The reason I say this is that scientists sometimes have a tendency to throw caution to the wind and engage in speculation, which then gets reported by the media as "scientific fact." When said speculation turns out to be false, or is superseded by other models for which there is more evidence, laypeople get the wrong idea that scientists sit around all day making shit up, and when it turns out to be wrong, they just make more shit up, and on and on it goes.
So media bears a large share of the blame for this, as usual. But that said, it would be nice if there was some way for scientists to identify in their academic papers when they're engaging in tentative hypothesis, and when they're elaborating on a well-established and rock-solid theoretical model.
Amongst the latter would be evolution and anthropogenic climate change. Just had to throw that in there.
But as an example of the former, let's look at a paper by Michael Rampino, professor of biology at New York University, who recently published a paper in Monthly Notices of the Royal Astronomical Society proposing that the periodic mass extinctions that have occurred on Earth might be caused by the interaction between the Solar System and a thin layer of dark matter along the galactic plane. Rampino writes:
A cycle in the range of 26–30 Myr has been reported in mass extinctions, and terrestrial impact cratering may exhibit a similar cycle of 31 ± 5 Myr. These cycles have been attributed to the Sun's vertical oscillations through the Galactic disc, estimated to take from ∼30 to 42 Myr between Galactic plane crossings. Near the Galactic mid-plane, the Solar system's Oort Cloud comets could be perturbed by Galactic tidal forces, and possibly a thin dark matter (DM) disc, which might produce periodic comet showers and extinctions on the Earth. Passage of the Earth through especially dense clumps of DM, composed of Weakly Interacting Massive Particles (WIMPs) in the Galactic plane, could also lead to heating in the core of the planet through capture and subsequent annihilation of DM particles. This new source of periodic heating in the Earth's interior might explain a similar ∼30 Myr periodicity observed in terrestrial geologic activity, which may also be involved in extinctions. These results suggest that cycles of geological and biological evolution on the Earth may be partly controlled by the rhythms of Galactic dynamics.The difficulty, of course, is that dark matter is still yet to be detected, despite years of search. We can observe that there's something out there that, from its gravitational effects, seems to make up most of the universe's mass. But what it's made of, and what its properties are, are completely unknown. "WIMPs" -- the Weakly Interacting Massive Particles Rampino references in his paper -- are one candidate for the constituents of dark matter. But they, too, are yet to be confirmed to exist, despite multiple experiments designed to detect them at the Large Hadron Collider.
So Rampino is proposing that a 31 ± 5 million year mass extinction cycle (5 million years representing a 15% variability either way) links to a 30 to 42 million year galactic-plane-crossing cycle (which represents a 16% variability either way) via a mechanism connected to a type of matter we've never seen and whose properties can only be guessed at.
Map of the "dark matter halo" surrounding a galaxy [image courtesy of the Wikimedia Commons]
Einstein, however, decided to take the "problem of the constancy of the speed of light" and turn it into the "law of the constancy of the speed of light" and see what mathematical predictions came out of that assumption. And then, run experiments to see if those predictions worked. Lo: the Theory of Relativity, with its wild time dilation and Lorenz Contraction weirdness.
All of which is a long-winded way of saying that there's nothing wrong with speculation. I just wish there was some way for scientists to differentiate between when they're proposing a speculative hypothesis and reporting on an experimentally-supported theory.
Maybe they should write speculative articles in "Comic Sans." I dunno.
I say this because I'm seeing stories come up all over the place, just in the last couple of weeks, claiming that "dark matter killed the dinosaurs." Which Rampino himself would admit is not justified at this time (note in the passage I quoted how many times he uses the words "could," "might," and "may"). And when someone else proposes a different mechanism to explain the periodicity of extinctions, it'll also get reported as fact, and laypeople will have further evidence that all scientists do is come up with wild tales all day long.
So I really should revise my initial statement. It's not that scientists are their own worst enemies. It's that popular media are the scientists' worst enemies. That, and the fact that the public still doesn't really understand how science is done (look at the ongoing confusion about what the word "theory" means).
And given the fact that a significant proportion of the public still doesn't accept the findings of science that aren't speculative, the last thing we need is to sow more doubt in people's minds by misrepresenting the parts of science that are still only conjecture.