Observer effect is one of the most misunderstood science concepts. Because Quantum Physics is difficult to understand, the concepts like observer effect are interpreted in multiple ways and often wrongly. Let us understand Observer effect once and for all.
The definition of observer effect is –
The observer effect is the disturbance of an observed system by the act of observation.
So in theory, any object, regardless of its size, could be subject to the observer effect if it is observed with “sufficient precision”.
For macroscopic objects, the deviation in measured property and the same property of the system disturbed by the measurement is so small that it can be ignored.
as an example,
When a thermometer is inserted into a liquid, the liquid gets in contact with the sensor of the thermometer and there is slight transfer of heat from one to another. This indeed changes the measured value. Observer effect!
But it is so small that it does not affect our day to day measurements and can be neglected for all the practical purposes.
Now, Let’s delve into the microscopic world and discuss how at quantum level observer effect plays a role!
Because what happens at quantum level is difficult to understand, we will take help of classical mechanics view to gain the idea behind what might be happening at atomic level.
So lets get right into it!
Imagine a Hydrogen atom, and we want to know the position of the single electron present in a Hydrogen atom at its ground state. Now, if we compare the size of a nucleus and 1s orbital – the radius of 1s orbital is approximately “Billion” times larger than the radius of Nucleus. (Yes Beeping Billions times!)
Size - On Quantum scale, classical concepts like "size" do not always apply in the same way as they do on the macroscopic scale
1s orbital - Volume inside which there is maximum probability of finding an electron
For the sake of understanding, consider:
Nucleus : Radius of 1s orbital :: Cricket Ball : Radius of Cricket Stadium
Now, from this analogy, there is a high possibility of finding our pet electron inside the stadium boundary. ( High possibility because electron has a wave function and it extends till infinity! ) For now let us assume that the electron is to be found only inside this stadium boundary
More on wave function and probability density function in later articles, stay tuned! :)
Now, the electron can be anywhere inside the stadium, how to know where it is exactly?
Let’s fire a photon into the stadium and assume it hits the electron and reflects back at us and we look at it. What just happened is – we got the position of the electron inside the stadium! Wow! BUT because the photon hit the electron, before that reflected photon reaching us, the electron’s position got changed!
Now, we only know the position of our pet electron for that exact moment when the photon hit our eyes, we do not know where our pet electron was before this moment and we also do not know where it will be in future!
The position and momentum of our pet electron, in quantum mechanics, is described by a probability distribution called the wave function. It contains all the information that can be known about a particle (our pet electron)
Now because before we knowing the location of our pet electron, it could have been anywhere and after knowing the position also it can be anywhere but for that one exact moment when we receive the reflected photon we know the position of the electron and instead of wave function giving us probability it gives us exact answer (exact position) and we say that the wave function collapsed!
Very very important inferences regarding collapse of the wave function!
- Because the photon hit the electron, for that moment, position of electron was known – was a specific value for the wave function and because it was a discrete value and not probability we say that the wave function collapsed!
- After the wave function collapsed, electron did not stop moving! It’s state changed. And new wave function now describes that electron!
- The photon which hit the electron, even if not fired by a us, and let’s say it was coming from somewhere else and it hit the electron, got reflected back and hit our eyes – we would still know the position of the electron and for that moment the wave function will still collapse! But listen to this – there is no need for “Conscious Observer”! Even if a conscious human being doesn’t look at it, the phenomenon will still occur, the electron will still get affected by the photon hitting it, the state of the electron will still change!!
So, the observer effect is not about you looking at something and you causing the outcome of what is happening. Stay away from those who tell you – you looking at something changes the outcome of anything! Even if you don’t look, plants will still grow, Sun will still rise and earth won’t stop moving! So don’t let the halo effect let you believe in things which don’t exist in reality. Critically evaluate the claims people make and stay vigilant and keep learning! 🙂
Following scientific definitions now would not seem that difficult to understand.
The wave function describes the probability distribution of the electron’s position and momentum, and that the collapse of the wave function occurs when a measurement is made, causing the electron’s position to become definite.
the electron’s position is uncertain until a photon hits it, which causes the wave function to collapse and the electron’s position to become known.
The observer effect does not require a conscious observer and that any interaction with the electron, such as a photon hitting it, will cause the wave function to collapse.
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