We are aware that Hawking believed the "M-theory" to be the greatest option for a comprehensive theory of the cosmos. What is it then?
Every theoretical physicist has imagined reconciling our grasp of the infinitely small world of atoms and particles with that of the endlessly enormous scale of the cosmos since Einstein's formulation of the theory of general relativity in 1915. While the former is accurately anticipated by the so-called Standard Model of fundamental interactions, the latter is effectively characterized by Einstein's equations.
According to our current understanding, there are four fundamental forces that account for how physical objects interact. At the macroscopic level, two of them—gravity and electromagnetism—are significant to us because they are factors in our daily activities. Only when dealing with subatomic processes do the other two, known as strong and weak interactions, become important since they operate on a very small scale.
Three of these forces have a coherent framework provided by the standard model of fundamental interactions, but gravity cannot be reliably incorporated into this framework. General relativity fails to work at very small distances, despite accurately describing large-scale events like the orbit of a planet or the dynamics of galaxies. The standard model states that particular particles mediate all forces. The graviton is a subatomic particle that functions as gravity. However, calculating the interactions of these gravitons makes them seem absurd.
Any scale should be able to use a coherent theory of gravity, and it should take the fundamental particles' quantum nature into consideration. This would provide the renowned theory of everything by incorporating gravity into a single framework together with the other three fundamental interactions. Of course, a lot has been accomplished since Einstein passed away in 1955, and today M-theory is our top contender.
revolutionized strings
The fundamental concept of M theory can be understood by going back to the 1970s, when researchers realized that tiny oscillating strings (also known as energy tubes) might be used to represent the cosmos instead of point particles. This new perspective on the basic elements of nature turned out to be the answer to a lot of theoretical issues. Most crucially, it is possible to interpret a certain string oscillation as a graviton. Additionally, string theory, unlike the conventional theory of gravity, could mathematically describe its interactions without encountering odd infinities. Thus, a comprehensive framework at last embraced gravity.
Theoretical physicists spent a lot of time and energy trying to grasp the implications of this revolutionary discovery. However, the history of string theory has had its share of ups and downs, as is typical of scientific inquiry. It anticipated the presence of a particle known as a "tachyon" that travels faster than the speed of light, which first perplexed people. This prediction seriously questioned the validity of string theory because it ran counter to all experimental observations.
However, this issue was resolved in the early 1980s when "supersymmetry" was incorporated into string theory. Every particle is said to have a superpartner according to this, and by an amazing coincidence, the identical condition also really causes the tachyon to disappear. This first achievement is frequently referred to as "the first string revolution."
The requirement for ten space-time dimensions in string theory is another noteworthy aspect. Only four of them are currently known to us: depth, height, width, and time. Although there have been some suggestions for fixes, this is no longer seen as a problem but rather as a wonderful feature.
We might, for instance, be compelled to exist in a four-dimensional reality without having access to the other dimensions. Or the additional dimensions might be "compacted" to a point where we would not notice them. However, various compactifications would result in various physical constant values and, thus, various physical laws. Our world could be just one of many in an infinite "multiverse" ruled by many physical laws, according to one conceivable explanation. Many theoretical physicists are approaching this topic, despite the fact that it may sound weird.
M-theory
But string theorists were still troubled by a critical point. Five distinct coherent string theories were identified by extensive classification, and it was not evident why nature would select one of the five.
M-theory was then utilized in this situation. In 1995, during the second string revolution, scientists claimed that the five coherent string theories are only distinct manifestations of the M-theory, a single theory that occupies eleven space-time dimensions.
Each of them involves string theories in various physical settings, but they are all still valid. Most theoretical physicists now consider M-theory to be the theory of everything due to this incredibly intriguing image and the fact that it is mathematically more consistent than other contender theories.
But up to this point, M-theory has had trouble making predictions that can be tested in experiments. At the Large Hadron Collider, supersymmetry is now being tested. Superpartner evidence, if discovered, would eventually support M theory. But making testable predictions and designing experiments to prove them continue to be difficult tasks for modern theoretical physicists.
The majority of excellent cosmologists and physicists are passionately driven to discover the most elegant, straightforward explanation of the universe. And even though we haven't arrived yet, without the bright brains of someone like Hawking, we wouldn't stand a chance.
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