1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B Why is matter solid?

  1. Nov 14, 2016 #1
    The double slit experiment shows, that particle only become solid when observed, shouldnt be matter behind walls aka where it is not watched be only a potential wave and not be solid at all?
    Is that what Max Planck meant when he said:

    “All matter originates and exists only by virtue of a force which brings the particle of an atom to vibration and holds this most minute solar system of the atom together. We must assume behind this force the existence of a conscious and intelligent mind. This mind is the matrix of all matter.”

    so something has to be watching everything we call matter but is not viewable to the humand/animal eye, or it would vanish into pissibility?
  2. jcsd
  3. Nov 14, 2016 #2


    User Avatar
    Science Advisor
    Homework Helper
    2017 Award

    Hello Dieter, :welcome:

    'Solid' is a term we reserve to describe an aggregation mode of many many atoms/molecules.
    There is nothing watching everything. All we do in physics is try to describe what we observe and cast that in models (theories) that can be tested by allowing predictions to be verified or falsified. In the latter case the theory is usually abandoned.

    I don't think Planck's quote is still considered sensible. In fact I find it internally contradictory: "Da es im ganzen Weltall aber weder eine intelligente Kraft noch eine ewige Kraft gibt" followed by "so müssen wir hinter dieser Kraft einen bewußten intelligenten Geist annehmen" ?
  4. Nov 14, 2016 #3
    Hi BvU,
    but it is well observed, that atoms and small particles only break free from beeing possibility wave, in the double slit experiment, when they are observed. Therefore isnt it right to assume something is observing the whole thing which is behind/under walls or floors, or it would return into beeing a possibility wave?
  5. Nov 14, 2016 #4
    if I have to argue about this stuff I would say nature is observing itself...or at least the interactions of the wall and the great heat sink that is the universe that surrounds it.

    I am pretty certain walls remain in tact when no human is watching.

    as far as "pissibility" I refrain from comment.
  6. Nov 14, 2016 #5


    User Avatar

    Staff: Mentor

    The double-slit experiment shows no such thing. It does show that particles do not have a definite position unless and until the position is observed - but the word "observe" means something very different in quantum mechanics than it does in ordinary English, and "definite position" has very little to do with solidity. Unless you want to spend some time learning quantum mechanics (and the first step in that process is unlearning the things you think you know that just aren't so) It's best to start with a classical understanding of solidity.

    In fact, no object is completely solid; if you press on the surface it deforms. Materials like hardened steel deform only slightly even under enormous forces so we ignore the deformation and think of them as completely rigid, while materials like rubber deform more easily. Some materials spring back to their original shape after being deformed and other's don't; the surface of a sandy beach is more rigid than the surface of a trampoline, but it's a lot easier to leave footprints on the beach than on the trampoline.

    All of these effects can be calculated from the interactions between the atoms that make up an object with each other and with the atoms that make up whatever is pressing on it. However, the individual particles are never pressing on one another the way that one billiard ball presses on another; all the forces are coming from the electromagnetic interactions between the charged particles (electrons and nuclei) that make up these atoms.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted