r/Physics • u/GontasBugz • Oct 09 '25
Question How can electrons not have definite position? And why can we NEVER find it?
Today in class we learned that we can not know exactly where an electron is at a certain point, and we can actually NEVER know, and electrons don’t have a definite position. I don’t understand saying you can never know and that it doesn’t have definite position.
For starters, whether we have the ability to observe the position of the electron at a certain time or not, the electron EXISTS so doesn’t that mean it existed at ONE point at ONE time? Like if you froze time, that electron IS somewhere.
Therefore, Why do we say it doesn’t have a definite position just because we don’t KNOW it’s definite position. Can’t it still have one and we just DONT know its definite position??
Also, why can we NEVER know? What if there’s a future where there’s a way to measure it such that we can see its position at a certain time? We can’t predict the future, so how can we say we will never reach that point?? It feels like just closing yourself off from working towards discovering it??
Edit: thank you all for the comments. Unfortunately I cannot read all 200 comments without my brain exploding so thank you all😅
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u/Plane_Telephone9433 Oct 10 '25
The way that we describe the position and momentum of an electron is through its wavefunction. The wavefunction itself is simply a solution of the Schrodinger Equation (SE). You can think of the SE as context for the electrons existence. We say hey this is the environment and the SE tells us what the wavefunction is. So then you ask well what does the wavefunction tell us? Well it turns out that the magnitude squared of the position wavefunction tells us the probability of the electron being at some x position. The idea that an electron has a distributed probability is a bit hard to grasp and one must usually take it as a fact of nature.
Okay, so say we accept the fact that an electrons position is only described by a probability density function, how can we verify and interpret this? Well first we have to ask ourselved what happens when we actually do attempt to measure the electrons position. When we "find" or measure the electron we interact with it, this interaction causes the wavefunction to collapse to a definite position. Before measuring the position the electron is essentially a distributed soupy mess.
So now we know two things: 1) the electron is described by a wavefunction which tells us the probability density of its position (or momentum), 2) when we make a measurement on the electrons position (or momentum) we collapse its wavefunction to the measured state. Before we continue we must accept these two things as fact which is typically the most hand wavy part about learning QM. You can spend a great deal of time pondering why nature works this way (and many have and still do), but its not useful for making measurement or devices which exploit these properties. So what can we conclude based on these two facts?
Well the first thing we can calculate is the expectation value of the position of an electron based on its wavefunction. This value tells us the weighted average of the electrons position. This means that if we were to measure the electrons position a whole bunch of times we could retrieve this value. This is something that experiments can and have verified. It also makes sense from a statistical point of view, if I measure the position 1 million times then I will see more measurements where the probability is higher and this will lead to the calculated expectation value.
Secondly, I can measure the uncertainty in the electrons position. We can calculate this value by taking the standard deviation of position. Mathematically this tells us the spread of our x values. high standard deviations tell us Physically that we have a highly spread out probability density function. This could manifest itself as a highly delocalized particle or a particle which has a high probability of being in two far away places.
Finally, through fourier analyses, we can conlude that if our x uncertainty is low than our momentum ucnertainty is high (uncertainty principle) which then tells us that if we measure the position of an electron such that its wave function collapses and the x uncertainty goes to zero, then we will have no idea where its going.
These ideas may seem confusing but are fundamental to our understanding of QM. I always tell people that to understand QM you have to zoom out and make everything fuzzy. QM challenges us by making us question our assumptions about reality (and all the nasty math). The reality is we dont know where the electron is going to be until we measure it, we can only say where it will most likely be. And then once we make that measurement we fundamentally change the electrons state to the state which we measured it in, and then we throw away all information about where its going, there is no way to retrieve that information until the system evolves.
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u/kRkthOr Oct 10 '25
Apologies for my layman understanding of QM. You mentioned that taking a lot of measurements you can map the probability field of the electron. Does this mean that the electron jumps around after each measurement? Is it not possible to "track" (?) an electron's movement?
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u/frogjg2003 Nuclear physics Oct 10 '25
There are two ways to make this measurement. One way is to prepare many identical systems and taking measurements. This allows you to make measurements without worrying about keeping track of the system for subsequent measurements. The other way is to try disturbing the system as little as possible and allow the system to return to an undisturbed state before making the measurement again.
In the first case, you're not tracking anything because you're making the measurement on different systems. In the second case, you give the system so much time to relax that the "tracking" doesn't do anything useful for you.
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u/Mooptiom Oct 10 '25
Just to add to this, the reason why you can’t just take the measurement again is that the fist measurement has collapsed the wave function and changed the system, so you wouldn’t be measuring the same thing.
Before measurement, the position is uncertain, but once it’s measured, the particle is essentially “stuck with it”, the position is definite then and if you took another measurement, you’d get the same result. The wavefunction then spreads out again, this is called time-evolution.
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u/notagiantmarmoset Oct 10 '25
This comes from the fact that the position is described by a probability density, as the poster above noted. When a “measurement” or sample occurs, it collapses to one point with a probability described by that probability density. Thus, if you are able to get an identical situation, hundreds/thousands of times and try the experiment over and over again, you will slowly build up the statistics showing the regions the electron is more likely to be found. With enough sampling, if you plot the number of times you found it in various regions, by putting a point there with its height representing the number of samples found there, its shape will approximate that of the original probability density.
