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Synopsis

The modern standard cosmology ΛCDM describes almost perfectly the cosmic microwave background observations, but the resulting expansion rate of the universe (the Hubble parameter) is in serious disagreement with local measurements. This Hubble tension can perhaps be resolved by a brief episode of dark energy contributing about 10% of cosmic energy density for just a few thousand years about 50,000 years after the Big Bang.  This high-redshift Early Dark Energy (EDE) scenario can be tested at lower redshifts, since new N-body simulations show that EDE predicts earlier structure formation than ΛCDM, for example 50% more clusters at redshift z âˆ¼ 1 and 10x more galaxies at z ~ 10. Such predictions are being tested by new observations, including by James Webb Space Telescope.  JWST’s infrared capabilities allow its cameras to see starlight from even the highest-redshift galaxies.  JWST’s better resolution than Hubble Space Telescope is also revealing  new aspects of galaxy and planet formation.  Earth is a Goldilocks planet, in the Sun’s habitable zone and also with just the right amount of radioactive heating by thorium and uranium for a long-lived magnetic field and plate tectonics — both of which may be necessary for the evolution of complex life. Such Goldilocks exoplanets, taking into account the abundance of Th and U deduced from the star’s spectrum, should be among the first planets to be searched by JWST for biosignatures.