granpa
Member (Idle past 2370 days) Posts: 128 Joined: 10-26-2010
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Message 7 of 31 (616059)
05-19-2011 7:48 AM
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Reply to: Message 4 by nwr 05-19-2011 1:07 AM
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standard model
point particles are part of the standard model
This message is a reply to: | | Message 4 by nwr, posted 05-19-2011 1:07 AM | | nwr has replied |
Replies to this message: | | Message 9 by nwr, posted 05-19-2011 8:35 AM | | granpa has replied | | Message 30 by Son Goku, posted 07-10-2011 8:52 AM | | granpa has not replied |
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granpa
Member (Idle past 2370 days) Posts: 128 Joined: 10-26-2010
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Message 10 of 31 (616063)
05-19-2011 8:52 AM
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Reply to: Message 9 by nwr 05-19-2011 8:35 AM
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Re: standard model
Point particle - Wikipedia
quote: In quantum mechanics, there is a distinction between an elementary particle (also called "point particle") and a composite particle. An elementary particle, such as an electron, quark, or photon, is a particle with no internal structure, whereas a composite particle, such as a proton or neutron, has an internal structure (see figure). However, neither elementary nor composite particles are spatially localized, because of the Heisenberg uncertainty principle. The particle wavepacket always occupies a nonzero volume. For example, see atomic orbital: The electron is an elementary particle, but its quantum states form three-dimensional patterns. Nevertheless, there is good reason that an elementary particle is often called a point particle. Even if an elementary particle has a delocalized wavepacket, the wavepacket is in fact a quantum superposition of quantum states wherein the particle is exactly localized. This is not true for a composite particle, which can never be represented as a superposition of exactly-localized quantum states. It is in this sense that physicists can discuss the intrinsic "size" of a particle: The size of its internal structure, not the size of its wavepacket. The "size" of an elementary particle, in this sense, is exactly zero. For example, for the electron, experimental evidence shows that the size of an electron is less than 10-18 m.[6] This is consistent with the expected value of exactly zero. (This should not be confused with the classical electron radius, which, despite the name, is unrelated to the actual size of an electron.)
This message is a reply to: | | Message 9 by nwr, posted 05-19-2011 8:35 AM | | nwr has seen this message but not replied |
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