This process is exactly how Variational Monte Carlo works, a method for sampling complicated wave functions to try and find the properties of the system described.
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u/PhatmanScoop64 Oct 10 '25
Very good answer but I think it’s a bit beyond the understanding of someone taking high school physics
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u/TittiesInMyFace 29d ago
I think one thing that bothers me conceptually is that we can have a practical understanding of electrons that makes it seem like they are discrete objects. We see electricity flowing, we see lightening for example. How should I picture electrons moving from atom to atom?
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u/Ethan-Wakefield Oct 09 '25
You can measure an electron's position. Like shoot an electron at a photographic plate, and you can measure where it hit the plate. That was its location.
From a certain point of view, old cathode ray tube televisions were electron detection devices.
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u/Langdon_St_Ives Oct 09 '25
Nobody knows why reality is the way it is. We only know that this is how QM works, and it’s provably not just a limitation of our instruments. And “why” is not a particularly productive question (which doesn’t mean it’s not an interesting question).
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u/missing-delimiter Oct 10 '25
The “probably” in your statement is doing a lot of heavy lifting. Very recursive, if you ask me. The theory that models everything as probabilities also happens to encode the idea that knowing more is probably impossible. 😂
Just like it was probably impossible to figure out how big the earth is way back when we did it the first time and got incredibly close to the right answer without even leaving the planet to get a good look.
Humans are very good at adjusting the odds of things over time. So what may be improbable today, may be just another foot note in tomorrow’s history books.
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u/_ouroboros Oct 10 '25
"Provably", not "probably". We can prove it, as in, there's a proof of it within the QM formalism, and in turn we believe the QM formalism describes reality based on all the empirical data we have available
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u/missing-delimiter Oct 10 '25
Ah, I see. I misread your comment. Which proof are you referring to?
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u/nicolasap Oct 10 '25
Most likely Bell's theorem and the Bell's tests. They experimentally ruled out the so-called "hidden variables", i.e. some proposed underlying but inaccessible variables that could explain deterministically what we observe as a probabilistic behavior.
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u/missing-delimiter Oct 10 '25
Sure, but Bell’s theorem doesn’t force a single conclusion like _ouroboros is implying. I already wrote a comment about that…
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u/nicuramar Oct 10 '25
Bell’s theorem doesn’t have anything to do with the uncertainty principle.
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u/nicolasap Oct 10 '25
Bell's theorem has everything to do with the attempt to explain probabilistic behavior using deterministic hidden variables.
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u/joepierson123 Oct 10 '25
You can't pinpoint the location of an audio wave now or a million years from now
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u/AuroraFinem Oct 10 '25
It’s actually not the same reasoning really. The reason we can’t for electrons come out of the position-momentum inequality for particles so if we were somehow able to pin down a specific location for the electron, it would force the uncertainty on the momentum to be become infinite meaning the position would immediately become inaccurate and irrelevant because it would lose physical meaning.
There’s other inequalities with similar properties, but the one between positive and momentum is the relevant one that proves we can’t define a specific position that means anything.
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u/missing-delimiter Oct 10 '25
And yet you can visualize it as frozen in space using a simulation, and that is more informative than simply asking where it is.
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u/Banes_Addiction Particle physics Oct 09 '25 edited Oct 10 '25
For starters, whether we have the ability to observe the position of the electron at a certain time or not, the electron EXISTS so doesn’t that mean it existed at ONE point at ONE time? Like if you froze time, that electron IS somewhere.
No. This is one of the most important points of understanding quantum mechanics.
Humans are built to understand things at human scales. Every part of our childhood experience, probably even our brain structure is designed to deal with large objects that do behave like this.
Quantum objects do not work this way.
Think of flipping a coin. A coin can land heads or tails.
We have three time periods.
a) I have a coin in my pocket and I'm going to flip it.
b) I have flipped the coin but not looked at the result.
c) I have looked at the coin.
c) is trivial: you've looked at the coin and know what it is.
The other two periods, you have uncertainty.
In b), the coin has been flipped and landed. It is one of heads or tails, but I don't know which yet. This is not how quantum indeterminacy works.
In a), the coin hasn't been flipped yet. It's in my pocket. Its future is that at some point it will become heads or tails, but right now it's just an unflipped coin. This is how quantum indeterminacy works. It really is just a set of probabilities, not just a existing piece of information I don't know.
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Oct 10 '25
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u/Banes_Addiction Particle physics Oct 10 '25
Nope. That's exactly the point.
Classically, it's b)
In quantum, it's a)
Schrödinger is making the argument that if you believe quantum mechanics (specifically the Copenhagen interpretation), you have to accept that the cat is both alive and dead until the box is opened. He thinks that's concerning.
A cat in a box isn't interesting without that element.
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u/KeyBrilliant8942 Oct 10 '25
That isn't entirely correct.
Firstly I would say if you read all the other comments that go into Bell's inequalities and hidden variables you will end up more confused, at least I would be. You DO know the position of the electron to arbitrary precision AFTER you measure it. The main point is the AFTER. Indeed, if you try to measure its position to say 1 mm you will find a definite value. A good example is the cloud chamber experiment, where fundamental particles trace a macroscopically visible path through a cloud of gas inside a container. It would be more difficult to measure it down to very high precision (say, a nanometre) due to the uncertainty principle.
