In university I studied Earth Sciences and had to write many research papers. One of my favourite topics to write on when the subject allowed it was the Cretaceous/Tertiary extinction event — the extinction event that eliminated the dinosaurs. So I know more about this topic than most people do, although it’s been quite a while since I graduated and much of that knowledge has faded. For example, while the popular media trumpets with finality that a massive asteroid strike in the Gulf of Mexico was the reason for the extinction, there are a number of problems with this theory that are never mentioned. I believe it’s the sensationalistic nature of the theory that has given it such a stranglehold on popular culture and which has promoted it to the status of uncontested fact. In reality, there is a fair amount of dissent among people who study the topic and if anyone cares to comment, I will elaborate on this point. Suffice it to say, there are a large number of apparently conflicting bits of information that don’t jive with a giant bolide being the ultimate cause and, in fact, point to other possiblities — although these as well have their issues. My point is that the question is far from resolved among scientists, even if everyone thinks they know the answer.
Something, however, that has always stuck with me in doing that research is the statement in one paper I read about there being no real pattern to the kinds of animals that became extinct — nothing that could be used as a predictor for what animals lived and what animals didn’t. The devastation happened equally to animals on land as in water, etc. [Aside: notably, however, a truly inexplicable thing is this: How is it that crocodiles and turtles survived when no dinosaurs did?] At any rate, the author of this paper made the statement that the only pattern he could see was that pretty much anything over 22 pounds disappeared. This was a bizarre observation to me, and over the years it’s popped into my head once in a while. That’s what geeks do. We ponder stuff like this.
In light of that knowledge I had had in my thoughts the following idea for a while: it is a well understood fact that the earth’s rotation has slowed with the passage of time. This is due to tidal and other frictional forces acting against the momentum that drives the spin of the earth. This means that if you were to go way back in time and stand on a scale, you would weigh less than you do now. The centripetal force due to the rotation of the earth that you would have experienced back then (i.e. your tendency to fly off of its surface) would have lessened the effect of gravity on you, thus literally making you lighter as measured by a scale. Your mass would be the same, but your weight would be less. I wondered if dinosaurs were such large animals back then simply because the effective gravity back then was not as strong, thus allowing such massive growth. Perhaps a large dinosaur transported to our time would be crushed under its own weight. Certainly any stroll through a dinosaur museum makes you marvel at how such a large animal could have even stood up. It seems reasonable to me that the faster rate of spin of the earth at the time had something to do with allowing creatures of such massive size to evolve in the first place.
But as far as this slow, creeping force of nature creating a clear and sudden extinction event in the geologic record… that just doesn’t compute.
However a couple of weeks ago I hit upon another idea. What if it was a large bolide colliding with the earth that caused an accelerated slow-down of the earth’s rotation. I don’t know the physics behind this or what kind of a rotational slow-down would cause what kind of a change in the weight of things. But I do know that the change in weight would affect larger creatures much more dramatically than smaller creatures. This is because if you have two objects and one of them is twice the size of the other, that object is not double the weight of the lighter one; it is eight times the weight of the lighter one. So a small change in the rotational energy of the earth may not have been felt so much by the smaller animals, but may have had a dramatic impact on the larger ones.
So my thought is that perhaps the collision of a bolide with the earth 65 million years ago had some of the effects that scientists are saying. And, make no mistake, the effects would have been devastating. However, in reading the descriptive accounts of what is said to have happened, it is a bit miraculous that anything at all survived — including any plants, which would have absolutely caused the death of everything else up the food chain. More likely, in my humble estimation, was that the effects were not quite as cataclysmic as is so often described. A possible side-effect of the collision that I have never heard or read of is this rotational slow-down. Is it possible that perhaps a small reduction in the rotational speed of the earth played an important contributing role in extinguishing the larger animals and letting the smaller ones — under about 22 pounds — live?