I have a question: if we describe photon as a bundle of energy and electron as particle of some mass, within the diameter of the electron, what forms the mass? In what form does the mass exist? Is it in the form of energy? Can anyone tell me a physical concept of the form of mass of an electron which is thought to be one of the elementary particles? I just find the concept of mass really vague.
Mass and Energy
Mass and energy are essentialy the same thing, and when you look at them at a scale as small as an electron, the distinction becomes a bit blurred.
As for what form the mass takes, you can either take the classical interpretation as a really really tiny ball, like a particle of dust, or you can put your trust in the relitively new and not quite proven superstring theory. The supersting theory says that all subatomic particles are made of vibrating strings, and the way in which a string vibrates in all 23 dimensions determines the type of matter that it composes. The classical theory is far easier to understand, but has little basis on theory and is basicly more of an assumtion.
As for what form the mass takes, you can either take the classical interpretation as a really really tiny ball, like a particle of dust, or you can put your trust in the relitively new and not quite proven superstring theory. The supersting theory says that all subatomic particles are made of vibrating strings, and the way in which a string vibrates in all 23 dimensions determines the type of matter that it composes. The classical theory is far easier to understand, but has little basis on theory and is basicly more of an assumtion.
this is a good question that can be addressed on several levels.
first off, the statement that mass and energy are the same can be confusing. what we traditionally refer to as the mass of an electron or other "matter" particle should really be called the "rest mass". If a particle can be slowed down so that it has zero velocity, then it has a rest mass. (another way to say it is if we can find a reference frame where the particle has zero velocity, then it has a rest mass.) This is the energy that was required to make the electron in the first place. Any additional energy a particle has above its rest mass is kinetic energy (assuming it's not affected by any forces). However, a photon cannot be slowed down to zero velocity - as Einstein realized, it has the same velocity "c" in all reference frames. Therefore it does not have a rest mass, and all the photon's energy is kinetic energy.
so, what is the electron made of? as ocalhoun said, it could be a superstring, but we don't have any experimental evidence of that. the established model of physics that describes all the matter and forces (besides gravity), called the Standard Model, describes electrons in terms of "elementary particles". This means that the particles are the most fundamental building blocks and cannot be broken down into any smaller parts. All of the energy is distributed between the different particles - there is no energy that exists that is not in particles. The particles in the Standard Model are divided into two groups - "matter particles" and "force carrier particles". The matter particles are the electron, muon, tauon, electron neutrino, muon neutrino, tauon neutrino, and the up, down, strange, charm, bottom and top quarks, and all of their anti-particles. The force carrier particles are the photon, W and Z bosons, the gluons, and the Higgs boson. I won't go into what all of these particles are, but there are lots of good references on the web about them.
Although all the energy is in particles, the particles can undergo reactions that redistribute the energy between the particles. For example, a radioactive nucleus can undergo beta decay, where a neutron in the nucleus decays to a proton, electron and electron anti-neutrino. The amount of energy stays the same, but the particles and their velocities are different. If we assume the neutron was at rest, then most of its energy (rest mass) was used to make the proton, a much smaller bit was used to make the electron, a much much smaller bit was used to make the anti-neutrino, and the remaining energy went into kinetic energy of the proton, electron and anti-neutrino.
However, there are clues that the Standard Model is not the whole story, especially in astrophysics. You may have heard of "Dark Matter" or "Dark Energy" which so far has only been detected due to its gravitational effects. However, this is not "pure energy", it is still particles; we just don't yet know all the details of how the particles interact with the rest of the universe. It also may be that we eventually find out that particles we consider to be elementary actually have an internal structure, such as a superstring, but for now we don't have any evidence of that.
first off, the statement that mass and energy are the same can be confusing. what we traditionally refer to as the mass of an electron or other "matter" particle should really be called the "rest mass". If a particle can be slowed down so that it has zero velocity, then it has a rest mass. (another way to say it is if we can find a reference frame where the particle has zero velocity, then it has a rest mass.) This is the energy that was required to make the electron in the first place. Any additional energy a particle has above its rest mass is kinetic energy (assuming it's not affected by any forces). However, a photon cannot be slowed down to zero velocity - as Einstein realized, it has the same velocity "c" in all reference frames. Therefore it does not have a rest mass, and all the photon's energy is kinetic energy.
so, what is the electron made of? as ocalhoun said, it could be a superstring, but we don't have any experimental evidence of that. the established model of physics that describes all the matter and forces (besides gravity), called the Standard Model, describes electrons in terms of "elementary particles". This means that the particles are the most fundamental building blocks and cannot be broken down into any smaller parts. All of the energy is distributed between the different particles - there is no energy that exists that is not in particles. The particles in the Standard Model are divided into two groups - "matter particles" and "force carrier particles". The matter particles are the electron, muon, tauon, electron neutrino, muon neutrino, tauon neutrino, and the up, down, strange, charm, bottom and top quarks, and all of their anti-particles. The force carrier particles are the photon, W and Z bosons, the gluons, and the Higgs boson. I won't go into what all of these particles are, but there are lots of good references on the web about them.
