Quantum mechanics?

Discussion in 'Physics & Math' started by Borg255, Apr 7, 2001.

  1. Borg255 Registered Member

    I read somthing about quantum mechanics. It was talking about an atom or somthing anyway... it said that what they were trying to messaure was somthign about spin up and spin down between two particles that had intereacted and that if particle A had down spin particle B had up spin but untill you measure it they both have both types of spin. does this mean that if a person doesnt see somthing it doesnt exist or isnt real or somthing? Help....

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  3. NanoTec Registered Senior Member

    Spin is a property of charged particles. If you think about the charge moving about a coil of wire, it has two directions to move, and for each direction it creates a different magnetic field. Spin is similar. If two particles with opposite spins occupy the same state then the two spins cancel and there is no direct measurement despite the presence two different spins.
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  5. Crisp Gone 4ever Registered Senior Member

    Ehr, excuse me, but ...

    Hi all,

    First of all, Nanotec:

    Spin is not only a property of charged particles, it's a property of all particles. The particles that make up matter (elektrons, protons and even the uncharged neutrons) have spins denoted by s = 1/2. Fotons have spin 1, and combinations of all systems can have a whole variety of spins.

    That's one possibility: when combining spins it is also possible that they do no cancel out. A system of two elektrons can have both spin 0 (where the two spins "cancel", although this phrasing is not 100% politically correct) or it can have spin 1.


    In quantummechanics it is true that a particle can have both spin up and spin down combined, while measurement can only give either spin up or spin down. It's a strange effect that's referred to as the "superposition of states".

    It's a bit difficult to explain in QM terms, so let me use the analogyof Schrödinger's cat: if you put a cat in a box ( = atom), and seal it off, how do you know if the cat is alive or dead ( = spin up/down) one day after you did that ? You don't know, so you decide it is both alive and dead, with one possibility being more probable than the other. The only way to know for sure is to open the box and look at it ( = measurement). The idea of the cat being both alive and dead might seem strange, but using this idea in QM seems to work out fine

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  7. Ash Registered Member

    Re: Ehr, excuse me, but ...

    Crisp, what youre saying seems conceptually acceptable, however, realistically, in the physical world, wouldnt it be truer to say that mr. schrodingers cat was alive, but asleep? in the physical world we have to accept that the cat cannot be alive and dead; altho they are qual probabilities. so tho your particals may 'appear' to have both spin up and spin down, they can only have one or the other, its just that we dont have the technology to measure it. unless QM accepts the concept of parallel universes?
  8. Crisp Gone 4ever Registered Senior Member


    Hi Ash,

    Now this is the tricky part: you can't say that the particles appear to have both spins up and down. From the moment you perform a measurement, you will find that it is either in spin up or spin down, but you will not measure both at the same time. As long as you're not looking at the particle, it is in some weird state of both spin up and down. The same goes for Schrödinger's cat: if you open the box, you will find the cat either alive or dead (and not asleep as you nicely dubbed the mixed state).

    The point is that as long as you have the closed box (with the cat inside) in front of you, quantummechanics tells you that you cannot for sure know that the cat is alive or dead. You have to look inside the box to rule out one of the two possibilities.

    You can argue that a macroscopic object like the cat cannot be in some mixed state of being both alive and dead. I personally think you can't, since this is not experimentally verifiable: from the moment you look at the cat to see if it is in that mixed state, you perform the measurement and make the wavefunction collapse towards one of the two possibilities (as it is called).

    I should add that the act of measurement is still not very well understood in quantummechanics. A few months back I stumbled across a PhD student's page whose thesis consisted of investigating what place the concept of measurement has in quantummechanics. Just to say that this topic is still investigated today.

    Yes, this is also another possible interpretation for quantummechanics. So far I haven't had the time to read up on the many-worlds (parallel universe) interpretation - apart from some very basic stuff - , so unfortunately I cannot comment on which of the two interpretations works out best.


