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----------------------- 2232 - Electron - What is the shape of an electron?
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- Learning is done in steps. Each of the Reviews below is a step in this learning process. Sometimes you have to start at the beginning and build the vocabulary and the understanding at each step. At times it seemed I was looking up every other word. Books and dictionaries are now replaced by the internet and search engines. But, the learning process is the same.
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- So much has been discovered about electrons. The charge has been measured to 16 places. The orbits have been defined for all the elements. The spin and magnetic moments have been measured and still new mysteries are being uncovered.
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- Excerpts from earlier Reviews on the subject of electrons:
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- 1652 - Electrons are all around us. The mysteries continue as you separate two entangled electrons. Somehow the two electrons always know the others energy state regardless of how far they are apart.
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- 1255 - What have we learned about the electron? When an electron is in motion a moving electric field generates a magnetic field. When an electron is moving through a magnetic field it generates a force. This is what creates an electric motor.
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- 1226 - Why are there three generations of electrons? Electrons, Muons and Taus? Electrons make up all the atoms and are responsible for the chemical binding that creates all the molecules.
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- 731 - Each shell of the atom allows electrons to form standing waves of complete wave cycles in each shell. If you heat an electron giving it more energy it turns into a Muon. Heat some more and it turn into a Tau.
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- 507 - If you try confining an electron it will begin behaving like a wave. The wavelengths of electrons are much shorter than the wavelength of light. How can a particle have no size and no structure, and sill have a definite mass and behave as though it has a spin?
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- 2232 - What is the shape of an electron? If you recall pictures from your high school science books, the answer seems quite clear: an electron is a small ball of negative charge that is smaller than an atom. It operates like a planetary system orbiting the proton at the center.
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- A simple model of an atom has the nucleus made of protons, which have a positive charge, and neutrons, which are neutral. The electrons, which have a negative charge, orbit the nucleus.
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- The electron is commonly known as one of the main components of the atoms making up the world around us. It is the electrons in the shells surrounding the nucleus of every atom that determine how chemical reactions work and how molecules are formed.
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- As far as physicists currently know, electrons have no internal structure and thus no shape in the classical meaning of this word. In the modern language of particle physics, which tackles the behavior of objects smaller than an atomic nucleus, the fundamental blocks of matter are continuous fluid-like substances known as “quantum fields” that permeate the whole space around us.
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- In the language of quantum fields an electron is perceived as a quantum, or a particle, of the electron field. We must adapt our definition of shape so it can be used at incredibly small distances to get into the realm of quantum physics.
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- Seeing different shapes in our macroscopic world really means detecting, with our eyes, the rays of light bouncing off different objects around us.
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- We define shapes by seeing how objects react when we shine light onto them. While this might be a weird way to think about the shapes, it becomes very useful in the subatomic world of quantum particles. It gives us a way to define an electron’s properties such that they are similar to how we describe shapes in the classical world.
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- Since light is nothing but a combination of oscillating electric and magnetic fields, it would be useful to define quantum properties of an electron that carry information about how it responds to applied electric and magnetic fields.
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- As an example, consider the simplest property of an electron: its electric charge. It describes the force and the acceleration the electron would experience if placed in some external electric field.
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- Another property of an electron is called the magnetic dipole moment. It tells us how an electron would react to a magnetic field. In this respect, an electron behaves just like a tiny bar magnet, trying to orient itself along the direction of the magnetic field.
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- What quantum property describes the electron’s shape? There are several of these properties. The simplest and the most useful for physicists is the one called the electric dipole moment
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- In classical physics, the dipole arises when there is a spatial separation of charges. Magnets have north and south poles,or dipoles. An electrically charged sphere, which has no separation of charges, has a dipole moment of zero.
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- Imagine a dumbbell whose weights are oppositely charged, with one side positive and the other negative. In the macroscopic world, this dumbbell would have a non-zero electric dipole moment. If the shape of an object reflects the distribution of its electric charge, it would also imply that the object’s shape would have to be different from spherical.
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- The electric dipole moment in the quantum world is very different. There the vacuum around an electron is not empty and still. Rather it is populated by various subatomic particles zapping into virtual existence for short periods of time.
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- The Standard Model of particle physics has correctly predicted all of these sub atomic particles. If an experiment discovered that the electron had an dipole moment, it would suggest there were other particles that had not yet been discovered.
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- These virtual particles form a “cloud” around an electron. If we shine light onto the electron, some of the light could bounce off the virtual particles in the cloud instead of the electron itself.
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- This would change the numerical values of the electron’s charge and magnetic and electric dipole moments. Performing very accurate measurements of these quantum properties would tell us how these elusive virtual particles behave when they interact with the electron and if they alter the electron’s dipole moment.
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- It could be that among those virtual particles there are new, unknown species of particles that we have not yet encountered. To see their effect on the electron’s electric dipole moment, we need to compare the result of the measurement to theoretical predictions of the size of the dipole moment calculated.
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- So far, the Standard Model accurately described all laboratory measurements that have so far been performed. Yet, the Standard Model is unable to address many of the most fundamental questions, such as why matter dominates over antimatter throughout the universe.
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- The Standard Model makes a prediction for the electron’s dipole moment requiring it to be so small that experiments would have had no chance of measuring it. But what would have happened if an experiment actually detected a non-zero value for the electric dipole moment of the electron. Predictions would need to change.
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- Such an experiment could be done in the Large Hadron Collider near Geneva, Switzerland. In the Hadron Collider two counter-rotating beams of protons are accelerated and forced to collide, generating various sub-atomic particles.
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- Theoretical models have been proposed that fix the shortcomings of the Standard Model, predicting the existence of new heavy particles. These models may fill in the gaps in our understanding of the universe.
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- To verify such models we need to prove the existence of these new heavy particles. This could be done through large experiments, such as those at the international Large Hadron Collider by directly producing new particles in high-energy collisions.
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- Alternatively, we could see how those new particles alter the charge distribution in the “cloud” and their effect on electron’s dipole moment. Unambiguous observation of electron’s dipole moment in such an experiment would prove that new particles are in fact present.
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- To measure the electric dipole moment we need to find a source of very strong electric field to test an electron’s reaction. One possible source of such fields can be found inside molecules such as thorium monoxide. Shining carefully tuned lasers at these molecules, a reading of an electron’s electric dipole moment could be obtained, provided it is not too small.
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- However, as it turned out, it is too small. Physicists have yet to observe the electric dipole moment of an electron. This suggests that its value is too small for their experimental apparatus to detect. This fact has important implications for our understanding of what we could expect from the Large Hadron Collider experiments in the future.
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- The fact that all experiments have yet to observe a dipole moment actually rules out the existence of heavy new particles that could have been easier to detect at the Large Hadron Collider.
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- It is quite amazing that studying something as small as an electron could tell us a lot about the universe. And, this study tells us that there is a lot we don’t know.
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- Stay tuned , we have a lot more to learn from the simple electron.
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- (More reviews on this subject are available if you are interested)
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- January 10, 2019
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-------------------------- Friday, January 11, 2019 --------------------------
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