• Question: If we are all made up of empty space down to the 10^-5 degree ( thats 99.9999%!) why can we not walk straight through walls!? and fall straight through a chair everytime we sit down? Surely we should have a better thoery of how the natural forces act...?

    Asked by ddkcdk to Adam, Geoff, Rob, Sheila, Suzie on 23 Mar 2011 in Categories: .
    • Photo: Suzie Sheehy

      Suzie Sheehy answered on 21 Mar 2011:

      Hi there, good question thanks.

      We are indeed made up mostly of empty space (I assume that like me, you’ve been watching Brian Cox’s programs on TV!), and it came as a big surprise to scientists in the early 20th century when they discovered this!

      The reason we can’t walk straight through walls is because of the electrical forces of the atoms that we’re made from. Electrons repel each other – so if you bring two atoms near each other the electrons whizzing around the nucleus will repel. It’s such a strong repulsive force that it stops us from walking through walls or falling straight through a chair!

      It seems strange that such tiny things should produce such strong forces, and in particular that the force we experience every day (gravity) is SO much weaker than the electromagnetic force, or the forces in the nucleus. The difference between the forces is still a mystery – we don’t know why they are all so different!

      But we’re trying to find out by studying matter in it’s most basic forms – fundamental particles. That’s one of the reasons that we’ve built the Large Hadron Collider near Geneva, to try to find out more about the forces of nature.

      I hope that helps, let me know if you want to know more!

    • Photo: Sheila Kanani

      Sheila Kanani answered on 21 Mar 2011:

      Aw I love this q! I wish we could walk thru walls.

      I think we technically can, just the probability of that happening is really low!

      Its to do with quantum mechanics, tunneling, Pauli exclusion principle and other big words like that.

      But I think its also to do with repulsive forces ie electrons ‘repel’ other things with the EM force. This makes it so your particles and a wall’s particles repel each other to a point where you cannot go through the wall itself.

      Someone once told me a good analogy I like though:
      Imagine a ceiling fan. When your ceiling fan is off, you can easily put your hand through it and touch the ceiling. When it’s on full blast, the blades start looking almost like 1 object, and if you put your hand in there, it’s going to stop you.
      Now think about atoms and electrons etc orbiting at near-light speeds. So the wall may give the appearance of being 100% solid like a fan when it is on, but actually its made up of lots of particles all orbting real fast.

    • Photo: Adam Tuff

      Adam Tuff answered on 21 Mar 2011:

      Good question! Well, the answer lies in the strong nuclear bonds and the atomic molecular bonds – these essentially hold us together by holding each other together. These inter-molecular, inter-atomic forces are not easily broken.

    • Photo: Robert Simpson

      Robert Simpson answered on 23 Mar 2011:

      This is all due to the electromagnetic force. The atoms and molecules of your body are held together by electromagnetic forces and the surface of your body also. If we suddenly turned off the electromagnetic force then (asides fro everyone dying horribly in an instant) then you would pass through objects and fall into the Earth.

Comments

  • Photo: ddkcdk

    ddkcdk commented on :

    as for the strong nuclear force, everytime someone talks about it, i just end up thinking that why did we have to create a new force to explain the force holding together a nuclues? The obvious thing to me is that maybe there is a property of gravity that when two particles (in this case nucleons) are a certain distance apart, usually 2-3 nucleon diameters, the value of G (the gravtational constant) changes, and becomes greater, hence overcoming the electrostatic force (repulsion between protons) and holding the nucleus together. I dunno if im making sense… but i know what i mean;)…

    • Photo: Suzie

      Suzie commented on :

      that’s a good theory! I’ve never tried doing the maths, but I like the way you’re thinking that by changing parameters, one force becomes another in certain circumstances. We know that’s true and that the ‘weak’ nuclear force and the ‘electromagnetic’ force are actually the same thing. But I’m not sure how we’d fit gravity in… it’s an unsolved problem in physics.
      I hope this kind of problem might inspire you to get involved and maybe one day you’ll be able to tell me!

  • Photo: ddkcdk

    ddkcdk commented on :

    dont worry, i will!;)
    and this is why i like physics, because most of it doesnt make sense when you think about it…

    • Photo: Suzie

      Suzie commented on :

      not entirely sure I agree, i think most of it makes sense when you think about it deeply. Sometimes it’s just thinking about it in a certain way… and I like that everyone has their own ideas of how things work, even if they are all based on the same explanation we all visualise it differently.

  • Photo: waveicle

    waveicle commented on :

    gotta get rid of that 0.0000001% of atoms within the body!