• Question: What are particles?What causes them to exist?

    Asked by ibrah071 to Joel, Kristian, Tim, Venus, Zachary on 14 Nov 2013.
    • Photo: Kristian Harder

      Kristian Harder answered on 14 Nov 2013:


      Wow, this is really getting philosophical here! 🙂
      We’ve become quite good at describing what particles are and how they behave. They aren’t really what you would expect them to be judging from the term “particles”, because they aren’t really solid objects. They are more like a mixture of a wave and a particle. They spread out like waves, and that means they can do things that only waves can do, such as cancel each other out when peak meets trough, but when they interact with something else, they do it like point-like particles. You can see them as objects whose location as a point-like particle is described by (and evolves with) a probability distribution with wave-like properties.
      You can already see that it’s hard for me to describe it in words. The mathematics behind it is perfectly clear, but as famous physicist Niels Bohr put it once, “when it comes to atoms, language can be used only as in poetry”, because we don’t really have the right words for them.
      So, now, part two of your question: what causes them to exist. Well, the simple answer is: energy. 🙂 If you have energy, you can make particles (and anti-particles). Simples!
      But you probably meant it more along the lines of why these particles exist, and why they have the properties we observe? Well, no idea. You can give reasons for many things, but at some point you reach the end of it, and you just have to accept that this is how nature is like. You can say that apples fall down because they are attracted by gravity, but you cannot give a reason for why gravity exists. That’s just how it is. (Of course sometimes we do find a deeper reason – for example, we know now why magnetism exists. It’s just a relativistic effect of electric forces. Ask you teacher for details. 😉 )

    • Photo: Joel Goldstein

      Joel Goldstein answered on 15 Nov 2013:


      The word “particle” has lots of meanings. In mechanics, it means anything small enough that you can ignore its physical size, i.e. “pointlike”. In the term “particle physics” it normally means anything smaller than a nucleus (e.g. alpha particle). Often, however, it refers specifically to the fundamental particles like the electron and quarks.
      We know of almost 20 different types of fundamental particle, but no-one knows why there are so many, why they have the properties they do, or why they exist at all. Maybe one day we will discover a deeper theory in which they are not fundamental at all but made up of even smaller, truly fundamental particles, but then we would have to ask where _they_ came from.

    • Photo: Tim Hollowood

      Tim Hollowood answered on 15 Nov 2013:


      Particles are really to thought of tiny ripples on a field…like a magnetic field. In fact the ripple on the magnetic (and electric) field is the particle of light that we call a photon. Each particle has it’s own associated field so there’ also an electron field and a quark field. Particles can be created and destroyed because the fields interact. For example a photon can annihilate and create an electron and a positron (an anti-electron). These kinds of things are going on all the time. So in a way the fields are more basic than the particles.

    • Photo: Zachary Williamson

      Zachary Williamson answered on 15 Nov 2013:


      Ah, well we’re really reaching the limits of human knowledge with this question.

      We currently know of 12 fundamental particles (well, 13 now that the Higgs has been discovered). These are particles that can’t be subdivided into smaller components.

      This is considered to be a very unsatisfactory state of affairs, because why 12? That just seems needlessly convoluted. Even worse, our theory of how these particles interact with each other require certain constants in the mathematical equations. Where do these constants come from? Nobody knows!

      What we think is going on, is that what we currently see is a mere representation of a far more fundamental theory that we don’t know of yet. It would make a lot more sense for there to only be one fundamental particle, or even zero! One such theory is called string theory: that all the particles we see are just bits of space-time vibrating in different ways (no I don’t understand it either).

      Truth is we don’t really know. We have good reason to believe that the 12 fundamental particles we currently see will merge together into a smaller set of fundamental particles at high energies, but the energies we’re talking about are many, many orders of magnitude greater than anything we’re capable of exploring with our current technology 🙁

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