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Bad Skepticism: Why You Should Challenge Popular Assumptions

From swamp gas and waterspouts to alternative medicine, the harm of not challenging popular assumptions.  

by Brian Dunning

Filed under Logic & Persuasion

Skeptoid Podcast #506
February 16, 2016
Podcast transcript | Download | Subscribe



When I was in film school, I saw a trailer for a student documentary called Devilstone about a dry lakebed in Death Valley where the rocks leave long trails in the dry mud, as if they've moved around by themselves. I was hooked; it became an obsession to learn what was going on here. Eventually I made it there in person, and in 2002, became incredibly lucky and got video of strong winds pushing a shallow lake across the playa at nearly walking speed, with thin sheets of ice sailing along amid the rocks. Of course I'd heard all the nutty explanations, everything from magnets to psychics to "leylines".

But there were also explanations from the community of sound science, like moisture making the surface slippery and strong winds would push the rocks. And then in 2013 an explanation was published that was touted as the true one: ice would form "collars" around the rocks, making them buoyant enough to float, so they could then move around with the wind, dragging trails in the mud. But this made me scratch my head. I mean, come on: Who's ever seen a big, hefty rock floating around on the surface of a lake, kept buoyant by a convenient belt of ice inexplicably stuck to its equator? But it was peer-reviewed, published research, and I grumbled and forced myself to accept the conclusion of someone I had to assume knew more about it than I did. I decided to go with the popular assumption.

One of the popular assumptions that I grew up with was the explanation of "swamp gas" used for UFO reports, ghost lights, or just about anything that people might see at night. It was first suggested by famous UFO author J. Allen Hynek to explain some sightings that he thought might not be alien spacecraft. Over the decades, it became one of the default explanations for unknown lights in the sky, likely to be suggested by anyone in the media, at least who was not of a scientific bent. People had simply heard it enough, and seen it repeated in print often enough, that they assumed it was true.

But swamp gas was never a viable explanation. We went into it in detail in Episode #183, where swamp gas had also been proposed to explain the Naga Fireballs brightening the skies of Thailand. Swamp gas is flammable and is found in nature, but has never been known to spontaneously ignite, or to be present in sufficient concentration to burn in nature. And when it does burn in the laboratory, it combusts suddenly with a loud pop and a green flash. No way, no how, does swamp gas ever form a hovering point of light.

Swamp gas was a terrible explanation. It was an instance where accepting the popular assumption was wrong; but as with most such cases, the average person never happens to encounter a reason to doubt it. Such people are not ignorant or stupid or crazy, and they can hardly be blamed. When we're given bad information, and not given a reason to doubt it, we tend to accept that information. In many cases, we have to make a proactive decision to doubt the things pop culture throws at us, and often without a clear reason to do so.

It is a fact that sometimes we discover masses of frogs or fish on dry land, seeming to have suddenly appeared out of nowhere. We know what causes this, but for most of history, we didn't; and two giant assumptions became the de facto explanation. Assumption number one was that they fell out of the sky; an assumption that became so deeply entrenched that many stories even include reports of this part of it having been witnessed, or reports of fish found on the roofs of buildings. Accepting this assumption without critique, some in the modern era began turning to science in search of an explanation for how frogs and fish could get way up in the sky, and they came up with waterspouts. Waterspouts, it was said, lift the frogs and fish out of the water, transport them some distance, then drop them all in a tidy little bundle on the home of a surprised suburbanite. The waterspout explanation became the popularly accepted explanation, which everyone assumed was true, and to this day, is broadly given in the media whenever this phenomena is mentioned.

Both assumptions are wrong, of course. As we discussed in detail in Episode #170, waterspouts do not have any mechanism for lifting anything out of the water, and have never been observed to do so — see that episode if you want the details. But moreover, the underlying assumption that the animals fell out of the sky is also wrong. Many species of frogs, and a few species of fish, cross the land, often in groups, in certain seasonal conditions. On the very few occasions when the fish in question have been preserved to be identified, they've always turned out to be one of these species: mudskippers, walking catfishes, climbing perches, what have you. Waterspouts as an explanation for frogs and fish falling out of the sky was a case of terrible, terrible skepticism — and it came from failure to question accepted assumptions.

But neither swamp gas nor waterspouts have much of an impact on our daily lives or on the decisions we make. They're fun topics and provocative for conversational purposes, but it's not like they cost people money or livelihood. Other unquestioned assumptions do. One of the urban legends injected into pop culture over the past ten or fifteen years is the myth that great masses of plastic garbage are floating in the centers of our oceans. This story grew from a kernel of truth, of course: debris, much of which is floating plastic, does indeed get drawn to the central regions of the oceans by wind and currents. But this journey takes a year or more, during which time almost all plastics either sink are broken down by ultraviolet radiation and wave action so there's almost nothing left. According to NOAA's latest surveys, these mid-ocean gyres have an average of one particle of plastic "micro-debris" every 30-90 square meters. According to NOAA:

It is possible to sail through the "garbage patch" area and see very little or no debris on the water’s surface. It is also difficult to estimate the size of these "patches," because the borders and content constantly change with ocean currents and winds. Regardless of the exact size, mass, and location of the "garbage patch," manmade debris does not belong in our oceans and waterways and must be addressed.

