I've read from a lot of sources regarding Heisenberg Uncertainty Principle. I believe it is somewhat related to Schrodinger's cat.(why is that the assumption is that the cat is both 'alive AND dead', and not 'alive OR dead'?) But I do not understand the 2 theories.
Could someone explain these to me as well as how electron location cannot be pinpoint. (does this also mean a single electron can be in more than one place at one time?) Why is it that the observation or measurement itself affects an outcome, so that the outcome as such does not exist unless the measurement is made?

I would really appreciate an answer to these matter. Thank you very much. Smile

I dont think Heisenberg Principle and Schroedinger cat are related.

It basically means that you cannot have measurement accuracy of both items in the equations.

If you measure speed, you are measuring is rate of movement. When you are measuring the position, you stop it for a moment. How do you do both if one requires movement and one requires motion?

So the equation states that the more accurate the speed measurement is, the less accurate the measurement of the position is and vice versa.

I think we should start with "...the 2 theories". Technically the uncertainty principle is what it's defined, i.e a 'principle', and Schrodinger's Cat is a 'paradox' or more correctly one of Erwin Schrodinger's more famous 'thought experiment' -a simple google search should clear these confusions.
I'd like to write more of Uncertainty Principle & Schrodinger's Cat, but my Quantum Mechanics is very rusty, need to read up first

Very loaded questions and quite hard to explain in layman's terms. I'll try to get back to this discussion after I read my old lecture notes (no promises hahah)

p/s sakaic's explanation is a good starting point to understand the uncertainty principle

Here is my layman explanation of Uncertainty Principle.

Imagine a billiard ball rolling across the width of a billiard table. Now we shoot a few other balls from the bottom cushion.

top cushion
--------------------------------------------------------

<------ direction of target ball

--------------------------------------------------------

^ ^ ^ ^ ^

shoot balls to hit target ball

The balls that do not hit the target end up at the top cushion. There will be a single ball that hits the target and also end up somewhere at the top cushion. By measuring the position of the shooting balls and the time it takes to reach the top cushion, we can calculate the position and momentum of the target ball.

The only way to measure position and momemtum is to hit the ball with something and observe the effect, and this very act affects both.

Hope this is a valid way of explaining. Do correct me if otherwise. Please note that there is something called "quantum memory" which has been proposed to overcome the Uncertainty Principle.

I believe this though experiment is only an analogy to explain wave function.
it might have some loophole

What you are referring to here is quantum mechanic, which forms part of the modern physics. Together with Relativity theories, these two fields (which are about 100 years old only) challenges our conventional/traditional ways of perceiving the world through the classical/Newtonian mechanic view.

In modern physics, if we zoom into the fundamental elements that made up our world today (the chair, our body), the electron, the atom, the characteristic of these elements in the microscopic world sense is entire random and unpredictable. We are unable to say we know the electron at this location X and its momentum is Z. It is kind of weird as if electron is a matter (like a car), we certainly can know it location (like a car) and its speed.

One of the reasons to this is all fundamental elements exhibits duality principle, ie, they are matters, they are also waves. This is the famous wave-matter duality principle, and can be regressed up to human as mind-body duality. We can be impacted/killed be gravity, we can be impacted/killed by waves too. On a holistic view, we are like an object with solid matter, on a reductionistic view, we are a group of elements which are bonded via forces as described in electromagnetism.

Schrodinger's cat analogy provides us with an illustration that how weird our world can be where reality is a hybrid of two states of dead or alive cat. If we adopt the classical view and try to understand matter in the absolute world, the cat can only be either dead or alive.

It we leave this microscopic view of the universe a while, and look at macroscopic world of galaxies, same can be observed too. In relativity, space and time are relative depending on the observer state.

One of the weird deduction from quantum mechanic is the observer or the measurement itself would affects the outcome.

David Bohm, a leading quantum theorist addressed this:
A centrally relevant change in descriptive order required in the quantum theory is thus the dropping of the notion of analysis of the world into relatively autonomous parts, separately existent but in interaction. Rather, the primary emphasis is now on undivided wholeness, in which the observing instrument is not separated from what is observed.

I know it sounds hard to believe, but if we still believe that space and time is absolute and there is only one absolute reality , it could be us that is deluded instead.

You are quite right. I 'm just trying to explain it in a simple to understand way

on the bolded part,
So, even non-free electrons (electrons which made up an objects) also can be more than one place at a time. that means at a given point a particle of our human body is somewhere else and any particle of our human body is somewhere different from the former particle mentioned?