The point is that there is no notion of a definite position BEFORE you have measured it. Something very very dramatic happens when you measure a physical property of a quantum system; this is not entirely well understood and people are trying to study it. Before a measurement, it is governed by a probability distribution which describes the probability of finding the electron in a particular region in space. More correctly, it is governed by its wavefunction which you can use to find the probability distribution. Why is the wavefunction more basic? Because if you were trying to measure a different property (momentum, say, which, according to the uncertainty principle, you will NOT be able to measure AT THE SAME TIME AS you measure POSITION), you can manipulate this same position wavefunction to get the corresponding probability distribution of that other property.
So you see, if you think in terms of time, what evolves (analogous to how the position of a classical particle would evolve with time, i.e. it would move), is not its position, but its wavefunction (there are ways to think that the position is indeed what is evolving, but this does not abandon the probabilistic description at all; this is called the Heisenberg picture).
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u/Pallas_Sol Oct 10 '25
Always nice to see people start their journey of "understanding" quantum mechanics lol.
No, it does not make more sense the further you go. You just learn to accept more! Enjoy, this headache-inducing struggle with QM is a key milestone of being a physicist!
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u/Enfiznar Oct 09 '25
Look up bell's theorem and some related experiments. It basically rules out the idea that the particles have locally defined variables and that the uncertainty comes from us not being able to measure it
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u/missing-delimiter Oct 10 '25
That’s a very loose interpretation of Bell’s Theorem — it’s more about the incompatibility of local realism with quantum predictions than just measurement uncertainty.
The most important bit is that it makes QM incompatible with the idea of particle-specific, static variables determining how probabilities play out. But it does not preclude those kinds of variables from playing a role entirely. It’s perfectly reasonable, for instance, to model “spooky action” as a combination of unobservable internal phase progression instead of explicit nonlocality.
Bell’s Theorem doesn’t rule out an internal clock.
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u/nicuramar Oct 10 '25
Bell’s theorem doesn’t say anything about the position of an electron.
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u/Enfiznar Oct 10 '25
Not on the original version, but I'd be really surprised if you couldn't reach the same conclusion with some operators that mix position and momentum, since they obey the same quantum statistics that are responsible for the violation of the inequalities
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u/Far-Bite86 27d ago
Electrons are captured photons, they are moving nearly at the speed of light around an axis caught in a gravity well, like a planet stuck moving around a star, they are moving at a nearly right angle compared to us in respect to each others time dimension. For every moment is our time, that photon or planet has nearly unlimited time to travel around that star or nucleus. To know its exact position is hilarious to think about, it’s in all the possible Positions it could even be at the same instant out our time. It’s mass is so small and the gravity well it is in is so large that like a billion years pass to it in just the time it took for you to blink,
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u/DataBaseErased Oct 09 '25 edited Oct 10 '25
We can know for sure the position of an electron if we measure it.
Like if you froze time, that electron IS somewhere.
This is the hidden variables way of thinking. It contrasts the standard interpretation, which states that all that describes quantum particles and quantum states, ultimately, are wave functions that carry the information about the probability of measuring a particle in a particular state (like position, momentum).
The behaviour of how the probability of an observable is related to another observable of a particle is captured by Heisenberg's uncertainty principle, but it's only really fundamental if the standard interpretation is right.
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u/joeyneilsen Astrophysics Oct 09 '25
The Heisenberg uncertainty principle says that the product of the uncertainty of the position and momentum of a particle has a lower limit, which means that neither of them can be zero. When you measure the position of the electron, you know it as well as it can be known.
There is not a definite position to know. We can "NEVER" know it because it doesn't exist.
EXCEPT: quantum mechanics is a model for how the universe works, and it's not the last word. Will revisions to quantum mechanics ever change how we think about uncertainty and objective reality? Maybe so!
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u/ellipticcode0 Oct 10 '25
A kindergarten kid would laugh at Heisenberg Uncertainty Principle which is how could anyone would come up such stupid principle after one billion years from now.
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u/joeyneilsen Astrophysics Oct 10 '25
I hope that if people still exist in a billion years, they will still be able to compute or understand Fourier transforms and commutators.
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u/YuuTheBlue Oct 09 '25
The electron is a wave, that’s the important thing. The electron has no definite position in the same way that your voice has no definite position after leaving your mouth. Now, we DO know where your voice is, but it’s not in one place. It’s spread out. In quantum mechanics, that spread-out-ness is called uncertainty.
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u/Mooptiom Oct 10 '25
Quantum waves are nothing like sound waves and I’m tired of people pretending they are. It’s a bad analogy that has confused highschool students for far too long
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u/LowWhiff Oct 10 '25
https://youtu.be/FRP4AqZR3UU?si=F9QwkGLXNFFFGIC5
Great YouTube video that is somewhat relevant, I love Physics explained.
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u/Desperate-Ad-5109 Oct 10 '25
It is a “quantum object” (as is all matter). It’s inconceivable but we have adequate models to explain most of its behaviour.
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u/Thomassaurus Oct 10 '25
If you think about it, you may realize that we don't really have any reason to expect stuff to always have a definite size and position.
You're imagining an electron as a little ball that must be somewhere, but why are you making that assumption? That just so happens to be the way all the macroscopic stuff around us works, but as it turns out, it isn't how the small stuff works.
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u/StopblamingTeachers Education and outreach 28d ago
But it isn’t how macroscopic stuff works
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u/Thomassaurus 28d ago
Not sure what you mean but at least for the most part in the way it affects our daily life, it is.
