Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Please Explain This

  1. Jan 24, 2005 #1
    Please Explain This....

    I was referenced to this article in order to prove that we all are somehow "connected" to each other. Can someone please explain Bell's Theorem in simple terms and how it proves that we are indeed all "connected :confused: ."
    here's the article:

    http://www.ncsu.edu/felder-public/kenny/papers/bell.html
     
  2. jcsd
  3. Jan 24, 2005 #2

    DrChinese

    User Avatar
    Science Advisor
    Gold Member

    The referenced article says nothing about universal connection. You are no more connected to everything else in a non-local universe than you are in a local universe.
     
  4. Jan 24, 2005 #3
    ok, let me start from the beginning.... i was reading this webpage:
    http://www.gnostic-jesus.com/
    about 5 paragraphs into the article, it goes into everyone being "connected," and introduces Bell's Theorem. Maybe im reading things wrong but I didnt understand the referenced article about Bell's Theorem. So, DrChinese, you're basically saying that this website is a hoax and that quantum physics in no way proves that we are "universally connected?"
     
  5. Jan 24, 2005 #4

    JesseM

    User Avatar
    Science Advisor

    Here's a quickie explanation of the meaning of Bell's Theorem I wrote up on another forum (I don't agree it proves that 'we are all connected', BTW). First, check out this analogy from the book Time's Arrow and Archimedes' Point:
    The situation in one version of the EPR experiment is almost exactly like the situation with these imaginary Ypiarian twins, except that instead of interrogators having a choice of 3 crimes to ask the twins about, experimenters can measure the "spin" of two separated electrons along one of three axes, which we can label a, b, and c (this is not the only type of EPR experiment--the one that is usually tested experimentally is one involving photons called the Aspect experiment--but I'm discussing this one because it's so similar to the 'Ypiarian twin' analogy above). Whichever axis the experimenter chooses, she will find that the electron is either "spin-up" (+) or "spin-down" (-) along that axis, and if the other experimenter chooses to measure his own electron along the same axis, then when they compare results they will always find the electrons had opposite spins on that axis (you can only choose one of the three axes to measure though, because there is an uncertainty relation between spin on each axis similar to the position-momentum uncertainty relation). One might try to explain this by saying the electrons each started out with a well-defined spin along all three axes, with each having the opposite spin as the other along all three; for example, if you imagine one electron's spins along axes a, b and c were + - +, then the second electron's spins must have been - + -. But if you make this assumption that each had a well-defined spin along each axis, then some simple math shows that something called "Bell's Inequality" would be expected to hold. As this wikipedia entry on Bell's Theorem explains:

    But in reality, the Bell inequalities are consistently violated in the EPR experiment--you get results like P(a+, b+) > P(a+,c+) + P(c+,b+). Again, this shows that you can't just assume each pair of electrons had well-defined opposite spins on each axis before you measured them, despite the fact that whenever the two experimenters choose to measure along the same axis, they always find the two electrons have opposite spins on that axis. There are some ways to save the idea that the particle has a well-defined state before measurement, but only at the cost of bringing in ideas like faster-than-light communication between the electrons or the choice of measurements retroactively influencing the states of the two particles when they were created.
     
    Last edited: Jan 24, 2005
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?