Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Is matter mostly empty space?

  1. Jun 24, 2011 #1
    The most abundant element in the universe is hydrogen. The hydrogen atom, like all atoms, is composed of a nucleus orbited by a(n) electron(s). The most likely orbit of the electron in a hydrogen atom, according to the Bohr model, is about 5.3 X 10-11 meters. The volume of the hydrogen atom then is about 6.24 X 10-31 cubic meters. The single proton that makes up the nucleus of the hydrogen atom has a volume of about 4.19 X 10-42 cubic meters. Hydrogen's single electron's volume is approximately 9.2 X 10-44 cubic meters. If we compare the sum of the volumes of the electron and the proton to the volume of the entire hydrogen atom, the proportion of that atom that is empty space is 99.999999999314%!

    If my analysis is basically correct, it appears at first glance that matter is obviously not much different from space. Yet, we all know that matter is much different from space. The apparent difference is a result of the motion of the electrons in their orbits about the nucleus. The volume and solidity of matter is a product of motion.

    Jagella
     
  2. jcsd
  3. Jun 24, 2011 #2

    WannabeNewton

    User Avatar
    Science Advisor

  4. Jun 24, 2011 #3
    Interesting! I wonder how the result for hydrogen compares with iron? If a cubic meter of iron was reduced to a speck of solid matter (all space eliminated), would this speck be visible to the naked eye or would I need a microscope to see it?
     
  5. Jun 24, 2011 #4

    phinds

    User Avatar
    Gold Member
    2016 Award

    is there a question here somewhere?

    I'm not sure it's a product of motion ... I always thought it's because of the CHARGE
     
  6. Jun 24, 2011 #5

    Drakkith

    User Avatar

    Staff: Mentor

    That's the thing though, you cannot remove all the empty space. The closest thing I can think of would be in a Neutron star. It would cease to even be iron if you could remove the space in your block!

    While the charge is what keeps the electron bound to the nucleus, it is actually much more complicated. The electron can only be in specific energy levels around the nucleus due to quantum effects. In addition, the pauli exclusion principle tells us that two electrons (and all fermions to be precise) cannot have the same quantum numbers and occupy the same spot in space at the same time. Since the orbitals have distinct distances from the nucleus the result is a very large amount of "empty space". Although I'm not 100% sure it is entirely empty, as the electron wave form occupies the entire orbital I think. I don't know if that is just a math thing or if it actually happening. In any case I would personally say that the direct cause of all this empty space is the pauli exclusion principle. (Or rather the effect it is describing)
     
    Last edited: Jun 24, 2011
  7. Jun 24, 2011 #6
    1 m3 of iron has a mass of 7.874 t. Removing all the empty space would convert it to white-dwarf-type degenerate matter, whose density is approximately 1 t/cm3 (see http://en.wikipedia.org/wiki/White_dwarf#Composition_and_structure"); so the iron would be easily visible, occupying about 8 cm3.
    Of course, you could not call it iron any more (in the usual sense). The nuclei would retain their nature and separate identities, but they would no longer be iron atoms because of the collapse of the electron shells.
     
    Last edited by a moderator: Apr 26, 2017
  8. Jun 24, 2011 #7

    Drakkith

    User Avatar

    Staff: Mentor

    Just to point out, the matter in a white dwarf is not in a normal physical structure as in the iron bar. Most of the electrons are not bound to the nuclei and the whole thing is more of a plasma than a solid. But you are essentially correct in your explanation.
    Edit: Heh, looks like you edited your post between when I read it and replied. (Either that or I just misread it) Yes, that is pretty much spot on as far as I can tell.
     
    Last edited by a moderator: Apr 26, 2017
  9. Jun 24, 2011 #8
    Sure. Is it safe to say that matter is less a result of actual subatomic particles and more the consequence of its attendant physical phenomenon such as charge?

    Please elaborate. Are you saying that the repulsion between particles of like charge and attraction between particles of opposite charge is what gives matter its apparent solidity? Is all that empty space in an atom obscured by charge in the atom?

    Jagella
     
  10. Jun 24, 2011 #9
    Try it out for yourself. Look up the diameters or radii for electrons, protons, and neutrons and how many of each make up the iron atom. Then, find the diameter or radius for the iron atom. Calculate the total volume for these particles and the whole atom using the formula 4/3 π r3. Finally divide the sum of the volumes for the particles into the volume of the iron atom. The result is the proportion of the iron atom's volume taken up by particles.

    It may seem like a lot of work, but I've found it's a great way to learn about physics.

    Jagella
     
  11. Jun 24, 2011 #10

    phinds

    User Avatar
    Gold Member
    2016 Award

    What I'm saying is that the reason we can't walk through walls is that our electrons are repulsed by the wall's electrons. There is no "apparent solidity" in my mind since you are quite correct that matter is almost entirely empty space. What there IS is the inability of macro objects to pass through each other and of course we DO perceive that as solidity.
     
  12. Jun 24, 2011 #11
     
  13. Jun 25, 2011 #12

    phinds

    User Avatar
    Gold Member
    2016 Award

    Molecules SHARE electrons among their atoms (look up "molecular bonding") rather than having them cause any repulsion. Now, how the MOLECULES hook together I'll have to leave for someone who knows that stuff ...
     
  14. Jun 25, 2011 #13

    atyy

    User Avatar
    Science Advisor

    And also because of its fermionic nature. http://arxiv.org/abs/math-ph/0401004
     
  15. Jun 25, 2011 #14

    Drakkith

    User Avatar

    Staff: Mentor

     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Is matter mostly empty space?
  1. Empty Space forever? (Replies: 17)

  2. Empty Space (Replies: 8)

  3. What is empty space ? (Replies: 5)

  4. Does empty space exist (Replies: 5)

Loading...