  9. FA_Q2 Member Registered Senior Member


    QM does not need multiple dimensions to give a particle 2 states. In fact a particle can be a two places at the exact same time. It is a science of probability. In order to understand it you have to forget everything that you currently know. Not that I understand it, I don't think anyone does.
  10. wet1 Wanderer Registered Senior Member


    You can have top spin, bottom spin, or no spin. And each is a different particle.
    The act of actually measuring to see which changes what is percieved. You can either know which way it's spinning or how fast it's moving. You can not know both at the same time. (I think I remember this correctly) It's an oddball concept but one that is accepted by orthodox science as being correct. It;s kinda hard to grab it by the booboo if you know what I mean.
  11. Ash Registered Member



    is that really so? I thought it was that you couldnt measure a particles velocity as well as location at the same time. Meaning that by the time you measure its speed, its location has changed, or if you measure its position, its already whizzed away. if there is some truth in that, does that indicate that the particle is at two places at the same time?

    it still seems to me that its a case of not being able to clearly identify a chose in action rather than 'supposing' it exists in two places at the same time.
  12. Crisp Gone 4ever Registered Senior Member

    To quote Feynman: "Don't ask yourself how it can be like that, nobody knows".

    Hi Ash,

    What FA_Q2 said about the particle being able to exist at two places at the same time is correct, but you have to interpret it correctly: when you measure the position of the particle, you will find it to be at one location (and one only). If you would be able to rewind time, and perform the exact same measurement again, you could very well find it at a different location.

    This is one possible way to interpret quantummechanics, and it is commonly referred to as "the orthodox position" (which is the interpretation Einstein supported by the way). I'm not going into details here (that would take a bit too much time), but the following brief summary should get you on your way on finding out more on the orthodox position and how it has been proven unsustainable:

    In the 1920's, there was much debate on the possible interpretations of quantummechanics, notably between the Kopenhagen interpretation - where you postulate that the wavefunction in quantummechanics (QM) is related to the probability of finding a particle somewhere in space - and the orthodox position, where you postulate that the particle is in fact at one location but QM is unable to tell you where. In an attempt to prove that the Kopenhagen interpretation cannot be correct, Einstein, Podolsky and Rosen proposed a thought experiment which is nowadays known as the EPR-paradox: if you have a decay of a spin-zero particle into an electron and a position, then the conservation of angular momentum predicts that the two spins of the particles should have opposite signs (+1/2 for one and -1/2 for the other). If you would then seperate the electron and positron and lead them to several lightyears apart, you can get an apparent contradiction with relativity: measuring the spin of the electron would result in an immediate knowledge of the spin of the positron several lightyears further. (I say apparent because this contradiction has been resolved in the meantime). The fundamental assumption in the EPR argument is that no information can propagate faster than light (= principle of locality). They used this argument to say that their position, the orthodox position, was the only sustainable one: QM is unable to tell you the exact position of a particle, so there must be some variable (often called Lambda) that is unknown to us, but that should resolve this "inaccuracy" of QM. This variable is called a "hidden variable" and all theories trying to introduce this variable into QM are called "hidden variable theories". But in the 60's, Bell proved an inequality (Bell's Inequality) that states that any local hidden variable theory simply cannot hold. This basically smashed the EPR argument and the orthodox position.


  13. Ash Registered Member

    Re: To quote Feynman: "Don't ask yourself how it can be like that, nobody knows".

    First off i wanted to thank you for your detailed response. im a layman in the field of physics, but feel strongly drawn to it. i understand what youre saying about the orthodox theory being disproven, however it seems to me that QM does not prove its position either.

    maybe im not understanding correctly, but it appears that for QM to hold that a particle exists in two places simultaneously, something has to give, either the variable of time or space. for want of better words, there canbe either a 'time warp' situation so that a particle moves thru time and space and shows up somewhere else at the same time, or a 'tear' in space which (not that i know how that works precisely) would mean that the particle in one place has moved thru space but effectively landed up elsewhere at the same point in time due to some sort of a space warp/tear etc.

    Randon thought on matter: Also, if the QM theory stands and the same particle can be at two places at the same time then that same particle can be at an infinite number of places at the same time; hence populating our 'infinite' space with the same one particle.
    Last edited: May 18, 2001
  14. Crisp Gone 4ever Registered Senior Member

