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NUTRITIONAL DEATH HYPOTHESIS. “Why did the dinosaurs become extinct? Could cholecalciferol (vitamin D3) deficiency be the answer? (2019), by D. R. Fraser PhD, of the Sydney School of Veterinary Science, Australia. He took his PhD at Cambridge where he worked for nearly a decade in the MRC Dunn Nutritional labs, and presents a very interesting nutritional theory. https://lnkd.in/exW_KUxm View in LinkedIn

SUNLIGHT AS THE SOURCE. “The food of most animals contains, at most, only traces of cholecalciferol. An adequate supply of cholecalciferol can therefore only be obtained by exposure of skin to UVB radiation from the sun.” https://lnkd.in/e5hTuW74 View in LinkedIn

UNSOLVED QUESTIONS. However, paleontologists have rarely considered the biological or metabolic impact of a meteor and exactly how the dinosaurs might have died, especially those distant from a physical cause of death such as a tsunami. Most theories assume that the dust cloud caused plants to die off and reduce the dinosaur food sources. https://lnkd.in/e5hTuW74 View in LinkedIn

SKIN CONCENTRATION. “In other cells, its concentration is very low because of rapid conversion to cholesterol. Cholecalciferol is more popularly known as vitamin D3 but under natural conditions it is not a nutrient.” https://lnkd.in/e5hTuW74 View in LinkedIn

VITAMIN D METABOLISM. “A characteristic of animals that depend on solar UVB radiation to supply cholecalciferol is that its precursor, 7-dehydrocholesterol, the penultimate metabolite in the synthesis of cholesterol, accumulates in superficial skin cells.” https://lnkd.in/e5hTuW74 View in LinkedIn

INHOMOGENEITY. “Particle interactions can lead to primordial and/or evolutionary deviations from vanilla CDM. Primordial effects modify the evolution of density perturbations, and hence, for instance, the initial halo mass function.” (CDM = Cold Dark MatterCold dark matter). https://lnkd.in/e6ifiQMn View in LinkedIn

HALO SAUSAGE “A significant fraction of the halo near the Sun is in the Gaia-Enceladus/sausage, which is the aftermath of a major merger with a M ∼ 108 M⊙ dwarf galaxy (8−10) Gyr ago. The name arises from the fact the stellar component has radially biased orbits, and hence the distribution of vr is sausage like.” (M⊙ = solar mass units). https://lnkd.in/e6ifiQMn View in LinkedIn

COSMIC GEOMETRY. “It’s hard to measure the inner slope of the MW’s density profile, as baryons dominate at small radii. The large measured microlensing optical depth towards the Galactic centre implies large stellar densities in the inner MW, which appears to be in tension with the high DM densities at small radii of ‘cuspy’ density profiles.” (MW = Milky Way; DM = dark matter). https://lnkd.in/e6ifiQMn View in LinkedIn

DOMINANT ERRORS. “It should also be noted that there isn’t a rigid divide between theory/simulations and observations; modelling is required to interpret observations and the statistical errors are often now so small that systematic errors are significant, or even dominant.” https://lnkd.in/e6ifiQMn View in LinkedIn

OUR CORNER OF THE ‘VERSE. “There has been huge progress in understanding the properties and history of the MW in recent years thanks to the Gaia satellite. Gaia is an ongoing ESA space astrometry mission (2013-2022+?), measuring the positions, parallaxes and proper motions (change in apparent position) of > 1 billion stars in the MW (∼ 1% of the total number of stars). (MW = Milky Way). https://lnkd.in/e6ifiQMn View in LinkedIn