Lisa Randall: Dark Matter & Dinosaur Extinction

Lisa Randall

Lisa Randall

Your Curmudgeon admires theoretical physicist Lisa Randall. Our last post about her was Discovery Institute Quote-Mines Lisa Randall. Here’s her page at the Harvard website, which says:

Professor Lisa Randall studies theoretical particle physics and cosmology at Harvard University. Her research connects theoretical insights to puzzles in our current understanding of the properties and interactions of matter. She has developed and studied a wide variety of models to address these questions, the most prominent involving extra dimensions of space. Her work has involved improving our under-standing of the Standard Model of particle physics, supersymmetry, baryogenesis, cosmological inflation, and dark matter. Randall’s research also explores ways to experimentally test and verify ideas and her current research focuses in large part on the Large Hadron Collider and dark matter searches and models.

PhysOrg has an article about Dr. Randall: Physicist links dark matter to dinosaur extinction in new book. Here are some excerpts, with bold font added by us:

Dark matter: The world’s brightest physicists know it’s there, but can’t say for sure what it is. It is invisible, mysterious, and to most people — irrelevant to everyday life. But what if it could reach out and touch us? What if it already has, and so deeply that it just might be responsible for putting us here?

One Harvard physicist is exploring that idea, and pondering the possibility that dark matter may have triggered the most famous cosmic collision ever — the one that did in the dinosaurs and opened the way for mammals to take their place.

Good beginning, huh? Then we’re told:

Theoretical physicist Lisa Randall, the Frank B. Baird Jr. Professor of Science, sees intriguing lines of evidence that tie dark matter to comets in the solar system’s distant Oort cloud, and from there to the 66-million-year-old impact crater on Mexico’s Yucatán coast.

We can’t even imagine what the creationists will do with that idea. Let’s read on:

Randall first explored the idea last year in an article, co-authored with Assistant Professor of Physics Matthew Reece, in the journal Physical Review Letters. Inspired by the intricate chain linking dark matter, Earth, dinosaurs, and modern life, Randall decided to take a deep dive into the subject for her new book, “Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe.”

This is her paper in Physical Review Letters: Dark Matter as a Trigger for Periodic Comet Impacts. All you can see without a subscription is the abstract, which says:

Although statistical evidence is not overwhelming, possible support for an approximately 35×106 yr periodicity in the crater record on Earth could indicate a nonrandom underlying enhancement of meteorite impacts at regular intervals. A proposed explanation in terms of tidal effects on Oort cloud comet perturbations as the Solar System passes through the galactic midplane is hampered by lack of an underlying cause for sufficiently enhanced gravitational effects over a sufficiently short time interval and by the time frame between such possible enhancements. We show that a smooth dark disk in the galactic midplane would address both these issues and create a periodic enhancement of the sort that has potentially been observed. … We find that, marginalizing over astrophysical uncertainties, the likelihood ratio for such a model relative to one with a constant cratering rate is 3.0, which moderately favors the dark disk model. …

And this is her book at Amazon: Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe. Okay, back to PhysOrg:

“I was just fascinated by this story,” Randall said. “It was really nice for me to be able to communicate about dark matter through its potential connections to what we see today.”

The book, to be published Oct. 27, takes the reader on a tour of the universe, from the Big Bang to today, from the story of life to mass extinctions, from the distant galactic disk to Earth’s K-T boundary layer — a thin, globe-spanning blanket of dust that scientists believe is evidence of the cataclysmic impact that ended the dinosaurs’ reign.

Ol’ Hambo won’t like this — it’s not biblical at all! PhysOrg continues:

The book suggests that a thin disk of dark matter could have influenced weakly bound comets in the outer regions of the solar system as it revolved around the center of the Milky Way, and may have been the ultimate cause of the impact. Randall admits that the disk hasn’t been found, but said that current data allows for it, and that instruments that might detect it aren’t far off.

Aha — in principle, the hypothesis is testable. Here’s more:

If the dinosaur killer was a comet, the next question is, what gave it the initial push toward Earth? Scientists confronting that question have an additional clue: The impact that caused the dinosaurs’ extinction wasn’t the only one in the planet’s history. There have been several, in fact, and there’s some evidence that they occur at regular — at least on a galactic scale — intervals of between 30 million and 35 million years.