Unfortunately, the story gets deliberately exaggerated by everyone from extremists and ideologues to reporters and bloggers just looking to create sensationalism, so the imagery we have of this often shows great masses of floating trash. They just don't happen to tell you that these pictures are of fresh trash accumulating in polluted third-world harbors, and are not remotely representative of what's in the open ocean. Thus, the popular assumption that there are masses of trash floating in the oceans goes unchallenged.

But what happens when people invest resources based on these assumptions? Examples are found in the numerous projects proposed to clean up these assumed islands of trash. The worst of these contraptions plan to fuel a cleanup boat by burning the collected trash — imagine the disappointment when the boat arrives on station and there is only one micro-particle of fuel every 30-90 square meters. The best of these ideas plan to skim the surface with gigantic collection booms, thus destroying thousands of phytoplankton for each collected micro-particle. Nearly all would be grossly inefficient, burning massive amounts of diesel for virtually no perceptible improvement. Even automated solar electric proposals would be unlikely to ever recover their own weight in trash, and unless the entire fleet was 100% reliable, they'd end up contributing to a net gain in trash. The assumption that trash in the centers of the oceans is sufficiently dense to make collection efforts worthwhile is wrong, yet investment of time and money flows into it.

But take this to its next logical step: consider all the other popular assumptions that, unquestioned, result in waste or harm. Tens of millions of people have never thought to question the alternative medicine practice, or miracle diet scheme, that was advertised to them on some daytime talk show and that they've been spending money on ever since. And let's don't even get started on the Big Pharma conspiracy beliefs that have led honest, thinking people to shun medical care in the case of treatable illness. They're not stupid; they're simply acting as either you or I would if the information we had was the same as what they have. That's exactly why, even now, you and I should both question our assumptions.

Whatever it is you do for a living, it's a certainty that your industry relies on some popular assumptions that are wrong. Try this as an exercise: If your company has an email list or something similar, ask the question. Ask what commonly-accepted assumptions in your industry might be wrong. If you speak at an industry conference or event, ask the question of the audience. I promise you'll hear a few nominations, and you'll almost certainly re-examine something you always "assumed" was true. If you hear any interesting assumptions, email them to me.

So whatever became of my "devilstones"? I never did get comfortable with the "ice collars". I was satisfied that the ice sheets I'd seen had sufficient horsepower to move the rocks, so I contacted the park service for permission to conduct scientific research and mount monitoring equipment on the mountainside above the playa. I prepared a crowdfunding campaign to finance the purchase of a remote weather station with a camera and a network connection so I could monitor the conditions from home, then drive out there to take video as soon as the conditions were right. And just as I was ready to go, a team published their results in August 2014. They'd done almost exactly what I'd planned, and they'd had their equipment there a year before I had the idea. And they were right. They captured video of exactly what I'd seen in 2002. No ice collars or psychic energies needed. The popular assumption was wrong, and I'd been right to challenge it.

By Brian Dunning

Please contact us with any corrections or feedback.


Cite this article:
Dunning, B. "Bad Skepticism: Why You Should Challenge Popular Assumptions." Skeptoid Podcast. Skeptoid Media, 16 Feb 2016. Web. 21 Jan 2017. <>


References & Further Reading

Cohen, Eric. "The Postmodernization of a Mythical Event: Naga Fireballs on the Mekong River." Tourism, Culture & Communication. 1 Jan. 2007, Volume 7: 169-181.

Gilfillan, L., Ohman, M., Doyle, M., Watson, W. "Occurrence of plastic micro-debris in the southern California current system." California Cooperative Oceanic Fisheries Investigations. 1 Jan. 2009, Volume 50: 123-133.

Graham, J. Air-breathing fishes: evolution, diversity, and adaptation. San Diego: Academic Press, 1997. 54-56.

Kletetschka, G., Hooke, R., Ryan, A., Fercana, G., McKinney, E., Schwebler, K. "Sliding stones of Racetrack Playa, Death Valley, USA: The roles of rock thermal conductivity and fluctuating water levels." Geomorphology. 3 May 2013, Number 195: 110-117.

NOAA. "Great Pacific Garbage patch." Marine Debris Program. National Oceanic and Atmospheric Administration, 4 Feb. 2016. Web. 6 Feb. 2016. <>

Norris, R., Norris, J., Lorenz, R., Ray, J., Jackson, B. "Sliding Rocks on Racetrack Playa, Death Valley National Park: First Observation of Rocks in Motion." PLOS ONE., 27 Aug. 2014. Web. 6 Feb. 2016. <>


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