1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Horizon - Reality - Twin slit experiment

Discussion in 'Speaker's Corner' started by NeilFawcett, Jan 18, 2011.

  1. NeilFawcett

    Capodecina

    Joined: Nov 15, 2003

    Posts: 12,800

    Location: Marlow

    On this weeks Horizon they showed the 'Twin Slit' experiment. In this experiment, they have two tiny slits, which they then fire photos of light at.

    Imagine firing bullets through two neighbouring windows, with the pattern on the wall across the road, you'd expect to see two columns of marks.

    Do the same with two slits and fire single photons from a laser though, and they suggest you get three groupings? Stranger still they continued to suggest if you then look at the individual photos as they approach the slits to see what's happening, the phenomenon stops happening?

    Now my brain has trouble with this, so I'm wondering if someone can clarify it.

    Is it really three groupings? Or more than that in a traditional interference pattern?

    The suggestion is, there's some sort of interference (even though there's only ONE particle) so you don't get just the two expected groupings. If this is the case, when ONE particle is fired, is just one detected in the groupings, or even more strangely, are TWO detected in the groupings on the other sides of the slits?

    And there suggestion, just looking at the experiment somehow changed it? How can that be? Surely the 'look' must be actually affecting the experiment itself?
     
  2. Xordium

    Capodecina

    Joined: Apr 8, 2009

    Posts: 12,705

  3. mmj_uk

    Capodecina

    Joined: Dec 26, 2003

    Posts: 20,457

    Holographic Universe theory:
    http://www.youtube.com/watch?v=cJBoIz8yZDc
     
  4. Xordium

    Capodecina

    Joined: Apr 8, 2009

    Posts: 12,705

  5. slagsmal

    Gangster

    Joined: Apr 30, 2010

    Posts: 127

    I watched Horizon last night on iplayer, blew my mind when the double particle thing stopped happening as soon as it was observed.
     
  6. Castiel

    Capo Crimine

    Joined: Jun 26, 2010

    Posts: 63,652

  7. Wee Michelle

    PermaBanned

    Joined: Jul 28, 2008

    Posts: 235

  8. MikeHunt79

    Capodecina

    Joined: Jan 4, 2004

    Posts: 20,838

    Location: ¯\_(ツ)_/¯

    Maybe the particle splits up then rejoins?
     
  9. Emlyn_Dewar

    Capodecina

    Joined: Oct 15, 2003

    Posts: 12,274

    Location: Chengdu

    I watched this last night but I'm too closed minded to understand...
    Why did observing the experiment stop it from working?

    Read some generic links on quantum computers this morning to try and get some sort of vague, primary school understanding. My brain was damaged in the process.
     
  10. Castiel

    Capo Crimine

    Joined: Jun 26, 2010

    Posts: 63,652

  11. Castiel

    Capo Crimine

    Joined: Jun 26, 2010

    Posts: 63,652

    Last edited: Jan 18, 2011
  12. Wee Michelle

    PermaBanned

    Joined: Jul 28, 2008

    Posts: 235

    I understand the split beam (as much as you can, its really exciting).

    I get the jist of what they are doing here, they've offered 2 normal routes and 2 'blind' routes to see the overall difference with the 'watching/seeing' but I'm struggling with the conclusion and what it layers ontop of the original interfernce patern discovery.

    Will watch them just now ta
     
  13. Xordium

    Capodecina

    Joined: Apr 8, 2009

    Posts: 12,705

    Castiel, I am not sure layman's terms are possible here.

    To determine the outcome of any experiment in action you must interact with it. The experiment you are performing must interact with what you are measuring your observation with and likewise what you are measuring with must also interact with your experiment. With the measurements at this small scale the more exactly you measure one thing the less you can measure everything else.

    I have been thinking how to describe the "how does the observation change things" and the only thing I can think of is as thus (this is not my scientific speciality hopefully we will get someone clever in later).

    What you need to maybe think of is that an electron is something that can display the behaviour of either a particle or a wave. This is important because it adds a relativity component to it all which of course implies the circumstance of say an observation. In the same way people are not good or bad but display characteristics of the two depending on what conditions they are put under then electrons will also display the different behaviours of being particle-like or wave-like depending on a variety of factors. To go any further than that I think you really need to hit the books. I think it is maybe not too helpful to think of the observation as being some mystical component which both the horizon and the video I linked do in my opinion.
     
  14. NeilFawcett

    Capodecina

    Joined: Nov 15, 2003

    Posts: 12,800

    Location: Marlow

    Sure, but it can be completely non-invasive and not affect the outcome in any way!

    But the suggestion in Horizon was that something magical was happening just by 'looking'.
     
  15. Xordium

    Capodecina

    Joined: Apr 8, 2009

    Posts: 12,705

    It never does not interact what you make sure is that you are not changing the thing you are measuring. Nothing magical is happening just that the resulting behaviour has changed depending on what you are looking for.
     
    Last edited: Jan 18, 2011
  16. NeilFawcett

    Capodecina

    Joined: Nov 15, 2003

    Posts: 12,800

    Location: Marlow

    Of course you can analyse things in an non-invasive way?

    I fire a bullet into a wall.

    I then fire another bullet into a wall while filming it.

    Has the second bullet been affected in any way compared to the first?


    Back to Horizon - They implied the same with the individual photons. But I would agree, the outcome suggests the analysing did affect the outcome. But they did imply they have no idea why it affects it! So it would be akin to my second bullet veering every time I filmed it, and only when I filmed it.
     
  17. Xordium

    Capodecina

    Joined: Apr 8, 2009

    Posts: 12,705

    No, what you have just done is to perform a good experiment. Your measuring tool did not in any way change what you were measuring. I should not have said it can't be non-invasive what I should have said there was that there will never be no interaction. This is to crux of the issue at point in the Horizon program. Would you expect the same result if the bullet had to pass through the camera on the way to the wall? Use that to then make a conjecture on why. Again I would re-iterate it is not the particle itself that is changing but its behaviour.
     
    Last edited: Jan 18, 2011
  18. Morbius

    Wise Guy

    Joined: Jul 16, 2008

    Posts: 2,241

    To detect the presence of something, at the very least you need to bounce a photon off of it. This changes its momentum and so the experiment is affected.
     
  19. NeilFawcett

    Capodecina

    Joined: Nov 15, 2003

    Posts: 12,800

    Location: Marlow

    In your example yes, we have affected the outcome. But Horizon implied we have no idea why our viewing of the experiment means the photo behaves only as a particle, but when we stop looking we then get the interference like a wave? And I'm sure a lot of more clever people than us have considered the 'viewing' and it's affect on the outcome?
     
  20. Xordium

    Capodecina

    Joined: Apr 8, 2009

    Posts: 12,705

    I said this way back:

    What they should be saying as has been said thoughout this thread. When you perform that experiment and observe it you are observing with a measuring device that will change the outcome of the experiment. How exactly that measuring device then causes that outcome we see we do not know. But for the case of simplification they simply say we do not know how observing it changes it which is a completely different thing.
     


Share This Page