A new study proves parachutes are useless
A new study flies in the face of anecdotal evidence and raises questions about how we read data.
- Scientists working at medical schools across the United States discovered that parachutes don't lower the death rate of people jumping out of airplanes.
- The study flies in the face of decades of anecdotal evidence.
- The findings should be carefully applied, due to "minor caveats" with the experimental structure.
There is an old joke that says "If your parachute doesn't deploy, don't worry: you have the rest of your life to fix it." The findings of a new study may put that joke out of fashion, as intrepid scientists found that jumping out of a plane with a parachute didn't lower the death rate of test subjects compared to those who jumped without one.
A leap of faith in anecdotal evidence
The study, published in the light-hearted Christmas edition of BMJ, involved 23 test subjects who were randomly sorted into two groups. One would leap out of an airplane with a parachute while the second would do the same with a regular old backpack. Their survival rates were then compared after they hit the ground. Shockingly, it was found that the rates were the same for both groups!
The authors explained that "Our groundbreaking study found no statistically significant difference in the primary outcome between the treatment and control arms. Our findings should give momentary pause to experts who advocate for routine use of parachutes for jumps from aircraft in recreational or military settings."
A portion of the flow chart explaining the study structure. As you can see, it follows every regulation for a randomized trial with a control group.
Yeh et al.
In order to get people to agree to take part in the study, the scientists had to structure the experiment properly. The airplane was both on the ground and stationary, as they thought it would be impossible to get people to agree to leap from a moving plane several thousand feet up without a parachute. The authors admit this was a "minor caveat" in the study's design.
They don't admit this until the fourth or fifth paragraph into the paper, however, which leads to their larger point.
Beware of headlines
The authors explain that the whole study was designed to highlight the limitations of randomized trials and the dangers of not reading past the first paragraph of a study. They explain:
"The parachute trial satirically highlights some of the limitations of randomized controlled trials. Nevertheless, we believe that such trials remain the gold standard for the evaluation of most new treatments. The parachute trial does suggest, however, that their accurate interpretation requires more than a cursory reading of the abstract. Rather, interpretation requires a complete and critical appraisal of the study. In addition, our study highlights that studies evaluating devices that are already entrenched in clinical practice face the particularly difficult task of ensuring that patients with the greatest expected benefit from treatment are included during enrollment."
While this study is funny, the questions it raises are real ones. Many influential studies in psychology have been found to be flawed because they used W.E.I.R.D test subjects or were applicable only to a limited range of situations. By clearly showing how accepted procedures can be used to create an absurd little paper, the authors remind us to look closely at the findings of any study.
Admit it, you've read a headline before and then pretended like you read the whole article later when you wanted to talk about it. The point of this silly study is to show just how misleading a summation of a study can be and how important context is in understanding what experiments mean. So have a laugh, and remember to always read more than the study's abstract before you decide to take its supposed findings to heart.
Dominique Crenn, the only female chef in America with three Michelin stars, joins Big Think Live this Thursday at 1pm ET.
Scientists discover the inner workings of an effect that will lead to a new generation of devices.
- Researchers discover a method of extracting previously unavailable information from superconductors.
- The study builds on a 19th-century discovery by physicist Edward Hall.
- The research promises to lead to a new generation of semiconductor materials and devices.
Credit: Gunawan/Nature magazine
The number of people with dementia is expected to triple by 2060.
The images and our best computer models don't agree.
A trio of intriguing galaxy clusters<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQzNDA0OS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNTkzNzUyOH0.0IRzkzvKsmPEHV-v1dqM1JIPhgE2W-UHx0COuB0qQnA/img.jpg?width=980" id="d69be" class="rm-shortcode" data-rm-shortcode-id="2d2664d9174369e0a06540cb3a3a9079" data-rm-shortcode-name="rebelmouse-image" />
The three galaxy clusters imaged for the study
Mapping dark matter<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="d904b585c806752f261e1215014691a6"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/fO0jO_a9uLA?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>The assumption has been that the greater the lensing effect, the higher the concentration of dark matter.</p><p>As scientists analyzed the clusters' large-scale lensing — the massive arc and elongation visual effects produced by dark matter — they noticed areas of smaller-scale lensing within that larger distortion. The scientists interpret these as concentrations of dark matter within individual galaxies inside the clusters.</p><p>The researchers used spectrographic data from the VLT to determine the mass of these smaller lenses. <a href="https://www.oas.inaf.it/en/user/pietro.bergamini/" target="_blank" rel="noopener noreferrer">Pietro Bergamini</a> of the INAF-Observatory of Astrophysics and Space Science in Bologna, Italy explains, "The speed of the stars gave us an estimate of each individual galaxy's mass, including the amount of dark matter." The leader of the spectrographic aspect of the study was <a href="http://docente.unife.it/docenti-en/piero.rosati1/curriculum?set_language=en" target="_blank">Piero Rosati</a> of the Università degli Studi di Ferrara, Italy who recalls, "the data from Hubble and the VLT provided excellent synergy. We were able to associate the galaxies with each cluster and estimate their distances." </p><p>This work allowed the team to develop a thoroughly calibrated, high-resolution map of dark matter concentrations throughout the three clusters.</p>
But the models say...<p>However, when the researchers compared their map to the concentrations of dark matter computer models predicted for galaxies bearing the same general characteristics, something was <em>way</em> off. Some small-scale areas of the map had 10 times the amount of lensing — and presumably 10 times the amount of dark matter — than the model predicted.</p><p>"The results of these analyses further demonstrate how observations and numerical simulations go hand in hand," notes one team member, <a href="https://nena12276.wixsite.com/elenarasia" target="_blank">Elena Rasia</a> of the INAF-Astronomical Observatory of Trieste, Italy. Another, <a href="http://adlibitum.oats.inaf.it/borgani/" target="_blank" rel="noopener noreferrer">Stefano Borgani</a> of the Università degli Studi di Trieste, Italy, adds that "with advanced cosmological simulations, we can match the quality of observations analyzed in our paper, permitting detailed comparisons like never before."</p><p>"We have done a lot of testing of the data in this study," Meneghetti says, "and we are sure that this mismatch indicates that some physical ingredient is missing either from the simulations or from our understanding of the nature of dark matter." <a href="https://physics.yale.edu/people/priyamvada-natarajan" target="_blank">Priyamvada Natarajan</a> of Yale University in Connecticut agrees: "There's a feature of the real Universe that we are simply not capturing in our current theoretical models."</p><p>Given that any theory in science lasts only until a better one comes along, Natarajan views the discrepancy as an opportunity, saying, "this could signal a gap in our current understanding of the nature of dark matter and its properties, as these exquisite data have permitted us to probe the detailed distribution of dark matter on the smallest scales."</p><p>At this point, it's unclear exactly what the conflict signifies. Do these smaller areas have unexpectedly high concentrations of dark matter? Or can dark matter, under certain currently unknown conditions, produce a tenfold increase in lensing beyond what we've been expecting, breaking the assumption that more lensing means more dark matter?</p><p>Obviously, the scientific community has barely begun to understand this mystery.</p>
Scientists have found evidence of hot springs near sites where ancient hominids settled, long before the control of fire.