I was going to say that the landmasses could have been pretty different back then. But I took a quick look and it looks like they were broadly in the same place with respect to N / S hemispheres.
And South America and Africa were still quite close together.. the Pacific is even bigger than it is now. Literally a whole half side of the planet filled with water
Ugh why does it keep turning on rotation when changing the dropdown!
I'm trying to fix on a single point and move backwards in time to see the change but it keeps rotating the global every time... weird default functionality.
edit: weird, now it seems to work fine. I was disabling the 'rotate global' but it wasn't taking effect before
"By contrast, many species in the Southern Hemisphere would have been preparing to hibernate for the winter as opposed to gearing up for their reproduction cycles. That may have contributed to the survival of those species—particularly mammals, certain amphibians, birds, and crocodiles—who were more likely to be sheltering in burrows or caves at the time of impact."
That's standard pop-sci title inflation. The article is about how evidence from analyzing fish buried in debris tsunamis indicates that the impact happened in Spring (in the Northern Hemisphere). That is a genuine contribution to understanding what happened. You're right that the hibernation thing is pretty speculative -- but it's also a falsifiable hypothesis that other evidence could shed light on later, so it's not like we shouldn't talk about it.
One thing that isn't talked about as much as it should be, there's a possibility that 65 million years ago during the time of the dinosaurs, the earth's atmosphere was very thick.
All these Dinosaurs with their extremely long necks and bodies couldn't support their own weight if wandering around the earth today.
The mass extinction event may have occurred simply because the atmosphere changed and these giant beasts used to this exotic thick atmosphere could no longer support their own weight.
Are you suggesting that this is the cause of the extinction event, rather than an extraterrestrial impact? Or something more like the impact may have caused a significant change in atmospheric composition?
This would not explain the myriad other, much smaller species that also perished, not to mention all of the marine animals.
I'm not great at evaluating the quality of Journals (Chemical Industry and Chemical Engineering Quarterly is at least peer reviewed), but that article has been cited 0 times, and its abstract reads like a YouTube video trying to convince me Bush did 9/11.
> how can a giant dinosaur such as an apatosaur pump blood up to its brain (more than 13 m above its heart) when animal energetics and physics say that in no way can it do it. Do we have to change the laws of physics and biology? I don’t think so.
The "Science says it's impossible! Either we have to change the laws of science, or <my one pet alternative theory out of 10 million other alternatives> must be true!" is just really characteristic of that style.
We don't have soft tissue or a specific understanding of internal organs. Maybe they had multiple hearts with multiple vascular systems, or maybe the rate of blood flow and chemistry of energy production differed from animals we do understand. All we know for sure is that the brontosaurus was way too big for its biology to be understood by similarity to any extant creatures.
Maybe we'll be able to simulate dna, protein, and evolution at some point such that we can sample huge spaces to see if we can reconstruct creatures with similar features.
Also basic density calculations doesn’t favor the theory.
Even at 100bar, even with some weird composition difference (but not completely bizarre like sulphur hexaflouride) the atmosphere is on the order of 10-20kg/m^3.
Even with the most implausible ‘what a dinosaur is made of’ theories I can come up with, unless the larger dinosaurs were born carrying around 100+ m^3 balloons full of helium, it doesn’t seem doable. There literally isn’t enough space in them to have enough sacs of lighter than air gas for that to make sense.
Can't believe the downvoting. There's several major issues with the current dinosaur theory RN.
Four areas of scientific incongruities regarding these animals’ large size are 1) insufficient muscle strength, 2) insufficient bone strength, 3) unacceptably high blood pressure within the tallest dinosaurs, and 4) the paradox of pterosaurs having grossly insufficient power to fly in atmospheric conditions similar to the present
Today there are no reptiles capable of generating the power needed to fly, and yet during the Mesozoic era reptiles grew to be the largest flying animals that ever existed. The largest of these pterosaurs was the Quetzalcoatlus. It had a chest size as large as a horse and stood as tall as a giraffe ... [Y]et some paleontologists continue to insist that there is no scientific paradox regarding how the pterosaurs could have flown ... [P]terosaurs could not have flown in today’s atmospheric environment. The application of aerodynamic equations show pterosaurs falling far short of meeting the requirements for obtaining flight in today’s atmosphere, and the experimental efforts using RC models provide physical evidence confirming these conclusions. It should be alarming to all scientists and science educators that some paleontologists continue to claim that they understand how pterosaurs flew when the evidence is so overwhelming in refuting their claim ...
Most of those incongruities were solved as soon as people stopped trying to model dinosaurs after lizards. The pterosaurs one was solved when they stopped modeling them after birds.
I'm not sure the blood pressure one was solved, but given we have current animals with features that could solve their problem, it's not too much to expect that it's not a fundamental problem and we will find how it was solved when we get a detailed enough picture of their necks.
This is HN, please cite your sources. For example, the sentence starting "Today there are no reptiles..." comes from this website [0], which is run by somebody who freely admits that he's not a paleontologist and who sure seems to have some fairly...unusual views on biology.
The examples you listed, the giant Sloth, the Mastodon, and the giant Armadillo are all actually smaller than a modern elephant so you're not really making your point with those links.
The giant sauropods are thought to have been 10 times heavier than an Elephant.
Ten times heavier! That's enormous.
And the wandering albatross you linked to is said to have existed 50 million years ago in the article.
Wikipedia has entire section on Quetzalcoatlus and hypotheses around if and hoe it could fly. The consensus seems to be that it’s possible (with no mention of a denser atmosphere as a precondition or even a factor) just depending on how the musculature is modeled around its skeleton.
I've heard that oxygen levels are lower now than they have been in the past (this seems to change a lot on geological timescales), and that high oxygen levels may help allow megafauna's existence. I wouldn't think it's so much the buoyancy as it is about all the other biological machinery that can operate more efficiently at higher oxygen levels. Oxygen levels are largely driven by algae and plant levels, which of course could have been dramatically affected by the impact.
It's also possible you'd be better received espousing an alternative to conventional science if your handle didn't sound like a reference to Flat Earth Theory.
The cretaceous atmosphere had a higher oxygen concentration (roughly 50% more oxygen than today). It was denser, but the idea that it provided structural support for large animals is ridiculous. Part of the reason animals could be larger then (from "giant" insects to genuinely-giant dinosaurs) is that the extra oxygen meant smaller lungs (or better absorption for non-lung-havers) required to support higher energy use. It isn't because the atmosphere literally stopped them from falling down. It's still a gas, and gravity hasn't changed.
Hah, while that could help a bird (if ACTUALLY 10 bar, which is insanely high - 145 psi, compared to 14ish now), it wouldn’t help as much as you would think. At STP, air is 1.3kg per cubic meter, and at 10 bar, it’s still only 11kg per cubic meter. Water is 1000kg/cubic meter.
So yeah you could get some bigger birds, but t-Rex or brontosaurus weren’t meaningfully supported by the atmosphere in such a scenario even if they had some kind of lifting bladder, which no one has seen any fossil evidence of anyway.
The amount of additional mass required to have a 100 bar atmosphere instead of 1 bar is rather incredible, and there is so far no plausible method known for such mass to disappear.
If it was somehow subducted, then hey maybe. But we also don’t know of any way for that to occur right now.
>> The amount of additional mass required to have a 100 bar atmosphere instead of 1 bar is rather incredible, and there is so far no plausible method known for such mass to disappear.
Earth's atmosphere is constantly being blown away by solar wind[1]. I guess after 65 millions years this would add up. But I'm still not convinced if it's possible to loose enough air this way to lower pressure 100 times.
If 'several hundred' is, say 500 tons (not sure which definition of ton exactly there, but we'll go with the biggest one of 2240 (or a metric long ton - 1016kg).
That would put it at 508,000kg/day (or 5.08 x 10^5 kg)
If there are 365 days in a year, and 65 million years, we're talking 23.7 billion days (give or take).
So roughly, if the 'high end' estimate was always the case (who knows), and has been happening every day since 65 million years ago, we'll have lost 1.2 x 10^16 kg of atmosphere. Which is a lot of gas.
They estimate the total current mass at approximately 5.1352 ± 0.0003 × 10^18 kg
With yearly shifts in mass due to water vapor on the order of 1.2 to 1.5 × 10^15 kg.
As large as the amount of gas that has boiled off (making those assumptions), and if my math is correct, the total amount of gas is 2 orders of magnitude larger. Doing some random scribbling, I THINK it would add up to .2% of the total CURRENT amount of dry air in the atmosphere.
