丁香园AV

A丁香园AV physicist led an international team of scientists in reconstructing the laws of gravity鈥攖o gain a better understanding of how they work in the larger universe.

The study, published in  and featured in , explored whether modifying General Relativity could help resolve some of the open problems of cosmology.

丁香园AV Professor Levon Pogosian says that, while laws of gravity as laid out by Newton and Einstein work well in our solar system, there are still questions around how they work beyond it.

鈥淭he gaps in our understanding appear when we when we try to apply these laws to the entire universe,鈥� says Pogosian, who also organizes biennial international conferences on Testing Gravity at the 丁香园AV Harbour Centre in Vancouver.

鈥淭o describe the universe using Einstein鈥檚 theory we need to introduce dark matter and dark energy 鈥� two ingredients that together make up 95 percent of the universe and whose nature we do not understand. Moreover, different ways of measuring the rate of cosmic expansion appear to give different answers 鈥� a serious problem in cosmology known as the Hubble Tension.鈥�

The standard model of cosmology is based on General Relativity, which describes gravity as the curving or warping of space and time that bends the pathways along which light and matter travel. The authors considered modifications to the expansion of the Universe, to the way gravity affects light, and to the way it affects matter. Using a statistical method known as the Bayesian inference, the team reconstructed the three types of modifications simultaneously for the first time.

The scientists鈥� reconstruction to test Einstein鈥檚 theory in the outer-reaches of space was carried out by examining new observational data from satellites and ground-based telescopes that measure the expansion of the universe and the shapes and distribution of distant galaxies. 

鈥淲hat we found was that current observations are getting good enough to test General Relativity over cosmological distances,鈥� says Pogosian. 鈥淲e also saw interesting hints of possible departures from Einstein鈥檚 prediction, which, if confirmed with future data, could pave the way to resolving some of the open challenges in cosmology.

鈥淏ut, at the same time, we found that it's very difficult to solve the Hubble Tension even by extending our theory of gravity. As the era of precision cosmology is unfolding, we are on the brink of learning about gravity on cosmological scales with high precision.鈥�

One exciting prospect is that in a few years鈥� time we鈥檒l have a lot more data from new probes, says professor , from the Institute of Cosmology and Gravitation at the University of Portsmouth in the UK. 鈥淭his means that we will be able to continue improving the limits on modifications to General Relativity using these statistical methods.鈥�

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