﻿Plot Twist: Physicists Cancel Dark Matter & Create New Theory of Gravity
Sir Isaac Newton, one of the greatest scientists to have ever lived, has been
described as, “ the supreme genius and most enigmatic character in the history of science”.
He is known for his three greatest contributions : the nature of white light,
calculus and perhaps the most important of all— the Theory of Universal gravitation.
For years, this theory has been widely accepted as a pure fact, forming the base for many studies
and other related theories on the same. But now, physicists claim that it is
time to ditch Newton's theory, in favor of a new theory of gravity.
Welcome to Factnomenal and in today’s video we take a close look at the theory that
some physicists believe should replace our current
theory of gravity and why. ——————————————————————————————
Defining Gravity
Legend has it that in 1665, Sir Isaac Newton, an English physicist and mathematician,
observed an apple fall from a tree, prompting him to ask what is probably one of the most
important questions ever asked — why did the apple fall towards the ground?
Why not sideways or even upwards?
While he stayed at the family farm, between the years 1665-1666,
when the bubonic plague struck England, the chance observation in the family
apple orchard led him to discover that gravity is a universal force.
Not only did it apply to things like apples falling to the ground, but he
also applied the same theory to understand the planetary system, the moon, the sun and beyond.
He compared the straight path of the apple falling towards the ground,
to the curved path of a fired cannonball. He wondered what would happen if the cannonball
were to go faster and faster, coming to the conclusion that it would eventually
“fall” around the curve of the earth forever and never really hit the ground.
It is this “forever falling” motion that describes
the movement of the moon around the earth and the earth around the sun.
Thus was born the theory of gravity.
Though there had been others, who had thought about it way before him, Sir Isaac Newton was
the first person to ever create and publish a comprehensive theory of gravity that applied to
all objects, large and small. Being an excellent mathematician,
he applied mathematical equations to support the same, that were way ahead of its time.
Gravitation is the force of attraction that pulls any two bodies towards each other.
All objects in the universe attract each other with a certain amount of force,
some with a far greater force and some with a force that is either too weak or negligible.
According to Newton's law of gravitation,
“Every object in the universe attracts every other object,
such that the force exerted will be proportional to the product of the
masses and inverse of proportional to the square of the distance between the two”.
His thorough calculations and study showed that gravitational force is a central, universal,
mutual and mass-dependent force that is
independent of the medium and the surrounding environment.
Up until then, no other study on gravity or
explanation of planetary systems and orbits had ever been given.
So, even though there would be criticism and newer, better calculations of the same
theory in the years to come, from the likes of Albert Einstein for example,
until that happened, Newton's theory of gravitation was taken as gospel.
Problems with Newton's Theory
As groundbreaking and revolutionary as Newton's theory of
gravitation was, of course— it was far from perfect.
There were some inherent problems with his calculations which did leave some room for doubts.
With the help of Newton's laws of physics, we can easily model the motions of the planets in
the Solar System quite accurately. However, during the 1970s is when
scientists happen to hit a roadblock. They discovered that these laws didn’t
quite work when it came to disc galaxies. What was happening here is that the stars
at their outer edges were moving much faster than what was predicted by Newton's theory,
since they were so far from the gravitational force of all the matter at their center.
When it comes to the planet Mercury, it was observed that Newton's Laws
couldn’t quite predict its motion accurately.
Mercury has something called a precession— meaning its orbit around the sun varies slightly,
every time that it goes around the sun. The shift in its orbit is much more severe than
which had been predicted by Newton's laws. No one was quite able to explain why.
In 1859, French Mathematician Urbain Le Verrier offered what could be a possible solution.
He suggested that it’s quite possible astronomers may have missed out on something,
which wasn’t too far-fetched of an idea. After all, it was Le Verrier who himself
noticed the oddities in the orbit of Uranus, and through closer study of the variations
actually deduced the existence of Neptune. So perhaps, he was on to something yet again.
He suggested that the odd motion of Mercury could be attributed to something called ‘dark matter’.
He claimed that it was due to a mystery planet called Vulcan,
that was throwing off the precession of Mercury and because of its extreme
proximity to the sun, we weren’t able to actually see it in the sky.
The problem is, though—astronomers were never able to find this so-called
planet. Le Verrier, too, was unable to explain Mercury's strange orbit.
But soon, that mystery was solved— with Einstein's theory of General relativity.
