Exposing PseudoAstronomy

August 13, 2010

Why You Can’t Believe ANYONE Who Says They Know the Size and Distance of a UFO


Hi all, sorry that I haven’t been writing for a few weeks, I’ve been really busy with work, with a revised impetus to finish my Ph.D. ASAP since I have a possible offer of a post-doc.

Anyway, the topic for today is UFOs. UFOs are actually a subject that I have specifically avoided on this blog for the most part because they encompass a huge set of phenomena, from abductions, to sightings, to anal probing, to alien-human hybrids, to reptilians under the Denver airport and more. Yeah, a lot of stuff.

This particular post will be very focused on a single subject: Why you can’t believe any report that states a UFO’s size, distance, and speed. And also, for the purpose of this post, if it wasn’t already obvious, UFO is a place-holder for what people think are IFOs … identified flying objects as alien craft. An “actual” UFO is just that – an unidentified flying object, not an, “I saw a UFO that was a craft with 3 lights on it and it was 100 meters long!” That’s an identification.

Size, Distance, and Speed

These are three characteristics of a moving object that are often used in UFO reports, either any two of them, or all three. For example, a UFO report witness may state, “I saw a craft that was 3 miles across, maybe 1000 feet up but moving very slowly, unlike any aircraft we have.”

Such a report, however, has no basis in reality.

There, I said it. Quite dismissive, isn’t it? However, once you understand the basic idea, you’ll see why any report or witness that claims any two or all three of these qualities is either simply naïve or just making it up.

We’ll Start with Speed

When a police officer measures your speed, they do so when you are usually several tens or hundreds of feet away, either with a laser or radar or something similar. When they’re doing this, you must be moving either towards (usually, so they can get behind you and catch you) or away from the police officer. And not just in that general direction, but almost directly towards or away.

Why? No, it’s not just because roads are generally straight, it’s because if you are moving at a diagonal, the police officer will only get a measurement of the velocity towards or away from them. Your velocity across their line of sight cannot be measured by their device.

Similarly, that is the first problem with a UFO report that claims a speed. Let’s for the moment say the object actually is a flying craft. Even so, The observer will only be able to estimate the speed across their line of sight, so effectively left-right and/or up-down. Any motion towards or away from them cannot be measured accurately because it would rely upon the trigonometry of calculating the change in size of the object due to perspective.

As I said, that’s the first problem with speed. The second problem with it is the crux of this issue and why size and distance are impossible to report.


Anything you see in your vision covers a certain angle. Let’s take a computer monitor, since if you’re reading this chances are you are familiar with a computer monitor. As you read this sentence, if your face is fairly close to the monitor, then the letters are relatively large, covering a large angle across your vision. Now if you move your head away from the screen, then the letters cover a smaller angle of your vision, and hence appear smaller.

You have an innate sense of how far away the screen is from your head. Chances are that you can extend your arm and touch the screen. It’s probably between 1 and 4 feet from you (0.3-1 meter). Because you know how far it is from you, you also can estimate its size. You also have context to estimate its size. It’s probably sitting on a desk, or if you’re on a laptop then maybe on a couch, desk, your lap, or unfortunately an airplane tray table. Years of experience have taught you how large the objects around you are, and you can place the computer screen within that context to estimate its size.

Let’s extend this to a different place, the produce section of your local grocery. You grab a small pepper, let’s say a serrano. You hold the serrano pepper up to your face, and it appears rather large. You look at the far wall over to the heads of iceberg lettuce. Relative to the lettuce, the pepper looks much larger — it covers a larger angle of your vision. But you know that serrano peppers are smaller than heads of iceberg lettuce. You have context, and you have every day experience, and you know how far away these objects are from you because you have easy things you can measure by.

Take it to the Sky

In the sky, things are different. Very different. You have no context. You cannot reach out your hand and measure how far away something is. You don’t know how large objects are because you cannot take a measuring stick there and use it. If a fly were buzzing two inches (5 cm) from your face, it would look bigger than an airplane flying at 30,000 ft (9 km). Similarly, a bird flying 100 ft up (30 m) will look gigantic relative to the international space station.

This is why you cannot measure the size nor distance of a UFO. Its size depends upon its distance, and its distance depends upon its size. And, its speed depends upon its distance (a kid on a tricycle just outside your house will appear to move faster than a car on a highway 10 miles (15 km) away).

If you don’t know how far away the UFO is, which you don’t because you have no way to measure it, then you cannot know how large it is physically. You are solely relying on the apparent angular size. Similarly, if you don’t know how big it is, which you can’t know because you have no context, then you have no way to estimate how far away it is.

