What is the physical makeup of an electron?

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In summary: CF. Vanadium 50In summary, an electron is a point particle with a negative elementary charge and a mass of about 511 \; \mathrm{keV}/c^2. It is a lepton, i.e., participates only in the electroweak interaction. When asked what something is, the most accurate description is detailing the physical properties of it, such as mass, charge, etc.
  • #36
An electron is a negatively charged sub atomic particle in an atom that is around the nucleus of the atom in the electron cloud. The electron is a very light mass subatomic particle and you can take away an electron from an atom or give electrons to an atom which will result in an ion(cation or anion).
 
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  • #37
Fastman99 said:
This question is similar to asking what is a photon? Photons and electrons and other elementary particles are not actually little billiard balls that are flying around high speeds. They are both quantum excitations of their respective fields.

The entire universe is filled with a photon field, and it's mostly empty. You can think of it as an empty EM field as well. At every point in space there is a quantum harmonic oscillator for each possible spatial frequency, and thing about quantum harmonic oscillators is that only allowed energy levels come in steps of hw. The minimum energy of the oscillator is 3/2hw in 3 dimensions, and then it goes up to 5/2hw, then 7/2 hw, etc. One step above the zero-point level is considered one photon at that spatial frequency. The photon could have a range of frequencies, and be localized in some way, or be more spread out and less localized.

Just think of it of a field as an infinite set of harmonic oscillators at every point in space, and think of the particles as quantum vibrations of this field.

In a similar way, there is an electron field that fills of space with a zero-point energy, and it has certain linearly quantized energy levels above the zero level that indicate the number of electrons. This explains why every electron has exactly the same mass, charge, spin, and g-factor. Saying an electron is the same thing as saying a quantum vibration of the electron field, but the latter is too wordy. The electron vibration can be localized, as in a vibration around an atom, or more spread out like a free particle, or an electron in a double slit experiment.

The big difference between the electron field and the photon field is that with electron vibrations, they can't stack directly on top each other. This is described as the Pauli Exclusion rule. The electron field is a fermion field, described by the Dirac equation. Two electron vibrations can be in almost the same state very close to each other, but they can never occupy the same exact state.

I like to visual all quantum particles, whether they are photons or electrons, as 3 dimensional fuzz balls, and those fuzz balls oscillate and move around and sometimes disappear according the probabilistic laws of QFT. It's the sudden collapse of the fuzz balls that's most shocking to me, (wavefunction collapse is mysterious).
Suppose we had a 50 or 100 GeV electron beam, like SLAC or the CERN LEP accelerator, and we shot it through this field of an infinite set of harmonic oscillators, or photons. What would happen?

In the normal Compton scattering, where the electron is at rest in the Lab, above a few MeV photon energy, an inelastic Compton scattering would begin to produce real electron-positron pairs, and we would see the extra positrons and electrons. The cross section for Compton (Klein-Nishina) scattering is ≈0.665 barns (6.65 x 10-25 cm2).

Now gamma shift into the reference frame where the electrons are 50 or 100 GeV, and we should see the electrons colliding with the infinite set of harmonic oscillators or photons in the vacuum (and even with the CMB). Shouldn't we see the inverse Compton effect, with high energy gammas, and possibly even positrons comming out of the vacuum chamber? Can't we use this test to put an upper limit on the density of photons or harmonic oscillators in the vacuum?
 
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  • #38
Most of these harmonic oscillators with significant energy levels are in their ground state, which means there is no photon to interact with. High-energetic charged particles in space can interact with the CMB without problems. For protons, this leads to effects like the GZK cutoff.
 
  • #39
mfb said:
Most of these harmonic oscillators with significant energy levels are in their ground state, which means there is no photon to interact with. High-energetic charged particles in space can interact with the CMB without problems. For protons, this leads to effects like the GZK cutoff.
Energetic electrons interact with the CMB (cosmic microwave background) via the SZ (Sunyaev–Zel'dovich) effect. See http://en.wikipedia.org/wiki/Sunyaev-Zel'dovich_effect. Is your "field of photons" density less than the CMB?
 