So, on the microscopic level a thing can be in more than one state at an instantenous time, am i right?

and dont you guys think that the term used here, dead and alive is too foggy and vague, unclear. Shouldnt it be more accurate- 50% dead and 50% alive?

This post has been edited by mrsmile: Aug 28 2010, 03:45 AM

Nope, this is not what it means. In the case of electron, its position and momentum can not be measured/defined to certain accuracy. It is not the same in saying that the election can be located at more than a place at a time.

One major deduction from quantum theory is the behavior of particle doesn't seem to follow any conventional law of physics that we know today. Example in classical mechanic, an object moves along a trajectory that is determined by the forces that act on it. It permits, at least in principle, what happen next if the attributes (location, motion) of an object is known up front. In a snooker table, you can predict where the ball goes after you fire the cue.

However in the case of electron, the rule above doesn't apply. Which electron will exite/decay and which electron (within the poll) will react to an external stimulus are not deterministic and predictable.

One very important question is how would physicists perform any studies on a field that is not deterministic and predictable??? Using thought experiment, statistic, calculus and matrices. For example, Schrodinger equation describes how the quantum state of a system changes in time.

I would say that the hybrid of dead and alive state represents quantum characteristic better than 50% dead and 50% alive, as the later doesn't tell us any state at all.

Einstein, on the other hand, doesn't support the above deduction, and suggested the EPR_paradox.



Quantum mechanic tells us that our knowledge on the microscopic world is not complete and rather limited.

Behavior like quantum tunneling (like David Copperfield walked through the great wall of China), quantum entanglement (two related objects are still impacting each others no matter how far apart we made them), suggest that there are a lot of misery yet to discovered.

For case one, one of the proposal to explain it is electron is not actually missing in action and returns, rather it went to another higher dimensions (we can not proof it physically, but could calculate it at least in theory) and returns, hence the tunneling effects. Same for case two, the two objects were entangled in a higher dimensions which cannot be seen physically, all these postulates leads to the discovery of String Theory and TOE.

I will try to make this easier for u, by making this organized.



[Heisenberg Uncertainty Principle]
uncertainty principle states that the product of position and momentum of let say, a particle, is constant. so, if you were to measure the position, you will never be able to measure its momentum accurately; and vice versa.
this is deduced from the following fact:
if you wish to measure the, position of, let's say, a particle,
the most direct way is by observing it, which means we will have to shine photons (light particles) on it, the photons were bounced back to our observing tool, and we get the image.
however, true for you get the accurate position and motion of that particle at that instance, because you see it,
however the photons that you introduced earlier, causes changes in the momentum in the particle, for it contain momentum too and causes change that can't be neglected.
to minimize this effect you would use less photon, so the overall momentum change is small, but now you can't observe the particle that accurate anymore.
now you get the idea of uncertainty principle? this principle will the the basic for quantum mechanics, and it revolutionize the physical world.



[Schrodinger's cat]
this case is somewhat related to electron too.
imagine a particle, which can spin, (electron is the most popular example)
a dot like electron is Spin=0, that is it looks the same from every point.
Ace in poker card is Spin=1, you will have to turn it 360 degree to get the same picture as you've started.
a Queen in poker card is of Spin=2, you will just have to turn in 180 degree to get the same image.
spin=3 is 360/3 degree to get back the same picture and etc.
and the spin property is not to be confused with the spin direction below (0 or 1)
(not quite relevant actually)

now, an electron can be imagined as a Top or planet spinning on its own axis.
with only one axis, wat is the possible direction of spin? to the left and to the right?
let's represent each different direction with digits.
to the left=0, to the right =1.
so the direction of spin of an electron can be used to represent data using binary codes. 10101000101010 .... bla bla those things?
that is quantum computing. or spintronics.
and researches are being made in constructing the future quantum computer, data will be processed and stored by spins of electrons, rather than the numerous transistors.
now imagine, what is the electron don't spin to the left or right, instead it spin upwards or downwards?
so is it 0 or 1?
can we assume that it's spinning in both left and right? this is not wrong after all right?
so it is both 0 and 1 at the same time, this is called superposition.

now we're gonna put this into a real situation.
we will link the binary output of the electron spin to the trigger of a gun, and the gun is aimed at a cat.
if the output is 0, the gun will not fire; if it is 1, the gun will fire, and the cat dies.
now, the electron is in superposition state, and the output is both 0 and 1,
so the cat is both alive and dead at the same time.
this was the idea of schrodinger, so that is the name.



