This is one of the best memes I've ever seen in my life. It reminds me of the quantum race in Futurama, and the professor says "no fair, they looked at it" (maybe not exact words but the sentiment is there)
I get that part. With absolutely no disrespect or jokes to the person who asked why there was a duality to the meme, I was actually wondering if the question was another joke I wasn't understanding. (Many comment-based double entendres fly over my head, unfortunately.)
Still though, this whole area of science is confusing, especially when trying to understand EM radiation from antennas. You can shake some electrons in a metal wire and generate a wave (of photons?) that can cause the electrons in another wire to ocillate. (It's really weird when you think a little on that.)
I have heard the word "photon" being used in regards to EM recently, and that is confusing me a bit. It seems legit on the surface when thinking about how energy is transferred, but it also kinda doesn't. Would you happen to have any clarity on that?
I would suggest reading the book QED: The Strange Theory of Light and Matter by Richard Feynman. He won the Nobel Prize for his theory of how light and matter interact and it has been tested to more accuracy than even Einstein's Theory of Gravity.
The book is written for anyone to understand without any mathematics.
What makes his explanations so simple is he is adamant that photons are particles and explains everything as particles interacting.
So your question about EM becomes: an electron in a metal emits a photon, the photon travels until it hits another electron in a piece of metal, that electron's energy is measured and you received the signal.
Thanks for the details. I am to the point now that the concepts are clear enough that solid literature could fill in some blanks. (It's taken me about a year or so before I could actually begin to visualize wave/particle concepts. Not gonna lie: PBS Space Time and Sabine Hossenfelder videos helped a ton.)
Ok, cool. The issue was that I had previously visualized the EM wave as being more akin to how electrons flow through wires, but with more magic involved. Once I started to revisit many my core conceptual beliefs, there was a ton that didn't make sense. Basically, you just gave me some validation, thanks. (There aren't too many people in my life that are interested in the nuances of photons, believe it or not.)
Light (in fact everything) is a wave, with some traditional particle properties added in. It's relatively easy to wrap your head around the weirdness from that point of view. It's almost impossible to make sense of it from a "particle with wave properties" view.
It's also worth noting that it is not observation, but measurement that matters. All observation is measurement but not all measurements are observations.
Basically, to measure something, you need to hit it with something else. Using a particle analogy (since the wave version is FAR less intuitive), imagine a pool ball, rolling down a table. You can only detect balls hitting the cushions. To measure where it is, in between, you need to roll additional balls across the table. In traditional physics, these balls can be thrown as lightly as you like, as accurately as you like. Unfortunately, the wave nature of the system imposes lower limits on this. When you throw a ball, it changes the ball it hits. To gain information, you end up damaging or destroying the system you are measuring.
In quantum mechanical terms, the wave function is collapsed. In fact, it's combined with the new particles you used to measure things.
In the original post. When you're not looking, the wave of the photon passes through both spits, it then interferes with itself. Only when it reaches the detector is it collapsed (by interacting with the atoms of the detector). When you try and measure which slit it went through, you introduce a new wave. This changes the shape of the original, and makes it appear like a particle.
It’s almost impossible to make sense of it from a “particle with wave properties” view.
"I want to emphasize that light comes in this form-particles. It is very important to know that light behaves like particles, especially for those of you who have gone to school, where you were probably told something about light behaving like waves. I'm telling you the way it does behave- like particles."
Richard Feynman, "QED The Strange Theory of Light and Matter." Introduction, Page 15.
As you read deeper, it's more and more obvious. Light is neither. It's a quantum mechanical object that has no direct analog in classical physics.
Under some conditions, the wave properties are dominant. In others, the particle. In most quantum mechanical problems, both are present.
My main point is that you get log jammed if you try and add the wave properties to a particle concept. There's nothing it can properly connect to. However, a wave can look like a particle, if you set it up right, and squint hard enough. In graph form, it's normal distribution with standard deviation close to zero. Basically a spike, with some slight rounding. It's far from perfect, but it gives our limited brains an anchor to work from.
I would agree that light is neither but Feynman is very adamant that it's a particle and he describes all the properties of light using a particle only model. It's much simpler conceptually to keep everything as a particle than treating light as a wave that sometimes collapses to a particle.
In his book he used the Mayan numbering system as an analogy. You can do everything in math by counting one by one, it's only extremely cumbersome. In a similar way he saw waves as a mathematical method to make calculating particles easier in some situations. But underlying the fancy math, it's still counting one by one.
Feynman argues that you can calculate and observe everything as only particles but you can never observe waves and have to make waves instantly transform into particles if you treat them as waves.
Look at the PBS Spacetime link someone else provided, but in this case the looking is knowing which slot individual electrons or photons go through. Thus, wave pattern when which slot is not known; random scatter pattern when you know which slot.