  • #40
If you consider a volume in some object cooler than 3K and without any sources except blackbody radiation, yes.
 
  • #41
A comment by P. A. M. Dirac from Proceedings of the Royal Society of London (1962) may be helpful here. Title: Particles of finite size in the gravitational field.

"So from the physical point of view, the possibility of having a point singularity in the Einstein field is ruled out. Each particle (electron) must have a finite size no smaller than the Schwarzschild radius.

I tried for some time to work with a particle with radius equal to the Schwarzschild radius, but I found great difficulties, because the field at the Schwarzschild radius is so strongly singular, and it seems that a more profitable line of investigation is to take a particle bigger than the Schwarzschild radius and to try to construct a theory for such a particle interacting with the gravitational field."

The next larger significant size (not so strongly singular) is the radius 3Gm/c squared. This size could provide gravitational confinement without gravitational collapse to infinite (or unknown) density. This size is too small to measure.
 
  • #42
If we want to know, what exactly is an electron, we need to know how electrons (and positrons) are produced (materialized). So much has been learned about this process that it is difficult to keep up. First, we know electrons are produced from photons (produced from electromagnetic energy). We know an electron can absorb a photon. This absorption is a direct conversion of photon energy to mass. Energy added to the electron increases its mass. A photon consists of equal amounts of positive and negative electric field energy. And so, we cannot materialize an electron without also producing a positive charge particle. The electron has extremely high energy density with a radius less than 10 exp -18 meters while the photon with sufficient energy to produce an electron, positron pair has a wavelength that is large, with far less energy density than the electron. A photon, when absorbed by an existing (high density) particle will become a high energy density entity. This is the first step required to produce mass particles.
 
  • #43
As noted, nobody knows 'exactly' what any of the fundamental particle are.

The best we can do so far is to describe characteristics according to quantum mechanics...spin, mass, charge, etc, whatever is incorporated in the Standard Model of particle physics...A complementary and different perspective might be afforded via string theory and that is a nice approach since it relates all the elementary particles to one another...as energy vibrations.
 
  • #45
Much has been learned, and we can now discuss a limitation on the smallness of things called a "cutoff". A quote from Leonard Susskind follows:
"A cutoff sounds like a cop-out, but there is an excuse. Physicists have long speculated that the Planck length is the ultimate atom of space. Feynman diagrams, even those involving gravitons, make perfect sense as long as you cease adding structures smaller than the Planck length - or so the argument goes. This was the almost universal expectation about space-time -- that it would have an indivisable, voxelated structure at the Planck scale."
This is from the book, The Black Hole War (page 335).
If the electron radius is equal to the Planck length or 1.616x10^-35 meter, this is much larger than the electron Schwarzschild radius and so, (at first evaluation) we may find that the electron cannot collapse to its Schwarzschild radius, 2Gm/c^2 and it cannot collapse to the larger radius, 3Gm/c^2.
Another quote from Leonard Susskind follows:
"But extraordinary things are happening. In recent years, we have been accumulating evidence that the machinery in the interior of particles (electrons) is not mush bigger, nor is it much smaller than the Planck length." (page 214)
When the electron radius value is reduced to the Planck length (or slightly larger) due to gravitational time dilation (blueshift) and an equal amount of gravitational length contraction then the size (close to) 2Gm/c^2 is attainable.
 
  • #46
Naty1 said:
The best we can do so far is to describe characteristics according to quantum mechanics...spin, mass, charge, etc, whatever is incorporated in the Standard Model of particle physics

With the knowledge we collectively have we can probably do a lot better than that. One of the best known fundamental prescriptions of QM, Dirac's "Principles of Quantum Mechanics" describes the motion of the charge of the electron that travels at the speed of light. Why it should do that and what it means in terms of the electron's structure and observable parameters is a not-so-well-known but arguably important Physics cottage industry and there is quite a bit of literature on the subject.
 
