Faint young Sun problem and variable physical constants

Abstract

ABSTRACT The faint young Sun problem has been of great concern to astrophysicists and paleoclimatologists at least for the past five decades. Solar evolution models predict that the luminosity of the Sun 4.6 billion yr ago was less than 75 per cent of what it is today. This would mean that all water on Earth was frozen, and thus life could not have evolved as we know it. We attempt to show here that the variable physical constants (VPCs) approach, wherein constants are treated as scalar fields, could naturally resolve the problem. We use an analytical model that predicts the solar luminosity to be lower in the past to show that by properly including the VPCs in the model, the faint young Sun problem is mostly resolved: The young Sun flux intercepted by Earth was only 6 per cent lower 4.6 Gyr ago than it is today. We introduce the concept of cosmological and local energies in the context of VPC scalar fields, which is compliant with general relativity and cosmology: The cosmological energy is not available for conversion into thermal and radiative energies, whereas the local energy is.