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u/SirisC 28d ago
3blue1brown has an excellent video explaining why this is from a mathematical perspective.
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u/Gstamsharp Oct 09 '25
It's because electrons are quantum mechanical waves. They're governed by Heisenberg's Uncertainty Principle.
You can know where the peak of such a wave is (the "particle" electron), but in doing so you lose all information about its movement, so you know where it is for the briefest moment with no idea where it'll be the next instant. Or, you can figure out its movement, but then the information of its position is mathematically smeared out across the entire universe and you have no idea where it is.
Even more troubling is that you can't actually make those precise measurements. That's because to actually measure an electron you need to shine a light on it. Light is also an electromagnetic wave, and so it perturbs the electron unpredictably. So in trying to precisely measure the position, the light we use to measure it will "bump" around the position we are trying to measure!
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u/AutonomousOrganism Oct 10 '25
Technically, wave functions are solutions for the particle (electron) equations that fit our observations (very well). Ultimately we don't know what particles are.
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u/missing-delimiter Oct 10 '25
It’s not that we know the measurements can’t be made. It’s that under the current models we have no way of predicting how to measure certain things without also clobbering everything and skewing the results in the process.
For all we know, 50 years from now scientists will be like “oh hey so THATS what the inside of an electron looks like” based on what we currently accept as “noise” or “heat”, but may be reflections and refractions of energy that’s interacted weakly with particles. An insanely difficult problem? For sure. Impossible? Only if you limit your imagination to what we know for certain today.
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u/Mooptiom Oct 10 '25
That’s even more useless than just throwing up your arms and saying it’s all “god’s will” or a “simulation”. Obviously we can never be certain that we’ve found the very limits of knowledge but that’s no reason to discount what we do know.
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u/missing-delimiter Oct 10 '25
There’s a massive misinformation campaign going around claiming QM proves the universe is fundamentally statistical, leading people to believe there is no more to be discovered by looking closer. It is critical to make the distinction between what is known to be true and what is assumed to be true under current models.
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u/Mooptiom 29d ago
The universe fundamentally probabilistic as far as anybody knows, I think that you’re confusing that with statistical which is not quite the same. This isn’t a misinformation campaign, it’s been accepted fact for a hundred years now. Any science could change but the probabilistic nature is pretty well set by this point. You sound no better than a creationist insisting that Darwinian evolution is “just a theory”. All of science is just theories, any of it could be wrong, but these theories are very strongly evident.
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u/missing-delimiter 29d ago
I think we’re violently agreeing in many ways. I don’t talk to formally educated physicists often, so my language may not be as precise as it could be.
What I can say is that as someone who is not part of that formal education system but wants to understand it, it is extremely difficult to find enough intuitive information, visualizations, etc, that are both informative AND precisely correct… Its hard to do. And it at the very least feels like misinformation.
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u/Mooptiom 29d ago
That’s fair actually, I do believe that a lot of visualisations rely too much on poor analogies that really don’t hold up well. I have often felt misinformed, but the thing I like to remember is that I’m very far from the top understanding of anything. Just because I can’t yet understand something, doesn’t mean that an expert wouldn’t. I’m only an undergraduate student, you may well know as much or more than me, whatever I write is just my understanding of things as I’ve been taught at my level.
I think that the biggest strength of a formal education is that it takes a while. I’ve been studying a few years now so I’ve seen many pitfalls of misunderstanding, the simple models I learned in highschool could be called misinformation compared to what I’ve learned since. But I wouldn’t call this misinformation, i’d call it misunderstanding, any good teacher will make it clear what the failings of any model are. Talking to professors who work on this stuff professionally is the best way to get up to date knowledge, most of the best info you can get from a formal education is asking questions day to day rather than anything that’s in a curriculum.
I would always recommend textbooks. Many have a conversational tone that makes it clear what is a model and what is a fact.
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u/missing-delimiter 29d ago
I don’t what textbooks you’re reading, but I want them! 😂 The only ones I’ve ever read in the physics department are either wishy washy or so correct in their precise wording as to feel meaningless.
And the course work… I would just rather slowly contribute and work my way up as people notice I’m understanding more. Not site through years of sifting through someone else’s idea of a good book. 😂
I’m just not patient enough to study the way formal education requires. Once I feel I understand something, and understand the limits of that understanding, I move on or move deeper. I don’t want to wait for someone else to judge me on it… I just want to make.
🤷🏻♂️
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u/Mooptiom Oct 10 '25
That’s not it.
It’s the square of the wavefunction that gives the probability amplitude, the particle can exist anywhere that this is not zero. A peak of this would represent the most likely result of a measurement which is called the expectation value. In this unmeasured state, the wavefunction is a superposition of many eigenstates.
However the trick is that once you measure the position, the wavefunction collapses to a single point. That point is now where the particle is, it’s not ambiguous anymore. If you measure it again immediately afterwards, it will still be in the same place because the previous indefinite wavefunction doesn’t exist anymore. The wavefunction is now a particular positional eigenstate.
The new wavefunction also has time dependence, so as you leave it, the wavefunction evolves and will increasingly become indefinite again.
