The universe is expanding at an accelerating rate, and scientists don’t know why. This phenomenon seems to contradict everything researchers understand about the effect of gravity on the cosmos: it’s like throwing an apple in the air and it keeps going up, faster and faster. The cause of the acceleration, dubbed dark energyremains a mystery.
A new study of the international Dark Energy Investigation, using the 4-meter Victor M. Blanco Telescope in Chile, marks the latest effort to determine whether it is simply a misunderstanding: that expectations about how gravity works on the scale of the entire universe are incorrect or incomplete. This potential misunderstanding could help scientists explain dark energy. But the study – one of the most accurate tests to date of Albert Einstein’s theory of gravity on a cosmic scale – reveals that the current understanding still seems correct.
The results, written by a group of scientists including some from NASA’s Jet Propulsion Laboratory, were presented on Wednesday August 23 at the International Conference on Particle Physics and Cosmology (COSMO’22) in Rio de Janeiro. The work helps set the stage for two upcoming space telescopes that will probe our understanding of gravity with even higher precision than the new study and perhaps finally solve the mystery..
More than a century ago, Albert Einstein developed his General relativity theory to describe gravity, and so far it has accurately predicted everything from the orbit of Mercury to the existence of black holes. But if this theory can’t explain dark energy, according to some scientists, then maybe they need to change some of its equations or add new components.
To find out if this is the case, members of the Dark Energy Survey looked for evidence that the strength of gravity has varied throughout the history of the universe or over cosmic distances. A positive discovery would indicate that Einstein’s theory is incomplete, which could help explain the accelerating expansion of the universe. They also looked at data from other telescopes besides Blanco, including the ESA (European Space Agency) Planck’s Satelliteand came to the same conclusion.
The study reveals that Einstein’s theory still works. So no explanation yet for dark energy. But this research will feed two future missions: that of the ESA Mission Euclid, slated for launch no earlier than 2023, which benefits from contributions from NASA; and NASA Nancy Grace Roman Space Telescopescheduled for launch no later than May 2027. Both telescopes will look for changes in the force of gravity over time or over distance.