interresting explaination... I would explained it with the exemple of water refraction. and with the baywatch (pamela!) theory... :D that's why I love your videos actually :)
@jeffshubert because you are standing at a fixed point, as soon as you move so would change of these other light streams, your brain takes the seperate images from your eyes and tries its best to add depth and percetion. and a better question is can these streams be broken up to produce a hologram or even a spectrum?
personally I think this guy is on crack, light will only flip the image if reflected off a surface, the parabola path he describes would not flip the image. Light doesn't choose the path of least resistance, thats electricity dumbass. I fully believe that the light does actually reflect of the surface, and the temperature of the surface does allow an increase of the angle of incidence. Perhaps if the surface were hot enough, the image would "float" above the surface, but not flip the image
@ricktbdgc the flipped image effect is because the refracted light does not all come from the same place. You can visualise this better by taking the graph at around 5:50 in the video, adding a second light source further away and drawing another parabola from the new source to the existing sink.
I respectfully don't think the professor's description is correct. Lights rays radiate in many directions. Placing a solid object between the object and the observer will not cause the light to seek the path of least resistance and go around the object. It will be blocked.
Mirages are caused when light refracts as it passes from colder air across a sharp boundary to significantly warmer air.
@subsystems Well, actually he is right. There is a good set of videos by the Vegas trust that show Richard Feynman explaining quantum electrodynamics, the theory that governs this behavior, for which he and other got the Nobel prize. In there, he explains how it works in that theory, where all paths are given equal weight, and one sums up all the paths for the light - in many simple cases much cancels out, making it possible to do the calculation. In this case involving refraction , mirrors, etc
@jonahansen I understand what you are saying but the professor is saying the light will bend to, in a sense, "seek out the path of least resistance". This cannot be entirely true because light going around an object would be the path of least resistance instead of striking the object. If what he were saying were correct, we would always be able to observe objects placed behind other objects, always.
@jonahansen Furthermore, what is forcing the path to be parabolic as he clearly states? Parabolic paths by definition require a constant acceleration. The entire field of optics relies on light rays that travel in straight lines through different mediums and change directions as the refraction index changes. Never have I seen any parabolic formulas for light paths used, only straight paths. I can imagine a hyperbolic path where the 1st approximation is the light paths along the asymptotes.
@subsystems I'm not that good at physics, but i believe that the light travels in a parabolic path, due to the fact that the change of the air temperature isn't abrupt, but smoothly decreases with height, hence making the light travel through several layers of air with different temperatures, making it refract hundreds maybe even thousands of times, through the same number of mediums.
I don't like this description- I think it is perfectly possible to explain what is happening by saying what is happening locally change the direction of the light. But this seems to suggest that the light "knows" what the shortest path is before it leaves.
Obviously this would have huge philosophical implications, such as, what would happen if I decided to cool the air down after the light has left. I think it should be mentioned that light travels in the shortest route- but for another reason.
@jamma246 You are entitled to your opinion---and your objection was raised when Fermat made his proposal. The modern view is that light waves travel on all possible paths. Those paths that are close to the path that takes the least time are all in phase and add up; those that take longer times arrive out of phase with each other and cancel out. The light does not know which path to take---it takes all of them. This idea was applied to particles in Feynman's version of quantum mechanics.
@MrOldprof Exactly, and this is the better interpretation. With the interpretation given in the video, it is made to sound like the photons know before they depart for their journey which the shortest path is going to be and head down the according path. I remember being told this when I was young and being very confused by the idea.
(In fact, I wouldn't even say that this is an issue necessarily for QM, it would be able to work in classical mechanics without "sentient photons")
Well, I always thought it had to do with angle of incidence, refraction, something like that, sorta like how depending on how you look up through an aquarium, at certain angles the water acts as a mirror, where at different angles it is clear. I am sure the professor assumes most people kinda grasp the idea. It's all relative to where you are. I will say though that the professor explains it the way I would rather hear someone explain an otherwise mundane event. Eventful!
I really couldn't care less if this is 'accepted' by physicists... You're implying photons have human level self awareness and are able to make conscious, logical and rational decisions. Not even some humans can do that. That is preposterously dicey on so many levels...
Anyway, tell me when you manage to take one of these sentient photons out for tea and have a rational discussion on quantum mechanics with it, will you? Thanks.
@Versudan Nobody is implying photons have human-level self-awareness. The way light finds the shortest-time path locally (which it DOES, as said in the video we observe this everywhere) implies no more self-awareness than the way your computer can find the smallest-size file in a given directory. The only difference is that the behaviour of computer is steered by what you what from it, while the behaviour of light is "hard-coded" in the physical laws of the universe.
@leftaroundabout He's saying that light has the ability to detect what medium it's traveling through and change it's course accordingly. He said nothing about the laws of physics dictating that, he's saying the photons are making this choice actively of their own volition. Whether he's claiming that's the litteral truth or he just really screwed up how he explained it I'm not sure, but the way he said it sounds preposterous.
