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!

Is this how particles interact?

  1. Apr 19, 2009 #1
    protons attract electrons,
    neutrons are neutral to protons+electrons
    antimatter particles attract regular matter

    also one more thing, does it take lots of energy to fuse neutrons into an atom nuclei?
    Last edited: Apr 19, 2009
  2. jcsd
  3. Apr 19, 2009 #2
    Electrically yes, because they have opposite charge. But when they get really close to each other, weird things happen. In other words, an electron never spirals into a proton as a comet might fall into the Sun. This is the sort of thing that quantum mechanics deals with.

    Electrically yes. But neutrons are important in the strong force, which holds nuclei together. When neutrons are present, the strong force can overpower the electrical repulsion of protons, or else no elements but Hydrogen would be possible. I don't think you'll ever find a nucleus of just two protons for example.

    Oh, and gravitationally, these particles attract each other, but that's typically negligible.

    This is a little ambiguous. An electron and a positron attract each other electrically because they have opposite charge. but a positron is not electrically attracted to a proton because they have the same charge.

    However, it's an interesting question to think about how matter and antimatter interact gravitationally. In other words, would antimatter fall up?
  4. Apr 19, 2009 #3
    What would you consider an alpha particle to be? :smile:

    Oops: alpha particles are two protons and two neutrons; my mistake!
    Last edited: Apr 19, 2009
  5. Apr 19, 2009 #4
    I'm not sure I quite understand your question, but here goes...

    When light nuclei fuse together, energy is released not consumed. For example, inside a star, Hydrogen and Helium will fuse together into heavier elements. In older stars, where the very lightest nuclei have been used up, other nuclei like Carbon will also fuse. This kind of fusion releases energy, and it's why stars shine.

    But to fuse heavy nuclei together, you have to put energy in. For example, nature makes gold and silver out of lighter nuclei using the tremendous energy produced in a supernova explosion. Without such an energy source, heavier atoms would never be found. This has profound implications. Before the first supernova, a planet like the Earth rich in elements, could not have existed.

    If I recall correctly the threshold between light and heavy in this context is Iron. Nuclei lighter than Iron can fuse release energy, and nuclei heavier than Iron require energy to be fused together.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook