fossilesqueElectrons are easy
EngywookNow everything is clear. Thanks!
HaagelAlso please don’t look at it
I mean, you can but it won’t be there.
HSR🏴☠️Actually, it can be there, but then you won’t know how fast it’s moving.
☂️-think of it as a camera.
if you set it up with a high speed to take a picure of a bouncing ping pong ball you will know its precise location at the moment of the shot.
if you set it up with a low speed you will see a blur of the path it took, but not a precise location.
mercThat’s not a good analogy because typically cameras don’t change the things they’re observing. But, a camera with a flash…
Imagine a guy driving down a dark road at night. Take a picture of him without a flash and you’ll get a blurry picture.
Take a picture of him with a powerful flash and you’ll get an idea of exactly where he was when the picture was taken, but the powerful flash will affect his driving and he’ll veer off the road.
You can’t measure something without interacting with it. This is true even in the non-quantum world, but often the interactions are small enough to ignore. Like, if you stick a meat thermometer into a leg of lamb, you’ll measure its temperature. But, the relatively cool thermometer is going to slightly reduce the temperature of the lamb.
At a quantum level, you can no longer ignore the effect that measuring has on observing. The twin-slit experiment is the ultimate proof of this weirdness.
ZeratulSorry I didn’t just Google, but could you give me a rundown of the twin slit experiment?
It’s probably worth finding a good educational video about.
Basically, the particles really are waves. Even though they’re particles.
Sure. So, imagine a rectangular pool of water. You have a little weight on one end of the pool bobbing up and down producing waves. Then you put a wall halfway down the pool with two gaps in the wall. The waves from the wave-generator hit the gaps and go through. At the back wall of the pool you can measure the wave height. What you see is that at some points there are big waves, and at other point no waves at all. What’s happening is that the waves coming through each gap travel different distances. If the wave from one gap is at a trough when the wave from the other gap is at a peak, they interfere with each-other and the water doesn’t move much. If, instead, the distance is right so that both waves are at a trough or both waves are at a peak, the wave height is doubled at that point.
If the weight bobbing up and down is very regular, the pattern stays very regular. The places on the back wall with no waves are always in the same spot, and the places with big waves are in the same spot.
Now, do a similar experiment but instead of using water, you use light. To keep the waves all the same wavelength / frequency, you need a laser. So that laser shines forward and hits a barrier with two small slits in it. When the laser hits a wall after that you get the same pattern of bright spots and dark spots. Light is acting like a wave and the light waves are interfering with each-other in the way you’d expect.
But, what if you turn the laser way down. You can reach a point where instead of getting a continuous pattern on the back wall of the experiment, you only get an occasional “blip”. What’s happening there is that the intensity of the laser is so low that you get a single photon being emitted, passing through the slits and hitting the back wall.
So, this basically shows that light is acting like a particle. It is emitted from the laser, passes the slits, and hits at one single, specific point on the back wall. So, this shows that light is both a particle in some ways (individual light “packets” can be emitted and strike one specific spot on the back wall), and it’s a wave, because the light passing through the two slits interferes and produces a strong/weak pattern on the back wall.
But, the truly mind-blowing part of the experiment is what happens if you record the positions of each hit on the back wall when the laser is tuned way down and only emitting one photon at a time. If you record the location of the hits (or say, use something like photographic film that you expose over multiple days while you run the experiment), what you see is that there are points where you get many single-photon hits on the back wall, and points where you don’t get any single-photon hits on the back wall. And, the points where you don’t get any hits are exactly the points where you get dead zones from the wave interference when you run the laser at full intensity. Even though you’re only allowing one photon to go through at once, it’s still acting as if it’s going through both slits in some way.
The obvious question at that point is “Which slit is it actually going through?” So they measured that, and as soon as they could determine which slit the photon went through, the interference pattern disappeared. Instead it looked exactly how it would look if you blocked the other slit. But, when they stopped measuring which slit the photon went through, the interference pattern comes back.
This revealed a few fundamental things in quantum mechanics:
Thank you so much. This made it more than a little more clear. I’d heard of this before but never took the time to understand, and this comment really helped. I studied math, thankfully avoiding the confusing physics fun.
Ah, then the addition of two sine waves offset by a certain phase would have been easy for you to understand. It’s always hard to guess how much someone will already know.
Thanks sir
The D Quuuuuill“Well… You see… When its a particle it spins. When its a wave its still doing that. How does a waveform spin you ask? Listen. Shut the fuck up. The math is really weird and some of this stuff just happens and you can’t visualize it in your head. We didn’t believe it at first either but after 50 years of experiments we have to just accept that reality is consistent with the math even if we don’t fully conceptualize what that means even”
IndiBronyWe are all just folds in this wonderfully weird thing we call spacetime!
The prions of spacetime.
Out here folding along.
Hah! Time. Like that’s a real thing.
Nice reference to PBS Space Time. The YouTube channel where I just get bullied with science, and for some weird twisted reason I like it.
pbs space time is awesome, and this description is even more so.
