Is the Hubble crisis connected with the extinction of dinosaurs?

Abstract

It has recently been suggested that a gravitational transition of the effective Newton's constant $G_{\rm eff}$ by about 10%, taking place 50-150 Myrs ago, can lead to the resolution of both the Hubble crisis and the growth tension of the standard $\Lambda$CDM model. Hints for such an abrupt transition with weaker gravity at times before the transition, have recently been identified in Tully Fisher galactic mass-velocity data and also in Cepheid SnIa calibrator data. Here we use Monte-Carlo simulations to show that such a transition could significantly increase (by a factor of 3 or more) the number of long period comets (LPCs) impacting the solar system from the Oort cloud (semi-major axis of orbits $\gtrsim 10^4AU$). This increase is consistent with observational evidence from the terrestrial and lunar cratering rates indicating that the impact flux of kilometer sized objects increased by at least a factor of 2 over that last 100 Myrs compared to the long term average. This increase may also be connected with the Chicxulub impactor event that produced the Cretaceous-Tertiary (K-T) extinction of 75% of life on Earth (including dinosaurs) about 66 Myrs ago. We use Monte-Carlo simulations to show that for isotropic Oort cloud comet distribution with initially circular orbits, random velocity perturbations (induced eg by passing stars and/or galactic tidal effects), lead to a deformation of the orbits that increases significantly when $G_{\rm eff}$ increases. A 10% increase of $G_{\rm eff}$ leads to an increase in the probability of the comets to enter the loss cone and reach the planetary region (pericenter of less than 10AU) by a factor that ranges from 5% (for velocity perturbation much smaller than the comet initial velocity) to more than 300% (for total velocity perturbations comparable with the initial comet velocity).