In 1917, Albert Einstein originally included a cosmological constant in his field equations of general relativity in order to achieve a steady-state static Universe. Shortly after Edwin Hubble’s discovery of the expanding Universe in 1929, Einstein removed the cosmological constant, calling it the “greatest blunder of my life”. In the late 1990s, astronomers measured the distances to extremely distant exploding supernovae and discovered that the Universe is actually accelerating (not just expanding), and therefore reintroduced the extra dark energy vacuum term in the cosmological equations.
A 2018 Hubble Space Telescope finding confirmed a nagging discrepancy about the Hubble Constant –the rate at which the Universe is expanding–showing the universe to be expanding faster now than was expected from its trajectory seen shortly after the big bang. Researchers hinted that there may be new physics to explain the inconsistency known as the ‘Hubble Tension’ “The community is really grappling with understanding the meaning of this discrepancy,” said lead researcher and Nobel Laureate Adam Riess of the Space Telescope Science Institute (STScI) and Johns Hopkins University.
An enormous amount of gravity from a cluster of distant galaxies causes space to curve so much that light from more distant galaxies is bent. This “gravitational lensing” effect has allowed University of Copenhagen astronomers to observe the same exploding star –SN Requiem–in three different places in the heavens, and may help solve the mystery of cosmic expansion and reveal the nature of dark matter and dark energy.
Welcome to the biggest mystery in physics: one of the great known unknowns of the universe is the nature of dark energy, an antigravitaional force field making the universe expand faster. Current theories range from end-of-the universe scenarios to dark energy as the manifestation of advanced intelligent life. It is the proverbial elephant in the “cosmic” room. (more…)