I'm liking this because you won the argument, but really all you're doing right now is being pretentious. It IS slowing down on anything above the quantum level, which is great for all purposes of humans since we don't live on the nucleus of atoms. We are much larger than atoms, and the phenomenon that we're observing is on our scale, not the scale of the atomic world. Let's leave the semantics at home and not argue things that don't matter for the purpose of the video's explanation
and that''s why I said you won the argument. What you said is correct and it us about absorption but all I'm saying is that it's an unnecessary argument to make.
So..? Gravity and heat can have a similar effect on light? If you have two similar objects in space, one hot and one cold. Would there be a measurable difference in how the light is being bent?
The "intelligent light" explanation is pretty childish in my opinion, explaining how reflection and refraction work is much more accurate, interesting and elightening.
I have a question about light, raised by some kid genius I also saw on youtube. The question is: If the speed of light is constant, how can it slow down and accelerate in some instances? Does this mean that there is a higher speed threshold than the speed of light?
@ishthealaskan When people talk about the speed of light, they are usually talking about the speed of light in a vacuum which is constant, however light travels differently depending upon the different mediums that it is traveling through. The higher the index of refraction something has, the slower light will travel through it.
Halucinations cannot be photographed. But, illusions created by reflected light can be, its not much different than any other visual experience. Otherwise you would not be able to photograph yourself in a mirror. But I will not buy the Xin mirage until I see the same area without the flood and fog. I did notice that the trees did not produce eddy currents though, but water flow looked manipulated. Also saw no equivalent scene to reflect. Projection upon a fog possible, but why ?
Angle or incidence must equal angle of reflection, so all those other lines on the mirror was garbage.
Also, light cannot change or choose direction, light only travels in a straight line... Refractive index of mediums are different leading to refraction of light.
Ok. So wheres the photographs of any mirages to compare with the one over Xin river? There aren't. So keep spinning this to dumb more and more ppl down. What does your intuition tell you? That its a photograph of an illusion? YOU CAN'T PHOTOGRAPH AN ILLUSION. If so then feel free to photograph a lemonade stand for me the next time you feel the need to walkabout through the sahara desert........ LOLllllllll.
Your link was attached to the Ghost city appears above Xin'an River story as an explanation. But your explanation was based on the image being seen as either a mirror on the surface or an object on the other side of you vision ending up in that mirror mirage... So in that story how does a city and trees then suddenly appear in the mirage if there is no city that looks like it anywhere nearby? Its not reflecting the buildings around the Xian river, its a completely different city (google maps)
Nothing can go faster than the speed of light. Except the whole Univers, that is. Look at the Hubble constant and the redshift data from ancient objects. One thing is the light they have emitted, another is where these objects really are, well behind the observable universe and the event horizon, much faster than the s.of.l. Cheers, great tutorial on mirages.
@Richy15251 "it is absorbed by electrons and re-emitted a fraction of a second later and thus appears to have slowed down"
This is true. It makes the whole phenomenon even less understandable to my mind. I means we aren't dealing with one photon finding a path that takes the least time, we are dealing with a series of absorbed and emitted photons which spend time as electrons but conspire to travel the shortest path only.
@Richy15251 Light can change speeds depending on the medium it travels. The Lorentz formulas for relative-gamma can be used just as easily when light is slowed down in water as much as they can when light moves in a vaccuum. The change in the speed of light from one medium to the next (like the air to a pool) is what causes refraction. Light's speed slows under water, and we see this slowing as an optical illusion. (pools appear from above to be more shallow than they actually are.)
@Richy15251 Your explanation is a good description for how light seem to be slowed down in a medium when you look at its particle behavior. However, light will also behave like waves. When light waves passes through a medium, they will indeed be slowed down, or refracted as this phenomenon is known as.
So basically when it comes to quantum particles there will always be many ways to describe why they act like they do.
@Richy15251 you know that not all frequences can be absorbed by electrons... so how would light be absorbed by electrons (and then re-emited at the same frequency somehow) so that it would appear to be slower? also why different materials slow down light more than others?
@Richy15251 It's not really "misleading", they just can't explain quantum mechanics in a quick video about mirages .. (well they "can", but you know what I mean ..)
@Richy15251 Light can and does slow down. There are several circumstances where light travels slower than usual. One of these is an experiment being conducted where light traveling through a super cooled liquid(I think its a liquid) and then shot by a laser beam will actually slow down to speeds where we can actually use it practically to send and receive data.
That is true. But I myself was once misled about this. They way it was described, I was thinking a lot about how it was possible to slow down the speed of light. There simply wasn't a way that made any kind of sense. I was pretty annoyed later when I found out that the speed of light doesn't really change inside glass, but people never properly explained what actually happens! This can cause confusion. Sometimes omitting information can be harmful :-)
Light can not go slower. When it passes through matter, it absorbed and re-emitted, and this takes time. The photons still travel at the speed of light. The problem is that the photon that arrives at the observer is not the same photon that entered the object in question.
