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The theory that dinosaurs’ gravity was weaker got a new convert from an unexpected source in February 2013. Jose Canseco, an American Baseball outfielder, created an Internet storm when he tweeted:

“You ever wonder why nothing REALLY big exists today in nature. Animal tissue of muscles and ligaments could not support huge dinosaurs even standing up or pump blood up 60 foot necks. Gravity had to be weaker to make dinosaurs nimble.” [1]

It didn’t take long for the panic to start among the self-proclaimed science elite of the Internet. Jose Canseco has nearly 500,000 Twitter follows so perhaps they were visualising hoards of people starting to research dinosaurs’ gravity for themselves. Everyone might start to ask the simple question, “How do these experts know gravity was the same on the ancient Earth?” The intellectual fire-fighting was soon in full panic mode.

Early responses to Jose Canseco didn’t even bother to try to pretend to address the science behind the theory. Bill Nye, the science guy, dismissed him with the comment:  

“Reading his recent tweets about the remarkable size of the ancient dinosaurs ... it doesn't sound (read) as though he's especially fluent in physics.” [2]  

Various Internet dinosaur experts decided they could improve on these vague dismissals of the reduced gravity theory with superior reasoning in their internet blogs. Brian Switek, freelance science writer on National Geographic and the author of a new book on dinosaurs, [3] felt confident that paleontologists had already "debunked the proposal that Jurassic gravity was weaker" in a 2011 paper on sauropod gigantism. But in practice this paper simply refers to two old (1980s) papers by Economos and Hokkanen that assume gravity was the same - neither of these old papers provides convincing evidence that gravity hasn't changed.

But Brian Switek used this to help present his own theory that it must be dinosaur evolution - not ancient gravity - that allowed super-sized sauropods to evolve air sacs so they could become super light enough to grow big.

“... there’s no evidence that the Earth’s gravity was weaker during the heyday of the dinosaurs. Even as continents shifted around, the Earth’s gravity didn’t change. Canseco’s idea of “nimble” dinosaurs sprinting around in low gravity isn’t grounded on any actual evidence.” [4]

Although he didn’t think “that giant dinosaurs got an assist from higher oxygen levels, either.” (Which is another well-known theory of course).

“Not only did the air sacs allow the dinosaurs to breathe more efficiently – more like birds than mammals – but the soft tissues invaded bone to make the skeletons of these dinosaurs lighter without sacrificing strength.” [4]

So basically the dinosaurs were all hollow to make them lighter (that doesn’t sound quite as convincing as “evolved air sacs” does it?) In practice sauropods would need about half their volume taken up by empty air sacs to account for their reduced weight.

This theory also doesn’t explain giant mammals, but he glossed this over with:

“All these factors conspire to create a reproductive threshold that mammals just can’t cross. For mammals to get much larger, they would have to carry young for longer and likely provide increased parental care. The extinct Paraceratherium and steppe mammoth, two of the largest land mammals ever, might represent how large it’s possible for mammals to get…” [4]

So that’s a different theory again to explain the large size of prehistoric mammals. But just assuming that mammals could grow larger than today's size does not explain why present day mammals are now smaller than these giant mammals. There is a clear size reduction from supergiant mammals, giant mammals to present day mammals spread over tens of millions of years. This giant mammal theory just ignores this size reduction completely.

Also, neither of these two theories explains giant insects in the Carboniferous. That fact needs yet another explanation for their large size. That’s three different theories to explain large size in dinosaurs, giant mammals and Carboniferous insects. It hardly seems like Occam's razor type critical thinking. [5] The reduced gravity theory explains all these facts with the one theory because surface gravity has been gradually increasing: it is one theory that affects every land-based life form over 300 million years of geological time.

Matthew Francis, a physicist and science writer, also confidently explained how Jose Canseco must be wrong.

“I’m not sure exactly how much weaker gravity must be in either Canseco’s or the other hypotheses. …. For the sake of argument, however, let’s assume the largest land mammal was as big as any animal can get: the 20-ton Paraceratherium, which lived in the Oligocene (about 23-34 million years ago). This is consistent with some earlier estimates, which means that gravity in the Jurassic Period (when Supersaurus lived) must have been about half what it is today, or something else must have been going on. …

(Note: I still haven’t determined the source where weaker gravity is proposed, so I’m inferring its arguments from later papers. ... [6]

Now since he tells us “I still haven’t determined the source where weaker gravity is proposed...” it seemed he might welcome a heads-up about reduced gravity theory. Unfortunately my comment:

Reduced gravity on an Expanding Earth is discussed here [6]

Quickly resulted in the link to the presentation being removed with the response:

“… I will not allow YouTube links to dubious hypotheses on my blog. As both my post and Brian’s state, there is no need for different gravity in ancient times, and no physical mechanism by which it could be reduced.”  [6]

A link to a technical paper didn’t get any better response.

How about a link to a technical paper on reduced gravity. Is that allowed?


“That is hardly a technical paper, and would not pass peer review in any reputable journal because it has no scientific merit. There is no reason to believe Earth’s gravity was weaker in previous times. Dinosaurs could stand up under their own weight and the large flying reptiles had no trouble getting airborne. Additionally, there’s no evidence Earth changed size for reasons I wrote extensively about in the original blog post, and there’s certainly no way it could change mass. I am terminating this discussion now. You can write about your ideas in your own space, but this blog is devoted to science.”  [6]

Bizarrely,  despite his apparent claim to the contrary, his original blog hadn't discussed the science to any depth and he had even stated, "nobody has proposed the idea that Earth was lighter in the past as a solution to dinosaur size anyway". He seemed unaware that several authors have noted this connection and was determined to avoid discussing this even after I highlighted it for him.

