New observations confirm Einstein’s theory of gravity and lend support to the existence of dark matter.
By now, the news that Einstein has been proven right can at best elicit a yawn. Every few months a new set of observations or an experiment is pitched as another confirmation of his insights into the nature of our universe. But the latest such report comes with an added bonus of shooting down alternate theories of gravity and goes on to suggest that the conjectured dark matter invisible to astronomers, but observable only through its gravitational effects, actually seems to lurk in the universe.
An analysis of more than 70,000 galaxies by University of California, Berkeley, University of Zurich and Princeton University physicists demonstrates that Einstein’s theory remains our best bet for understanding what happens at a cosmological level, at magnitudes billions of times larger than our Solar System. To understand the analysis, it is necessary to go back to how Einstein saw gravity. According to his theory, mass distorts the very fabric of space-time, so light travelling near a large mass travels a longer path than light near a smaller mass because of this distortion. As astronomers have peered deeper and deeper into space, they have been forced to postulate a mysterious dark matter to explain the distortion they observe. Discomfort with this dark matter has led scientists to propose alternate forms of gravity that do away with dark matter yet explain the distortions visible to astronomers.
The latest analysis chose to examine these contesting theories by measuring a ratio termed EG. The ratio was used to factor out distortions involved in carrying out measurements of distant galaxies. The observed value turns out to be 0.39 while Einstein’s theory predicts a value of 0.40, much closer than the prediction of any other model. While this does not tell us what dark matter is, it does suggest that it may not be a figment of some theoretician’s imagination.
Hartosh Singh Bal turned from the difficulty of doing mathematics to the ease of writing on politics. Unlike mathematics all this requires is being less wrong than most others who dwell on the subject.