Although all the energy is in particles, the particles can undergo reactions that redistribute the energy between the particles. For example, a radioactive nucleus can undergo beta decay, where a neutron in the nucleus decays to a proton, electron and electron anti-neutrino. The amount of energy stays the same, but the particles and their velocities are different. If we assume the neutron was at rest, then most of its energy (rest mass) was used to make the proton, a much smaller bit was used to make the electron, a much much smaller bit was used to make the anti-neutrino, and the remaining energy went into kinetic energy of the proton, electron and anti-neutrino.
However, there are clues that the Standard Model is not the whole story, especially in astrophysics. You may have heard of "Dark Matter" or "Dark Energy" which so far has only been detected due to its gravitational effects. However, this is not "pure energy", it is still particles; we just don't yet know all the details of how the particles interact with the rest of the universe. It also may be that we eventually find out that particles we consider to be elementary actually have an internal structure, such as a superstring, but for now we don't have any evidence of that.
So, in a sense, fashioncrimewave, do you mean that everything exists in a form of energy, and the reason why we can touch things is due to the electromagnetic forces, cos for now we can't describe what the elementary particles are actually composed of?
| allanxiao wrote: |
| So, in a sense, fashioncrimewave, do you mean that everything exists in a form of energy, and the reason why we can touch things is due to the electromagnetic forces, cos for now we can't describe what the elementary particles are actually composed of? |
yes, everything is a form of energy. right, we can touch and pick up objects because of the electromagnetic forces between atoms. The EM forces are what allow you to hold an object in your hand, rather than having it fall right through. They are also to cause of friction forces and all kinds of other stuff.
As far as what are the particles made of - right, we don't know that. It could be that the particles are all varieties of superstrings or something exotic. Or, it may be that they are just the most fundamental building blocks, they are not composite objects.
It's also worth noting that it is incorrect to characterize particles as "balls" or to talk about the diameter of them. In current scientific theory, all particles are point particles. They have no size. An electron is just a probability cloud until observed, at which point its wavefunction collapses to a non-dimensional point.
But to answer the original question... the standard model has it that the entire universe has this field within it everwhere called the Higgs field. "Mass" is just the result of an interaction with this Higgs field. The more a particle distorts the Higgs field, the greater the observed mass. That distortion is such that it is self-sustaining, which leads to inertia - a particle in constant (non-accelerating) motion or at rest will tend to remain so because the field around it stays constant.
The thing that makes certain particles distort the field is the Higgs boson - the holy grail of modern physics.
So an electron distorts the Higgs field, but a photon does not. A down quark distorts the field more than the electron - but it's not that a quark is "bigger". It just has a larger Higgs interaction - more of an effect on the Higgs field.
The fact that mass and energy are interchangeable should become a little easier to see now. All mass is is a distortion of the field. When you "destroy" the mass, the field, which had been pulled into a distorted shape, "snaps back". The energy released by that snapping... E = mc². Going the other way is similar. If you apply E units of energy to distort the Higgs field, you will measure m = E ÷ c² as "mass" that you have created.
But to answer the original question... the standard model has it that the entire universe has this field within it everwhere called the Higgs field. "Mass" is just the result of an interaction with this Higgs field. The more a particle distorts the Higgs field, the greater the observed mass. That distortion is such that it is self-sustaining, which leads to inertia - a particle in constant (non-accelerating) motion or at rest will tend to remain so because the field around it stays constant.
The thing that makes certain particles distort the field is the Higgs boson - the holy grail of modern physics.
So an electron distorts the Higgs field, but a photon does not. A down quark distorts the field more than the electron - but it's not that a quark is "bigger". It just has a larger Higgs interaction - more of an effect on the Higgs field.
The fact that mass and energy are interchangeable should become a little easier to see now. All mass is is a distortion of the field. When you "destroy" the mass, the field, which had been pulled into a distorted shape, "snaps back". The energy released by that snapping... E = mc². Going the other way is similar. If you apply E units of energy to distort the Higgs field, you will measure m = E ÷ c² as "mass" that you have created.
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