The Act of Observation

Discussion in 'The Science Forum' started by Dashing_Chap, Aug 15, 2011.

Welcome to the Army Rumour Service, ARRSE

The UK's largest and busiest UNofficial military website.

The heart of the site is the forum area, including:

  1. Blah Blah Quantum Mechanics etc etc.

    As every man and his dog knows the act of observation on a quantum object has an effect on said object regarding it's location and trajectory (I think). I wonder what triggers this to happen? At what stage can this alter the quantum object? Does the observer need to be conscious and intelligent? Can a simple organism with vision like a shrimp or something like Schrodinger's kitten have an effect just by looking? What is it exactly that makes the quantum object change it's state?

    Isn't it strange that beings made up of atoms, none of which have ever been individually alive, can have an effect on other atoms just by the act of observation?

    What would happen if all consciousness was removed from the universe? What if all the observers were eliminated? Would quantum objects behave differently? Does this mean that our own role as audience in the great act is actually a significant part for us to play in the universe show? Bearing in mind of course that our acts of observation alter reality and if we're removed then reality itself must surely be different?

    Pass me the Old Tom.


  2. And other things - spin, for example. You seem to be confusing two different phenomena - the uncertainty of quantum superposition states, which collapse as a result of any measurement, with the requirement to use higher energy probes to more accurately measure things. The latter simply gives you a limit on measurement accuracy, especially for very small things, because the tools you are using are not passive, therefore have their own effect on the objects being measured.

    The rest of the answers deal with superposition states (so quantum entanglement, wave-particle duality etc).

    1. Any phenomena where the quantum superposition state cannot be maintained.
    2. At any stage.
    3. No. Purely physical phenomena, such as black holes, or interacting whit photons, can do the same.
    4. As the answer to 3 is no, the level of intelligence doesn't matter. Obviously, both cats' and shrimp eyes are sufficient for the task.
    5. See 1.

    6. Yes. But then so are lots of things about quantum mechanics.

    7. Nothing much.
    8. Nothing much - you are confusing the requirement for a measurement with that for an observation (the latter implying, in English, the requirement for an observer).
    9. No.
    10. No. The "anthropomorphic principle of cosmology" only applies at the weakest, trivial, level - that being, clearly it must be possible for a universe to exist where there is appropriate physics that intelligent life can develop, because we are in a universe where intelligent life has developed.
    11. Well, if you assume that all of my answers were different, or that I am wrong, then you would expect there to be some change. But, as we're an insignificant part of the biomass on a small planet in an unfashionable corner of a moderate sized galaxy, then you wouldn't expect the change to be significant.

    Gin? At that time in the morning. Heathen. Whisky or brandy, please. Rum, if you really have to (but take it outside!)
    • Like Like x 1
  3. jim24

    jim24 Book Reviewer

    Never had any of these problem explained when I did my Observers course
  4. I was just about to say everything that Idrach said...honest.... :)
  5. Is us agreeing on something merely the collapse of a superposition state or something more sinister? Or is that smiley for the first sentence rather than the qualifier?
  6. DC- you're asking the wrong questions: the really interesting ones as far as I'm concerned
    are 'why do quantum theories only appear to apply at the atomic and sub-atomic levels?' or, supposing they can be applied to macroscopic objects, which exist in a state of uncertainty until measured in some way, then 'who collapses the wave function of the universe?'. Gin? How good of you to offer... :)
  7. There are two answers to this - both of which are "correct" for some way of looking at things.

    1. Quantum theories do apply at macroscopic levels, it is just that the difference between quantum behaviour and classical (Newtonian / Relativistic) behaviour becomes insignificant as the object gets more massive. Just as the difference between Newtonian and Relativistic behaviour is insignificant at low velocities.

    2. Working out the quantum wave equation for a macroscopic object would be so mind-bogglingly difficult (and extremely tedious) that scientists prefer to ignore the issue and wave answer 1. around in the hope nobody calls them on it.

    But wave functions don't collapse - they aren't superposition states. (Edited to add: but they used to be described as doing so before the theory of quantum decoherence replaced that part of the model.)
  8. Fine then, ruin my Einstein quotation... I'll be honest here and own up to the fact that my knowledge of QM is limited to the books that I have read about it, which tended to focus on its formulation, rather than the more recent work done on it; Bell's inequalities is the most recent work of which I'm aware, and he came up with those in the 70s!
  9. And gin? At this time of the morning? Bucks Fizz, surely (or margaritas or similar if you are poolside in the sun, of course.)
  10. Sure- mix with sugar and lemon juice, top up with Bolly and you've got yourself a French 75- just what I need at the moment! Wouldn't use Old Tom though. Plymouth navy strength is for winners :nod:
  11. Nothing more sinister than a random collision of massless particles probably... I just can't find anything to argue about but will keep a shrimps eye on the subject ok...
  12. BZ Mr Casino, I should have asked this and I think I did hint at it somewhere on that other illustrious thread which mustn't be named. What I'm really interested in is at what point does this collapse take place? What size does the object have to be to start behaving normally and at what point does it start appearing in two places at once and all that weird stuff?

    Also, how do black holes have an effect on quantum objects? I was under the impression that they had to be measured by an act of observation and that the observer would supposedly have to be living.

    BTW I'm a history graduate and this is completely out of my field, fab topic for the perplexed though.

    I think a few posts have been removed, shame really as there was a rather technical debate going on there.

  13. Two widely separated minds act as one. Sounds like spooky action at a distance to me.
  14. Whenever the particle is in a situation where there are different observable-universe consequences depending on which state it is in. Or, when you have a linked particle pair, when a similar thing happens to the entangled particle.

    Everything has a wave function. It is just that the more massive the particle, the more compressed the wave function (trivially, a higher energy photon is more massive and higher frequency, therefore shorter wavelength. As the wave function tends to be expressed relative to wavelength then the more massive the photon then the smaller the wave function. The same applies to other objects although the maths is less obvious.)

    So the length over which you, as a macroscopic object, is subject to quantum uncertainty is very very tiny. At a certain mass (which I can't be bothered to calculate or even google) it will be less than the Planck length therefore can be disregarded for pretty much all purposes, even quantum ones. So, actually, the electrons in the hydrogen atoms in the keratin molecules in your hair actually have a more spread-out wave-function than you - in absolute, not relative terms.

    This is actually the point behind Schrödinger's cat - it was designed to demonstrate that there are weaknesses in the Copenhagen interpretation, especially as applied to macroscopic objects. Cats are either dead or alive (note to TP fans, yes - but "bloody annoyed" is a sub-state of alive!) Although radioactive source is acting in a quantum manner, the Geiger counter, flask shattering device and flask, even the poison, are all acting in a non-quantum manner. And the state of the cat is the same, regardless of whether we bother to look inside the box or not.

    By the way - it isn't "two places at once", unless you are talking about something strange, rather "smeared over an indeterminate area". It is when there is a barrier (natural or artificial) somewhere in that area, ie creating 2 states - this side of the barrier or that side, that a measurement occurs.

    Because they create a state where there are, extreme, consequences, depending on the exact position of the particle. If you set up Young's double-slit experiment, does the behaviour change if you are not watching it? If you record it with a camera and watch it later? Cameras not generally considered being alive.

    I think part of the problem is we are confusing the word "observation", which, in English at least, has the requirement for an observer, with "measurement" which can be accomplished by devices or situations. But I think I've said most of this before?

    Does that make me an anti-Higgsy or just an inverse spin one (not that these are necessarily exclusive categories - it rather depends on the nature of the Higgsy)?

  15. Interesting vid, you can download the whole series from The Teaching Company TCC via a well known pirate like bittorrent site.