Counter-intuitive science

December 5, 2008

What do you do when you come across a bit of science and engineering that seems totally counter-intuitive? Do you try to construct arguments for why it can’t work and must be a hoax of some kind? Or do you accept that maybe you just don’t (yet) understand the underlying concepts and need to work on improving your knowledge? Maybe you could even try experimentally verifying the concepts yourself, if no special equipment is required? Personally I have always thought that the concept of angular momentum is totally mind-bending, but children verify that this is a real phenomenon every time they spin a top, or ride a bicycle without falling over.

I imagine that your response will depend a lot on the context involved. If you’re sitting in a science class and you generally trust your instructor, you’re probably going to accept whatever you’re told. But in fact, at least for college-level courses, you’re not supposed to just take the instructor’s word for things–that’s why they have labs, so you can excruciatingly recreate classic experiments to verify the concepts for yourself.

On the other hand, if you distrust your source, you’re liable to have the other kind of response. For example, adherents of intelligent design construct all sorts of ad hoc and easily debunked reasons why evolution cannot work as described, and seem to think that mainstream biologists are all either self-deluded or participants in a grand conspiracy. Many of the rest of us might consider the Internet, taken as a whole, to be a not-completely-trustworthy source, and if we see something peculiar on the Web we might be tempted to assume that it’s just a joke or a hoax of some kind.

I mention this as a lead-up to the following hilarious little story that’s current bouncing around some science and tech blogs: A couple of years ago, Jack Goodman posted a YouTube video showing a wind-powered cart he built to demonstrate the concept of “direct downwind faster than the wind” (or DDFTTW for short) travel. It is certainly counter-intuitive at first glance: if you are traveling directly downwind faster than the ambient wind speed, then you are going to be feeling the wind in your face! How could that wind possibly be providing the energy source to make you move forward? And yet (not to give away the story), this is a real effect that does not somehow violate the laws of physics.

Recently, debate over this was reignited when a new video was posted on YouTube to demonstrate the effect beyond any doubt and prove that it is not a hoax:

Perversely, it seems to have only increased the debate about what’s going on. The story was picked up by the tech blog BoingBoing, which took a somewhat skeptical view of things. The pseudonymous poster of the video, spork33, has patiently responded to questions and counter-claims in the comments over there, which seems to have only made the skeptics more vocal in their complaints.

Science blogger Mark C. Chu-Carroll posted a blog entry at Good Math, Bad Math in which he attempted to intellectually eviscerate spork33 and his colleagues:

Via BoingBoing comes a bunch of bozos who believe that they can create a “wind-powered” vehicle that moves faster the wind that powers it. This is, obviously, stupid.

Chu-Carroll goes on to argue that the treadmill demonstration in the video has no relationship to conditions “in the field”, using the same kind of dismissive language. He finishes up with this gem:

Everyone should be able to understand the physics involved here. My third grade daughter can understand this. This isn’t difficult. There’s nothing tricky or subtle about it. If you have a vehicle moving at the same velocity as the wind, the wind cannot possibly exert any force on the vehicle. No force, no acceleration. Period. How can supposedly intelligent, educated people not know this?

Unfortunately for MarkCC, since this phenomenon is completely on the level, he is the one who comes off looking like, well, a bozo.

[UPDATE: Mark has printed a retraction on his blog and apologized for his intemperate language. Curiously, he says he needed to work through the math to convince himself that the device could actually work. Personally, the "math" is the last thing I'd trust in a situation like this--the various comment threads are full of mathematical calculations by skeptics who claimed that their results show that the device can't work. Their calculations might have even been correct, but the way they formulated their models was wrong, so the results were meaningless. I'd much rather trust my eyes, but evidently Mark and many other skeptics just couldn't bring themselves to believe that the demonstration in the video wasn't using some sleight-of-hand.]

For a proper explanation of the physics involved, you could browse through the lengthy comment threads at BoingBoing or Good Math, Bad Math. It’s a fascinating read if you have the time. Fortunately, Dave Munger has a post at Word Munger where he gives a succinct explanation of what’s going on, and in which he addresses the major questions that have been raised on the other threads. (Dave is perhaps better known for his blogging at Cognitive Daily, and as a founder of Of course, there are still many skeptics who continue to argue in the comments thread on Dave’s post.

Even though DWFTTW travel is totally cool just by itself, the thing I find most intriguing about this whole episode is the mindset of skeptics. I know that I’ve been guilty of this sort of thing too, where I’m totally convinced that such-and-such is a fact, and I discover later that just the opposite is true. What psychological factors cause us to believe what we believe? And what techniques can be used to help change the mind of a skeptic, when it is clear that simply presenting a factual exposition is not going to do the trick? Dave, if you see this, perhaps this question would make a good topic for your Cognitive Daily blog.

posted in miscellany by Kurt

3 Comments to "Counter-intuitive science"

  1. Anonymous wrote:

    Nice writeup and well thought out. DDWFTTW(Directly downwind faster than the wind) has been done so many times now by so many different people that I no longer consider it a physics experiment, but rather a sociological one — the point of your article.JB

  2. Kurt wrote:


  3. Anonymous wrote:

    Angular momentum is very well explained in Feynman’s lectures. No mystery left.

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