The closer they are, the greater the repulsive force. If electrons are truly point particles, they can be brought infinitely close together, resulting in an infinite repulsive force. It turns out this property of point particles wreaks havoc with trying to extract sensible predictions from the theory. Eventually, a "fix" was found for this, but one that works well for only three of the four fundamental forces of nature it works also for the fourth force, gravity, but only when gravity is so weak that it can be neglected.
#New moon strings theory free#
Why all the interest in string theory?īesides the potential to unify particle physics, there are several other reasons string theory is extremely intriguing.įor one thing, it is naturally free of the sort of "infinities" that plagued particle physics in the mid-twentieth century. Consider two electrons, which repel because they have a like charge. They are simply too small. We must be clever and find convincing indirect evidence. If string theory is true, why have our most detailed probes of the elementary particles never revealed any such "stringy" structure? Why do we see only point-like entities? The answer is simple: elementary strings, if they exist, are far too tiny to see. It is unlikely that even the most sophisticated microscope or particle accelerator that could be constructed would ever have enough resolution to directly "see" the strings of string theory. This is similar to the fact that we typically do not see the individual pixels on our computer screen when looking at it. This potential to unify particle physics is one of the very compelling aspects of string theory. To get a feel for how this works, let's recall that in the quantum world there is a close relationship between the frequency with which something oscillates, and its energy. Einstein provided the first example, suggesting that the energy of a quantum of light - a photon - is related to its colour, or frequency of oscillation: the higher the frequency, the higher the energy. Moreover, in Einstein’s relativistic world, there is also a relationship between energy and mass: E = mc 2. If we combine these two relationships, we see that in a world that is both quantum and relativistic (our world), there is a close relationship between the frequency with which something oscillates - an elementary string in our case, and its physical mass, i.e., the mass of the elementary particle it is mimicking. Thus, the different elementary particles we see - the electron, the photon, the quarks, and so on - may all be the same entity: an elementary string, just singing different notes. Just as different oscillations of a musical string produce notes of different pitch, and combinations produce tones of different timbre, different oscillations of an elementary string correspond to different values for the physical properties of the string, such as its mass or spin.
How might an elementary string account for all known elementary particles? Again, the basic idea is simple: an elementary string, open or closed, can oscillate in many different ways, similar to the strings of a guitar or violin. In simplified form, these can be pictured as shown in the figure below. According to string theory, on the other hand, there is only one elementary constituent: a tiny, one-dimensional "string," which can either have both its ends free, called an open string, or both its ends joined to form a loop, called a closed string. As far as experiments can tell, all these particles are point-like, or zero-dimensional - they have no spatial extent at all. According to particle physics, there are a fairly large number of elementary constituents - building blocks from which everything is constructed: the electron, the photon, the quarks, and so forth. The basic idea of string theory is simple.
String theory is an attempt to complete the quest for unification: to formulate all the laws of physics within a single mathematical framework. The greatest achievements of theoretical physics have been feats of unification: Newton's realization that an apple falling to the ground and the Moon orbiting Earth can be explained by one and the same gravitational force Maxwell’s theory describing electric and magnetic phenomena as different sides of the same coin Einstein's theory of general relativity fusing together space, time, and gravity and the discovery - in the context of the standard model of particle physics -that electromagnetism and the weak force are different aspects of a single, more fundamental force called the electroweak force.
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