Hey, wait a minute — if those collisions aren’t random, then they’re designed! Maybe the Discoveroids can apply their magic filter to determine that the intelligent designer — blessed be he! — intended for things to work out as they did.

There’s much more to the PhysOrg article, so you’ll probably want to read it for yourself. We’ve already given you plenty to think about, so this is where we’ll quit — but we’re certain that we haven’t heard the last of this. We look forward to the creationists’ response.

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14 responses to “Lisa Randall: Dark Matter & Dinosaur Extinction

  1. The periodicity of mass extinctions/large impacts on Earth has been disputed ever since Sepkoski first proposed it in the 1980s. Since then, our understanding of mass extinctions has greatly improved, as has the number of discovered impact craters on Earth. The multiple mass extinctions in the Cambrian (mainly affecting trilobites, but there’s also a signal in the brachiopod record) have never been blamed on impacts. The end-Ordovician mass extinction has not been blamed on an impact by any geologist, as far as I know. There is a purely speculative gamma-ray burst hypothesis, but there is zero evidence for it. However, there was a relatively high number of asteroid-asteroid impact events in the Asteroid Belt during the Ordovician, based on CRE dating (cosmic ray exposure dating). I’m not terribly familiar with the near-end Devonian extinction, but I’ve heard a wide varieties of responsible factors proposed. The end-Permian extinction was likely impact-related (Wilkes Land Impact Crater in Antarctica, antipodal to the Siberian Traps Flood Basalt). The end-Triassic extinction has been satisfactorily explained without impacts. The Cretaceous-Tertiary extinction of the dinosaurs + others was definitely caused by multiple impacts (Chicxulub, Boltysh, Shiva) 65 million years ago, despite the lingering objections by a micro-minority of non-objective geologists. Chicxulub was ~antipodal to India’s Deccan Traps Flood Basalt, but the Shiva Impact is the more likely culprit there – it cracked open India’s crust, allowing for outpouring of lava. The end-Pleistocene extinction of all large mammals everywhere, except Africa, is well blamed on a combination of human overhunting & climate warming. However, the impact thing has been suggested as well for this (“Clovis Comet”), but serious & legitimate objections have been raised to suggest that this doesn’t work.

    The dark matter disc hypothesis doesn’t “feel” right because Sol & just about every other star in the Milky Way are located in the same galactic disc – gravity is binding everything together into a more or less common location & everything is rotating together. If there is non-synchronous rotation of a hypothesized, non-uniform, dark matter disc in relation to Sol & other stars, then maybe – maybe – this new idea might have some merit. But perturbations go on all the time throughout the Solar System & the Milky Way & the Universe. How does one distinguish dark matter-induced perturbations from normal matter perturbations?

  2. Oh – there are some near-end Triassic impact craters here on Earth (Rochechouart in France & Manicouagan in Canada). Some have suggested a link to the end-Triassic mass extinction, but the age difference between them is relatively significant.

  3. Ceteris Paribus

    James St. John inquires: “How does one distinguish dark matter-induced perturbations from normal matter perturbations?

    Well, I don’t know if this will work for everyone, but I find that keeping regular appointments with my analyst helps a lot.

  4. @James St. John: Thanks for the great summation of mass extinctions. I’ve copied it into my permanent notes.

  5. Mike Elzinga

    I read the PRL paper last year when it came out and thought it was quite a stretch but interesting enough to be taken seriously.

    If you click on Figure 1 in the abstract shown in Curmudgeon’s link, you see the periodic oscillation of the solar system through the galactic plane. The amplitude of this oscillation is about 80 pc and its period is roughly 70 Myr; so it passes through the galactic plane about every 30 to 35 Myrs.

    The calculations involving the perturbations of ordinary matter in the galactic plane indicate that these are too weak to kick stuff out of the Oort cloud or perturb the asteroid belt sufficiently to account for the periodic impacts on Earth. Another alternative – that there is a higher density of matter within the galactic plane – is also questionable because the density, as far as it can be measured, doesn’t seem to be that much different within the volume of space in which the solar system oscillates.

    So an alternative might be dark matter; and the PRL paper does show this to be a possibility given the estimates of the amount of dark matter that has condensed within the galactic plane.