Absorption and re-emission don't happen in straight line, and so the distance is increased. Increased distance means more time. But the speed of each photon is still the same in all materials: the speed of light.
The way i learned it. Since light is a wave, as it approaches the hot road, it speeds up. Since to bottom of the wave is going faster than the top, it turns. This is the same principle that gives rise to sound channels. Is this incorrect? I am only 16 so i have by no means set my mind on the idea. I just learned it in a Berkley physics lecture that i found on youtube.
@jakevikoren Yes, it is correct. But Fermat talked about the path that takes the least time compared to nearby paths---the physics is the same as Huygens principle (the idea you state) but the mental picture is quite different. Roger Bowley
I wish my high school teachers went as in depth as this. They explain things so simply, and sometimes that complicates the theory because its not explained properly :/ I love watching these videos especially the ones related to my school topics because it helps a lot ! Thanks !
I wouldn't say that light takes the quickest road, but that it uses the path of least resistance, which means the path that requires the least amount of energy to go. And that makes total sense in a world of inanimate objects, because they don't 'want' to go a certain way and thus go where they are pushed or drawn the most easily by their own energy or by outside influences.
I cant help but offer another analogy to the viewers, this time explaining the principle of least time (I love explaining things!). Here goes!
Imagine you are at a distance away from a river bank, and a ways downstream you see a lovely damsel in distress having trouble staying afloat in the river. To reach her you have a few options as to which path you can take.
You could run in a straight line, directly to said damsel, minimizing the distance traveled.
...You might alternatively decide to run directly to the river bank, then swim diagonally to the lady in peril.
...or why not run diagonally to the bank and swim directly, after all, you can run much faster than you can swim, and with this path you minimize the swimming distance.
However, the best path you can choose is the one that minimizes the amount of time it takes to save m'lady :), where both your running and swimming paths are angled.
In the example, the starting point is analogous to an object emitting light, and the damsel is you observing the object. The river bank and the river itself represent two separate mediums the emitted light travels through (air and water for example)
The principle of least time states that light will always take this shortest time path to travel to the observer.
So this is just a silly question from a non-physicist...but if you took a laser with a visible beam, would you see it bending as part of the mirage? I know the curvature would be pretty small, but I was just curious.
And I'll agree with the other comments - the refraction model makes much more intuitive sense than the "path of least resistance" explanation we see here.
"imagine this is the sky, actually it's just my filing cabinet" thnx for that ;) also i was taught that light only reflects in away as that the index of incidence is = to the index of refraction are you saying that it doesn't always reflect that way however the equilateral way is most likely ? just seems the more out of highschool science i get the more i realise almost everthing i learned was wrong jsut so they could simplify a concept.
Uh... weren't we tought in physics class that the changing density of the hot air on the road actually directly bends the light due to refraction? This shortest path thing is rather odd, I've heard it before but what is wrong with the classical photons-as-particles model in this case?
@8DX Agreed. A changing index of refraction is a much simpler and richer explanation. This video seems to contrived, making it harder to understand by trying to oversimplify it.
@HiAdrian - harder to understand - and also in my mind just giving a completely incorrect idea of light as something that "knows" the shortest route, or "choosing" the quickest route.
To answer an earlier question about the relationship between mirages and hallucinations of an oasis, keep in mind that the mirage would be of the sky, which would be blue, which would look like water.
A mirage is not a hallucination, but a person prone to hallucinate would be more likely to do so if they saw a mirage.
Cold air is denser than warm air and has therefore a greater refractive index. As light passes from colder air across a sharp boundary to significantly warmer air, the light rays bend away from the direction of the temperature gradient. When light rays pass from hotter to colder, they bend toward the direction of the gradient. If the air near the ground is warmer than that higher up, the light ray bends in a concave, upward trajectory.
The mirror example confused me. The angle of incidence equals the angle of reflection; the only path that light can take from a source (in this case the person on the right) that ends up reaching the left person's eyes is the symmetrical one because that is the only way that light reflects off a mirror.
His explanation is wrong. If the blue car's light would only take the path that was fastest, we would not see the blue car directly at all, only its mirage.
@hikergate "His explanation is wrong... we would not see the blue car directly at all, only its mirage."
The key is 'local' paths.
If you listen, he is always careful to state that it is the local shortest path. Think of a very lumpy hill side: There is a top to the hill. But also there are the lumps on the side of the hill. The top of any lump is a local peak because every direction goes down _locally_.
Similarly light has local shortest paths where all adjacent paths take longer.
I can't see how anyone could think this explanation doesn't make sense...it seems to me that light, like water and electricity, follows the path of least resistance.