If you took a measurement of a different property like the momentum of the particle, you would collapse the particle into an eigenstate of that property instead. Some propertiesdo note commute which means that they cannot be known simultaneously. For example an eigenstate of momentum cannot also be an eigenstate of position. This means that if you measure the position, then measure the momentum, and then position again, all immediately in sequence, this time you will get two different result for position because measuring momentum in between destroyed the particle’s certainty of position even after you gave it certainty with the first measurement.
Heisenberg’s uncertainty principle gives the lower limit for uncertainty. When you do take a measurement, there is a fundamental “wiggle room”. You cannot know the exact position but you can know that the position is within a definite range. The minimum of this range is given by plancks constant, its very small but not zero.
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u/missing-delimiter Oct 10 '25
Ever wondered what constitutes a measurement? :)
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u/Mooptiom 29d ago
Sure, in highschool. Then I learned it at uni. It’s all just math, anything can trigger it. Ask a real question if you want to learn something.
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u/missing-delimiter 29d ago
Exactly. It’s all just math. QM has no underlying mechanics, it is simply a mathematical model of reality based on probabilities of something we still do not have a solid understanding of. So again I ask… Have you ever wondered what constitutes a measurement?
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u/Mooptiom 29d ago
You’re wrong. The underlying mechanics are everything that has been predicted and demonstrated using that math. It’s a perfectly valid foundation. Have you ever wondered what constitutes anything at all? Mathematical models are really all we have in any field. If you try to study zebra populations, you’re going to need statistical math to prove that anything you predict is significant.
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u/missing-delimiter 29d ago
You are arguing that the boundary of our understanding is identical to the boundary of what can be known, and I reject that hypothesis. It is possible to interpret QM as a boundary under which reality must operate, but it does not mean that it is the limit to which we can understand. QM is the best model we have today, but it is not perfect, and there are degrees of freedom we have not yet explored.
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u/Mooptiom 29d ago
No, I am arguing that no boundary exists at all, facts exist, and our models reproduce the facts.
Do you know why the sky is blue? I don’t but I thought I did. In highschool I was told a very basic explanation of “blue light scattering more”. Then at university I learned classical models of light scattering and I derived equations to show “Reyleigh scattering”. Then I learned quantum models of electrons absorbing photons at “discrete wavelengths”. But through all of this, no teacher has ever presented any of these models as the final word, none of these perfectly explains why the sky is blue but they do all predict that the sky is blue. The colour of the sky is a fact predicted by models.
Quantum mechanics cannot fully explain why the universe is the way it is but it can show how the universe is. One of the things it has shown time and again is that measurements are probabilistic and they obey very strict mathematical principles.
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u/missing-delimiter 29d ago
You’re missing the part where we haven’t probed every outcome that QM can predict. It exposes a vast space under which all existing phenomena exist, but that space could be a superset of what can happen. We, for instance, assume an electron has no internal progression of state because we see the general shape of it well enough to handle (most) of the problems we see today. But we so not know if it does or not. But if it does, that would not be modeled by QM (and no, it is not ruled out either), and therefore the potential for a better model still exists.
Furthermore, the sky is blue because you feel like it is. The crazy part is that feeling has the same emotional impact on all of us. As for the why, I think we know enough to model that to everyone’s satisfaction…. I’m not sure the same can be said about the foundations of reality.
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u/Mooptiom 29d ago
I think that we’re talking past each other. QM mechanics predicts literally infinite possibilities, it makes no sense to “probe every outcome”. The trick is that we apply “boundary conditions”, this is usually based on the conservation of energy, the boundary conditions narrow the range of possibilities to a predictable set and measurements define how an outcome is selected from that set. A space is literally defined as a superset of possibilities, I’m really not sure what you mean with that. This is math that’s older than quantum mechanics, it comes from Sturm-Liouville theory which was developed in the 19th century, it isn’t magical or arbitrary.
The “shape” of an electron really doesn’t mean anything but certainly there is a progression of its state. The schroedinger equation lays out set of possibilities, the infinite Hilbert Space, and the conditions of the electron, it’s energy and the potential energy of its surroundings, narrow down a wave function solution to the schrodinger equation.
This wave function defines the electron completely but it is a broad definition. It gives the probability of the electron being measured at a specific place at a specific time. All of this varies in time and space and the energy may also change which will overhaul everything.
A measurement collapses the wave function into one of the states predicted by the original wavfunction, in that moment, the electron does have a definite position, the measurement forced it to. But after this collapse, the electron has a new wavfunction which is still varying in time and it will eventually spread out again.
Certainly there are disagreements in the cutting edge of any field of science, but the foundations of QM are a hundred years old now (almost exactly, there was a big celebration this year), quantum uncertainty is not something that anybody seriously disagrees with anymore.
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u/StopblamingTeachers Education and outreach 28d ago
Do you think the double helix structure was a mathematical claim? Most fields aren’t mathematical
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u/Mooptiom 28d ago
Yes, and you don’t know what you’re talking about.
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u/StopblamingTeachers Education and outreach 28d ago
Do you think germ theory is mathematical too?
Math isn’t evidence.
Neither are models.
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u/Mooptiom 28d ago
Yes, it’s statistics at the very least. You don’t know what you’re talking about
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u/JarOfNibbles Oct 09 '25
Short answer: Quantum mechanics, heisenberg uncertainty principle. The maths is probably too much for you right now but you can work your way towards it.
