Analysis of the chemistry of dinosaur egg shells can reveal if the dinosaur was warm blooded (i.e. in a broad definition of "warm blooded" they had an internal body temperature consistently and significantly above that of the environment) or cold blooded.
Evolutionarily, dinosaurs are between reptiles (which are generally cold blooded) and birds (which are generally warm blooded), so there is no strong reason to favor one hypothesis over the other, particularly now that we known that many dinosaurs has something like feathers. The closest widely familiar bird, evolutionarily to the dinosaurs, is the chicken.
All dinosaur eggshells analyzed to date support the hypothesis that the dinosaurs involved were warm blooded, although some had more of a differential with respect to the environment than others.
The different dinosaurs varied in how much their body temperatures were higher than their environment. The Troodon samples were as much as 10 C warmer, while the Maiasaura were 15 C warmer. The Megaloolithus samples showed the smallest range of 3 C to 6 C warmer.
"What we found indicates that the ability to metabolically raise their temperatures above the environment was an early, evolved trait for dinosaurs," Dawson, the lead author of the study that published last week in the journal Science Advances, said in a news release.
Whether dinosaurs were cold or warm-blooded has been a long-running debate among paleontologists. A study from 2014 suggested they were neither, occupying a middle ground.Via CNN.
The 2014 study isn't necessarily inconsistent with this one, because it recognized the possibility of a middle ground between warm blooded and cold blooded, which the current study doesn't appear to (and may not have a way to distinguish).
to continue an earlier post
ReplyDelete" The problem with MOND
But Harvard University astronomer Avi Loeb isn’t convinced. He says that the physics of normal matter means it could not create the large-scale variations that astronomers see in the Cosmic Microwave Background. Radiation would smooth out small-scale disturbances in normal matter over time. But because dark matter doesn’t interact with radiation, it lets these variations grow from seeds to galaxies.
“The main issue with MOND is that it does not explain the evolution of the Universe from its initial conditions, as evident in the Cosmic Microwave Background (CMB) to the present day,” Loeb says. He adds: “If there was only ordinary matter in addition to the CMB and no dark matter (which by definition does not couple to light), then galaxy formation would not have happened at all.”
For his part, Kroupa admits their simulation still needs significant work before it can fully capture galaxy formation and evolution. At the moment, the MOND universe inside their computer can only capture the initial phase of galaxy formation. His team wants to build on the model until their galaxies can grow and evolve."
https://astronomy.com/news/2020/02/controversial-simulation-creates-galaxies-without-using-dark-matter
in response to your claims about Ethan Siegel,
Harvard University astronomer Avi Loeb also affirms that dark matter is the best explanation
I'm genuinely surprised it took until Feb 2020 for the first MOND computer simulation, as opposed to say in the 90s when dark matter was first done.
Avi wants to see if MOND simulations can explain ALL aspects of large scale structure, which both he and Ethan said dark matter is able to do, via computer simulation.
FYI. It would really be best if you keep comments to the post being discussed. I have a feature that points out new comment anywhere on this blog and won't miss it. It also makes it easier for other readers to follow the discussion and perhaps contribute.
ReplyDeleteThe reason the MOND simulations are so much harder to do is that they are so non-linear. The math is much more difficult.
There isn't a good reason to think that MOND which can reproduce dark matter phenomena at a galactic scale, wouldn't also do so at the structure formation cosmology scale. This simulation supports that conclusion. Certainly there is no evidence theoretical or simulation based that shows that dark matter particles are the only way to get large scale structure. Nobody disputes that ordinary matter with Newtonian gravity is not going to do it, but that isn't what is in dispute.
What Ethan and Avi are guilty of, however, is failing to recognize how much dark matter explanations get wrong at the galaxy scale and below, and also even in colliding clusters. Insisting on not taking MOND or other modified gravity theories seriously until it is proven in "ALL aspects of large scale structure" when the dark matter particle theories (CDM) that product the existing large scale structure results have been pretty definitively shown not to be the mechanism of dark matter phenomena at galaxy and cluster scales is just special pleading and bias towards a pet theory.
Ethan and Avi are also guilty of ignoring emerging problems with CDM in the early universe. Dark matter does not solve all cosmology issues. For example, the impossible early galaxy problem and the 21 cm signal of temperatures in the early universe are both cases of observations that are at odds with CDM predictions in serious ways.
ok, i thought like reddit once a post gets old that's it.
ReplyDeletewhich is why i post on your newest ones.
Ethan and Avi are both qualified astrophysicists with Avi at Harvard faculty.
"What Ethan and Avi are guilty of, however, is failing to recognize how much dark matter explanations get wrong at the galaxy scale and below,"
my intuition is MOND at the galaxy scale and below, some form of dark matter for CMB and large scale structures.
the MOND simulation was for galaxy formation shortly after big bang with simplification, is this right?
"The reason the MOND simulations are so much harder to do is that they are so non-linear. The math is much more difficult."
well now that's it been done, shouldn't there be rapid progress, given how powerful computers are now.
"Ethan and Avi are both qualified astrophysicists with Avi at Harvard faculty."
ReplyDeleteLots of esteemed academics are ignorant of what's going on in subspecialties of their own discipline. The academy doesn't favor generalists.
"well now that's it been done, shouldn't there be rapid progress, given how powerful computers are now."
Yes and no. We're making progress, but even less difficult simulations used for lambdaCDM are more art than science. All of them make immense spherical cow type approximations and getting fine grained enough takes far more computing power than we have. One reason to do a primarily galaxy scale simulation is not because MOND works well there, but because you can deal with smaller clumps of space and time and matter that way while still getting results in a management amount of time.
Another piece of shoddy work by Ethan: https://www.forbes.com/sites/startswithabang/2020/02/21/these-4-pieces-of-evidence-have-already-taken-us-beyond-the-big-bang/#750486087a0b
ReplyDelete