A theoretical explanation on the existence of Dark Matter

Protons, electrons, and neutrons bundled together in an atom are the particles what make most of the visible universe, including the earth, the sun and the distant stars of the galaxies. When we look up the sky, we may don that this stunning enormity mostly consists of the aforesaid particles right? Antagonistically one of the most fundamental discoveries in the 20th century was just opposite and stated that these universally accepted particles constitute less than 5% of the Universe. Yes 5%, so what about the rest 95% then? The rest of the universe is believed to be made up of an enigmatic unnoticeable material known as the dark matter along with a repelling gravitational force known as dark energy.

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What is Dark Matter is a fascinating question that gives goosebumps even to some of the finest minds in the field of astrophysics and cosmology. Dark Matter does not interact with baryonic matters and is invisible to light and other forms of electromagnetic radiation, making it impossible to detect even with the most enhanced and sophisticated instruments. So, if we cannot see it and cannot detect it, how can we be so sure of its existence? The answer lies in the gravitational effects these dark matters have on the center of the galaxies as well as the galaxy clusters. 

Standard physics states that stars on the edges of a spinning galaxy should move with a slower acceleration compare to the stars orbiting near the boundary conditions of the galactic center, where the galaxy’s visible matters are intensely concentrated. But when theoretical observations were made, it was perceived that the speed of the stars were almost same throughout the stretchable distance of the galactic disc. These observations proved the theoretical conventions that an invisible force is somehow inoculating an invisible gravitational force on the stars orbiting around the edges of a spinning galaxy thus making them accelerate much faster.

There is numerous postulate made on the dark matter and yet a few of them can explain that what it might be? One of the most fundamentally accepted postulate is that Dark matters consists of exotic particles which don’t interact with the photons and electrons but somehow exerts a gravitational pull. Other hypothesis stresses on the modified theory of gravity, which states the existence of manifold forms of gravity, and the far-reaching gravity governing galaxies which are quite different from the gravity to which we are familiar.

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The discovery of dark matter was a complete shock to the scientists. Previously they anticipated that the attractive forces of gravity will slow down the expansion of the universe w.r.t time. But little to their expectations, the simulation results send a shock of paranoia among the scientific society, when the results showed that the expansion is actually increasing instead of slowing down. It was almost as throwing a ball up the air hoping it to fall down, but only to see it going up and up. 

Physicists now believe that the expansion of the universe is due to the repulsive force engendered by the quantum fluctuations in the halo spaces of the galaxies. To be added, the force gets stronger as the universe expands and thus known as the dark force energy. Unlike dark matter, there is no conceivable explanation for dark energy and is thought to be the fifth fundamental force called quintessence, which fills the universe like a fluid. 

Dark energy is steady with the cosmological constant, a mathematical perpetual used by Albert Einstein in his equation of general theory of relativity to fit it in the impression of a stagnant universe. According to the theory, he suggested that this ‘constant’ is a reclusive force which thwarts the gravity thus preventing the galaxies from disintegrating within itself.

Now that we have discovered the universe is expanding with a dark energy in the form of a cosmological constant, we can define the true image of the stretchable space-time into vast cosmos. But even with all this explanation still, leaves the best minds wondering that why and how this strange force arrived in the first place.

Can probability help us find the answer to the beginning of the Universe?

Probability is a term which is presumably known to all human beings. If you ask people about probability, chances are they will tell you about the ’50-50’ odds of a coin getting flipped to either side of head or tail. Asking further details will fetch you answers like ‘probability of Manchester United winning the league’ or ‘probability of scientists discovering extra-terrestrial life in the Universe ’.  

If we closely analyze all the aforementioned answer we can predict that the governing rules of the probability are quite specific. Yet the exact meaning of the term is not dictionarized. When we toss a coin, how do we know that the coin is really fair? The obvious way is to get the answer is to toss it and measure the proportion of heads and tails. The laws of probability are then used to turn the measured proportion into a belief and install it in our conscious mind. Then we assume that the coin flipped is fair.

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But is this definition of probability fair? I mean ‘probability has now become a sort of subjective belief rather than objective frequencies’. In 1920, one mathematician declared the non-existence of the term probability. The apparent lack of objectivity has led him to come to such a conclusion.

Imagine what if probability does not exist. Data Analysis becomes a matter of opinion. So to avoid these horrendous situation scientists advocated techniques for analyzing experimental results that offered to use an objective measure of probability called ‘p-value’.

But with the passage of time even the concept of ‘p-value’ started to fade away and gained the critics as a nonsensical theory. Newer methods such as Bayesian method has been suggested in the recent decades. This method is comparatively more robust and has a wider range of theoretical use. Despite the vast application of probability, the concept of probability still instills doubt among many renown scientists.

How probable is our universe?