    The exotic world of elementary particles

    Hi Ash,

    Okay, saying that a particle can exist at the same place at the same time is probably a bit confusing. Allow me to explain in more detail how the classical interpretation (Kopenhagen) of QM works:
    • When the QM Schrödinger equation is solved, you get what is called a "wavefunction" as a result. It is the interpretation of this wavefunction that is the conflict between the several interpretations of QM. The Kopenhagen interpretation states that this wavefunction is related to the probability of finding a particle at a certain position.
    • In general, this wavefunction is quite large (by which I mean it extends over a large area of space). In the Kopenhagen interpretation, this means that the probability of finding a particle at a certain position also extends over a large area of space: the probability is non-zero for multiple positions.
    • So if you would measure the position of a particle, you would have several different outcomes, with some probability (for example: you are more likely to find the electron in the conductor and less likely outside). As an example, let's use this electron/conductor: Suppose that the QM calculations predict that the probability of finding the particle inside the conductor is 9/10 and 1/10 of finding it outside. This roughly means that if you were able to perform the exact same measurement of the position 100 times over and over again that the particle would be inside the conductor 90 times and 10 times outside the conductor (the conditions of the measurement have to be exactly the same for all 100, otherwise you are not able to compare the measurements!!!)

    So QM doesn't really state that a particle can be at two places at the same time, but it predicts that it can turn up on two totally different places if you measure its position. The fact that it can turn up on two totally different places is a direct consequence of the spatial spread of the wave function, and this is why sometimes you hear that a particle doesn't have a well-defined position but "is spread out in space". The tricky part is that we cannot directly verify that it is spread out in space, since measuring the position will give one exact position only.

    This sounds very weird indeed, but remember that the human intuition of "my computer is sitting right here on my desk and is not spread out all the way to my bathroom" does not work out in the exotic world of elementary particles.


  15. FA_Q2 Member Registered Senior Member

    " The tricky part is that we cannot directly verify that it is spread out in space, since measuring the position will give one exact position only. "

    I seem to have picked up somewhere that you cannot measure where a particle is. Only the space that it may be in. From what I understand the closer you get to measuring the exact point where it is the further you move it from that point, making it impossible to say exactly where a particle lays.
  16. Crisp Gone 4ever Registered Senior Member

    Hi FA_Q2,

    Actually I think it is the other way around: you can calculate where a particle may be (in technical terms: a probability distribution for the position). If you measure the position, you get an exact answer (for example: the particle is at x = 0, y = 0, z = 10 and not "the particle is somewhere between "x = -10 and +10 and z = -5 to 5").


  17. Time/02112 Senior Member Registered Senior Member

    What about Element 115?


    Element 115, the key to understanding how the ultra-secret "Black
    World" has created aircraft capable of manipulating gravity and
    space/time, has been identified, and the recent discovery of element
    118, which decayed into element 114, further helps identify the

    The most important attribute of this heavier, stable element is that
    the gravity A wave is so abundant that it actually extends past the
    perimeter of the atom. These heavier, stable elements literally have
    their own gravity A field around them, in addition to the gravity B
    field that is native to all matter.

    The Key To Gravity-Control Systems

    No naturally occurring atoms on earth have enough protons and
    neutrons for the cumulative gravity A wave to extend past the
    perimeter of the atom so you can access it. Now even though the
    distance that the gravity A wave extends past the perimeter of the
    atom is infinitesimal, it is accessible and it has amplitude, wave
    length, and frequency, just like any other wave in the
    electromagnetic spectrum. Once you can access the gravity A wave, you
    can amplify it just like we amplify other electromagnetic waves.

    And in like manner, the gravity A wave is amplified and then focused
    on the desired destination to cause the space/time distortion
    required for practical space travel.

    This amplified gravity A wave is so powerful that the only naturally
    occurring source of gravity that could cause space/time to distort
    this much would be a black hole.

    We're amplifying a wave that barely extends past the perimeter of an
    atom until it's large enough to distort vast amounts of space/time.


    We synthesize heavier, unstable elements by using more stable
    elements as targets in a particle accelerator. We then bombard the
    target element with various atomic and sub-atomic particles. By doing
    this, we actually force neutrons into the nucleus of the atom and in
    some cases merge two dissimilar nuclei together. At this point,
    transmutation occurs, making the target element a different, heavier

    As an example, in the early 80's, the lab for heavy ion research in
    Darmshtot, Germany synthesized some element 109 by bombarding Bismuth
    203 with Iron 59. And to show you how difficult it is to do this,
    they had to bombard the target element for a week to synthesize 1
    atom of element 109. And on that subject, this same lab has projected
    that in the future they should be able to bombard Curium 248 with
    with Calcium 48 to yield element 116 which will then decay through a
    series of nuclides which are unknown to them, but are well known to
    the scientists at S4 located within the complex of the Groom
    Lake "Area 51" installation.

