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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 atmosph

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.

margalabargala 5y ago
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.
zardo 5y ago
I would love to see a scientific paper on the bouyant dinosaur theory.
- Flatcircle 5y ago
  lol, why the downvoting? I didn't say it was a fact, I said it was a possibility. https://dl.icdst.org/pdfs/files2/abe347ca228406be4720d5554a69b2a4.pdf https://dl.icdst.org/pdfs/files2/abe347ca228406be4720d5554a6...
- Flatcircle 5y ago
  https://www.researchgate.net/publication/26553081_Atmospheric_pressure_at_the_time_of_dinosaurs https://www.researchgate.net/publication/26553081_Atmospheri...
  - feoren 5y ago
    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.
    - robbedpeter 5y ago
      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.
  - zardo 5y ago
    Just skimming for what I was interested in, I don't see anything to suggest that a thicker atmosphere would provide support for a large land animal. That would require structures in the animal kept at below ambient pressure. e.g. heated air sacs
    - lazide 5y ago
      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.
Flatcircle 5y ago
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 ...
- marcosdumay 5y ago
  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.
- onychomys 5y ago
  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. [0] https://dinosaurtheory.com/flight.html https://dinosaurtheory.com/flight.html
- swagasaurus-rex 5y ago
feoren 5y ago
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.
- deleted 5y ago
  [deleted]
caymanjim 5y ago
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.
- londons_explore 5y ago
  But at say 10 bar of pressure, flight would be much easier... Is there any evidence for or against the surface pressure of earth being higher in the past?
  - lazide 5y ago
    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.
    - 988747 5y ago
      >> 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. [1] https://www.sciencealert.com/earth-loses-hundreds-of-tons-atmosphere-to-space-every-day https://www.sciencealert.com/earth-loses-hundreds-of-tons-at...
pfdietz 5y ago
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).

margalabargala 5y ago

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.

zardo 5y ago

I would love to see a scientific paper on the bouyant dinosaur theory.

Flatcircle 5y ago
lol, why the downvoting? I didn't say it was a fact, I said it was a possibility. https://dl.icdst.org/pdfs/files2/abe347ca228406be4720d5554a69b2a4.pdf https://dl.icdst.org/pdfs/files2/abe347ca228406be4720d5554a6...
Flatcircle 5y ago
https://www.researchgate.net/publication/26553081_Atmospheric_pressure_at_the_time_of_dinosaurs https://www.researchgate.net/publication/26553081_Atmospheri...
- feoren 5y ago
  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.
  - robbedpeter 5y ago
    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.
- zardo 5y ago
  Just skimming for what I was interested in, I don't see anything to suggest that a thicker atmosphere would provide support for a large land animal. That would require structures in the animal kept at below ambient pressure. e.g. heated air sacs
  - lazide 5y ago
    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.

Flatcircle 5y ago

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 ...

marcosdumay 5y ago
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.
onychomys 5y ago
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. [0] https://dinosaurtheory.com/flight.html https://dinosaurtheory.com/flight.html
swagasaurus-rex 5y ago

feoren 5y ago

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.

deleted 5y ago
[deleted]

caymanjim 5y ago

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.

londons_explore 5y ago
But at say 10 bar of pressure, flight would be much easier... Is there any evidence for or against the surface pressure of earth being higher in the past?
- lazide 5y ago
  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.
  - 988747 5y ago
    >> 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. [1] https://www.sciencealert.com/earth-loses-hundreds-of-tons-atmosphere-to-space-every-day https://www.sciencealert.com/earth-loses-hundreds-of-tons-at...

pfdietz 5y ago

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).