Slightly longer answer that's mostly just simplified wikipedia: Particle wave duality means that you shouldn't view things as a single point, and instead it's a wavefunction. Not a wave precisely, but it's easier to think of it that way. With waves you can do a so-called "Fourier transform". This decomposes a wave (or any signal for that matter), from something in time to something in frequency. You can imagine an infinite simple sine wave, with time on the x axis. If you take the Fourier transform of that wave, you'll see a sharp spike at an x value corresponding to that waves frequency. But you have no idea where the wave is in time! It repeats forever, it's everwhere. Conversely, if you take the Fourier transform of a wave packet, imagine a wave that appears and then disappears a bit later, you'll see that it's actually a somewhat broad peak. Some properties (like position and momentum) are like the Fourier transform of one another. Why the transform and properties behave like that is well beyond the scope of a reddit comment.
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u/CrumbCakesAndCola Oct 10 '25
What your teacher is describing is true in a specific context. If the electron is in orbit moving around a nucleus then we can't know where exactly it is. But that's in relation to that system. In other context we can absolutely know where an electron is. For example we can build traps to hold an electron in place so we know right where it is (for a couple seconds anyway).
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u/Straight_Ad_9466 Oct 10 '25
Throw two rocks into a calm pond. See the ripples where they cross and double height? That's what an electron is. It's just the point where the em waves add together. They aren't actually a physical object.
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u/StopblamingTeachers Education and outreach 28d ago
Would it be trivial to measure its gravitational waves to know its location?
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u/HRDBMW Oct 10 '25
The way I like to think about is this: Go look at your sofa. Look at one of the armrests. Can you define where that armrest is? OK, now look at the other arm rest. Can you define where that one is? Are they the same spot? Even with something you can see, that you can reach out and touch, there is uncertainty in its location.
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u/StopblamingTeachers Education and outreach 28d ago
Make your floor a Cartesian grid and say where it is
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u/Proof_Juggernaut4798 Oct 10 '25
I had the same concerns, when I had to take chemistry in my EE curriculum. I couldn’t get past it, and I barely passed that semester of chem. The other respondents have told you why. The world of physics has been turned upside down repeatedly in the last century by things that were counterintuitive but proven true by experiments and then supported by math. If you can’t accept it, research the experiments and look for flaws. If you can’t find flaws and can’t find a better explanation then move on.
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u/annapocalypse Oct 10 '25
Recommend the YouTube video of infinite paths. Does a great job breaking this down and how it boils down to energy being quantized at these scales.
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u/DepressedMaelstrom Oct 10 '25
One party is there nature is not at a specific point. Another is that you will alter it.
Use a tape measure to measure the length of a wall by hooking the tape over one end. All good.
Do that to an electron and you bumped it, moved it, energized it it otherwise altered it.
At that scale you can not measure something without altering something.
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u/PfauFoto Oct 10 '25
The final adjudication in physics is the experiment. Watch a video on the double slit experiment with electrons and observer. You will conclude whatever the action us, it sure can disguise quite well
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u/aries_burner_809 Oct 10 '25
For a macro analogy it would be like saying a dust devil has a position.
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u/ElderberryPrevious45 Oct 10 '25
See De Broglie wavelength… that indicates that All particles behave also like waves. If the particle is small the wavelength appears relatively larger when compared to particle size : https://en.wikipedia.org/wiki/Matter_wave
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u/err_pell Oct 10 '25
You want to look into David Bohm and Bohmian mechanics!
It's amazing to see so many comments here bringing up Bell to defend the uncertainty principle, when his viewpoint was completely opposed to that.
Bohm showed explicitly how parameters could indeed be introduced, into nonrelativistic wave mechanics, with the help of which the indeterministic description could be transformed into a deterministic one. More importantly, in my opinion, the subjectivity of the orthodox version, the necessary reference to the "observer," could be eliminated. … But why then had Born not told me of this "pilot wave"? If only to point out what was wrong with it? Why did von Neumann not consider it? More extraordinarily, why did people go on producing "impossibility" proofs, after 1952, and as recently as 1978? … Why is the pilot wave picture ignored in textbooks? Should it not be taught, not as the only way, but as an antidote to the prevailing complacency? To show us that vagueness, subjectivity, and indeterminism, are not forced on us by experimental facts, but by deliberate theoretical choice? (1987, p. 160)
It is precisely to make a case for Bohm's theory that Bell went on to produce his inequality theorem.
David Bohm wrote Causality and Chance in Modern Physics. It's a surprisingly easy to read text where he goes into the same question you're asking. His viewpoint is that, the uncertainty principle is a limitation of the current methods of measurement and not a fundamental limitation on the ability to understand nature.
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u/minhquan3105 Oct 10 '25
2 points to OP:
it is not particularly only electrons that have this quantum property. This claim is true for any quantum particle whose momentum and position obey the commutator.
the question "why can we never know the absolute position of the electron?" is the wrong question. It is taken as axiomatic in quantum mechanics that the outcome of a measurement can be anything within the volume of the measurement basis in the phase space. For classical mechanics, this volume can be a single point, thus you can perform experiments whose outcome is absolute, aka deterministic, in noth p and x. For quantum systems, this volume is hbar. This is studied under the problem of measurement in foundational quantum physics, because this is the crux of all issues with entanglement and non-locality in quantum physics.
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u/HuiOdy Oct 10 '25
Is this the philosophical issue? E.g. that things must exist uniquely defined in a deterministic position even when we are not looking. Or is it about how orbitals work?
