Some physical constants are used to define units of measurement, so their values in those units of measurement is exact.
These include:
* Speed of light in vacuum c = 299 792 458 m s−1
* Planck constant h = 6.626 070 15 × 10−34 J s (or J/Hz)
* Electron charge magnitude = 1.602 176 634 × 10−19 C
* Electron-volt eV = 1.602 176 634 × 10 −19 J
* Avogadro constant NA = 6.022 140 76 × 1023 mol−1
* Boltzmann constant k = 1.380 649 × 10−23 J K-1
Other units have exact values in terms of other units, merely out of convenience:
* 0 º Celcius = 273.15 Kelvin
* Atmosphere = 760 Torr = 101 325 Pa
* Standard gravitational acceleration gN = 9.806 65 m s-2
The conversion factor for the inch indirectly defines all imperial/English system distance measurements in terms of the speed of light.
5 comments:
you might look at this and even blog
arXiv:2408.00358 [pdf, html, other]
Quasilocal Newtonian limit of general relativity and galactic dynamics
Marco Galoppo, David L. Wiltshire, Federico Re
Comments: 6 pages, 2 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph)
A new Newtonian limit of general relativity is established for stationary axisymmetric gravitationally bound differentially rotating matter distributions with internal pressure. The self-consistent coupling of quasilocal gravitational energy and angular momentum leads to a modified Poisson equation. The coupled equations of motion of the effective fluid elements are also modified, with quasilocal angular momentum and frame-dragging leading to novel dynamics. The solutions of the full system reproduce the phenonomenology of collisionless dark matter for disc galaxies, offering an explanation for their observed rotation curves. Halos of abundant cold dark matter particles are not required.
I did see it and bookmark it. It will get a closer look and may or may not be blogged.
On the units issue, I was working with a Scottish engineer on a (south) North Sea gas project and made reference to English units. He said, in an offended tone, "Those aren't English units - those are Christian units!"
I did see it and bookmark it. It will get a closer look and may or may not be blogged.
compare "A new Newtonian limit of general relativity is established for stationary axisymmetric gravitationally bound differentially rotating matter distributions with internal pressure. The self-consistent coupling of quasilocal gravitational energy and angular momentum leads to a modified Poisson equation. " with Deur
new species of humans
https://www.sciencedirect.com/science/article/abs/pii/S0047248423000908?via%3Dihub
Journal of Human Evolution
Volume 182, September 2023, 103411
Journal of Human Evolution
Morphological and morphometric analyses of a late Middle Pleistocene hominin mandible from Hualongdong, China
Author links open overlay panelXiujie Wu a, Shuwen Pei a, Yanjun Cai b, Haowen Tong a, Ziliang Zhang c, Yi Yan a d, Song Xing a, María Martinón-Torres e
, José María Bermúdez de Castro e, Wu Liu aShow more
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https://doi.org/10.1016/j.jhevol.2023.103411
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Abstract
Excavations in Hualongdong (HLD), East China, have yielded abundant hominin fossils dated to 300 ka. There is a nearly complete mandible that fits well with a partial cranium, and together they compose the skull labeled as HLD 6. Thus far, detailed morphological description and comparisons of the mandible have not been conducted. Here we present a comprehensive morphological, metric, and geometric morphometric assessment of this mandible and compare it with both adult and immature specimens of Pleistocene hominins and recent modern humans. Results indicate that the HLD 6 mandible exhibits a mosaic morphological pattern characterized by a robust corpus and relatively gracile symphysis and ramus. The moderately developed mental trigone and a clear anterior mandibular incurvation of the HLD 6 mandible are reminiscent of Late Pleistocene hominin and recent modern human morphology. However, the weak expression of all these features indicates that this mandible does not possess a true chin. Moreover, a suite of archaic features that resemble those of Middle Pleistocene hominins includes pronounced alveolar planum, superior transverse torus, thick corpus, a pronounced endocondyloid crest, and a well-developed medial pterygoid tubercle. The geometric morphometric analysis further confirms the mosaic pattern of the HLD 6 mandible. The combination of both archaic and modern human features identified in the HLD 6 mandible is unexpected, given its late Middle Pleistocene age and differs from approximately contemporaneous Homo members such as Xujiayao, Penghu, and Xiahe. This mosaic pattern has never been recorded in late Middle Pleistocene hominin fossil assemblages in East Asia. The HLD 6 mandible provides further support for the high morphological diversity during late Middle Pleistocene hominin evolution. With these findings, it is possible that modern human morphologies are present as early as 300 ka and earlier than the emergence of modern humans in East Asia.
Introduction
Over the last half a century, abundant late Middle Pleistocene hominin fossils have been found in China. For a long time, the mainstream narrative to explain hominin evolution in China has been lineal and uniform. These late Middle Pleistocene hominins have been named as early Homo sapiens or archaic H. sapiens. They were thought to be intermediate between Homo erectus and early modern humans, and the ancestors of modern humans in East Asia (Wu, 1990, 2006; Wu and Poirier, 1995). However, such an opinion has never been widely accepted.
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