AUGUST 25, 2022
Our universe is expanding at an accelerating rate and no one is really sure why. This seemingly contradicts current scientific knowledge of how gravity works and how it affects the world we live in. The cause of this acceleration is called “dark energy,” and it remains a mystery. But NASA scientists are helping probe this enigma by testing gravity. According to the space agency, this phenomenon where the universe is expanding at an accelerating rate is almost as if you threw an apple in the air and it continued to move upwards, getting faster and faster.
The latest effort to understand whether this is all a misunderstanding comes from a new study from the Dark Energy Survey (DES). DES is an international collaborative effort that maps hundreds of millions of galaxies, detects thousands of supernovae and finds patterns of cosmic structure.
The new study uses the 4-metre Victo M Blanco Telescope in Chile to conduct what according to the space agency are the most precise tests yet of Albert Einstein’s theory of gravity at the cosmic scale. It finds that the current understanding appears to be correct. The results were presented at the International Conference on Particle Physics and Cosmology in Rio de Janeiro.
Einstein’s Theory of General Relativity was developed more than a century ago and describes gravity in a way that has so far accurately predicted various phenomena, including the existence of black holes. But, according to some scientists, there may be a need to modify some of its equations or add new components if it can’t explain dark energy.
To test that out, DES members looked for evidence that gravity’s strength has varied throughout the universe’s history or over distances. If that were the case, it would indicate that Einstein’s theory is incomplete, which would bring us closer to explaining the universe’s accelerating expansion.
In addition to the Blanco telescope, the members also examined data from ESA’s Planck satellite. But the study found out that Einstein’s theory still holds, meaning that there is still no explanation for dark energy.
In order to arrive at this conclusion, scientists needed to look deep into the universe’s past. They did this by looking at objects that are really far away. A light-year is about 9.5 trillion kilometres, or the distance that light can travel in a year. This means that an object one light-year away appears to as us as it was a year ago. That means that galaxies billions of light-years away appears to us as they were billions of years ago. The observations made by the scientist matched what is predicted by Einstein’s theory, once again leaving dark energy with no explanation.
This research will be furthered by two upcoming NASA missions. Euclid, slated for a 2023 launch and Nancy Grace Roman Space Telescope, scheduled for a 2027 launch. Both telescopes will help scientists look further back in time to further probe the presence of dark energy.