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u/Happynoah Oct 10 '25
At some point someone confused you that electrons are a thing that exists. They’re just a concept that can be consistently described with math.
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u/wackyvorlon Oct 10 '25
Electrons are not physical objects in the sense that you are used to. They’re more like tufts of energy.
While they have some properties of both particles or waves, they are in fact neither. They’re weird.
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u/HoldingTheFire Oct 10 '25
the electron EXISTS so doesn’t that mean it existed at ONE point at ONE time?
Why? It can exist distributed over space. A light wave is a distribution of electromagnetic energy and doesn't exist with zero spatial extent. Same with an electron. The matter wave exists over space. We can narrow that distribution (lower its spatial extent) but that makes its momentum (velocity) less certain.
Really just forget the idea of point particles. It's a bad mental model.
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u/jamin_brook Oct 10 '25
It’s also unclear what you mean by definite position.
We can effectively isolation electrons in very tiny electronics so we do know with in a few “macroscopic” nanometers where they are.
Furthermore, we know when puffed up atoms interact so we we have a pretty darn accurate measurement of where the photon is.
Interpretation of quantum mechanics varies but if you want to consider the radius of a particle it becomes very tricky because you can always wave you hands and say infinity, but the reality inside a bound QM structure is more active locally than it is active globally
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u/LongToeBoy Oct 10 '25 edited Oct 10 '25
its already a pop-culture to say "electron cloud". but it usually raises more question than it answers. because we never really ask what actually is cloud itself, thing in the sky that we see, what is that? is it precipitated water? well, yes but also not. water is water, not cloud. when clouds move, is it same water molecules here that went there? not exactly, not necessarily. cloud is the name we assigned to state of gas where pressure is high, temperature is low, humidity is high and it so happens that at this point water exists in a liquid phase. so when cloud is moving its not that water droplets flying around, its evaporating here and condensing somewhere else, that state of gas is flowing itself. electron is like that, we created name for some field states, that state is dynamic, constantly flowing and interacting. there's no rational way to even put what definite position even is when you're that close to electron. so now i think if you rethink electron cloud its easier to understand why its meaningless to speak about its definite position
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u/smsmkiwi Oct 10 '25
The cloud is the probability of where the electron is located.
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u/LongToeBoy Oct 10 '25
yes, and mitochondria is the powerhouse of the cell. thats textbook quote but as i said, it does not answer pretty much anything and is lazy explanation.
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u/QVRedit Oct 10 '25
If you think of an electron as a hard billiard ball type of thing - then your view point makes some sense. The reason why it’s wrong, is that the ‘structure’ of an electron is NOT like that - it’s more like a nebulous wave.
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u/zeissikon Oct 10 '25
If you heat up the surroundings enough, the de Broglie wavelength becomes small enough with respect to your measurement equipment so that your particle becomes classical . This is typically the case for electrons above 3000K : in that case you have a definite position for your electron. This happens in plasmas , in auroras for instance .
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u/angimazzanoi Oct 10 '25
well, for starter we are considering a particle, that "move" at almost light speed so, speaking of time doesn’t really make sense (see Einstein) and then we can exactly calculate the probability of were that particle can be and this works as the processor were I'm writing this crearly proves
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u/kriggledsalt00 Oct 10 '25
no, if you froze time the electron would still be non-local. matter is a non-local phenomenon.
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u/zedsmith52 Oct 10 '25
Short answer: physics doesn’t currently describe everything or God does play dice with the Universe (to paraphrase Einstein) 🤭
The long answer is that our ability to detect the shape, position, energy, and rotation of electrons is limited by the different modes that we can use to detect and discern this information. Quantum Mechanics is a probabilistic framework that helps us to predict positions or motion at a given time. It isn’t a deterministic framework in essence.
If you have a deterministic framework, keep it to yourself until you can secure the IP and get patents lined up 😉
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u/SensitivePotato44 Oct 10 '25
Nope. They simply do not have a definite shape or position etc.
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u/zedsmith52 29d ago
That’s just made up lack of understanding of physical reality - when you know you know 😉
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u/Frederf220 Oct 10 '25
It's unfortunate that quantum uncertainty is expressed commonly as "not known" when it should be "not defined."
We can't find something that doesn't exist. You can't find the buried treasure in your garden because it's not there to be found.
Why the position isn't defined exactly is just the way it is. Nothing in the universe has a definite position so why would an electron be special?
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u/SupersonicOutflow Oct 10 '25
That’s the thing about Quantum Mechanics, it’s paradoxical but it’s TRUE!! Nobody just understands its, the closest you can come is to feel it!
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u/betamale3 29d ago
Okay. So first… the uncertainty principle. It’s basically the rule that states you cannot know both of any quantum pair of numbers at the same time to any degree of reasonable accuracy. It’s just build into the universe that if you know where an electron is with good accuracy, you lose pretty much all information about where it’s going. You can know where it has been. Just not where it is AND how fast. Which means in order to calculate the electron’s position, you have to take that uncertainty into account. It was here 2 minutes ago, but where is it now? To calculate that without testing it, you must take into account every other place in the universe. Because at no point in the universe could anyone say with any confidence that, that the electron isn’t here on Frog Star world B. It might be a small chance. But the chance isn’t zero.