But perhaps we must not forget he seemed to be in a full-on fire-fighting mode, so I should have read his words more carefully:

"Admittedly, this may seem like using a sledgehammer to crush a gnat. I’ve expended a lot of words and diagrams to combat a few short tweets from a baseball player, ..."  [6]

Must really mean... “I'm in a major panic.” Perhaps this is why he doesn’t seem to have done any research before he began writing, by a search for “dinosaur gravity” on Google for instance. I should have realized this of course, after all I'd already noted that at least one American professor seems to have tried to misrepresent me to presumably discredit the theory of ancient reduced gravity.

So here we have a perfect example of various Internet “experts” telling us they know they are right and nothing anyone says will make them believe any differently. They refuse to even consider if gravity was less and don’t want to know any of the evidence in support of it. How boring is that?

Strangely I’d also just received my copy of The Earth Expansion Evidence: A Challenge for Geology, Geophysics and Astronomy book this same week. [7] The book contains articles by 41 doctors and 12 Professors of various sciences and it has three about reduced gravity. The personality of these scientists means they enjoy thinking outside the box in the hope of discovering something new and amazing about how our world works.

Update: Jose Canseco recants reduced gravity theory

The controversy didn't end with those first two blogs. Brian Switek and Matthew Francis were still so upset about ancient reduced gravity they continued to "explain" to Jose Canseco on Twitter how reduced gravity was unquestionably wrong because it didn't agree with the popular science viewpoint. After a long session on Twitter, Jose Canseco finally declared he had recanted his beliefs and confessed he must have been mistaken.

But Canseco also managed to ask a last ostensibly innocent question: How could dinosaurs' blood pressure be so large? This prompted another blog by Brian Switek explaining that blood pressure is considered an unresolved problem, [8] apparently still unaware that it can yet again be simply explained by an ancient reduced gravity.

The reaction of internet bloggers to the idea that gravity was less during the dinosaurs' era is interesting on many different levels. These two bloggers both freely admit that their first and primary reaction to the concept of reduced gravity was an overwhelming emotional response that it must be wrong and it was this feeling that stimulated them to explain in detail the popular scientific view that the Earth's surface gravity hasn't changed since the dinosaurs' time.

Except - their explanations are far from detailed. Between the two of them they only highlighted one scientific reference briefly discussing gravity variation whilst ignoring several scientific references analysing the notion in greater detail. Although the main short statement in the science paper cited is clearly an assumption - “we have to assume that there were no secular variations in Earth’s gravity” it was upgraded in the blog to claim that gravity variation has been “debunked” by scientists. The alternative view that there seems to be evidence indicating that gravity may well have changed, as discussed in much greater detail in a range of publications by authors such as Prof C. John Mann, Prof Sherman P. Kanagy, Prof S. Warren Carey, John Davidson, Dr James Maxlow, William Erickson, Dr Ramin Amir Mardfar, Dr Carl Strutinski, Prof. Giancarlo Scalera, myself and others was simply ignored. Many of these references, as well as a number of others about reduced gravity are noted in the freely available introduction to my book so there is no good reason for not knowing of their existence. A simple Internet search would have found this information and I am sure there are many other sources as well.

The blog which mainly discussed the physics of how gravity might have changed on the Earth succeeds in completely avoiding mentioning that a smaller less massive Earth would have the same gravity calculated by the reduced gravity theory. It never wonders why this agrees with the reduced Earth diameter proposed by several geologists based on geological evidence. It even managers to avoid mentioning the Expanding Earth theory at all during the entire blog, mostly considering the easily dismissed alternative idea that the Earth was less dense and therefore larger in the past. It seems unclear why the blogger thinks the density of the Earth would change but unsurprisingly he finally dismisses his own proposal of a larger, less dense Earth. This simplistic argument is then used to claim surface gravity can't vary. My queries about this in his comments section, and the suggestion that a smaller less massive Earth is a more obvious conclusion, seemed to annoy him so greatly he deleted various parts of my comments while simultaneously claiming that he had proved that "there’s no evidence Earth changed size".

I find this devotion to popular science very hard to understand. Despite their own claim that these blogs are discussing ancient gravity in detail they noticeably fail to do so. It's as though they have no personal curiosity about the world and believe no one else should be allowed to explore new ideas either. Perhaps they just feel safer maintaining the popular science viewpoint instead of examining the true nature of reality.

Another blog by Matthew Francis finally pondered why it was so obvious to him that he "could state with confidence that gravity didn’t change much in the last 100 million years." [10]  Strangely I'm also left wondering exactly the same thing.

Further Reading

Jose Canseco Just Explained Gravity to the Internet Gawker.com
No, Jose Canseco, ‘ancient gravity’ did not create the dinosaurs Gawker.com
My Beloved Brontosaurus: On the Road with Old Bones, New Science, and Our Favorite Dinosaurs by Brian Switek
Dinosaur Reproduction, Not Ancient Gravity, Allowed Super-Sized Sauropods to Evolve by Brian Switek
Occam's razor here
Was weaker gravity responsible for large dinosaur size? by Matthew Francis
The Earth Expansion Evidence: A Challenge for Geology, Geophysics and Astronomy. Selected Contributions to the Interdisciplinary Workshop held in Erice, Sicily, Italy, 4-9 October 2011 at the Ettore Majorana Foundation and Centre For Scientific Culture here, here & here
Official Site of Jose Canseco
Of Barosaurus and Blood Pressure by Brian Switek
Learning science communication from baseball players by Matthew Francis

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Updated 24May13