[location of electron cannot be pinpoint]
well this is rather an extension from uncertainty principle.
from classical mechanics' point of view,
yep we can imagine every day's matter are made from discrete and tiny particles.
a block of, gold, can be divided and divided again, until we get a single gold atom.
a gold atom is a particle, and then as science advanced forward,
someone called Rutherford bombarded gold foil (sheets made from gold particles) with alpha particles (helium)
and he discovered there's inner structure within an atom, i.e. the nucleus and electrons.
so we imagine them as planets orbiting around a star, electrons orbiting around a central nucleus,
where electron is a tiny billiard ball, and proton and neutron are balls which are way larger.
this became the basis of what we learn, in chemistry as well as in physics other than quantum mechanics,
here we learn them as 'tiny balls', which means we are suppose to be able to see them or, pinpoint them or etc.

in quantum mechanics things are way more different.
the founder of quantum mechanics James Clerk Maxwell said: the true logic of this world is in the calculus of probabilities.
this is the basic idea, and it is true.
things at this scale can't be measured using conventional method anymore.
because we can't measure a single particle accurately.
but the use of probability can measure a whole bunch of particles,
for example 100000000 coins to be tossed.
if one coin is tossed you can only predict the probability of it getting head, that is 0.5. but you won't know the outcome.
with 100000000 coins, you know there will be half of the coins showing head and the other half showing tails.
the case is same with measuring particles.
we use probability to calculate everything.

how do we, for example, know the position of the shells of electrons?
1st shell 2nd shell 3rd shell?
do we measure the electrons' exact position?
no, the real method is, we take numerous photographs, and we see the position of the electrons in the atom.
then we plot the position where electrons appear and join them together, we get an area in which electrons pass by them.
so in fact it is 'cloud of electrons' that we are measuring,
more accurately saying, it is a wave function.
same as you plot many points on a graph paper, then you join the points and you get a graph, and then you calculate the wave function.

the same principle applies for many other things in quantum physics.
maths and probability plays a key role in quantum physics, and in string theory too.
on these, we don't rely on conventional method of deriving conclusion and physical laws anymore.
from this point onward, everything is based on mathematical calculations and equations.
and then we interpret the math into sentences, physics laws, and even predict new things.
and then only we testify them with experiments.

this is the other way round as in the conventional method,
in which we carry out experiment first, and observe, make inference, interpret data and make conclusions, generalizing the laws.





and one thing that most people might not realize.
let me ask you a question,
why mass possess gravitational force?
why charged particle (like electron) possess electrical charges?
why mass has inertia? preserves its original state of motion?
and, why is 1+1=2?

can't be explained right?

the point is, there's a limit in physics in which we are allowed to explain things.





alright i hope you enjoy reading although it is quite long.
the books i've read are even longer.
hope I helped. feel free to seek further help from me,
btw do correct me if I'm wrong on anything,
I'm just a 17 years old kid anyway.
still learning.

KeNGZ, you are currently 17 years old and exploring quantum mechanic? Interesting, at such age, I am sure a lot of us were exposed to Classical/Newtonian mechanic only. Even some university graduates who took up theorecical physics/quantum mechanic subjects could not understand and appreciate what quantum mechanic actually means. In short, it is not a field for everyone. It defies/challenges what we "thought" we know about the fundamental of matter, self, objective reality and consciousness.

Do keep it up if you are interested in this field.

Back to the topic, please find below an article by Michael Talbot, one of the respectable author in the field of quantum mechanic.

http://www.globalone.tv/group/quantumquest...e-a-holographic

It touches quantum entanglement, electrons still communicating with each others even they are 10 feet or 10 billion miles apart. One explanation to this is, the separation of the electrons is illusionary, the objective reality doesn't exist.

It links up quantum mechanic to the concept of "oneness, wholeness", which forms the centric ideology in Eastern philosophy, like oriental philosophy of Zen.

It tries to explain neuro sciences.

It touches a bit on evolution too.

The holographic idea is consistance to string theory, just like the sun (photon) shines onto a 3-D physical body, and the "shadow" is 2-D which is where we lives (illustration only). As we are living in the lower dimensions (3D, 1T), our perceive reality (in many cases, we believe it is a separation) could be a projection of a "unified object" of a higher dimensions. This could explain why the election missing in action in quantum tunneling and also why there are 11 dimensions as calculated/predicted in string theory.

It also touches on mind-particle duality. Our senses act like lenses which polarizes the wave (photon (light), sound, electric-magnet) and construct a so called physical image (perceive reality). That could be the reasons why the blinds, color blinds and those who could not hear are having a different perceive reality that those who can, as their hologram creation of the perceive reality is different.