A thicker atmosphere would provide more static lift, but flapping wings in thicker atmosphere would require larger muscles and use more energy. There are scholarly writings out there on this topic, but I'm not familiar enough with any of them to have an opinion. I know there's a school that argues pterosaurs couldn't fly today solely due to lower atmospheric density, and a school that argues they could. I think the lower oxygen levels would still be the primary barrier due to energy requirements.
Pressurized gas can act like a liquid. And at sea level, thick atmosphere would certainly be pressurized.
smaller lungs aren't relevant to the issue that comes up regarding extremely large dinosaurs.
Because it's not an issue of lung capacity, or oxygen supply per liter of blood.
We're not talking about animals that are comparable to modern day elephants.
Have you seen the size comparisons of dreadnoughtus to blue whales? They are enormous. The physics start to come into question. Just the sheer weight of skin and muscle hanging on bone. Even if the bones are hallow and even if the muscle is somehow more efficient due to increased oxygen in the blood.
Like a whale plopped on dry land, they'd collapse under their own weight standing up. Much less, hunting, mating, and fighting.
furthermore the thick atmosphere theory helps solve another tricky mystery which is the, Mesozoic Paleoclimate Paradox
During the Mesozoic era a remarkably homogeneous flora of tropical and temperate plant species covered the Earth. Plants such as ferns, laurels, palm trees, and Magnolia that could not withstand freezing, thrived at 70 degrees north and south latitude. Many of the same plants that existed near the equator were also thriving at the Polar Regions of the Earth.
For decades paleoclimatologists have tried to explain the Mesozoic paleoclimate paradox. If they matched the vegetation of the lower and middle latitudes then their climate models were too cold at the higher latitudes. If they matched the warm temperatures of the Polar Regions then their models projected an unrealistic hot sauna for the rest of the planet that again conflicts with the geological evidence.
The reason their climate software models fail to match the Mesozoic climate is because perhaps the paleoclimatologists make the incorrect assumption that the Mesozoic atmosphere was the same thickness as the present. As stated earlier, the variation of temperatures around a planet whether it is day or night or according to latitude, is a function of the thickness of a planet’s atmosphere. Planets or moons with no atmosphere will have the most extreme difference in temperatures, planets such as the present day Earth and Mars that have relatively thin atmosphere will still have these differenced in temperatures but much less extreme, while extreme thick atmosphere planets such as Venus and the Mesozoic Earth show almost no temperature difference at all according to latitude.
Bible scholars generally favor the idea that the expanse mentioned in Genesis - a heavy atmosphere of water vapor that is said to have given the entire earth a tropical climate - could have had a significant effect on atmospheric density, which I personally find an interesting correlation when discussing this topic.
Combined with the snap frozen mammoth hypothesis, it's interesting to think that if there were a heavy atmosphere of liquid, and it suddenly fell, it could explain why dinosaurs are non-feasible in todays atmosphere, why a sudden change in atmospheric density could be possible, the paradox of a whole-earth tropic, the snap frozen mammoths, and also the sudden extinction of large land animals such as dinosaurs.
(Anecdotally, a question I wonder: is it feasible that humans would live longer in higher pressures and lower UV levels, such as to 900 years?)
This is completely absurd. The density of air is about 1/1000th the density of body tissue. The effect you are talking about there is negligible, and would remain so even if the atmosphere doubled in mass (hell, if it increased by a factor of 10).
> Some 66 million years ago, a catastrophic event wiped out three-quarters of all plant and animal species on Earth, most notably taking down the dinosaurs. The puzzle of why so many species perished while others survived has long intrigued scientists.
More importantly, it means that even if we annihilate our specie because of our stupidity, life has great chances going on and in millions of years perhaps, the earth might be governed by another intelligent specie.
> Simple computer models initially suggested this disaster could render our planet inhospitable in as little as 150 million years from now. But late last year the journal Nature published a much more sophisticated simulation by a team from the Laboratory for Dynamic Meteorology in Paris, and this suggests we have got at least a billion years before this apocalypse.
That's an interesting thought, when you think about long term survival of a species, how much does all this technology help?
If you think about humans surviving the same asteroid impact that killed the dinosaurs, I think we would have a good chance, some people would stay in underground bunkers and eventually repopulate the Earth, but the majority of the population would probably die, and a lot of technological progress would be lost.