But whatever anomalies the term ‘probability’ carries, it is still regarded as one of the most advanced analyzing tool in the field of science including the Universe. So let’s see how probable our Universe is by applying the theory of probability? We have a vague idea about the creation of the Universe. As Big Bang happened around 14 billion years ago, an external inflation expanded at near about nine times the speed of light. This external inflation hypothesizes the existence of quantum forces which created rapid- expanding regions of space and time, one of which became our Universe. Given on the above facts, we can imagine how immense of a geometrical structure the universe is. Yet to our surprises, it is in fact just one of the infinite number of the bubble like Universes which constitute the totality of existence, dubbed the Multi-verse.

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Multiverse is an amazing proposal and may only be solved by applying the theories of probability. This situation is so difficult to imagine that some of the scientists don’t even want to believe the existence of multiverses. For example, using the standard definition of probability, which means dividing the total number of universes by the numbers making up the multiverses, a theorist can state the ‘probable outcome of our Universe’. But if the external inflation is happening from the very beginning, there will an infinite number of Universes like ours now. And the numbers making up the Multiverse is also infinite. Thus the whole situation of finding the probability of our universe is becoming infinite which is quite obsolete.

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This part of astrophysics has been one of the most difficult conundra to break for many scientists. One way to solve the puzzle is to assume that the forces driving the bubble universes leads them to inflate at an even higher rate as they get larger. This stretches the very fabric of space and time within the Multi-verses. But then Einstein’s light-speed limit will become archaic along with the fact that these regions will become forever undetectable due to their faster speed. It will be very tough to find the exact answers to this kind of compelling questions, but theorists are still quarreling over the details and by applying the theory of cosmic probability calculation perhaps one day we may finally arrive at the answer to the very beginning of our Universe.

 

Antimatter revolutionized astrophysics. Will anti-memory transform neuroscience?

 

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Antimatter, a well-known term to all the physicists and physics lover all over the world. In 1928, British physicists Paul Dirac combined the theories of quantum physics and special relativity to define the comportment of an electron moving at a relativistic speed. He formed an equation which ultimately won him the Nobel Prize in 1933 but more importantly he came up with a problem which in turns defines Antimatter.

Just like the equation x^2=4 has two possible answers (x=2 and x=-2), Paul’s equation too had two possibilities – one was for the positive electrons and another was for the negative electrons. But we know classical physics states that energy of particle should always be in a positive number. So, Dirac construed the equation to mean that for every particle there exists a corresponding antiparticle, exactly matching the particle but with opposite charge. This defined Antimatter and the rest is history in the field of Astronomy.

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However, today I am not going to discuss Antimatter though the article is faintly related to it. Anti-memories is the limelight today. Just like Antimatter revolutionized the field of astrophysics and deepened our quest in truly understanding the universe, Anti-memories could help us grabbing the mysterious connection of the memories happening inside our brain.

When a new memory is created or the old ones are recalled, a strong impulse of electrical activity happens in the deepest itineraries of neurons inside our brain. The memory is characterized by this new connotation between neurons. But the most intriguing part is that a new theory suggests, that the time when a memory is created, an anti-memory is also produced. The theory is backed by animal research and mathematical models. The “anti-memory” theory suggests that the connections between neurons are made in a way that they produce the exact opposite pattern of neural impulses when an old memory is recalled to that of when a new memory created. Scientists believe that this phenomenon helps the brain to balance the activities in a chronological way.

The electrical activities in our brain are superbly and precisely balanced. When someone is emotionally excited, there is a stronger connection between the neurons, a process which is normal in every human brain. However, if the same emotional excitation happens in excess, then the bond becomes weaker and the electrical impulses suppress a bit. The imbalance electrical activities in the brain are thought to trigger some of the cognitive problems of brain disease such as autism and schizophrenia.

Trying to understand the effect of this electrical imbalances, scientists concluded that the possibility of a second process is there, where re-balancing the excitation caused by a new memory happens and thus keep the whole system in check. Just like we have matter and antimatter, there must be an anti-memory for every memory. This particular mirroring of the excitation of the new memory with its inhibitory anti-memory averts a roaring squall of brain activity, ensuring that the system stays in balance. While the memory is still present, the activity it caused has been restrained. In this way, anti-memories work to suppress the original memory without erasing it.

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Anti-memory countering the brain activity of a memory. Credit: HC Barron et al/Neuron

The proof of anti-memory so far came from the lab experiments where animals like small rats and mice’s were taken as test subjects and experimented on to get better grasps on the practical aspects. The results were truly fascinating. The experiments included a direct recording of brain impulses through electrodes connected inside the brain of the test subject. And since connecting probes inside a human brain will be glared upon, so far this has not been tested on any human yet.

So, Anti-memories can play a major role in the human thought processes by stopping the memories from impulsively activating each other. Just as the discovery of the Antimatter revolutionized the field of physics in the 20th century and still, the exploration into Anti-memory can help us find a new paragon which will lead to better understanding of our brain.