But by the classical laws, this would mean that the light would need to be sentient -aware of its surroundings so as to know that there was a shorter path. Electricity is different in that the resistance is a property of the medium through which it travels, but the light has the "choice" of continuing in what we perceive to be a straight line, or changing its direction (without being steered by wires) to a shorter path.
@Naddig74 The thing is this explanation is incorrect as far as I can see (please correct me if I am wrong). Light follows all possible paths, not the fastest one. However, even though light follows all possible paths, we only see the photons that travel in the direction that our eyes are located at.
@socer777 First, your use of the word photon is indecorous; second, light does follow all possible paths, but we can only see the light waves that are traveling at the lowest energy state, viz. the point of reflection that demands the shortest distance for the light wave to travel to the reflection point and from that point to your eye i.e. the single symmetrical point between you and the object you see in the reflection. Any asymmetrical points, e.g. all other paths, are unseen,
@fcdog555 The only problem with using the word photon is that refraction is a property of waves, so 'light beam' would be a bit better. Photon is still accurate.
Second, light does follow all possible paths, but it is important to note that not all paths are possible. In the drawing with the mirror, only the symmetric path is possible. The others are impossible and terribly misleading.
@Spudtion Well here is a simple experiment to prove you wrong that all of the shown paths are possible, but only one is visible. Okay, so set a long mirror on the floor; place some to stand ahead of the mirror the the mirror is closer; now walk towards the person, as you get closer the line of symmetry will move up the mirror; the only way this could make sense is if light traveled in all possible paths.
@fcdog555 You're proving the wrong thing. The light does bounce from the source to all points on the mirror (assuming a diffuse source), but not all of those rays will then bounce from the mirror to one particular observer location - as shown in the diagram.
My statement was that 'in the drawing with the mirror, only the symmetric path is possible'. The other paths that were drawn are indeed impossible. There are infinitely many other paths that aren't drawn though, which would be possible. These are the superset of the ones you would explore in your experiment, and they would all be symmetrical.
@Spudtion hmm what exactly do you mean they are impossible? You are being kind of vague. If you mean they are impossible to see, well then duh. If you are saying they are impossible for light then travel, then you are wrong.
@fcdog555 I mean they are quite literally impossible. Your experiment is entirely irrelevant and I think you're still hung up on the concept of there being unseen paths. There ARE unseen paths. They simply aren't seen because the position of the observer is not in the path. There are NOT 'unseeable' paths caused by different energy states.
When light bounces off a reflective surface the angles between the rays of light and the normal to the surface at that point will be exactly the same.
@Spudtion Okay, well here is an experiment: Lay a mirror down; place a light bulb ahead of it; stand in front of the mirror; turn light bulb on; now you are trying to tell me that even though this light source is producing light in ever direction possible (ignoring the dark spot that would be underneath the light of course), there are still paths in which no light can travel?
@fcdog555 ok. In your example, assume the source and the observer are at the same height and the same distance from the mirror. Light will go from the source to a point on the mirror 1/4 of the way from the source to the observer. It will not, however, go from that point on the mirror to the observer. Yes, there are impossible paths.
I remember once, on a very hot day, I walked along a very hot tarmac road.. I was probably 16 at the time.. one of those dream summers.
mirages and fields, it was like catcher on the rye.
my sandals picked up literally 2 inches of melted tarmac on the soles, it stayed there for as long as i had the sandals, best sandals in the world IMO at the time.
Ah those summers of youth.. how wonderful they seem now.
yet knowing what mirages are now is even more wonderful.
Ye I was thinking about the same thing. Could it be a bit like what we experience when looking from air into water? The refractive index of hot air is smaller than that of colder air but because the edge is not absolutely sharp like with water it bends instead of making a sharp angle. The effect however is the same, we see the image in a different place than it should be.
No matter where i stand in a room, i can see a small beam of light, which is reflecting off a wall caused by a lazer. My question is... How come i can see it from anywhere in the room.
Mirros dont absorb and colour, they reflect it all. (Non-mirror) walls absorb most of the light from a lazer or lightbulb etc and so if the red lazer hits the wall, a lot of red is absobd at that spot, the red is then refrcted or emmited from the wll outward in any direction.
haha. The fact that there is little reflection, or mainly absorption, makes this even more fascinating. if only a small amount of the original light source is reflected due to absorption, its amazing that still in almost any point in a room if you stare at the dot on the wall, you can see it clearly. but more than that, the room itself does not appear to have been lit. I love science.
I was thinking of the image produced 'on' the wall. Just because, I know it is more in line with how i was thinking originally. I know, you can only see a lazer, if you look down the beam to its origin, or see the photons reflecting off a particle in the air. But this is not really what i am asking.
Just the like the proff in the video explained, the light reflects in all directions, but not all of the reflecting rays contribute to the image at the same time. So depending on where you stand in the room, all you're doing as an observer is changing the angle b/w you and the original beam of light as it reflects from the wall, and since it reflects in all directions, you will be able to see it from anywhere in the room, unless the path is blocked by something in the way.
