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Fundamental particle?

  1. Jan 9, 2007 #1
    I have a question that may seem kind of simple, but I would like to hear your thoughts about it.
    Is there such a thing as a fundamental particle of which all other particles are made of, or even if is even possible for such a thing to actually exist? A particle of continuous matter (no empty spaces inside) , what density would it have?
    The reasons for this question are many.
    For example, if an atom has the size of a stadium its nucleus has the size of a pea, so what before could have been consider as the smallest block of matter is actually almost empty space with all its matter in a comparatively tiny size of its space, and then subatomic particles were discovered. Are they too made up of even smaller particles?
    And if no such fundamental particle actually exists, then what is the true nature of matter?
     
  2. jcsd
  3. Jan 9, 2007 #2

    Gokul43201

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  4. Jan 9, 2007 #3
    Ok the cern web page is nice but still im not satisfied,they take it for granded that matter is made up of particles, which somehow are bulding blocks, which then makes it necessary to ultimately find a true fundamental particle,otherwise the whole concept of particles would be undermined.
    Im asking wether it is actually even logicall for something like a fundamental particle to actually exist,what would its volume be? what would its density be? what would its mass be?
     
  5. Jan 9, 2007 #4
    Strings in string theory
     
  6. Jan 10, 2007 #5
    You're right - in modern particle physics is is ASSUMED that particles are point-like (have no structure) and are described by one of the relativistic quantum equations (Dirac, Klein-gordon, etc.)
    These questions are not very helpful at our current state of understanding (except for mass, which can be anything you like). Physicists find it more useful to ask questions like "How does an electron scatter off this particle?" If the scattering agrees with what is predicted by your chosen equation, then your equation is working. If it doesn't agree, then you have evidence that your particle is NOT a fundamental particle, but is made up of smaller particles. This is how we got evidence of quarks (that make up protons and neutrons). So far as we can tell, electrons, neutrinos, quarks, photons, W and Z, are all fundamental particles.
     
  7. Jan 12, 2007 #6

    mjsd

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    To be fair, I will assume that your question is asked in the views of science not in philosophy. So the quick answer is WE DON'T KNOW YET. And perhaps we will never know (?)


    Haha,... slowly and surely philosophy has to come in at some point... What do you mean by "actually exist"? how do you/we define existence? Would something be regarded as "exist" if no one there to actually ask the question in the first place? Does existence infer meaning? Oh... as you can see it starts becoming very hairy indeed.

    It appears that your definition of existence involves something that must possesses volume/density/mass... But first the good old questions: what is energy? Does it exist in the sense of a particle? Or are energy and particles the same thing? Also, what is spacetime? Why do time goes forward only? If we can answer these to our satisfaction, perhaps your original question would be answered. Your question cannot stand alone, a plethora of related questions which help define your question must also be addressed.
     
  8. Jan 12, 2007 #7

    ZapperZ

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    mjsd brought up several very important points. Unlike philosophy, physics must be based on very clear and unambiguous description, and this is done via the language of mathematics. Because of that, we have to clearly define almost every concepts and idea that we use. If you do not do that, then this discussion belongs in Philosophy, and I will move it there. However, if you wish to have a physics answer and physicists to answer to it, then you have to be very clear in what you are asking and discussing.

    Now if you keep that in mind, you then need to reexamine that question that you ask. In particular, you should ask "Do I really know what I'm asking?" This is especially true when you ask if something "actually exist". Examine something that you have accepted to "exist". Look at the criteria that you used to accept that it exists. You will notice that what you have is a series of "characteristics" or "properties". You recognize an apple because of its (i) shape (ii) taste, etc... via your senses. A biologist may characterize it with other properties to recognize it as something that fits into the specie with other apples.

    The point here is that practically ALL of the things you accept to 'exist', involves your detection of a set of characteristics. If you are aware of the rules that you have unconsciously accepted to designate something to exist, then you can now examine how, in physics, we accept the existence or the validity of such-and-such concepts, such as an electron. This is crucial because we now have to detect and study things that we cannot see with our eyes, since our visible range is very limited in the scheme of things. It will allow you to know why we know the top quark exists and has been verified, even when we do not detect it "directly".

    So for this to be a physics question, the question itself must be clear enough for physics to answer. If not, it will simply become a series of blind speculation that usually leads to nowhere.

    Zz.
     
  9. Jan 12, 2007 #8
    Thank you for your responses, to give my question more direction I would like to ask you now, if there are experiments where matter (particles) are scattered in a wave diffraction pattern then why is it that physicists still consider these (particles) as particles with wave properties that come into play as probabilities of position associated, and not just waves?
    If all matter is waves then the hits of the particles on the detection screen would be just the interaction of the (particle) wave with the screen wave.
    Off course one would then ask, waves of what?
    Maybe matter waves?
    Just like (particles) of matter.
     
  10. Jan 12, 2007 #9

    ZapperZ

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    OK, now this is a different question, and it is now more fundamental and basic than your earlier question because this is more quantum mechanics than high energy/elementary particle physics. You are now discovering that you have to learn how to crawl first before trying to run.

    There is an FAQ in the General Physics forum on this so-called 'wave-particle' duality that you have refered to. You need to keep in mind that when physicsts talk about such thing, it is more in line of trying to communicate to the general public. In reality, we very seldom use such phrases in our communication with each other. Why? Because there is no wave-particle duality! <shock rings through the forum!>

    How can I get away with saying that? By pointing to the fact that in quantum mechanics, there is one and only one consistent formulation that describes ALL the behavior of these so-called "quantum particles" that sometime have wave-like behavior and sometime have particle-like behavior. So when you simply have one description that can do this, there is no duality. It is only when we try to describe such a thing within the context of classical mechanics do we use such dichotomy or separation, because in classical physics, wave and particle cannot be intermix and cannot be describing the same object. So you have to use two separate description. No such thing is done in quantum mechanics.

    So now, armed with that info, can you look again at your question and see if you might now want to change what you have understood so far?

    Zz.
     
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