  • #47
You are so correct, there is much literature on the subject of electron structure. With careful selection from available literature, we can do a lot better. Charge motion at speed of light is necessary to explain electron angular momentum (and magnetic moment). John A. Wheeler has suggested that the electron is the result of gravitational collapse. See page 1215 in the book, Gravitation. In the book, The Enigmatic Electron, author, Malcolm H. MacGregor writes, "One electromagnetic configuration --- is a current loop formed by a rotating point-like charge."

In a (2008) paper titled, The Dirac-Kerr-Newman electron, theorist Alexander Burinskii writes, "Recall that the angular momentum J = h bar/2 for parameters of electron is so high that the black hole horizons disappear and the source of the Kerr-Newman spinning particle (electron) represents a naked singular ring." We can see (in this concept) the electron size cannot be as small as its Schwarzschild radius because charge velocity greater than c would be needed to obtain angular momentum (h bar/2). The minimum radius with the charge moving at the speed of light is (3Gm/ c^2).

Malcolm MacGregor has said, "It remains to this day one of the most arcane subjects in particle physics." And later, "---the spin of the electron--is a mysterious internal angular momentum for which no concrete picture is available, and for which there is no classical analog." Can we put these pieces of the electron puzzle together to create an improved electron description? I will suggest that this can be accomplished.
 
  • #48
To that I'll add that Martin Rivas' "Kinematical Theory of Spinning Particles: Classical and Quantum" gives quite a thorough and integrated review of very many approaches to modeling spin, especially in the electron. Unfortunately both MacGregor's and Rivas' books are out-of-print these days.
 
  • #49
I will try to find a copy of the Martin Rivas book. I am saddened to learn that the MacGregor book out-of-print. His book is very readable. This quote (page 72) points out a significant requirement. "Thus we are forced from stability considerations alone, to introduce a non-electromagnetic force that holds the electron together. If we were to consider an extremely small size for the electron, -- then gravitational forces could be invoked to solve the stability problem."
Though MacGregor does not pursue this solution, a number of theorists, including Brian Greene, John Wheeler and Alexander Burinskii expect that electrons have some properties very much like a micro black hole.
 
  • #50
I should probably warn that the math comprehension requirements for Rivas' book are fairly steep. He kind of starts where Ballentine's QM textbook leaves off.
 
  • #51
Even in classical electrodynamics one can describe the electron as an orbiting massless charge embedded in its synchrotron radiation and obtains the fundamental properties, also the mass and the de Broglie wave.
The /size/ of the mass needs quantum mechanic considerations
 
  • #52
In post # 47, a minimum electron radius value, (3Gm/c^2) was noted. From this radius, a fundamental mass value is defined, using a ring shape with the angular momentum (h/4pi). The charge spins at light velocity so that the effective mass times velocity times radius will equal angular momentum.
m c (3Gm/c^2) = h/4pi
(m)^2 = (h/4pi) (c/3G)
m = (hc/12pi G)^1/2
m = (1/2) (2/3)^1/2 (Planck mass)
I suggest this mass value is the fundamental value that has a specific relationship to the electron mass, the muon mass and the tau mass.
The photon wavelength that has energy to produce two particles with each particle mass value equal to (hc/12pi G)^1/2 is (3pi hG/c^3)^1/2 meter. This wavelength is:
wavelength = 2pi (3/2)^1/2 (Planck length)
The ratio of this fundamental wavelength to the wavelength (h/2mc) is approximately 1.025x10^-22 to one. I will suggest that this is also equal to [h/(2pi)^2] divided by (2mc^2) where the m value is the electron mass. This ratio is 1.025028393x10^-22. If these ratio values are precisely correct then the true G value must be very close to 6.671745197x10^-11. Improved experiments will determine if this is correct.
 
  • #53
First off I'm no physicist but an EE. So my question might seem odd, but in light of everything that was said until now, why has nobody (except for one guy I believe) proposed string theory to try to explain what elementary particles are (electron included)? Is this because it is still an "unproven" (untested) theory?

String theory seems to be acknowledged by many recognized scientists, so perhaps it is a valid one at answering the initial question: what is an electron?