So if the light wave in a mirage is following the path of a parabola; at what point does the image flip upside down? Are superior mirages usually black mirages or darker in appearance, or is that photonic cancelation? How does a mirage differ from gravitional lensing?
Why do mirages cause hallucinations in the desert? Can a mirage be a rainbow? I think a lot more is involved than just temperature inversions. Demonstrate some mirages and reftaction in the laboratory!!
i was tracking until you started drawing the pictures, now i'm a little confused. i'll have to research this a little more, but thanks for the quick lesson! i understand it better than before now :)
another great video, thanks for the quick overview of mirage.
just to clarify - is it that light itself doesn't find the quickest path, rather light takes the multiple paths and we only see the one that reaches as first?
as far as i know it has been experimentally disproven. also, it doesnt fulfill the requirements of a theory. also, it has nothing to do with this video.
It's a confusing concept as I always thought light will travel in straight lines and yet there is talk about the bending of a lightwave. I thought bending of a light wave would only happen near something as insane as a black hole.
Although truly fascinating and worth a big pile of brain thinking stuff time.
the speed of light is only constant in a vacuum, it slows down when it enters water or say a diamond, or in this case speeds up as enters less dense air.
I'm not sure how this would affect the theory of relativity,
Wait a minute...isn't the speed of light Constant? Wasn't that the big thing with Einstein's Relativity, E=mc^2? Is this mirage thing to keep things constant?
its constant in a vacuum. in a medium, the local speed of light is lower.
thats why you see the blue glow when you look down into the water at a nuclear reactor. electrons are being accellerated close to the actual, constant speed of light, which is much higher than the speed of light in water. and that causes something like the light-equivalent to the sonic boom, each particle leaves behind a wave of photons travelling in a conical shape. its the only way to detect neutrionos.
when you see a reflection inside an aquarium, on the inside between water and glass, its a similar kind of reflection. so these mirages still are a kind of reflection. its a reflection along a surface that seperates two different densities, and an area inbetween where it is mixed and you have a continuum doesnt matter.
That's the thing, it just does it. As the professor explained, the concept itself sounds stupid and makes no sense, but works out every time when you actually apply it.
the light still travels along all the other paths, its just that those dont lead to your eye. if the path _would be_ a little slower, it doesnt mean that no light travels there, it just hits your nose or eyebrow. you can still see it by moving your eye to where the slightly off path is the shortest one.
so it doesnt require any cleverness or foreshadowing of events by the photons. its just how the ones you see seperate from the rest.
Think of it like this, you have a small flow of water and you place an obstacle in front of it, like a ball of cotton, the water will divert around the obstacle even though the shortest path matematically is to go straight through the obstacle, the water will eventually seep through the ball of cotton but it in slower amount and it will take longer.
Light continuously bounces and scatters off molecules in the air, when it hits a gradient of cold and hot air a smaller amount of light will penetrate the denser cold air compared to the hot air and will take a longer time to do so. It's simple statistics, when looking into the mirage you will mostly see light which traveled through the hot area.
water follows gravity until it hits the object, then changes path, flows around, and resumes following gravity. LIGHT NEVER DOES ANYTHING REMOTELY LIKE THAT. so your explanation is incorrect. light will move the path that will be the shortest right from the beginning. water never does anything like that, it doesnt start flowing where no obstacles will be before reaching them.
wrong explanations only add to confusion. dont use analogies if they just dont work.
simple, it doesnt. the light travelling on slightly longer paths just hits your nose or eyebrows...
the light that follows all the other paths its still there, it just doesnt hit your eyes. and light, viewed from the side, is invisible. but it allows the person standing next to you to see what you do.
its still correct. refraction requires a surface that seperates two mediums of different densities.
now there may be a continuum between those two mediums/materials inbetween. it doesnt matter, you still get the same effect. some optical glass fibers have a continuum between high density and low density glass, some have smooth surfaces, it doesnt matter both kinds work well.
Richard Feynman gave a great lecture about mirrors and about how light travels through all possible paths and we see the sum of all possible paths. The more I learn about nature the more amazing this universe seems to be.
I remember learning that in Physics in high school, but it was one thing I just could 'not' wrap my head around. But, once he said symmetry from Snell's Law, it made a little more sense, but not full sense.
Damn science you scary.
drpenance 2 days ago
I feel like something's missing from this...
MrTanookiMario 5 days ago
i like how most replies are an elaboration and possible correction of what the last person said
SpikeZeek 3 weeks ago 6
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interresting explaination... I would explained it with the exemple of water refraction. and with the baywatch (pamela!) theory... :D that's why I love your videos actually :)
docsharp00 1 month ago
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docsharp00 1 month ago
Given the other streams of light that are present, why wouldn't the composite image be rendered due to the principle of superposition?
jeffshubert 1 month ago
@jeffshubert because you are standing at a fixed point, as soon as you move so would change of these other light streams, your brain takes the seperate images from your eyes and tries its best to add depth and percetion. and a better question is can these streams be broken up to produce a hologram or even a spectrum?
SpikeZeek 3 weeks ago
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personally I think this guy is on crack, light will only flip the image if reflected off a surface, the parabola path he describes would not flip the image. Light doesn't choose the path of least resistance, thats electricity dumbass. I fully believe that the light does actually reflect of the surface, and the temperature of the surface does allow an increase of the angle of incidence. Perhaps if the surface were hot enough, the image would "float" above the surface, but not flip the image
ricktbdgc 2 months ago
@ricktbdgc the flipped image effect is because the refracted light does not all come from the same place. You can visualise this better by taking the graph at around 5:50 in the video, adding a second light source further away and drawing another parabola from the new source to the existing sink.
ghelyar 1 month ago
Very interesting :)
ElectricSheep10 4 months ago
I respectfully don't think the professor's description is correct. Lights rays radiate in many directions. Placing a solid object between the object and the observer will not cause the light to seek the path of least resistance and go around the object. It will be blocked.
Mirages are caused when light refracts as it passes from colder air across a sharp boundary to significantly warmer air.
I think he meant hyperbolic instead of parabolic.
subsystems 4 months ago
@subsystems Well, actually he is right. There is a good set of videos by the Vegas trust that show Richard Feynman explaining quantum electrodynamics, the theory that governs this behavior, for which he and other got the Nobel prize. In there, he explains how it works in that theory, where all paths are given equal weight, and one sums up all the paths for the light - in many simple cases much cancels out, making it possible to do the calculation. In this case involving refraction , mirrors, etc
jonahansen 3 months ago
@jonahansen I understand what you are saying but the professor is saying the light will bend to, in a sense, "seek out the path of least resistance". This cannot be entirely true because light going around an object would be the path of least resistance instead of striking the object. If what he were saying were correct, we would always be able to observe objects placed behind other objects, always.
subsystems 3 months ago
@jonahansen Furthermore, what is forcing the path to be parabolic as he clearly states? Parabolic paths by definition require a constant acceleration. The entire field of optics relies on light rays that travel in straight lines through different mediums and change directions as the refraction index changes. Never have I seen any parabolic formulas for light paths used, only straight paths. I can imagine a hyperbolic path where the 1st approximation is the light paths along the asymptotes.
subsystems 3 months ago
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Isenmouthe 2 months ago
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@subsystems I'm not that good at physics, but i believe that the light travels in a parabolic path, due to the fact that the change of the air temperature isn't abrupt, but smoothly decreases with height, hence making the light travel through several layers of air with different temperatures, making it refract hundreds maybe even thousands of times, through the same number of mediums.
Isenmouthe 2 months ago
this cant be right, dont ask, it just isnt
its same as music, and i mean, absolute hearing, we are blind
its faster then we.- actually you, can imagine.
hello
dovlaBass 5 months ago
I don't like this description- I think it is perfectly possible to explain what is happening by saying what is happening locally change the direction of the light. But this seems to suggest that the light "knows" what the shortest path is before it leaves.
Obviously this would have huge philosophical implications, such as, what would happen if I decided to cool the air down after the light has left. I think it should be mentioned that light travels in the shortest route- but for another reason.
jamma246 5 months ago
@jamma246 You are entitled to your opinion---and your objection was raised when Fermat made his proposal. The modern view is that light waves travel on all possible paths. Those paths that are close to the path that takes the least time are all in phase and add up; those that take longer times arrive out of phase with each other and cancel out. The light does not know which path to take---it takes all of them. This idea was applied to particles in Feynman's version of quantum mechanics.
MrOldprof 5 months ago
@MrOldprof Exactly, and this is the better interpretation. With the interpretation given in the video, it is made to sound like the photons know before they depart for their journey which the shortest path is going to be and head down the according path. I remember being told this when I was young and being very confused by the idea.
(In fact, I wouldn't even say that this is an issue necessarily for QM, it would be able to work in classical mechanics without "sentient photons")
jamma246 5 months ago
oh,so that's the explanation...never imagined that...i thought the light was simply reflected because the surface was very hot or something ...XD
frizstyler 5 months ago in playlist frizstyler's Favorited Videos
Well, I always thought it had to do with angle of incidence, refraction, something like that, sorta like how depending on how you look up through an aquarium, at certain angles the water acts as a mirror, where at different angles it is clear. I am sure the professor assumes most people kinda grasp the idea. It's all relative to where you are. I will say though that the professor explains it the way I would rather hear someone explain an otherwise mundane event. Eventful!
punishedexistence 5 months ago
@punishedexistence I thought that as well. This doesnt make sense, light travels in more or less straight lines, not parabola
murdakah 5 months ago
I really couldn't care less if this is 'accepted' by physicists... You're implying photons have human level self awareness and are able to make conscious, logical and rational decisions. Not even some humans can do that. That is preposterously dicey on so many levels...
