Shining Light Through Solid Balls Using Quantum Mechanics—Poisson's Spot Experiment

hey everybody today I'm going to be showing you how to shine light directly through solid objects using the laws of quantum mechanics now the particle theory of light introduced by Descartes and also taught by Newton was that lie always moves in a straight line because lie is actually made out of tiny little particles and those particles just like any other particle can only move straight from where they're shot out of so basically the reason you can't see me when I move this basketball in front of my face is because there's light coming off of my face the cameras directly in front of my face so the only way that the light can get from my face to the camera is in a straight line and so if I move the basketball in front of my face the basketball has to block that light and so there's no way that you can see my face because the basketball is blocking it and that is the particle theory of light but it turns out that's not exactly true we do know that light is made out of particle like things called photons but it turns out that these photons don't always behave like particles they also have some wave-like nature and in that case that means that these particles aren't always going to move in a straight line now these particles of light called photons have wave-like properties but what is it that's actually waving if you have one photon how can it also be a wave well nothing is actually waving in the photon what it actually means is that in between the light coming off of my face and getting measured in the camera the particle behaves like a probability only meaning that we only have a certain probability of discovering that photon somewhere else in space now obviously the highest probability of finding a photon is usually directly in front of where it got shot out of so that's why in most cases when I hold this basketball up in front of my face you don't see me because we had the highest probability of blocking the photons when we have a ball directly in front of where they're being shot out of but here's where things get weird according to the wave-like nature of light the highest probability of the location that I can find a photon coming from my face when I hold this basketball up in front of my is directly in the center of the basketball so that may sound weird what I'm telling you is that you should be able to see me directly at the center of this basketball you should be able to see my face through it but why don't you see me well it turns out it's only true for things that are very smooth so for example let me grab a smoother ball like this metallic sphere here so if I hold this metallic sphere up in front of my face I'm telling you that according to the wave-like nature of the light you should be able to see directly through this ball into my face when I hold it between me and the camera but still you don't see me for some reason now this should just sound absurd at this point I'm telling you that light should go directly through the center of any sphere no matter what it's made of made of solid steel or anything light should just go directly through it and come out the other end but I've just shown you two examples of you not being able to see light coming through a ball but why not does it mean that light doesn't actually have wave nature well no the reason is is because this ball is just too big because according to the mathematics of it the larger the sphere the smaller the probability of finding a photon directly in that path at the center of it so let's just get a smaller ball and see what we can see so now I have a tiny little ball and we can use a light source like my face or even a flashlight but now the light source is bigger than the ball itself so we're gonna have to get a smaller light source so in order to get this to actually work what you need is a point source of light and you can simulate a point source of light by using a laser pointer so I'm going to be using my laser pointer and shining it on the back wall here and then I'm going to be putting a small sphere in between here but it turns out that that tiny little dot of the laser pointer on the back wall there is still smaller than my sphere so I need to spread out the light a little bit to get that to be a larger area of light on my back wall here and I'm gonna do that just by using a lens so to spread out the light you can use a magnifying glass but I have just a smaller lens here with the higher power so I'm just going to use this lens here to spread out my laser light so that it appears larger on my back wall here for example here's how big it gets now so we're shining it back here now we have a large point on my back wall so all it's done is spread out the area of light here so I have my laser on the table there now all I need to do is place a small ball directly in its path and that's exactly what this is so I just have a magnetic sphere hanging on a metal wire here and this is going to be directly in the path of the laser so now we're just gonna look at the shadow of the ball on the back wall here now if all goes right we should see that the shadow that this ball forms on the back wall the very center of it will be the brightest part now let's see if this actually works okay let's turn on my laser okay I have a big spot on the back wall there you know let's get my sphere directly in the path okay it's now shining on the ball and we can see the shadow back there let's go get a closer look at the shadow okay here we go here's the shadow now look directly at the center of the shadow you can see the brightest point that shadow is directly in the center and so that's so weird so that point right there is actually called poison spot and the reason it's called poison spa is because poison was a scientist who didn't actually believe in the wave-like nature of life he thought it was only made out of particles and so he mockingly said that if it were actually made out of waves according to the math that would mean that if you had a perfectly spherical object then directly in the center of it would be the brightest part of the shadow and it turns out that that's actually true but it's kind of a difficult experiment to set up because in order to do it you have to have a very spiritual object and you have to have a point source of light like a laser so the question is what does it look like if you're directly in the center of this sphere here so now to show you something even cooler the center of the ball is where its brightest but I've cut a hole out of it so that it's shining to the back that's the center of that ball there so that's the center of the shadow right here so now if we look through this hole in the back you can see that you see the laser light up there and there's no ball blocking it whatsoever so basically at the center of the shadow is where it appears that there's no ball in front of the laser at all that's crazy so basically it's as though the light is coming directly through it so what actually happens is as the light comes from behind the sphere the entire circumference of the sphere now acts like it has a bunch of point sources around it and so as the light hits all of those point sources they all constructively interfere directly in the center of it so you can see when you add up all the waves of the individual point sources around the sphere that the direct center is the place where you have the highest amplitude meaning the most likelihood to find a photon where all the waves add up together so in this graphic here you can see how when light hits a spherical surface like this that those waves can actually constructively interfere so that the center becomes the brightest point now it turns out that you can talk about poise on spot without even mentioning the particle nature of light but the reason I mentioned particle nature of light because in general it's incomplete to call light either waves or particles you kind of have to talk about both of them all the time now in this experiment light wasn't actually going through the object what was happening is that that object was causing a change in the wave properties of that light such that it caused constructive interference of the light or it or it caused the probabilistic wave-like nature of light to constructively interfere directly at the center such that we had a higher probability of finding photons there so we kind of didn't bend the light but we bent its wave property so that it went around it and we could still see what was behind the sphere so in a way the light was able to go through it without actually going through it [Music] now thanks for watching another episode of the action lab I hope you liked it if you did remember to subscribe if you haven't yet and remember to hit the bell if you haven't yet then you can be notified when my latest video comes out and check out the action lab comm to check out the action lab subscription boxes we now have two boxes 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Channel: The Action Lab

Views: 1,972,910

Rating: 4.77601 out of 5

Keywords: poisson spot, arago spot, arago, poisson, poisson's spot, the action lab, action lab, quantum physics, quantum physics explained, science documentary, quantum mechanic, vacuum chamber, venus fly trap, hydraulic press, iron man, mysterious science, event horizon, stretch armstrong, science experiment, how to, neutron star, home science, blackest black, self pouring, vac man, cool science, black 3.0, foil ball, liquid nitrogen, black holes, quantum mechanics

Id: TM9alPcOMcU

Length: 10min 2sec (602 seconds)

Published: Sun Jun 23 2019

Reddit Comments

[u/Spottyhickory63]

I belive it’s king of random,