For long term survival you need to get off your planet, for which you probably need intelligence. Earth has around half a billion years left until it starts feeling serious issues with our sun. If our evolution took something like 10 percent longer things would be tricky
We could easily seed the rest of the solar system and even a few nearby other solar systems with basic archaea and what not capable of surviving on any large object with water, at least guaranteeing some form of life escapes the death of Earth. It takes intelligence to figure out how to do this, but we have enough intelligence and the means to do it right now, but we aren't since we're largely concerned specifically with human survival, and humans are much harder to keep alive and transport through space.
Or become a bacteria that has a really great chance at surviving in space and have your planet get hit by an asteroid. You go up in debris and colonize the galaxy over millions of years
Anyway, even if that always happens, that seems a bit too large a hill for evolution to notice it's not a global peak and route around. Unguided genetic evolution is scarily efficient, but not that much.
(Funny thing that memetic evolution may be able to make that decision, but if you are right, it's the problem by itself, so it couldn't fix it.)
The article says they analyzed sturgeon fossils that died in the impact, and they found they were in the growth phase typical of their reproductive season, so they don't know the year, but they know the season. The article is quite a read.
The author’s “brand” seems to be dayglo pink hair.
Scientists, these days, can sport a different attitude, compared to the horn-rimmed-glasses-and-elbow-patched-tweed of the stereotypical “scientist,” of popular culture.
I always get a kick out of the mission control videos.
Sounds convincing. But I found a flaw. Typically birds take their winter holidays in the warm continents, they don't shelter in caves. So birds would have gone extinct also. But they didn't.
So maybe they did shelter in caves, such as bats do, and then later decided it would be more appropriate to spend their winter holidays at the French Riviera or Cancun and not in their caves anymore. Because the bats messed up all those places. A stretch
Interesting. Are you planning to alert the journal that published the paper discussed in the article of this stunningly obvious error? It’s very frustrating that every journal doesn’t keep an HN commenter on staff so boneheaded blunders like this don’t continue to slip through.
86 comments
[ 246 ms ] story [ 427 ms ] threadhttps://dinosaurpictures.org/ancient-earth#66
It still looks like that today! A host of images showing it:
https://www.google.com/search?q=view+of+earth+pacific+ocean&...
The location [0] may be a little surprising. The shared view above is deceptive due to the land at the edges.
[0] https://en.m.wikipedia.org/wiki/Land_and_water_hemispheres#/...
Interesting. Not sure where you got that 85% figure though:
>> even in the land hemisphere, the water area still slightly exceeds the land area (with 53 percent water to 47 percent land)
I'm trying to fix on a single point and move backwards in time to see the change but it keeps rotating the global every time... weird default functionality.
edit: weird, now it seems to work fine. I was disabling the 'rotate global' but it wasn't taking effect before
https://www.worldatlas.com/articles/which-hemisphere-has-the...
FYI we call it autumn.
Springtime for mammals and marsupials Winter for dinos and fish Springtime for mammals and marsupials Come on humans, you've got your wish
All these Dinosaurs with their extremely long necks and bodies couldn't support their own weight if wandering around the earth today.
The mass extinction event may have occurred simply because the atmosphere changed and these giant beasts used to this exotic thick atmosphere could no longer support their own weight.
This would not explain the myriad other, much smaller species that also perished, not to mention all of the marine animals.
https://dl.icdst.org/pdfs/files2/abe347ca228406be4720d5554a6...
> how can a giant dinosaur such as an apatosaur pump blood up to its brain (more than 13 m above its heart) when animal energetics and physics say that in no way can it do it. Do we have to change the laws of physics and biology? I don’t think so.
The "Science says it's impossible! Either we have to change the laws of science, or <my one pet alternative theory out of 10 million other alternatives> must be true!" is just really characteristic of that style.
Maybe we'll be able to simulate dna, protein, and evolution at some point such that we can sample huge spaces to see if we can reconstruct creatures with similar features.
That would require structures in the animal kept at below ambient pressure. e.g. heated air sacs
Even at 100bar, even with some weird composition difference (but not completely bizarre like sulphur hexaflouride) the atmosphere is on the order of 10-20kg/m^3.
