Edmund Kwa
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What does the spin of a particle tell us ? And what does it means ?
Luke Burns: Check out: http://www.markusehrenfried.de/science/physics/hermes/whatisspin.html
Alexander Anderson-Natale: The spin of a particle tells us how it behaves under interchange.... Yes, that is true, but what does that mean for physical systems? Things with integer values of spin (0,1,2, etc.) can be in the same place at the same time in the same quantum state. These are called bosons, and a consequence of this is that at low temperatures bosons form condensates where they clump together around the ground state and create Bose-Einstein condensates. Things with half-integer spin (1/2,3/2,5/2,etc.) are called fermions and are a reason why you would still have electrical current even at zero temperature; electrons are fermions and even if they are at zero temperature they cannot be in the same quantum state and so they will always have some distribution of momentum in a metal (see: fermi surface).
There is a lot we could talk about spin, but it also can tell us how a particle decays. Spin is conserved, and so if a particle decays the spin of the products can give limits on the spin of the original object (with restrictions). For instance a spin 0 object can decay into two spin 1/2 objects, but so can a spin 1 object. How do we tell the difference? Well, the decay products will be distributed differently in the detector (eg they will have a different angular distribution) due to the different spins of the mother particles (the particle that decayed).
As a very theoretical side note, spin also has a deep connection to relativity.
There is a lot we could talk about spin, but it also can tell us how a particle decays. Spin is conserved, and so if a particle decays the spin of the products can give limits on the spin of the original object (with restrictions). For instance a spin 0 object can decay into two spin 1/2 objects, but so can a spin 1 object. How do we tell the difference? Well, the decay products will be distributed differently in the detector (eg they will have a different angular distribution) due to the different spins of the mother particles (the particle that decayed).
As a very theoretical side note, spin also has a deep connection to relativity.
Mithrahee Zor-El: +Alexander Anderson-Natale
right!, that sounds to be an well interpretative for more... "What does it means?", "for meaning?" to "tell" approach to some numbers(?) - hihi.
right!, that sounds to be an well interpretative for more... "What does it means?", "for meaning?" to "tell" approach to some numbers(?) - hihi.
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Izit quark the smallest particle in universe ?
Cliff Harvey: +Edmund Kwa There are two different kinds of waves that you should be careful to distinguish. Electromagnetic waves are not like quantum waves.
Electromagnetism has to do with the electromagnetic field. Every elementary particle is associated with a field, and the particle is a single quantum-mechanical unit of its vibration. So it is a quantum effect that creates the particles, however, the electromagnetic field is mostly known as a classical system, including most electromagnetic waves. Waves in a field are just like any other waves you are familiar with, just dont confuse them with quantum wavefunctions.
A quantum wavefunction is a more difficult and radical concept. It would be unreasonable for me to try to explain it here. It is a wave in the "space of possible states" of a physical system.
To try to answer your question, a quantum particle doesn't have a "wave form" and a "particle form". Roughly speaking, a particle will be more wave-like when it is physically extended, and more particle like when it is more condensed. If its position is measured, all of the wavefunction will collapse to a single point. If its momentum is measured, it will collapse a long plane-wave.
Electromagnetism has to do with the electromagnetic field. Every elementary particle is associated with a field, and the particle is a single quantum-mechanical unit of its vibration. So it is a quantum effect that creates the particles, however, the electromagnetic field is mostly known as a classical system, including most electromagnetic waves. Waves in a field are just like any other waves you are familiar with, just dont confuse them with quantum wavefunctions.
A quantum wavefunction is a more difficult and radical concept. It would be unreasonable for me to try to explain it here. It is a wave in the "space of possible states" of a physical system.
To try to answer your question, a quantum particle doesn't have a "wave form" and a "particle form". Roughly speaking, a particle will be more wave-like when it is physically extended, and more particle like when it is more condensed. If its position is measured, all of the wavefunction will collapse to a single point. If its momentum is measured, it will collapse a long plane-wave.
Edmund Kwa: +Cliff Harvey is this related to Heisenberg uncertainty principle ?
Josh Cogan: Hey +Cliff Harvey and +Edmund Kwa ,
Not sure if this thread is dead, but I thought I'd contribute. First off, electromagnetic waves are absolutely quantum waves. The better question is why could we explain light so well with only classical wave theory. If photons interacted very strongly with each other (ie they bounced off of each other with some non-miniscule probability) then classical theory wouldn't have sufficed. Also since you can stick many photons in an identical state, you dont' notice the quantized nature of the photon. (Contrast this with electrons who can only have 1 per state).
The Heisenberg uncertainty principle isn't really as magical as the Internetz would have you believe. Once you believe all particles (even electrons) are mathematically described by a wave equation, then the "uncertainty principle" is a really anti-climactic mathematical consequence of Fourier theory. It has physical consequences but not is not caused by a deep physical axiom.
If you do wanna really get confused by quantum information being non-intuitive, read the Stern Gerlach experiment which has nothing to do with (classical) waves, and everything to do with quantum wierdeness. I think Townsend's QM book gives an excellent 10 pages devoted to it!
Good luck!
Josh
Not sure if this thread is dead, but I thought I'd contribute. First off, electromagnetic waves are absolutely quantum waves. The better question is why could we explain light so well with only classical wave theory. If photons interacted very strongly with each other (ie they bounced off of each other with some non-miniscule probability) then classical theory wouldn't have sufficed. Also since you can stick many photons in an identical state, you dont' notice the quantized nature of the photon. (Contrast this with electrons who can only have 1 per state).
The Heisenberg uncertainty principle isn't really as magical as the Internetz would have you believe. Once you believe all particles (even electrons) are mathematically described by a wave equation, then the "uncertainty principle" is a really anti-climactic mathematical consequence of Fourier theory. It has physical consequences but not is not caused by a deep physical axiom.
If you do wanna really get confused by quantum information being non-intuitive, read the Stern Gerlach experiment which has nothing to do with (classical) waves, and everything to do with quantum wierdeness. I think Townsend's QM book gives an excellent 10 pages devoted to it!
Good luck!
Josh
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