Btw, what a great forum this is. Just recently found it. Since then I just can't help but try to read every single posts. Waaa, I'm going crazy :)
 
  • #54
Hi kended, String Theory and Quantum Gravity are well covered in the book by Lee Smolin, titled Three Roads To Quantum Gravity. Much work is needed if string theory is to accomplish its objective. A quote from the book follows:
"Modern physicists try -- to explain particles in terms of fields. But this does not eliminate all problems. Some of the most serious of these problems have to do with the fact that theory of fields is full of infinite quantities. They arize because the strength of the electric field around a charged particle increases as one gets closer to the particle. But a particle has no size, so one can get as close as one likes to it. The result is that the field approaches infinity as one appraches the particle. This is responsible for many of the infinite expressions that arize in the equations of modern physics."
He suggests, we may deny that space is continuous and so it is impossible to get arbitrarily close to a particle. We may also replace particles by little loops or strings. String theory is interesting but it is not yet mature enough to explain specifics such as electron mass.
 
  • #55
DonJStevens said:
Hi kended, String Theory and Quantum Gravity are well covered in the book by Lee Smolin, titled Three Roads To Quantum Gravity. Much work is needed if string theory is to accomplish its objective. A quote from the book follows:
"Modern physicists try -- to explain particles in terms of fields. But this does not eliminate all problems. Some of the most serious of these problems have to do with the fact that theory of fields is full of infinite quantities. They arize because the strength of the electric field around a charged particle increases as one gets closer to the particle. But a particle has no size, so one can get as close as one likes to it. The result is that the field approaches infinity as one appraches the particle. This is responsible for many of the infinite expressions that arize in the equations of modern physics."
He suggests, we may deny that space is continuous and so it is impossible to get arbitrarily close to a particle. We may also replace particles by little loops or strings. String theory is interesting but it is not yet mature enough to explain specifics such as electron mass.
Thanks for your reply DonJStevens.

I think I may have to read some more on this subject. It seems though that the book was written in 2002. So perhaps has the subject evolved a bit since then.

Now with the very recent "supposed" discovery (measurement) of the Higgs-Boson, I read that string theorists are even more excited as this would somehow fit their theory in relation to particle mass.

Anyhow I just thought that instead of saying that we "don't really know what an electron is", I would rather try to explain it using string theory that many great minds do believe in and where the mathematical constructs apparently make sense that is, until proven right.

Btw, your former job sounded very cool :)
 
  • #56
The charge radius of an elementary particle has nothing to do with the spatial distribution of its charge. The charge radius is a length scale characterizing a scattering cross-section.

In Quantum Field Theory, elementary particles are thought as excitations of the corresponding matter field that propagate carrying energy-momentum. These excitations may be created and destroyed by the action of sources. Consequently, the energy of the field's excitation due to two sources differs from the sum of the energy of the field's excitation due to the separate presence of each source. This is interpreted as a potential energy of interaction of two sources due to the exchang of virtual particles.

The sources of some kinds of particles become quantum operators themselves corresponding to a (conserved) Noether current density corresponding to a continuous symmetry of the theory. For example, the free-electron Lagrangian has a global U(1) symmetry, corresponding to the invariance of the Lagrangian with respect to an arbitrary change in phase of the "electron field". The corresponding noether current is the electric current density, that acts as a source term for the "photon field". The photon "listens" to the electric charge in its vicinity and mediates the electromagnetic interaction. Since the range of the interaction is infinite, the photons are massless, and there is only a kinetic term for the photon field. This effectively describes Quantum Electrodynamics (QED), the simplest (Abelian) gauge theory of the Standard model.
 
  • #57
So a photon that undergoes pair production does so because of because it is a perturbation energetic enough to inititiate the pair's own standing waves. But why at one point, not another? Why don't we just see a pair and the lower energy photon from, for instance, Co60, but instead see a high energy photon and the pair production photons later? Is that because this "Noether" field has to be in the correct configuration locally for the pair production to occur, or because the virtual particle must form, which isn't a given, but a statistical process?
 
  • #58
I just want to point out to the OP. You're getting down to the basic building blocks of matter. When ever you describe something, call it E, you break it down or you reduce it to it's parts or its properties, X Y and Z. I think Vanhees said it perfectly:

vanhees71 said:
To conclude: To the best of our knowledge today (i.e., in this case the standard model of particle physics) the electron is an elementary spin-1/2 Dirac particle with one negative elementary charge and a mass of about [itex]511 \; \mathrm{keV}/c^2[/itex]. It's a lepton, i.e., participates only in the electroweak interaction (let alone gravitation, which acts universally on anything that has energy and momentum).

It is so difficult to describe an electron because you're running up against the basic building blocks of the universe which cannot in principle be described. Notice that Vorhees described an electrong in terms of charge, mass, spin, and the forces with which it participates. So we have some reduction. But charge, mass, spin we cannot reduce those entities to anything else, at least not now, and they remain in principle undescribable.
 
  • #59
Despite of the great success of mathematics one should reconsider the building blocks from time to time.

Dirac invented his equation to describe the properties of spin 1/2 particles. The interaction of electrons are perfectly described by this equation.

Especially D. Hestenes investigated this equation in detail and found a description of the electron: The electron is circulating with speed of light which is described by the Zitter-Bewegung, generates an angular momentum - the spin, and with E = h x nu the Compton wavelength defines the circumference of the circulation.

But why the charge should circulate is still open.

All models in the past ignore the synchrotron radiation of the charge.
Even in classical physics a circulating charge embedded in its synchrotron radiation yields the angular momentum of the particle, the Compton wavelength as the wavelength of the radiation and the classical electron radius is the result of quantum mechanic interaction with the singularity. Circulation with v = c yields mass = field energy.

The spherical solution of the radiation just guides the charge onto a circular orbit and is thus the reason for the circulating charge.

Details are in G. Poelz "On the Wave Character of the Electron"
http://arxiv.org/abs/1206.0620
 
  • #60
This is a very good question to pose, as quoted by many people have tried to make a modle of a electron while its basic formation is known for the most part it would be a good project to go into to try and look inside of the electron
 
  • #61
Atom1 said:
This is a very good question to pose, as quoted by many people have tried to make a modle of a electron while its basic formation is known for the most part it would be a good project to go into to try and look inside of the electron

We've tried. We can't find anything inside it. And by "we" I mean thousands of people using multiple particle colliders and other experiments over the last 50 years.
 
  • #62
Since MacGregor and Rivas have been mentioned perhaps it is worth mentioning a moderately priced collection of papers What is the Electron?, edited by Simulik that includes papers by each of the them as well as others. It's quirky and in print.
 
  • #63
I obtained the book, What is the Electron, yesterday. Thank you xristy for mentioning this. The Einstein question (on back cover of book) is so very significant.

When he was asked what he thought about the large numbers of short lived heavy particles being produced in high-energy accelerators, Einstein pondered the question and replied, "You know, it would be sufficient to really understand the electron."

At the time little attention was paid to his remark. Yet the electron remains as mysterios today as it was in Einstein's time. The electron will be less mysterious if we learn why all electrons are identical. J. A. Wheeler said "That an electron here has the same mass as an electron there is also a triviality or a miracle." (see page 1215 of book Gravitation)
 
  • #64
DonJStevens said:
I obtained the book, What is the Electron, yesterday. Thank you xristy for mentioning this. The Einstein question (on back cover of book) is so very significant.

When he was asked what he thought about the large numbers of short lived heavy particles being produced in high-energy accelerators, Einstein pondered the question and replied, "You know, it would be sufficient to really understand the electron."

At the time little attention was paid to his remark. Yet the electron remains as mysterios today as it was in Einstein's time. The electron will be less mysterious if we learn why all electrons are identical. J. A. Wheeler said "That an electron here has the same mass as an electron there is also a triviality or a miracle." (see page 1215 of book Gravitation)

You could expand your statement to include all fundamental particles, as they are all identical to other particles of the same type.
 
  • #65
Drakkith, you are so correct, all particles of the same type are identical. This implies that nature has a specific set of requirements that must be precisely met for each particle (type). We expect that theorists will determine and define these strictly imposed requirements. The electron requirements will most probably be the first that we will understand.
 
