It is a pretty clever trick to figure out how old many of the water molecules on Earth are as this paper does.
Water is crucial for the emergence and evolution of life on Earth. Recent studies of the water content in early forming planetary systems similar to our own show that water is an abundant and ubiquitous molecule, initially synthesized on the surfaces of tiny interstellar dust grains by the hydrogenation of frozen oxygen. Water then enters a cycle of sublimation/freezing throughout the successive phases of planetary system formation, namely, hot corinos and protoplanetary disks, eventually to be incorporated into planets, asteroids, and comets. The amount of heavy water measured on Earth and in early forming planetary systems suggests that a substantial fraction of terrestrial water was inherited from the very first phases of the Solar System formation and is 4.5 billion years old.
Cecilia Ceccarelli, Fujun Du, "We Drink Good 4.5-Billion-Year-Old Water" arXiv:2212.05441, 18 Elements 155 (December 11, 2022).
[Submitted on 16 Nov 2022]
ReplyDeleteCan General Relativity play a role in galactic dynamics?
Davide Astesiano, Matteo Luca Ruggiero
We use the gravitoelectromagnetic approach to the solutions of Einstein's equations in the weak-field and slow-motion approximation to investigate the impact of General Relativity on galactic dynamics. In particular, we focus on a particular class of the solutions for the gravitomagnetic field, and show that, contrary to what is expected, they may introduce non negligible corrections to the Newtonian velocity profile. The origin and the interpretation of these corrections are discussed and explicit applications to some galactic models are provided. These are the homogeneous solutions (HS) for the gravitomagnetic field, i.e. solutions with vanishing matter currents.
Comments: 7 pages, 2 figures, accepted for publication as a Letter in Physical Review D
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2211.11815 [gr-qc]
Deur would be proud
Deur doesn't rely on that argument. He is arguing the self-interaction of the gravitational field and not a gravitomagnetic field (GEM). Indeed, his analysis is done in a static approximation in which all gravitomagnetic effects are disregarded.
ReplyDeleteThere have but a number of GEM papers, and by and large, I think the critics of those papers have the strong argument although the issues are quite subtle as discussed in a Physics Forum thread on point.
There have *been* a number of GEM papers . . .
ReplyDeletewhy'd not combining self-interaction of the gravitational field and a gravitomagnetic field (GEM) together
ReplyDeleteGEM is too small to matter and works in a different way that is completely orthogonal to self-interaction.
ReplyDeleteGEM is too small to matter and works in a different way that is completely orthogonal to self-interaction.
ReplyDeletethat is what others on PF say about Deur