Observer Effect. While playing a friendly game of chess, it becomes apparent that Reed and Mayweather have been inhabited by two members of an alien species who intend to observe how humans react when faced with an imminent tragedy.

While playing a friendly game of chess, it becomes apparent that and have been inhabited by two members of an alien species who intend to observe how humans react when faced with an imminent tragedy.While returning from a routine scavenger expedition on a mysterious planet, collapses from a sudden pain in his lungs, forcing to pilot the shuttlepod and make an emergency landing aboard Enterprise. Suddenly, Hoshi also becomes ill and delivers the devastating prognosis that Hoshi and Trip have been infected by an incurable virus that will leave them dead within hours, as well as anybody with whom they come into contact.Hoping to ease their pain, Phlox injects Hoshi and Trip with a sedative, causing them to drift off into a deep sleep. Suddenly, Trip and Hoshi sit up in bed, inhabited by the aliens who now wish to experience the sensation of human illness. Phlox, stunned to see Hoshi and Trip awake and talking, gets the shock of his life when the aliens admit their presence in his patients. Phlox is soon silenced when the aliens erase his recent memory, as they have also done with Mayweather and Reed.After the alien leaves Hoshi's body, she suddenly goes into cardiac arrest. Upon realizing that Phlox can't handle the defibrillator on his own, throws off his gloves and lifts his bio-hazard helmet; thus exposing himself to the deadly virus.Stoically, Archer accepts his dire fate and, and after placing in command, goes to stay with Trip until the end.

Trip, now inhabited by one of the aliens, sits up and confesses to a stunned Archer that he is an alien who has been occupying Trip's body in order to conduct research on humans. Archer is furious when the aliens admit to knowing about the deadly virus as well as having the power to cure those infected.Archer begs the aliens to intervene and save Hoshi and Trip, but his ardent plea falls on deaf ears. Compassion wins out in the end when the aliens bring Hoshi and Trip back to life as a reward for Archer's heroism.

In quantum mechanics we learn that the behavior of the very smallestobjects (like electrons, for example) is very unlike the behavior ofeveryday things like baseballs. When we throw a baseball at a wall, wecan predict where it will be during its flight, where it will hit thewall, how it will bounce, and what it will do afterward.When wefire an electron at a plate with two closely spaced slits in it, anddetect the electron on a screen behind these slits, the behavior of theelectron is the same as that of a wave in that it can actually gothough both holes at once.

This may seem odd, but its true. If werepeat this experiment lots of times with lots of electrons, we seethat some positions on the screen will have been hit by many electronsand some will have been hit by none. The observed 'interferencepattern' for these electrons is evidence of their dual wave-particlenature, and is well described by thinking of each electron as asuperposition of two 'states', one that goes through one slit, one thatgoes through the other.To add to this already mysteriousbehavior, this interference will only happen if both possible pathsthat the electron can take are not distinguishable. In other words, ifwe could somehow tell which slit the electron went through each time,we would no longer get the interference. The act of making ameasurement of the electrons path fundamentally changes the outcome ofthe experiment.Mats(published on ) Follow-Up #1: quantum. As a follow up to the previous answer, I'd like to share something I found interesting.

If one defines free will as something like 'non-deterministic', one can prove from three simple axioms that if you wish to claim we (experimenters) have 'free will', then we must conclude electrons have 'free will' as well.is an interesting way to demonstrate the 'measurement problem' in quantum mechanics, for in the traditional Copenhagen approach the evolution of a system is completely deterministic except for a measurement. If it turns out all of physics can be explained with the appropriate choice of lagrangian, can we really have the freewill to choose a random measurement?- Kevin M (age 29)Urbana, IL, USA. Thanks for the interesting link. Just to expand on a point mentioned in passing in that article, there is a strong distinction between the indeterminacy described by the theorem and the traditional concept of free will.

Readers should be forewarned that what follows somewhat spills over the edge of physics into philosophy.There are serious reasons (including the violation of the Bell Inequalities) to conclude that the sort of events described by quantum mechanics are 'free' in the sense that no prior fact about the universe can tell us which outcome we will observe. That doesn't mean that the necessary determining facts are hard to find; it means they didn't exist.On the other hand, when we think of 'free will' we have the sense that there was some prior 'will' which determined what we chose to do. However, the existence of any such will would violate the theorems as much as any other determining variable.Thus since the peculiar randomness of quantum events undermines the deterministic picture of the world it could be said to indicate a sort of 'freedom', but not anything resembling traditional 'free will.' Mike W.(published on ) Follow-Up #5: confusion between the uncertainty principle and the observer effect. Right, we have no indication at all that interaction with conscious beings (e.g. Us) does something different than interaction with any other large object in which some record is left of the results. Of course, the only events we are aware of are those of which we are aware, but we can leave that worry for the philosophers.

At any rate, the structure of quantum mechanics, in particular its violation of the Bell Inequalities, would run into big trouble if the random outcomes of quantum events were influenced by any local variable, including human will.So you're right on all your key points. Nevertheless, there is a relation between the 'observer effect' and the uncertainty principle. Mathematics requires that any wave, including purely classical ones, have a 'spread' relation: ΔkΔx = 1/2. That says that the spread (Δ) in the wavevector (k, sort of the inverse of the wavelength) times the spread in position (x) is greater than or equal to 1/2.