This is one of the good articles that I have read through this year.

To sum it up:

It denies the old school of local realism. Local realism is the combination of the principle of locality with the "realistic" assumption that all objects must objectively have pre-existing values for any possible measurement before these measurements are made. Einstein liked to say that the Moon is "out there" even when no one is observing it.

It supports the Copenhagen interpretation of wave function collapse, which is the Schrodinger Cat dead and live cat scenarios. The cat is at this hybrid state originally. Only after the measurement made (the people who observes the cat), his/her lens (eyes, ears) polarizes the wave function of "either" dead OR alive cat and collapse the other wave function (alive OR dead) and view the cat with only one state of either dead OR alive. The objective reality doesn't exists as the measurement (the people) also involves in the defining the state of the object observed, as what David Bohm stated:

A centrally relevant change in descriptive order required in the quantum theory is thus the dropping of the notion of analysis of the world into relatively autonomous parts, separately existent but in interaction. Rather, the primary emphasis is now on undivided wholeness, in which the observing instrument is not separated from what is observed.

Anyone who has not confused by quantum mechanic does not understand it ------- Neil Bhor

This post has been edited by nice.rider: Sep 7 2010, 07:50 PM

Schrodinger simply is saying that currently, the way we see physics, we think that things are genuinely undetermined until the act of observation.

It's that simple. It doesn't attempt to substantiate anything. It doesn't advance any theories. It's not a real experiment. It's just saying something in an extreme yet obvious way; in this case that we consider everything in the quantum world to be in an entangled state until the act of observation.

And the reason it was made is to just show how crazy entanglement theories sound.

Good explanation. Agreed that it was a thought experiment.

Eugene Wigner, who proposed that the consciousness of the observer is what causes collapse of the wavefunction. Colloquially known as "consciousness causes collapse", this interpretation of quantum mechanics states that observation by a conscious observer is what makes the wave function collapse.

The interpretation identifies the non linear probability projection transformation which occurs during measurement with the selection of a definite state by a mind from the different possibilities which it could have in a quantum superposition.

If "consciousness causes collapse" then we need to understand more about consciousness to understand the universe around us. So what was the universe and how did it behave before the first consious mind appeared?

aren't we here to answer d cute pikachu's problem and, well, discuss on quantum physics? ghahhaaha

---

Added on September 10, 2010, 1:24 amwell cute lil pikachu, an addition to my previous second post
this was what i wrote on the different thread 'energy'

in fact, the truth,
as stated by physicist like stephen hawking,
is as follow:
though we can define some quantities or explain things or define them in terms of more fundamental quantities (e.g. speed in terms of distance and time),
some concepts are so fundamental that any such attempt leads to a circulation definition like that just stated.
to escape from this, we will have to define such quantities 'operationally', which means we describe what they do,rather than what they are. i.e. we can explain how do they operate.
such as mass, we can explain it through the force an object experiences when exposed to gravity, that is, objects of same mass will experience the same force when placed at the same point or in the same strength of gravitational field.

why physics involves maths so much that one can't really understand it without maths?
because the physical world appears to be largely governed by the laws of cause and effect, and maths is used to explain such casual relationship,
and it is used to make prediction and measurement.
every single row of correct maths equation or formula that can be written is a valid representation of certain event in this physical world.

This post has been edited by KeNGZ: Sep 10 2010, 01:24 AM

And there are foundational issues like what is time, space, energy etc ...

You are correct in saying that consciousness is where we need to understood better.
There is one consciousness thread in this section, you could browse through it if you are interested.

For your question: What was the universe and how did it behave before the first consious mind appeared?

This is a philosophical question and deserves a philosophical answer:

The universe without consciousness/observers doesn't exist.

The universe IS because we observe....I think, therefore I am.

Without the ability to think/observe, oneself/universe simply doesn't exist. The "existence of oneself/universe" requires a prerequisite of "consciousness".

Can we name a universe/galaxy/solar system that exists but without a conscious mind/observer presents?

As you can see here, asking this question is a contradiction, hence a paradox.

A very good/intelligent question posted by you, though......

a very clear explanation

http://www.youtube.com/watch?v=HCOE__N6v4o

sometimes a complicated question does not really need a complicated answer

This post has been edited by zoomckng: Sep 24 2010, 08:45 AM

I think, therefore I am, applies to you, not the universe. See you think, so you are. If the universe depends on consciousness to exist, who consciousness might that be? Where would that consciousness reside without the universe?