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Do laws of gravity really need dark matter?

New research has suggested that the Mond postulate explains gravity with much more precision than the standard Newtonian Theory

Mond's main postulate is that gravity begins to behave differently from Newtonian physics when it becomes extremely weak, as happens at the edge of galaxies (Photo by Arnaud Mariat, Unsplash)

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Among the many wonders of outer space exists dark matter – a curious and baffling phenomenon that has drawn vast amounts of scientific research. But what exactly is dark matter? 

Numerous techniques exist for observing distant substances and material by scientists. While other technology, like radio telescopes, measures non-visual events, equipment like the well-known Hubble telescope measures visible light. In order to make the most sense of what they are seeing, scientists frequently spend years accumulating data and then going through it to be analysed.

Also read: Scientists find out more on universe's most energetic objects

Using Newton's rules of physics, we can simulate the motions of the planets in the Solar System pretty precisely. But in the early 1970s, researchers discovered that this was incorrect because stars in disc galaxies, which are far from the gravitational pull of all the mass in their centres, were moving considerably more quickly than expected by Newton's theory.

This led physicists to postulate that extra gravitational attraction from "dark matter," an invisible substance, was forcing the stars to accelerate. This idea has now gained enormous popularity. 

Although it has never been seen, astronomers believe that it accounts for 85% of the universe's matter. So, in a nutshell, no one is aware of what dark matter is.

The majority of large-scale events are fairly adequately explained by Newton's Theory of Gravity. The theory is not foolproof, though. But because Newton's theory has considerably simpler equations and works in the vast majority of situations, scientists continue to use it.

However, new research by researcher Indranil Banik and his colleagues at the University of St. Andrews has found that observations across a vast range of scales are much better explained by an alternative theory by the Israeli physicist Mordehai Milgrom in 1982 called ‘Milgromian dynamics’ or Mond – a theory devoid of invisible substances.

Mond's main postulate is that gravity begins to behave differently from Newtonian physics when it becomes extremely weak, as happens at the edge of galaxies. This explains why stars, planets, and gas near the periphery of over 150 galaxies rotate more quickly than would be predicted from just their apparent mass.

Also read: Life beyond Earth | Why do we seek planets outside the solar system?

His hypothesis predicts galaxy behaviour rather than just explaining it. Theories have the drawback of being able to explain almost anything. A recent article in Sci-Tech Daily explained, that an example of said drawback would be the multiple possibilities and notions one can come up with when one enters a fully lit room; it could be because the cosmic rays from the sun are reflecting off the surfaces of hidden mirrors in the room or that someone turned the light switch on.

Examining which theory makes more accurate predictions is one approach to distinguishing between good and bad theories. And the Mond postulate does exactly that - makes more accurate predictions. So, while dark matter can adequately describe the behaviour of galaxies, it is a less accurate theory in this area.

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