  • #66
Perhaps Don. We'll have to wait and see!
 
  • #67
We can see now what some theorists have recently written about the electron. In post # 59 a paper by G. Polz was referenced. In this paper the electron is analyzed as a toroidal ring. The author (G. Polz) also references other papers that are interesting to all who want to know more. The referenced paper by Williamson and van der Mark analyzes the electron as a photon trapped in a toroidal path. As we come closer to a correct electron model, the desire to understand becomes ever more intense. As Drakkith said: We'll have to wait and see!
 
  • #68
The book, What is the Electron? noted in post #62 is interesting. The Wave Structure of Matter is discussed (page 227 - page 250). From page 240: "Schrodinger and Clifford predicted that charge was due to wave structures in space. - - We observe this process and call it charge. But as Clifford and Schrodinger wrote, there is no charge substnce involved. It is a property of the wave structure at the center."

This book allows us to see some concepts by theorists who want to help us understand the electron. Thank you xristy for noting this book.
 
  • #69
Hey quick question? can't we just say that the electron is simply a particle of energy? What I meen is maybe the electron is like the photon just different. A photon is a carrier of energy because it has no mass therefor it can carry electromagnetic waves (that being energy). Cant we say look an electron maybe has more energy and therefor some of it must be converted too a mass?

Another question. When an electron feels attraction or repulsion it releases a photon. Therefor shouldn't the mass of the electron decrease albeit a very small amount? But that mass will always be conserved as it is absorb somewhere else?
 
  • #70
spuding102 said:
Hey quick question? can't we just say that the electron is simply a particle of energy? What I meen is maybe the electron is like the photon just different. A photon is a carrier of energy because it has no mass therefor it can carry electromagnetic waves (that being energy). Cant we say look an electron maybe has more energy and therefor some of it must be converted too a mass?

You can call it whatever you like. Ultimately it comes down to the specific properties of the electron described by science. Properties such as mass, charge, spin, etc. Whatever you want to label it as, those properties will not change.

Another question. When an electron feels attraction or repulsion it releases a photon. Therefor shouldn't the mass of the electron decrease albeit a very small amount? But that mass will always be conserved as it is absorb somewhere else?

This is not true. EM radiation is only released when a charged particle accelerates, not when it *feels* a force. The energy used to create this photon comes from the kinetic energy of the electron, not its mass. Electrons in orbitals around a nucleus experience a very strong attraction yet do not radiate.
 
<h2>1. What is the size of an electron?</h2><p>The size of an electron is incredibly small, with a radius of approximately 2.8 x 10^-15 meters.</p><h2>2. What is the mass of an electron?</h2><p>The mass of an electron is approximately 9.11 x 10^-31 kilograms, which is about 1/1836th the mass of a proton.</p><h2>3. What is the charge of an electron?</h2><p>An electron has a negative charge of -1.602 x 10^-19 coulombs.</p><h2>4. What is the location of an electron in an atom?</h2><p>Electrons are located in orbitals around the nucleus of an atom. The exact location and movement of an electron cannot be determined, but its probability of being in a certain area can be calculated.</p><h2>5. Can an electron be broken down into smaller particles?</h2><p>No, an electron is considered to be an elementary particle and cannot be broken down into smaller components. It is considered to be one of the fundamental building blocks of matter.</p>

1. What is the size of an electron?

The size of an electron is incredibly small, with a radius of approximately 2.8 x 10^-15 meters.

2. What is the mass of an electron?

The mass of an electron is approximately 9.11 x 10^-31 kilograms, which is about 1/1836th the mass of a proton.

3. What is the charge of an electron?

An electron has a negative charge of -1.602 x 10^-19 coulombs.

4. What is the location of an electron in an atom?

Electrons are located in orbitals around the nucleus of an atom. The exact location and movement of an electron cannot be determined, but its probability of being in a certain area can be calculated.

5. Can an electron be broken down into smaller particles?

No, an electron is considered to be an elementary particle and cannot be broken down into smaller components. It is considered to be one of the fundamental building blocks of matter.

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