    The length of time which an element exists before it decays
    determines its stability. Atoms of some elements decay faster than
    atoms of other elements, so the faster an element decays, the more
    unstable that element is considered to be. When an atom decays, it
    releases or radiates sub-atomic particles and energy, which is the
    radiation that a Geiger counter detects.

    Alien Craft

    The reactor found in the alien craft at S4, as widely mentioned by
    physicist Robert Lazar is primarily based on a superheavy element
    with an atomic number of 115. Element 115 will be designated
    as "Ununpentium" according to IUPAC guidelines. Its periodic
    designation and electron configuration appear in the diagram at the
    top of the page.

    The collision of lead and krypton leads to the new elements.

    BBC News Online Science Editor Dr David Whitehouse

    Two new "superheavy" elements have been made by bombarding lead atoms
    with energy-packed krypton atoms at the rate of two trillion per

    After 11 days, the scientists working at the Lawrence Berkeley
    National Laboratory, US, had produced just three atoms of element
    118. These contained 118 protons and 175 neutrons each in their

    The new elements decayed almost instantly to element 116, which
    itself was short-lived. But, for that brief moment, they were the
    only three atoms of these elements ever to have existed on Earth.

    Ken Gregorich, the nuclear chemist who led the discovery team,
    said: "Our unexpected success in producing these superheavy elements
    opens up a whole world of possibilities using similar reactions: new
    elements and isotopes."

    US Secretary of Energy, Bill Richardson, commented: "This stunning
    discovery opens the door to further insights into the structure of
    the atomic nucleus."

    Unstable combination

    Atoms consist of a central nucleus surrounded by a cloud of
    electrons. The nucleus consists of protons and neutrons.

    But not all combinations of neutrons and protons are stable. In
    nature, no element heavier than uranium, with 92 protons and 146
    neutrons, can normally be found.

    Scientists can make heavier ones by colliding two large nuclei
    together and hoping that they will form a new, heavier nucleus for a
    short time.

    One of the most significant aspects of the new elements is that their
    decay sequence is consistent with theories that predict an "island of
    stability" for atoms containing approximately 114 protons and 184

    "We jumped over a sea of instability onto an island of stability that
    theories have been predicting since the 1970s," said nuclear
    physicist Victor Ninov. He is the first author of a paper on the
    discovery submitted to Physical Review Letters journal.

    Atomic structure

    Synthetic elements are often short-lived, but provide scientists with
    valuable insights into the structure of atomic nuclei. They also
    offer opportunities to study the chemical properties of the elements
    heavier than uranium.

    I-Yang Lee, scientific director of the atom smasher at Lawrence
    Berkeley National Laboratory, said "From the discovery of these two
    new superheavy elements, it is now clear that the island of stability
    can be reached.

    "Additionally, similar reactions can be used to produce other
    elements and isotopes, providing a rich new region for the study of
    nuclear properties."

    Fast work

    Element 118 takes less than a thousandth of a second to decay by
    emitting an alpha particle. This leaves behind an isotope of element
    116 which contains 116 protons and 173 neutrons.

    This daughter is also radioactive, alpha-decaying to an isotope of
    element 114.

    The chain of successive alpha decays continues until at least element

    Questions, Comments, Concerns?
  18. FA_Q2 Member Registered Senior Member

    I have watched the tape Robert Lazar made and a few
    documentaries he has produced. He sounded intelligent until I applied basic physics on his scenarios. They don't work. He has no ground for anything that he has said. All he did was capitalize on the UFO psudoscience and make a few quick bucks. The gravity controlled drives are equally baseless. For some reason the gravity does not affect surrounding arias not to mention the A and B gravity types are not real. There is a strong nuclear force and a weak nuclear force (what they like to call gravity A or the stronger gravity) but it is not gravity. There is also NO research or evidence of any kind that the strong nuclear force goes beyond the atom. This is required for the theories to work.
    Last edited: May 20, 2001
  19. Time/02112 Senior Member Registered Senior Member

    Are you absolutley Certain?

    FA-Q2:> "There is also NO research or evidence of any kind that the strong nuclear force goes beyond the atom. This is required for the theories to work."

    Are you absolutley certain of this?

    (I beg to differ!)
  20. FA_Q2 Member Registered Senior Member

    Then show me accredited research and backing of that research. Don't pull and paranormal news or Bob Lazars out of the basement ether.

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