He showed that mass warps space.
This warping wouldn’t exactly affect those planets that are far away from the sun,
but for Mercury, being in such proximity, would experience its strange precession.
One simple way to visualize what is happening with mercury's orbit is to think of it as
rolling a penny along a surface that suddenly curves. As the penny goes around that curve,
it changes its speed and course. But if you are unable to see the curve,
it would seem as if the penny took an inexplicable turn on its own.
Thus, Einstein put a rest to the mystery of Mercury's orbit, boiling it down to
simply being an error in Newton's calculations that didn’t make room for such an exception.
But, does this mean that dark matter doesn’t exist at all?
Turns out, what we have theorized as the halo of dark matter that surrounds the galaxy,
much like the planet Vulcan, could simply be a figment of our imagination.
It also raises the question— could it also be that Einstein's General Relativity has a flaw?
This school of thought has actually been
present among many scientists and physicists for years and now.
A growing number of physicists are convinced that it’s time
to do away with the older theories of gravity and replace them with a newer, more modified one.
Rethinking Gravity with MOND
Newton's laws of physics and theory of gravitation sure have some minor
inaccuracies that don’t quite explain everything. But even the slightest bit of inaccuracy or error
is a major cause of concern. It brings to question whether
the theory is as applicable across the board as it was once thought.
Physicists have now been arguing that an alternative explanation of gravity,
one which requires no dark matter for its explanation,
and seems to be a considerably better theory. It is able to account for evidence at a wide
variety of scales, as compared to the ones that have preceded it so far.
In 1983, Israeli physicist Mordehai Milgrom, initiated a new research program in cosmology
called Modified Newtonian Dynamics or Milgromian Dynamics, or simply put, MOND.
In a series of three papers, Milgrom proposed a set of postulates describing
how Newton's laws of gravity and motion should be changed in regimes of very low acceleration.
The postulates were designed to explain the asymptotic flatness of galaxy rotation curves,
without ever needing to prove the existence of dark matter for the same:
He was successfully able to show that a number of other predictions follow
from his three postulates, and he proposed these predictions as tests of the theory.
So what is MOND all about?
Mond’s main hypothesis states that gravity begins to behave differently from Newtonian
physics when it becomes extremely weak as it occurs at the edges of galaxies.
This would explain why stars, planets and gas near the periphery of over 150 galaxies
rotate more quickly than would be predicted based on just their mass.
The conventional cosmological model heavily relies on dark matter and
holds the assumption that there is more dark matter than visible matter in the universe.
But this is where monds theory is different.
It doesn't make assumptions but rather, is able to predict and anticipate the future.
Dark matter content of galaxies is highly unknown and dependent on the galaxy’s history
and how it was formed— which is not always information that is available or known.
The most striking limitation of the traditional theory is
all related to dark matter. The current cosmological model
only works by postulating the existence of dark matter – a substance that has never been detected.
The issue with this, is that the original models suggested galaxies have dark matter halos
made a big mistake – they assumed that the dark matter particles provided gravity to
the matter around it, but were not affected by the gravitational pull of the normal matter.
Though this may have simplified the calculations, it doesn’t reflect reality.
The Traditional cosmological model and Mond were put to the test with a variety of astronomical
observations, including the rotation of galaxies and the motions within the galaxy clusters.
The study assigned a theoretical flexibility score of -2 and +2
for each instance that they were compared. The model that would receive a score of -2,
if it was able to predict something with clarity and accuracy without looking at the data.
A +2 on the other hand, suggests that anything goes.
Over the course of 32 tests that were conducted,
the physicists discovered that the conventional cosmological model
received an average score of -0.25 whereas the Mond received an average of +1.69.
This made it quite clear that Mond seems to be
more accurate and applicable to a much broader spectrum.
So far, the theory has no significant issues and feasibly accords with all the necessary facts.
As of now, there is still much debate over doing away with the conventional theory of gravity
and its implications; in favor of a newer and more accurate version of the same;
but it seems like surely with time, more and more physicists,
scientists and researchers are likely to lean towards Mond.
Although, completely doing away and cancelling dark matter
might not be happening anytime soon, a new theory like MOND could give us the
much-needed accuracy and ability to predict rather than speculate.
—————————————————————————————— So what do you think ?
Should the Milgromian theory replace Newton's theory of gravitation?
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