Anyway, tell me when you manage to take one of these sentient photons out for tea and have a rational discussion on quantum mechanics with it, will you? Thanks.
Versudan 6 months ago
@Versudan You don't have to wait, you can conduct the experiment yourself, no one is stopping you :p
SynysterCondom 6 months ago
@SynysterCondom I'm not the one claiming photons are sentient. That's their job, Mr. Troll.
Versudan 6 months ago
@Versudan Nobody is implying photons have human-level self-awareness. The way light finds the shortest-time path locally (which it DOES, as said in the video we observe this everywhere) implies no more self-awareness than the way your computer can find the smallest-size file in a given directory. The only difference is that the behaviour of computer is steered by what you what from it, while the behaviour of light is "hard-coded" in the physical laws of the universe.
leftaroundabout 5 months ago
@leftaroundabout He's saying that light has the ability to detect what medium it's traveling through and change it's course accordingly. He said nothing about the laws of physics dictating that, he's saying the photons are making this choice actively of their own volition. Whether he's claiming that's the litteral truth or he just really screwed up how he explained it I'm not sure, but the way he said it sounds preposterous.
Versudan 5 months ago
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Richy15251 6 months ago
@Richy15251
I'm liking this because you won the argument, but really all you're doing right now is being pretentious. It IS slowing down on anything above the quantum level, which is great for all purposes of humans since we don't live on the nucleus of atoms. We are much larger than atoms, and the phenomenon that we're observing is on our scale, not the scale of the atomic world. Let's leave the semantics at home and not argue things that don't matter for the purpose of the video's explanation
vampiracy 6 months ago
@vampiracy If you feel I'm being pretentious, alright but I'm just giving the explanation behind the phenomenon
verrybrainie said: "It has nothing to do with absorption." which is wrong, so i corrected him
Richy15251 6 months ago
@Richy15251
and that''s why I said you won the argument. What you said is correct and it us about absorption but all I'm saying is that it's an unnecessary argument to make.
vampiracy 6 months ago
ooh! so after a million reflections in two mirrors, there would be nothing but black? darkness? sins the light wont travle that far?
DJBassEnergy 6 months ago
So..? Gravity and heat can have a similar effect on light? If you have two similar objects in space, one hot and one cold. Would there be a measurable difference in how the light is being bent?
K3nz0sTube 6 months ago
The "intelligent light" explanation is pretty childish in my opinion, explaining how reflection and refraction work is much more accurate, interesting and elightening.
surferboy36O 7 months ago
I have a question about light, raised by some kid genius I also saw on youtube. The question is: If the speed of light is constant, how can it slow down and accelerate in some instances? Does this mean that there is a higher speed threshold than the speed of light?
ishthealaskan 7 months ago
@ishthealaskan watch?v=Krfjmn-l0Xk That's the video of the genius.
ishthealaskan 7 months ago
@ishthealaskan When people talk about the speed of light, they are usually talking about the speed of light in a vacuum which is constant, however light travels differently depending upon the different mediums that it is traveling through. The higher the index of refraction something has, the slower light will travel through it.
OMGoshVideos 7 months ago
@ishthealaskan Also you may be referring to time instead. When approaching the speed of light, time slows down.
Rockyroopam 6 months ago
Excellent video as always. I just have one criticism: The 't' in Fermat is silent.
peon17 7 months ago
Halucinations cannot be photographed. But, illusions created by reflected light can be, its not much different than any other visual experience. Otherwise you would not be able to photograph yourself in a mirror. But I will not buy the Xin mirage until I see the same area without the flood and fog. I did notice that the trees did not produce eddy currents though, but water flow looked manipulated. Also saw no equivalent scene to reflect. Projection upon a fog possible, but why ?
Gct5683 8 months ago
argh! if only he was my physics teacher in highschool! *sigh*
TheJasmineee 8 months ago
Troll physics?
Angle or incidence must equal angle of reflection, so all those other lines on the mirror was garbage.
Also, light cannot change or choose direction, light only travels in a straight line... Refractive index of mediums are different leading to refraction of light.
Seriously, old fat man good troll...
EcAStiC 8 months ago
Ok. So wheres the photographs of any mirages to compare with the one over Xin river? There aren't. So keep spinning this to dumb more and more ppl down. What does your intuition tell you? That its a photograph of an illusion? YOU CAN'T PHOTOGRAPH AN ILLUSION. If so then feel free to photograph a lemonade stand for me the next time you feel the need to walkabout through the sahara desert........ LOLllllllll.
yetzirahsan 8 months ago
@yetzirahsan "YOU CAN'T PHOTOGRAPH AN ILLUSION."