Even with the most implausible ‘what a dinosaur is made of’ theories I can come up with, unless the larger dinosaurs were born carrying around 100+ m^3 balloons full of helium, it doesn’t seem doable. There literally isn’t enough space in them to have enough sacs of lighter than air gas for that to make sense.
Four areas of scientific incongruities regarding these animals’ large size are 1) insufficient muscle strength, 2) insufficient bone strength, 3) unacceptably high blood pressure within the tallest dinosaurs, and 4) the paradox of pterosaurs having grossly insufficient power to fly in atmospheric conditions similar to the present
Today there are no reptiles capable of generating the power needed to fly, and yet during the Mesozoic era reptiles grew to be the largest flying animals that ever existed. The largest of these pterosaurs was the Quetzalcoatlus. It had a chest size as large as a horse and stood as tall as a giraffe ... [Y]et some paleontologists continue to insist that there is no scientific paradox regarding how the pterosaurs could have flown ... [P]terosaurs could not have flown in today’s atmospheric environment. The application of aerodynamic equations show pterosaurs falling far short of meeting the requirements for obtaining flight in today’s atmosphere, and the experimental efforts using RC models provide physical evidence confirming these conclusions. It should be alarming to all scientists and science educators that some paleontologists continue to claim that they understand how pterosaurs flew when the evidence is so overwhelming in refuting their claim ...
I'm not sure the blood pressure one was solved, but given we have current animals with features that could solve their problem, it's not too much to expect that it's not a fundamental problem and we will find how it was solved when we get a detailed enough picture of their necks.
[0] https://dinosaurtheory.com/flight.html
The giant ground sloth - https://en.wikipedia.org/wiki/Megatherium
Mastodons - https://en.wikipedia.org/wiki/Mastodon
Wandering Albatross - https://www.thehindu.com/sci-tech/energy-and-environment/ant...
Giant armadillos - https://en.wikipedia.org/wiki/Glyptodon
They aren't around because humans hunted them out. Except the albatross, those died out long ago.
The giant sauropods are thought to have been 10 times heavier than an Elephant.
Ten times heavier! That's enormous.
And the wandering albatross you linked to is said to have existed 50 million years ago in the article.
https://en.m.wikipedia.org/wiki/Quetzalcoatlus#Flight
It's also possible you'd be better received espousing an alternative to conventional science if your handle didn't sound like a reference to Flat Earth Theory.
Is there any evidence for or against the surface pressure of earth being higher in the past?
So yeah you could get some bigger birds, but t-Rex or brontosaurus weren’t meaningfully supported by the atmosphere in such a scenario even if they had some kind of lifting bladder, which no one has seen any fossil evidence of anyway.
The amount of additional mass required to have a 100 bar atmosphere instead of 1 bar is rather incredible, and there is so far no plausible method known for such mass to disappear.
If it was somehow subducted, then hey maybe. But we also don’t know of any way for that to occur right now.
Earth's atmosphere is constantly being blown away by solar wind[1]. I guess after 65 millions years this would add up. But I'm still not convinced if it's possible to loose enough air this way to lower pressure 100 times.
[1] https://www.sciencealert.com/earth-loses-hundreds-of-tons-at...
If there are 365 days in a year, and 65 million years, we're talking 23.7 billion days (give or take).
So roughly, if the 'high end' estimate was always the case (who knows), and has been happening every day since 65 million years ago, we'll have lost 1.2 x 10^16 kg of atmosphere. Which is a lot of gas.
But how much gas mass is in the atmosphere?
I ran across this interesting article/paper [https://journals.ametsoc.org/view/journals/clim/18/6/jcli-32...], which tries to quantify the dry mass and variations caused by water vapor.
They estimate the total current mass at approximately 5.1352 ± 0.0003 × 10^18 kg
With yearly shifts in mass due to water vapor on the order of 1.2 to 1.5 × 10^15 kg.
As large as the amount of gas that has boiled off (making those assumptions), and if my math is correct, the total amount of gas is 2 orders of magnitude larger. Doing some random scribbling, I THINK it would add up to .2% of the total CURRENT amount of dry air in the atmosphere.
So not enough to make any noticeable difference.
smaller lungs aren't relevant to the issue that comes up regarding extremely large dinosaurs.
Because it's not an issue of lung capacity, or oxygen supply per liter of blood.