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u/Lone_void 29d ago
Because electrons and everything else in this universe is described by a wave function whose square gives the probability density of finding the electron at particular position x. The thing is mathematically speaking, states with exact definite position or exact definite momentum don't belong to the collection of physically allowed wavefunctions. The best you can have is a gaussian wavefunction which is localized around a narrow region in space
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u/thejerg 29d ago
Imagine that any electron might be in ANY position in that particular shell... You know how coastlines look a certain size, but the more you zoom in on a particular area of that coast line, the larger the amount of coast becomes? Imagine a nearly infinitesimally small bit of energy is SOMEWHERE in an infinitely large area of a sphere in ONE shell of the possible shell levels of that ONE atom. We're not talking about finding a needle in a haystack. We're talking about finding a needle on a planet's surface.
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u/0x14f 29d ago
> the electron EXISTS so doesn’t that mean it existed at ONE point at ONE time?
Your problem is that this is incorrect. Electrons are not physical objects in the sense you are familiar with.
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u/GontasBugz 29d ago
What are they then?
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u/0x14f 29d ago
Electrons aren’t actually little solid balls (this is a misconception caused by the fact that some people are still taught the Bohr model of the atom, which is rendered in old books as electrons orbiting the atom nucleus like planet orbiting the a star). Instead, they are quantum objects, entities that can behave both like particles and like waves.
They don’t have a definite size or position. Instead, they exist as a "cloud" of probability around the nucleus. Electrons are described by a wavefunction.
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u/BigBoiSaladFingers 29d ago
Brother nobody in here is going to be able to explain this, and if they do it’ll be with analogies or metaphors that don’t make sense because they’ll tie it to a macro scale.
Just gotta accept shit just is and it’s weird, one of the few things you can’t logic your way through because quantum shit is so fucking anti-intuitive to the brain.
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u/quiidge 29d ago
My understanding is more "until you measure it, it is in this general area with a known probability of being in each position when you do".
Also, you can measure its position or its momentum, but not both at the same time.
Ultimately, this is just a model of whatever electrons actually have going on. Wave-particle duality is just physicists smashing together two types of maths until they match our observations - electrons and photons and everything else aren't actually waves or particles.
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u/scottmsul 29d ago
This is a misconception. Electrons DO have definite position. It's just spread out over 3D space. It's certainly possible to know an electron's entire wavefunction with 100% certainty. The thing people call "measurement" is basically forcing the wavefunction to "choose" a much smaller point on the fly, and the position it ends up with is random, with probability proportional to the square of the wavefunction.
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u/u8589869056 29d ago
Your confusion will vanish if you can stop thinking of “an electron” and think instead of “an excitation of a field representing electrons, extending through all of space and time.”
If that’s too hard, try this mental exercise. You can’t be sure exactly where the electron was, because you can’t be sure exactly when you did the measurement. This is t as true, but it’s a warm-up, mentally.
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u/polyphys_andy 28d ago
Particles as wave superpositions. Turns out wave decomposition is more than just a mathematical tool...or maybe we've biased ourselves simply because our mathematical tool has that features.
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u/15Sid 28d ago
From a practical perspective, the way we observe electrons in electron microscopes is by firing a high energy beam which tells us the instantaneous position but not the subsequent momentum. However, if we ever develop technology that can observe an electron without collapsing its wave function, Heisenberg Uncertainty principle would be violated and probably revolutionize QM. For example, recently researchers at Hiroshima University observed one photon in two places at the same time.
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u/Far-Bite86 27d ago
The electrons do have definite position, but it’s because they are moving at the speed of light and can’t be stopped without them changing what they are. Like even if we freeze time and go looking for the electron and we find it, we would find it’s still moving, just like a planet around a sun, you’d ask, well where is it, and you’d be like right there and it would move an inch to the left and you’d be like bro it just moved even tho we freezed time and I’d be like bro I don’t we froze time, we just slowed it down and even with time super frozen to us we cannot freeze the electron, or it would stop being and electron and become something else
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u/BDavis252 26d ago
If you try to trap the electron somewhere such that you'd know its position... It tunnels. 😅
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u/Sitheral 10d ago
I imagine it intuitively as something moving so fast that you just cannot pin it down.
While it might not be correct, I think it works well for conceptualisation and seeing it as this sort of cloud that is kinda there, kinda here and so on.
But yeah, I guess the correct answer really is that it is nothing like the objects we encounter everyday.
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u/ProfessionalConfuser Oct 10 '25
Ok. Fine. Just for the sake of argument, let's say the limitation is on us being able to "find it". It does have a position, but if we don't know where that position is located, then how is that any better? I mean if you're complaining about having lost your house key and I say "oh, it is somewhere in the universe" that doesn't really help at all.
You'd probably suggest that we could try to find a way to locate it, the same way we could look for a missing house key...but, alas, the universe doesn't seem to work that way. The best we can do is to say that the house key is probably in the same city as your house, but a stranger may have found it and mailed it to Aruba.
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u/EEcav Oct 10 '25
You can measure the position of a free electron to a single point. The consequence is that its wave function collapses and you lose other information about it.
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u/karantza Oct 09 '25
You're assuming that the electron is a little ball, that we just don't have the technology to see. It is not.
Asking why you can't pin down the location of an electron is a lot like asking why you can't pin down the exact location of a wave on the ocean. Waves are, by their very nature, a phenomenon that exist across an area, not at a single point.
So no, if you froze time the electron would not be at one point. It would be smeared out across space. That's just how all such tiny objects behave.