Bullied with science sounds like a fun band name
You seem to be up to date with this stuff; did we find out whether there’s more than one yet…?
Personally don’t like the idea of everyone reusing the same electon for everything… seems quite unhygienic. I’d rather we had at least one per person, maybe share it with people we trust, if we must…
AnUnusualRelicWe have to recycle nowadays. Besides we can’t have people throwing away perfectly good electrons. They could end up anywhere.
I’ve heard this weird concept repeated over and over but I’ve never once run across it in literature or in speaking to my particle physicist friend. Can you provide a source?
Thank you for the link. It makes sense I haven’t heard too much on it. More a postulation than a theory. And kind of untestable/ philosophical too.
well fak. came here for a good time,
now here for a long time.
reading about positrons and shit.
thx though
now here for a long time.
reading about positrons and shit.
thx though
You wrote a comment so good that I screenshotted it.
Awww thanks
- When it’s* a particle
- When it’s* a wave
- it’s* still doing that
Phone stuff. Sorry about that
ZacryonThat sounds nasty.
shrug I mostly browse Lemmy on my phone. I don’t give a shit enough to correct autocorrect mistakes. My message was clear even with piddly little autocorrect mistakes
Totally fine by me. I was just making a bad pun. (I’m not the one who corrected you.)
rude bot
Of course waves can spin, it just does so in some conceptual “dimension”.
NeatoIt’s a point but it doesn’t actually exist at any point. It exists in a cloud where it could exist anywhere in there.
You can observe it but doing so changes its behavior. Why? Well… Um… Maybe it’s just the simulation breaking down?
It’s because to observe something you have to interact with it. Dealing with particles is like playing pool in the dark and the only way you can tell where the balls are is by rolling other balls into them and listening for the sound it makes. Thing is, you now only know where the ball was, not what happened next.
In the quantum world, even a single photon can influence what another particle is doing. This is fundamentally why observation changes things.
isolatedscotchholy shit the pool explanation is so good, I’m gonna recycle it for sure
Swednecklike trying to measure a soft noodle lengthwise with a caliper
Good metaphor
NotyouSo, if we had a machine that could “see” without photons, we could observe an electron directly?
We have such devices, unfortunately they tend to use electrons instead (electron microscopes). We also have devices that just work by measuring the electromagnetic field (atomic force microscopes). Again though, to measure the field you have to interact with it, so you can’t do it immaculately.
When talking about particles, the interaction very rarely involves actual contact, as that tends result in some manner of combination. Two electrons for instance don’t really bounce off each other, they just get close, interact and then diverge. If a photon ‘hits’ an electron it gets absorbed and a new one is emitted. Look up Feynman Diagrams if you want to see some detail to this. I don’t think you need any deep knowledge to benefit from looking at them, they are really quite an elegant way to visually show the mathematics.
If you suggest every observation is an interaction then you inherently are getting into the relational interpretation. Which I am not saying you’re wrong to do so, I think it is the most intuitive way to think about things, but it is not a very popular viewpoint.
Do expand, please. It has been a while since I have studied this seriously. Do you have any examples of observations that don’t involve interacting with the system?
That’s not what I’m saying. My point is just that observation = interaction has a lot of implications. Particles are always interacting, so if the wave function represented some absolute state of all systems, then the statement would just be incorrect because the wave function would be incapable of ever “spreading out” as it is constantly interacting with a lot of things.
The only way it can be made consistent is to then say that wave functions are not absolute things but instead describe something relative to a particular system, sort of like how in Galilean relativity you need to specify a coordinate system to describe certain properties like velocity of systems. You pick a referent object as the “center” of the coordinate system which you describe other systems from that reference frame.
You would have to treat the wave function in a similar way, as something more coordinate than an actual entity. That would explain why it can differ between context frames (i.e. Wigner’s friend), and would explain why you have to “collapse” it when you interact with something, as the context would’ve changed so you would need to “zero” it again kinda like tarring a scale.
AHH, I think I see what you have misunderstood. I am not saying all interactions are observations, rather that observations are a subset of interactions, hence uncertainty.
Furthermore I think it would be more useful to say that the wave function only collapses when it is actually necessary to the interaction rather than when it interacts with ‘us’. Unless you can provide a counterexample. Privileging observations made by humans reeks of mysticism in my opinion and is the cause of a lot of the misunderstandings about quantum physics among laypeople.
Saying that observations are a special kind of interaction does seem to be privileging humans, though? What is different from measurements/observations and any other interaction?
I’m neutral on the subject of if there are non-observational interactions. Though I ask again, are you aware of any observations that do not involve interactions?
Why do you keep asking that? I already explained I’m not claiming observations = no interactions in extensive detail and you turn around and ask me that gain.
Because you seem to have a problem with me saying that all observations are interactions.
Futher, if it is true that if observations are interactions, then RQM must be true, surely it goes from a fringe interpretation to just simple fact unless you can find a counterexample?
At this point, I’m not even sure I quite see what your point is supposed to be.