We're not talking about animals that are comparable to modern day elephants.
Have you seen the size comparisons of dreadnoughtus to blue whales? They are enormous. The physics start to come into question. Just the sheer weight of skin and muscle hanging on bone. Even if the bones are hallow and even if the muscle is somehow more efficient due to increased oxygen in the blood.
Like a whale plopped on dry land, they'd collapse under their own weight standing up. Much less, hunting, mating, and fighting.
furthermore the thick atmosphere theory helps solve another tricky mystery which is the, Mesozoic Paleoclimate Paradox
During the Mesozoic era a remarkably homogeneous flora of tropical and temperate plant species covered the Earth. Plants such as ferns, laurels, palm trees, and Magnolia that could not withstand freezing, thrived at 70 degrees north and south latitude. Many of the same plants that existed near the equator were also thriving at the Polar Regions of the Earth.
For decades paleoclimatologists have tried to explain the Mesozoic paleoclimate paradox. If they matched the vegetation of the lower and middle latitudes then their climate models were too cold at the higher latitudes. If they matched the warm temperatures of the Polar Regions then their models projected an unrealistic hot sauna for the rest of the planet that again conflicts with the geological evidence.
The reason their climate software models fail to match the Mesozoic climate is because perhaps the paleoclimatologists make the incorrect assumption that the Mesozoic atmosphere was the same thickness as the present. As stated earlier, the variation of temperatures around a planet whether it is day or night or according to latitude, is a function of the thickness of a planet’s atmosphere. Planets or moons with no atmosphere will have the most extreme difference in temperatures, planets such as the present day Earth and Mars that have relatively thin atmosphere will still have these differenced in temperatures but much less extreme, while extreme thick atmosphere planets such as Venus and the Mesozoic Earth show almost no temperature difference at all according to latitude.
Combined with the snap frozen mammoth hypothesis, it's interesting to think that if there were a heavy atmosphere of liquid, and it suddenly fell, it could explain why dinosaurs are non-feasible in todays atmosphere, why a sudden change in atmospheric density could be possible, the paradox of a whole-earth tropic, the snap frozen mammoths, and also the sudden extinction of large land animals such as dinosaurs.
(Anecdotally, a question I wonder: is it feasible that humans would live longer in higher pressures and lower UV levels, such as to 900 years?)
You could test this by spending the rest of your life in a diving suit: https://en.wikipedia.org/wiki/Atmospheric_diving_suit
let us know how it works out.
Just to be clear, you're talking about the buoyancy effect that a denser atmosphere provides to land animals?
More importantly, it means that even if we annihilate our specie because of our stupidity, life has great chances going on and in millions of years perhaps, the earth might be governed by another intelligent specie.
https://www.sciencefocus.com/planet-earth/when-will-earth-be...
> Simple computer models initially suggested this disaster could render our planet inhospitable in as little as 150 million years from now. But late last year the journal Nature published a much more sophisticated simulation by a team from the Laboratory for Dynamic Meteorology in Paris, and this suggests we have got at least a billion years before this apocalypse.
But the next is not far away, just a few light years. Maybe we'll see this in the next comedy . So far it's only in a Stanislaw Lem novel.
Anyway, even if that always happens, that seems a bit too large a hill for evolution to notice it's not a global peak and route around. Unguided genetic evolution is scarily efficient, but not that much.
(Funny thing that memetic evolution may be able to make that decision, but if you are right, it's the problem by itself, so it couldn't fix it.)
Go back to the drawing board.
I'm glad to see even serious scientists can have fun sometimes.
Scientists, these days, can sport a different attitude, compared to the horn-rimmed-glasses-and-elbow-patched-tweed of the stereotypical “scientist,” of popular culture.
I always get a kick out of the mission control videos.
So maybe they did shelter in caves, such as bats do, and then later decided it would be more appropriate to spend their winter holidays at the French Riviera or Cancun and not in their caves anymore. Because the bats messed up all those places. A stretch
Interesting. Are you planning to alert the journal that published the paper discussed in the article of this stunningly obvious error? It’s very frustrating that every journal doesn’t keep an HN commenter on staff so boneheaded blunders like this don’t continue to slip through.
https://en.wikipedia.org/wiki/Enantiornithes
https://www.youtube.com/watch?v=QGR5yOrChMA