High obliquity, high angular momentum Earth as Moon’s origin revisited by Advanced Kinematic Model of Earth-Moon System

Matija Cuk et.al (2016) have proposed a new model for the birth and tidal evolution of our natural satellite Moon, born from lunar accretion of impact generated terrestrial debris in the equatorial plane of high obliquity, high angular momentum Earth. This paper examines their findings critically in the light of Advanced Kinematic Model (AKM) which includes Earth’s obliquity(ɸ), Moon’s orbital plane inclination (α), Moon’s obliquity (β) and lunar’s orbit eccentricity (e). It is shown that AKM’s valid range of application is from 45RE to 60.33RE. The evolution of α, β, e is in correspondence with the simulation results of Matija Cuk et.al (2016) but evolution of Earth’s obliquity has a break at 45RE. According to AKM, earlier than 45RE Earth should achieve 0° obliquity in order to achieve the modern value of eco-friendly 23.44° obliquity. Cuk et al (2016) silent on this point. AKM stands vindicated because using protocol exchange algorithm http://doi.org/10.1038/protex.2019.017, AKM has successfully given precise theoretical formalism of Observed LOD curve for the last 1.2 Gy time span opening the way for early warning and forecasting methods for Earth-quake and sudden Volcanic eruptions. This paper gives us an algorithm to determine the short term and long term changes in Earth’s obliquity which is related to Weather and Climate Extremes. Hence this paper gives us the mathematical tool for predicting the Earth’s climate extreme.

A mass threshold for galactic gas discs by spin flips

ABSTRACT We predict, analytically and by simulations, that gas discs tend to survive only in haloes above a threshold mass ∼2 × 1011 M⊙ (stellar mass ∼109 M⊙), with only a weak redshift dependence. At lower masses, the disc spins typically flip in less than an orbital time due to mergers associated with a change in the pattern of the feeding cosmic-web streams. This threshold arises from the halo merger rate when accounting for the mass dependence of the ratio of galactic baryons and halo mass. Above the threshold, wet compactions lead to massive central nuggets that allow the longevity of extended clumpy gas rings. Supernova feedback has a major role in disrupting discs below the critical mass, by driving the stellar-to-halo mass ratio that affects the merger rate, by stirring up turbulence and suppressing high-angular-momentum gas supply, and by confining major compactions to the critical mass. Our predictions seem consistent with current observed fractions of gas discs, to be explored by future observations that will resolve galaxies below 109 M⊙ at high redshifts, e.g. by JWST.