An asteroid killed dinosaurs in spring, which might explain why mammals survived
arstechnica.com
arstechnica.com
"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."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
FYI we call it autumn.
https://www.worldatlas.com/articles/which-hemisphere-has-the...
Springtime for mammals and marsupials Winter for dinos and fish Springtime for mammals and marsupials Come on humans, you've got your wish
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.
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.
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.
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.
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?
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.
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.
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.
This would not explain the myriad other, much smaller species that also perished, not to mention all of the marine animals.
> 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.
https://dl.icdst.org/pdfs/files2/abe347ca228406be4720d5554a6...
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.