    But as James St. John has already mentioned, it is not certain that there really is a 35 Myr cycle of extinctions that can be correlated with passage through the galactic plane or that can’t be explained by other independent events. Picking out a correlation with passage through the galactic plane is perhaps itself a stretch of the imagination.

    However, Randall’s paper does suggest another possible “experiment” for actually detecting the presence of dark matter; and it doesn’t necessarily rely on mass extinctions but could, instead, make use of other events that have a period of about 35 Myr. The problem at the moment is that we don’t know of any other such events that could be used as this kind of “experimental test” of the presence of dark matter.

    Furthermore, we won’t be around long enough to collect data from sensitive instruments that we place in orbit around the Earth that will then make several passes through the galactic plane in order to pick up the pattern.

    So the idea verges on being an interesting speculation at the moment.

  6. A few decades ago, there was an hypothesis about a body called Nemesis that orbited the sun at a great distance, and which caused periodic mass extinctions.

  7. @James St. John

    Great synopsis for mass extinctions. Thanks.

  8. I’ve heard about the oscillation thing before & the Nemesis hypothesis was mentioned in one of my college geology courses. The oscillation of Sol up & down through the galactic plane makes sense to me. The insufficient increase/decrease in normal matter density in the plane to account for perturbations seems like a plausible point, but the “Butterfly Effect” is a real phenomenon. Make a small change here – you get a big change over there later on. I’ve also heard the extinction periodicity blamed on Sol rotating around the Milky Way Galaxy (which happens) and passing through the spiral arms – each spiral arm causes perturbations & one or more impacts occur on Earth as a result – boom – mass extinction. That one’s a clunker, though – Sol doesn’t pass independently through the galaxy’s spiral arms. The spiral arms aren’t stationary – they rotate around the galaxy along with us. I think a Russian geologist proposed that one. Well, at least I recall reading a Russian article where that was proposed.

    I’m not quite sure there is extinction periodicity – I’m still up in the air on that one. I distinctly recall furrowed eyebrows by many geologists when it was originally proposed decades ago. I’m still not sure yet – but don’t take my word for it.

    There is an apparent correlation between the Big Five mass extinctions (end-Ordovician, near-end Devonian, end-Permian, end-Triassic, and Cretaceous-Tertiary) and flood basalt provinces – they both show quasi-periodicity. Some geologists lean a bit too much (in my view) on the volcanism-only thing in explaining the big mass extinctions. Siberian Traps is on the opposite side of the Permian-aged Planet Earth to Wilkes Land Crater (which admittedly isn’t well dated). Deccan Traps is kinda on the opposite side of the 65 million year old Earth as Chicxulub (but as mentioned in an earlier note, the Shiva Impact Crater likely explains the Deccan volcanism). Antipodal relationships between large impacts and large volcanic provinces have been well established on Mars. I’m pretty sure we’re seeing them on Earth, too. There is a flood basalt province in the Triassic – some have blamed that on the end-Triassic extinction. But is that one impact-related? Dunno.

  9. There has been some speculation that our sun may have a (very) distant companion and that when the two stars are at their closest to each other gravitational influences kick comets out of the Oort cloud, perhaps in both directions. But so far, this “Nemesis” hypothesis has little hard data backing it up.

  10. @James St. John: Another interesting antipodal relationship is the Columbian Basalt Plateau of Washington-Oregon and the Kerguelen Islands, although there’s little evidence of impact at Kerguelen other than a subtle concentric arrangement of fjords (possible faults) around a central peak. There’s a slight possibility that the central peak may have originated as the central rebound uplift of a massive impact, but admittedly it’s a stretch.

  11. As for the Creationist response, little kennie ham will simply dismiss it. Theistic Evolutionists will claim since Dark Matter is mysterious, and God works in mysterious ways . . . problem solved.

  12. If the Columbia Plateau-Kerguelen connection is real, then I have an impact to thank for the wonderland that is Yellowstone Park. The Columbia Plateau Flood Basalt Province is thought to represent the birth of the Yellowstone Hotspot, which tracked from ~southwestern Oregon through southern Idaho and into northwestern Wyoming during the late Cenozoic.

  13. Well a large number of high knowledge responses. Here is a lower knowledge response. More posts with Ms Randall’s picture. Just that simple.