The classical wave simply must have spreads in both these attributes, just as you can easily picture for water waves. We don't call this 'uncertainty' or make a philosophical fuss about it because, as you can see by eye, the spreads in position and wavevector are real, persistent things.What's weird about quantum waves, though, is that when they're 'observed' or 'measured' we don't see the full spread that was there in the wave. If you set up apparatus to measure x, you see an output that has a very narrow range of x, even if the input is a big spread of x. Likewise if you measure k, the output has a narrow range of k. It's as if the wavefunction 'collapsed' in a way guided by the type of measurement made.

As to which particular little range of, say, x it collapses to, there's just a probability rule. The detailed result is purely random, not guided by any prior content of the universe. That's what converts the quantum spread into quantum uncertainty.So people have good reason to link these effects and to be very puzzled by the whole business. As is common in cases of confusion, some people use the occasion to claim to be the center of the universe and to have magical powers. Other people buy it.Mike W., Shalin, Samson(published on ) Follow-Up #6: Quantum for the non-scientist. I have a friend (not a physicist) who reads unscientific articles on things like schroedinger's cat and superposition and the 2-slit experiment phenomena, and as a result comes to believe that quantum mechanics undermines the logical rules of our universe because you can say things like 'the particle is in two places at once' and applies it to more of reality than it should be.

I feel like I have a pretty good understanding that his problem lies somewhere in a bad understanding of the uncertainty principle and/or observer effect (similar to the I can make things happen that I want because of the observer effect issue discussed in the last comment, but not quite the same). I'm having a hard time articulating though, I was wondering if you could help?- William (age 26)Columbus, OH, USA. Hi William-We'd love to help on that, but it would be much more effective if your friend could follow up with some specifics in his or her own words. We've written so much on the topic, generally searchable via the phrase 'Bell Inequality', that we have little to add. I think it's fair to say that both quantum mechanics and relativity shake up a lot of basic ideas about the universe. That doesn't mean that they leave nothing of ordinary logic. Just that what's left is modified- especially in the case of quantum mechanics.Mike W.(published on ) Follow-Up #7: Unconscious observers.

Any measurement process that has a permanent effect on the system of interest causes the collapse of the wavefunction to a particular state, regardless of whether/how the results are interpreted by a human being. As long as the measurement device is on and recording, the state will be altered. Take temperature measurements, as an analogy. Although one tends to neglect, thermometers have a non-zero heat capacity in real life, therefore when you dip one into warm water, its temperature will be slightly decreased. Dip a thermometer in hot water, wait 1 minute, take it out and dip another one. The second time you measure will give you a lower measurement, compared to the case if you totally omitted the first measurement. This will happen whether you look at the mercury level or not, your dog watches the mercury level or not. What causes a change is the thermometer itself, not existence of a conscious mind watching it. In quantum case, the measurement device causes a change just because it records the state (not because of a side effect).Tuncp.s.

The vast majority of modern experiments of this type use automatic fast recording of the 'which-way' data that are measured. There's no direct observation by people until the overall results are done. As Tunc wrote, it's the recording which sets up some physical difference in the outside world that depends on which-way. That breaks the interference between the paths. Mike W.(published on ) Follow-Up #8: Bell's Inequalities and free will. I admire this website and it is very interesting. May I post a question regarding an answer that was given to a question concerning 'free will' in the electron double slit experiment?

The answer was #4 posted on 8/20/2010. This question is for Mike. Can you tell me please what you mean by 'strong distinction between the indeterminacy described by the theorem and the traditional concept of free will'. On the contrary it seems like Bell's theorem not only allows but demands 'free will'. By definition free will implies non determinate. If I had no free will to choose the experiment choice then it can be said that the outcome was predetermined since it was your action that caused the electron to take the particle or wave path.

MIT News Feb 20,2014. 'Closing the 'Free Will' Loophole. It's the reverse of what you would think.

Lack of free will on the part of the experimenter is the problem because then the particle detector setting can 'conspire' to influence the outcome. It is considered the third and last loophole in order to validate Bell's Theorem. Please comment if possible and by the way I enjoy the Ask the Van ProgramSincerelyJulius Mazzarella.

( Retired International Paper 2006 )- Julius Mazzarella (age 63)Middletown, Ohio U.S.A. You're quite right that a conspiracy involving both the 'random' or 'free will' detector settings and the supposedly entangled test particles could produce the observed violations of Bell's Inequalities.

It would have to be quite a conspiracy, in which apparently random events in two remote detectors and in some particle source were all pre-choreographed by some entity determined to mess with our minds. So the conclusion is that either quantum events have truly random outcomes, in principle not predictable from any prior facts about the universe, or absolutely everything is exactly determined in an amazing pseudo-random conspiracy.