Final Thoughts

Once you understand this concept, it is very, very easy to understand why skeptics will dismiss all reports of this kind of information (size, distance, and speed). It is also easy to understand why skeptics are unimpressed when an eyewitness — be they a hillbilly farmer, a metropolitan police chief, or an astronaut — state that a UFO they saw was 3 miles across, or a kilometer across and zipping through the sky faster than any known aircraft.

It’s, quite simply, not possible to know, unless you can physically measure at least either the actual distance to the object or its physical – not angular – size.


  1. […] This post was mentioned on Twitter by Reed Esau and Travis Roy, Travis Roy. Travis Roy said: RT @reedes: Why You Can’t Believe ANYONE Who Says They Know the Size and Distance of a UFO http://bit.ly/cobpMp (Exposing Pseudoastronomy) #ufo #stu […]

    Pingback by Tweets that mention Why You Can’t Believe ANYONE Who Says They Know the Size and Distance of a UFO « Exposing PseudoAstronomy -- Topsy.com — August 14, 2010 @ 1:06 am | Reply

  2. Of course many of the points raised make sense. And it was for the purpose of giving people useful reference points for the size of the objects that many of the UFOs that Billy Meier photographed, as early as 1964 and then beginning again in 1975, were photographed and filmed near objects of known size, such as trees, buildings, automobiles, etc. The photo analysis document, freely available at http://www.theyfly.com, also details some of the very precise means by which the size of the objects was determined.

    Through the testing and analysis it was also clearly determined that they were not small models close to the camera. I suggest reading the documentation, as well as that pertaining to the analysis of the sound recordings Mr. Meier also provided.

    Comment by Michael Horn — August 14, 2010 @ 10:04 am | Reply

    • “And it was for the purpose of giving people useful reference points for the size of the objects that many of the UFOs that Billy Meier photographed, as early as 1964 and then beginning again in 1975, were photographed and filmed near objects of known size, such as trees, buildings, automobiles, etc.”

      These photographs and any film taken is subject to the same problem. Without having a method of measuring the distance between the camera and the object there is no way to calculate the size. The information that a photograph/film is meaningless in reference to something it was filmed with due to point of reference. If you photograph and object and there is a tree in the picture, the photo will not necessarily provide any meaningful information about the object, only the tree.

      Comment by SouthFresh — August 19, 2010 @ 2:30 pm | Reply

  3. So are you saying that the scientists at Hessdalen who have been investigating light phenomena with the latest state of the art equipment are incompetent? To make their measurements they use the following equipment: radar, magnetometers, radio-spectrum analyzers, seismographs, cameras (some equipped with dispersion gratings), Geiger counters, infrared viewers, and lasers (Strand, 1985; 2000). Some of the equipment used is actually state of the art SETI radioastronomy equipment. Have you read any research papers at all about Unidentified Aerial Phenomena that most referred to as UFOs? Does this also mean that radar operators who having been detecting UFOs for 70 years are incapable of measuring UFO speeds and sizes? I find this article utterly bizarre…

    Comment by Susan Joy Rennison — August 15, 2010 @ 6:45 pm | Reply

    • Susan, you’ll note that I talked specifically about eyewitness reports about sightings. I did not talk at all about people who can measure the actual distances to objects. In fact, I’m fairly sure I explicitly stated that if you DO know the distance to the object, then all the other information is derivable.

      But if you’re driving down a country road and you see a UFO with your eyes and you claim that it’s a triangular craft 500 meters long hovering only 1 km up up and maybe traveling at 50 kph, that is not believable.

      Comment by Stuart Robbins — August 15, 2010 @ 7:05 pm | Reply

  4. This is a pet hate of mine.

    Every now and then I like to have a read of UFO eyewitness accounts and you so often see statements of size and distance.

    It doesn’t atke much critical analysis to see that there is no way those values could be known for certain. Especially when these reports are often said to be at night.

    I would be willing to bet that if these same people were to do to an air show and take a guess at the distances to the flying aircraft they’d be wrong.

    I am reminded of an anecdote I heard once, can’t remember where now. It featured two gentlemen standing in a field watching something dark flying about, seemingly in the sky overhead, in a way that no modern aircraft could.

    They paused to watch it and being unable to idenfy it, started to speculate on what it could be. It wasn’t until it floated down and passed in front of the trees at the edge of the field that they realised it was far closer than they had assumed and was actually a sead being blown about on the breeze.

    Comment by limey — August 16, 2010 @ 3:48 am | Reply

  5. Another anecdote. We were traveling at night in the countryside which we do a lot of. We saw a bright round light behind a barn. All 3 of us went Wow what is that. When we came closer it of course got bigger, and guess what, it was the a full moon. Being on the horizon and behind a barn threw all our senses out the window.

    Comment by Cy — August 17, 2010 @ 8:33 am | Reply

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