mistake in the letter. It turns out it is possible to get an image of the Sun's corona from the ground. However, it takes quite a bit of sophisticated equipment. I don't think Bro could see the Sun's corona using the simple setup he had. However, I am not positive. It's possible, just unlikely. The glare of the Sun and daylit sky will almost certainly wash out any image of the corona, unless there were very special circumstances: for example, high altitude (to get most of the Earth's atmosphere below you, out of the way), or very dry air.
Thanks to Bad Reader Martin Gaskell for pointing out my error.

This page last modified Saturday, 05-Mar-2011 18:03:18 UTC


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