Either view is logically consistent, but most of us accept the random version.As for how this randomness differs from the traditional concept of 'free will', the issue does not concern 'free'. It concerns 'will'. Something that comes from no prior fact about the universe is not what we usually think of as 'will', which flows from a prior mental state. If one thinks of 'will' as a non-local variable, then one could say that it might be involved. That doesn't seem to fit well with what we know happens to thoughts in response to various direct physical and chemical events in the brain, which is as local as any other physical object.p.s. That MIT article proposes using distant quasars to get the random detector settings. The idea is that it's really hard to imagine them both being in on the same extremely detailed conspiracy.

I heard that a fellow at the South Pole who started worrying about these issues when he took a class on them from me had an even better idea along the same lines. Use the cosmic microwave background radiation from opposite directions. Alas, at least in our standard picture, the homogeneity of the CMB is attributed to inflationary causal connections between every part of the visible universe. So even these experiments wouldn't logically rule out the conspiracy idea. They would certainly help dramatize its absurdity.Mike W.(published on ) Follow-Up #9: free will and quantum mechanics. A followup question/s for Mike W.

( Thank you for your time to shed some light on this. My problem may have been one of semantics which you helped shake loose. Don't worry I will not turn this into a philosophical conundrum.) My first follow up question is concerning the double slit experiment.

This is where to me it seems 'free will' and consciousness is an issue since the experiment always has the same outcome DEPENDING on which experiment you choose. If you can claim conscious free will made the choice then the outcome of the experiment really does depend on which experiment is 'freely' chosen and QM survives otherwise a deterministic outcome can be argued. From the experiment's 'perspective' this choice is random since you have the choice to break any predetermined outcome. I agree with you the entanglement issue does not require free will. The outcome will always be 50/50 at the 'head' of the experiment and oppositely correlated at the 'tail'.

( However far apart the 'tail' is.!amazing ) BUT the entanglement experiment to me does not EXCLUDE local free will at the start or 'head' of the experiment. Free will only activates the experiment, the experiment will do whatever it wants.

By the way you wouldn't know any really good beginners books on this topic would you? Sincerely Julius Mazzarella- Julius Mazzarella (age 63)Middletown. In one of the earlier answers you stated that light was not necessary for the observer effect, and that anything that could record which path the electron took would suffice to collapse the wave function.

But in a later answer you said that light interferes with the electron. Does every measuring device ('observer') require the addition of energy to the system (in the form of light or otherwise) that may merely be having a physical effect on the electron such that observing how the wave pattern is made is impossible? Or have experiments been done that control for this possibility, but in which observation nonetheless collapses the wave function?

I find that virtually every author is ambiguous on this point.- Peter (age 54)Boston, MA, USA. The key question is whether the different quantum possibilities lead to different large-scale outcomes. For example, the spin-up part of a state might lead to a bell ringing and the spin-down part not lead to that. These situations where different parts of the quantum state lead to diffeent large-scale effects are called 'measurements'. Any sort of coupling between the little quantum system and the large-scale world might be involved in a measurement.

Grim fandango work order. Electromagnetism, including light, is the most common coupling in our experience simply because most of the forces we're familiar with boil down to electromagnetism.I don't think that every measuring device requires the addition of energy to the small quantum system. In fact, some measurements destroy the little system.

For example, an ordinary photodetector destroys the photon it measures. So in that case the energy transfer is from the little system (photon) to the big one (photodetector).Mike W.(published on ) Follow-Up #11: What causes quantum interference loss. Many thanks for the opportunity to ask you a question.

Re a previous comment: Any measurement process that has a permanent effect on the system of interest causes the collapse of the wavefunction to a particular state.So if we had a camera set up that wasn't switched on to record electrons passing through a slit, we would have an interference pattern.If we turn the camera on a record, we get a wave collapse and a particle pattern appears. So am I correct the non-recording camera does not effect the system to produce wave collapse but the recording camera does? If so, what is it about the recording camera that affects the system. Is there energy emitted by the camera shutter and the capture of photons on its lens that causes the collapse? Does the non-recording camera also emit and absorb photos albeit not recording - that will affect the system?

What makes the 'recording' aspect so critical to the wave collapse. Many thanksAndrew- Andrew (age 47)Australia. Great question!In practice, even a non-recording camera would be enough to destroy the interference. Any light waves bouncing off the electrons will go on to interact in some way or other with things in the vicinity. That may not leave the sort of record that we can easily view, but it does leave a record. Things are just a bit different depending on which slit the light came from.

Now if the only light around came from the camera, then switching it off could restore the interference pattern.Here's one way to think about the 'recording' issue. Our division of phenomena into separate parts (the electron, the photons.) may be convenient for some purposes. Nature, however, doesn't have to divide up that way. Let's think of the different parts (electron, photon.) as aspects of a single reality. In some ways the properties of each particle are just like locations along different dimensions.

Two parts of a light wave that arrive at the same East-West and North-South location won't interfere unless they also are at the same up-down location. Likewise two branches of a quantum wave won't show interference unless all aspects of the wave (electron and photon) arrive at the same place along each path. The part of the electron wave that's linked with the light that scattered off slit A won't interfere with the part linked to slit B unless those different parts of the light also arrive at the same place as each other. That rarely happens.Mike W.(published on ).