I think you are just trying to fight rather than actually have a discussion so I’m not really interested in going on, but I will say one last thing to clarify what I am saying for other people who might be reading.
If you say observation = interaction then this inherently leads you to RQM which is like the definition of the interpretation. As I said at the beginning, I do support this interpretation, I think it’s the most reasonable approach, but it should be made clear this is a rather fringe point of view and not supported by most academics. You can see in the paper below only 6% of academics support it. And you clearly don’t seem to support it yourself as you seem to be pushing back against that rather than just agreeing with my statement it is the most intuitive way to think about things.
The plurality there support the Copenhagen view where observation really is given a special role.
Without going the route of RQM then you end up with something that is just objectively false as the wave function would be incapable of spreading out since particles are always interacting with things, rendering quantum phenomena impossible.
You can clarify instead by saying observation → interaction, that is to say, an observation implies an interaction, i.e. it inherently always entails an interaction but not interactions are observations, however, if you do this, you end up with the measurement problem. That is to say, you need to actually construct a theory to account for what kinds of interactions actually qualify as a measurement/observation. To quote John Bell…
What exactly qualifies some physical systems to play the role of ‘measurer’? Was the wavefunction of the world waiting to jump for thousands of millions of years until a single-celled living creature appeared? Or did it have to wait a little longer, for some better qualified system . . . with a PhD?
Specifying a theory of measurement is known as an “objective collapse” model and they make different predictions than traditional quantum mechanics because depending on where you set the threshold for what kind of interaction qualifies as an “observation” changes how much the wave function can spread out before being collapsed again by such an “observation.”
There are several models of this like the Ghirardi–Rimini–Weber theory and the Diósi–Penrose model but these are ultimately more than just other interpretations of quantum mechanics but ultimately entirely new theories.
It is not so simple just to say “observation is an interaction” and then pretend like the job is done, or else there would be no confusion in interpreting quantum mechanics at all. There is a lot more clarification that has to be made in order for it to make sense.
A Snapshot of Foundational Attitudes Toward Quantum Mechanics
Foundational investigations in quantum mechanics, both experimental and theoretical, gave birth to the field of quantum information science. Nevertheless, the foundations of quantum mechanics themselves remain hotly debated in the scientific community, and no consensus on essential questions has been reached. Here, we present the results of a poll carried out among 33 participants of a conference on the foundations of quantum mechanics. The participants completed a questionnaire containing 16 multiple-choice questions probing opinions on quantum-foundational issues. Participants included physicists, philosophers, and mathematicians. We describe our findings, identify commonly held views, and determine strong, medium, and weak correlations between the answers. Our study provides a unique snapshot of current views in the field of quantum foundations, as well as an analysis of the relationships between these views.
Its that an observation is always an energetic interaction. You can’t measure a system without interacting with it and at the particle scale every interaction has enough energy to affect the particle in some way.
I think a lot of the confusion people have is around the word “observation” which in everyday language implies the presence of an intelligent observer. It seems totally nonsensical that the outcome of a physics experiment should depend on whether the physicist is in the lab or out for a coffee! That’s because it is!
I have this beef with a lot of words used in physics. Taking an everyday word and reusing it as a technical term whose meaning may be subtly and/or profoundly different from the original. It’s a source of constant confusion.
Physicists seem to love their confusing language. Why do they associate Bell’s theorem with “local realism”? I get “local,” that maps to Lorentz invariance. But what does “realism” even mean? That’s a philosophical term, not a physical one, and I’ve seen at least 4 different ways it has been defined in the literature. Some papers use the philosophical meaning, belief in an observer-independent reality, some associate it with the outcome of experiments being predictable/predetermined, some associate it with particles having definite values at all times, and others argue that realism has to be broken up into different “kinds” of realism like “strong” realism and “weak” realism with different meanings.
I saw a physicist recently who made a video complaining about how frustrated they are that everyone associates the term “dark matter” with matter that doesn’t interact with the electromagnetic field (hence “dark”), when in reality dark matter just refers to a list of observations which particle theories are currently the leading explanation for but technically the term doesn’t imply a particular class of theories and thus is not a claim that the observations are explained by matter that is “dark.” They were like genuinely upset and had an hour long video about people keep misunderstanding the term “dark matter” is just a list of observation, but like, why call it dark matter then if that’s not what it is? They just inventing confusing terms then getting frustrated people are confused about them.
Yep! Same thing with black holes which are not holes at all!
Even very basic physics terms such as positive and negative electric charges lead to a lot of confusion for ordinary people. There’s nothing positive or negative about them, they’re just names for the fundamental property of protons and electrons that leads them to attract one another.
uisAt least physicists don’t call particles “Sonic Hedgehog” like biologists do with proteins
think of it as a camera.
if you set it up with a high speed to take a picure of a bouncing ping pong ball you will know its precise location at the moment of the shot.
if you set it up with a low speed you will see a blur of the path it took, but not a precise location.
My advanced E&M professor said “Imagine a sphere of radius zero. Trust me, it works.”