double slit experiment?

Question

friend brought this book over showing details of this thought experiment, but it didnt explain how an atom or photon changed into a wave when it is observed, how can an atom know its being observed? another section of the book explained how they started to observe the atom after it has been shot through the slit and it still changed form. I am not very educated in terms of physics so please keep your respones in laymens terms

i know that steve but how does the atom know its being observed

how can an atom change form simple by being observed

mike that doesnt answer my question, just shows how it is done and who did it

bs 999 the book explained in detail how there was no interference with there observations

bs 999 i watched the movie and it still doesnt answer my question it explained in detail of how the thought experiments work and not how the atom is changed due to an observer

sorry mike it doesnt, its either one or the other in the experiment

i have to disagree with you there scythian but you have answered my question they still dont know whats going on, in the experiment they are either one or the other

thats true bs 999 but they said there thought experiments do not interfere through observing, dont know how they did this but that is what it states, especially with quantom entanglemnet when they shoot it through differant tubes and what they do to one the other does

they only observed part of one while the other still changed

and what i meant about that is when they observed one no matter how far away they put it the other collapsed or changed to a wave

yes they were using quantom entanglement with the double slit using differant methods all of which leads to, how and why did it happen and i guess thats why the book did not explain it

Answer 1

After centuries of dispute about this, physicists have come to realize in the 20th century that particles and atoms and even molecules can have both wave and particle properties at the same time. Nobody understands how this works, but equations describe such behavior very accurately, and experiments back it up. As a recent example of an experimental feat done the other year, beams of light was brought together to create a "crystalline" array, while a beam of atoms in quantum state was diffracted from it! A complete reversal of roles in the classic x-ray crystallographic diffraction, where it's light that's the crystal and atoms that's the wave. No, things don't become either a wave or a particle merely because they're being (or not being) looked at. A difficult concept to understand in quantum physics is the quantum state function, which is often termed a probability wave, and when it is "measured", i.e, information gleaned from it, it undergoes what's called a "state function reduction", which we associate with particle-like behavior. To this day, nobody really understands how this works, so if you or your friend are puzzled about this, you're in very good company of many top quantum physicists who don't understand this either. Recent work in decoherence theory may help point the way to an explanation, however.

Addendum: In reading your replies to the other answerers, I think you are referring to the infamous "Quantum Measurement Problem", which baffled even some of the best mathematicians, such as von Neumann, who is probably chiefly responsible for suggesting the role of consciousness in quantum behavior. This hypothesis has fallen out of favor in recent decades in face of competing theories. Search "Quantum Interpretations" on this topic.

It's now generally agreed among physicists that it's meaningless to speak of a particle trajectory during the time of undisturbed quantum state function time development. In other words, if an atom is made to behave like a wave in going from A to B, where it's detected by some means at B, it's not meaningful to say it went on any specific path in going from A to B. Numerous experiments have been performed to show that it indeed has gone some path, in contradiction of equations in quantum physics, and it's never been demonstrated. In other words, we have to throw out easy and conventional ideas about little balls flying around in space, it just does not work at the quantum level. That's why we have the term "quantum WIERDNESS", and for good reason.

Addendum 2. Now I believe you're referring to "Quantum Entanglement" experiments, where a measurement in one place can have an immediate effect on the state function of another particle elsewhere, no matter how far away. There are many sophisicated versions of this type of experiment whereby an "observation" is attempted without actually disturbing the state function, but it's usually done by means of a "reversible observation", which still nevertheless disturbs it, even if only termporarily. This is a huge subject, and we're going to run out of space here real fast with this.

Answer 2

Hi there..I think i can answer thsi for you...Steve you didnt answer the question....The atom knew it was being observed because to "observe" the atom requires photons of light which have to bounce from the atom to your eye to be seen..the act of looking, because it requires light which will have to affect the atom to see it, therefore changes the result and thus the atom knows its being observed....

Hey here is a simplified cartoon movie by Dr. Quantum explaining the double-slit experiement perfectly...you will love it...it says it all:

http://youtube.com/watch?v=DfPeprQ7oGc

dissturb: But think about it....to actually observe something how would you do it...You would have to use something to "reflect" back to a measuring device for it to measure...the idea of using something else to "observe" (because you cant observe without requiring some other product in this equation -- in this case, light) is what is affecting the atom...It is only when it is not being observed (nothing affecting the atom) that the atom doesnt change.

Answer 3

An atom doesn not know, it just does what it does. This is an example of the principal of duality. Depending on the experiment you perform, matter can exhibit properties of waves, and waves or light can exhibit properties of matter (being affected by gravity for example).

Answer 4

http://en.wikipedia.org/wiki/Wave-particle_duality

It doesn't change form it exhibits wave(packet)-like behaviour and (simultaneously - ha!) particle like behaviour at all times.

Answer 5

they "observe" small particles by watching them hit other things.
And you generally know it when you hit something.