Hard to explain (in part because I'm not a scientist) but it isn't when you look at it, it's when the photon interacts with something. I'm gonna do my best, and if I'm hard to follow, that's because I suck at writing
Before interacting with something, a photon acts like a wave, kind of like a wave in water, or a sound wave. The wave goes through both slits at the same time, which causes it to split into multiple waves. In places where two waves meet, their magnitude is added together. That is, where the peaks of those waves meet, the peak gets higher. Where the valleys meet, they get lower. Where a peak meets a valley, they cancel each other out. The empty parts on the detector are where peaks met valleys, and there was no measurable wave in those parts.
When a photon interacts with something, it collapses from a wave to a particle, and interacts with the detector only in one spot. I've seen it compared to a speck of dust in a raindrop. Before that raindrop hits the ground, you know that the speck of dust is somewhere in the drop, but not where it is in the drop. When it hits the ground, the speck can only end up in one spot. When the wave collapses, the photon is forced to interact with the detector in only one place. The location is random, but is more likely in spots with a larger magnitude of wave. Those are the places with the spots on the detector in the top picture.
If the photon interacts with something at the slits, like a polarizing filter, it collapses before an interference pattern is able to form. No interference pattern means it ends up interacting with the detector in one of the two areas like in the bottom picture.
It's not just looking. The implication of the person looking is he's looking at which path the light took through the slit. If you measure which slit the particle of light went through, the pattern disappears.
Last I read about this was years and years ago, and the claim at the time from the source I learned about it from was that the cause of this behavior is unknown. Is it known now?
Depends on what you mean by unknown. The meme (and a lot of common understanding) doesn't know what it means to be observed. There is a leading theory, the Copenhagen interpretation. The biggest theory in opposition would be multi-world.
This topic can get so convoluted so quickly... I just deleted a testament cause I got carried away (and now proceeded to write a new one).
So the recap on the experiment is that an interference pattern shows when shining light through two slits, but it'll also show up when firing single particles through as well. When we try to see through which slit each particle went through, magically there's no more interference pattern and we only get 2 lines.
Short-ish answer: we sorta know why the pattern disappears when observed. It's the very simple fact that we cannot take a precise measurement without interacting with the system and, thus, affecting the outcome. Think about it, we're trying to know information about a single particle. The only way to get any information about it is to interact with it. Once we do, something changes that ends up preventing the interference pattern from showing up.
What we don't know for sure is why the interference pattern happens in the first place. There's a plethora of theories and interpretations, but we end up being forced to admit a probabilistic and extremely unintuitive, almost magical nature in quantum physics. It's something that many were uncomfortable with at first, hence Schrodinger's cat, and yet, the model of quantum physics that has resulted from these observations has stood the test of time, correctly predicting or explaining nearly everything thrown its way with the most notable exception being gravity. For everything else, what we now know as Quantum Field Theory, alongside the standard model, is the most accurate representation of quantum physics we have, even if it's not the last one we'll ever have. It's hard not to keep going because every sentence could become a rabbit hole on its own.
Little addendum now that I've wasted your time: my knowledge goes as far as YouTube allows. I'm a webdev with a morbid fascination with this subject. Fact check me, I prolly fucked up my explanation multiple times.
Do check out the channel called "history of the universe" on YouTube. Few videos are as educating and mesmerizing as the videos from that channel.
I vaguely remember an explanation that whatever device/mechanism is actually used to “observe” the experiment was affecting the behavior of the light. Boiling it down to “observation changed the outcome” makes you picture something that changes depending on whether you look at it with your eyes, but there’s a lot more moving parts to the whole thing.
Exactly. The apparatus used to take measurements slightly alters the thing being measured. It's not the act of looking at it with our eyes that causes any change.
An analogy that I find easier to understand is the tool used to measure tire pressure releases a small amount of air, thus changing the tire pressure (albeit negligible).
It's just proof that light behaves as a wave, because it generates an interference pattern like the first picture. The second picture is how it would theoretically behave if it was (only) a particle, which it isn't. The proof that light acts like a particle comes from a second experiment proposed by Einstein dealing with the photoelectric effect.
It actually does behave like a particle in this experiment if you use a measuring device to see which slit it went through. It's also enough to turn the heat up in the room. Then random air molecules take on the role of a measuring device.
Yeah, if you alter the experiment to try and prove duality then of course you can do that because light is both. The classic double slit experiment, as commonly understood and illustrated above, just proves the wave part though. You’re not going to see just two lines from shining a flashlight through a couple holes.
Eyes are a measuring device and using them here would not result in two lines. Using a different measuring device produces a different result. Nothing I’ve said is counter to anything you’ve said. The image is a joke, not a real experiment.
Its source is known. Unfortunately, it requires a different way of looking at everything. (It's all waves, even if it looks like a particle most of the time). Wrapping this up as simple pop science, that can be digested by most laymen, is difficult.
What we don't actually know is why everything is made of waves. We know the rules it follows, but not the underlying cause. Figuring that would would likely require an understanding of quantum relativity, something we only have a very weak handle on.