There are photographs of mirages in the video you just didn't watch.
Skindoggiedog 8 months ago
Your link was attached to the Ghost city appears above Xin'an River story as an explanation. But your explanation was based on the image being seen as either a mirror on the surface or an object on the other side of you vision ending up in that mirror mirage... So in that story how does a city and trees then suddenly appear in the mirage if there is no city that looks like it anywhere nearby? Its not reflecting the buildings around the Xian river, its a completely different city (google maps)
lorddavis11 8 months ago
Question:
Why does that final mirage image create the illusion that the reflected copy of the Civic's headlights are illuminated?
1RadicalOne 8 months ago
Excellent explanation. Thanks.
Ghooll 8 months ago
Thankyou!
So, in the mirror if other possible reflections are all existing, how are they ignored?
does that mean that the photons of light are all everywhere at once?
is the REFLECTED and ACTUAL image the same photon?
is there a chemical reaction when light reflects? It gives off heat, so that suggests it does, but how does this work?
NeckPickup 8 months ago
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jombo222 8 months ago
Great video! It really helped me understand mirages for my Science project. Also, fantastic accent :)
desaimaa 9 months ago
Could this give a different explanation to gravitational lensing that light doesn't like to go through dust around blackhole or galaxy?
FirstMaje 9 months ago
Nothing can go faster than the speed of light. Except the whole Univers, that is. Look at the Hubble constant and the redshift data from ancient objects. One thing is the light they have emitted, another is where these objects really are, well behind the observable universe and the event horizon, much faster than the s.of.l. Cheers, great tutorial on mirages.
mrrn100 9 months ago
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Richy15251 10 months ago 10
@Richy15251 "it is absorbed by electrons and re-emitted a fraction of a second later and thus appears to have slowed down"
This is true. It makes the whole phenomenon even less understandable to my mind. I means we aren't dealing with one photon finding a path that takes the least time, we are dealing with a series of absorbed and emitted photons which spend time as electrons but conspire to travel the shortest path only.
chrisofnottingham 9 months ago
@Richy15251 Light can change speeds depending on the medium it travels. The Lorentz formulas for relative-gamma can be used just as easily when light is slowed down in water as much as they can when light moves in a vaccuum. The change in the speed of light from one medium to the next (like the air to a pool) is what causes refraction. Light's speed slows under water, and we see this slowing as an optical illusion. (pools appear from above to be more shallow than they actually are.)
BlokenArrow 8 months ago
@Richy15251 Your explanation is a good description for how light seem to be slowed down in a medium when you look at its particle behavior. However, light will also behave like waves. When light waves passes through a medium, they will indeed be slowed down, or refracted as this phenomenon is known as.
So basically when it comes to quantum particles there will always be many ways to describe why they act like they do.
ErtyDaSwe 8 months ago
@Richy15251 you know that not all frequences can be absorbed by electrons... so how would light be absorbed by electrons (and then re-emited at the same frequency somehow) so that it would appear to be slower? also why different materials slow down light more than others?
Mandragore12345 6 months ago
@Richy15251 It's not really "misleading", they just can't explain quantum mechanics in a quick video about mirages .. (well they "can", but you know what I mean ..)
hasenj 4 months ago
@Richy15251 Light can and does slow down. There are several circumstances where light travels slower than usual. One of these is an experiment being conducted where light traveling through a super cooled liquid(I think its a liquid) and then shot by a laser beam will actually slow down to speeds where we can actually use it practically to send and receive data.
Mrjesse451 1 month ago
@thelleht I've heard of light being stopped in special chemicals. Check it: news . bbc . co . uk /2/hi/science/nature/1124540 . stm
Roshkin 10 months ago
@thelleht
That is true. But I myself was once misled about this. They way it was described, I was thinking a lot about how it was possible to slow down the speed of light. There simply wasn't a way that made any kind of sense. I was pretty annoyed later when I found out that the speed of light doesn't really change inside glass, but people never properly explained what actually happens! This can cause confusion. Sometimes omitting information can be harmful :-)
RealNC 10 months ago
@thelleht
Light can not go slower. When it passes through matter, it absorbed and re-emitted, and this takes time. The photons still travel at the speed of light. The problem is that the photon that arrives at the observer is not the same photon that entered the object in question.
Absorption and re-emission don't happen in straight line, and so the distance is increased. Increased distance means more time. But the speed of each photon is still the same in all materials: the speed of light.
RealNC 10 months ago
@thelleht Cherenkov radiation is an interesting phenomenon where the source of light goes faster than the light itself because of this slowdown.
NilsMcCloud 11 months ago
you guys doing great job.... thank you so much...
123naach 11 months ago
It dosen´t explain why the other refekting light cant be seen by the observer !?
mikaelnilsson75 1 year ago
The way i learned it. Since light is a wave, as it approaches the hot road, it speeds up. Since to bottom of the wave is going faster than the top, it turns. This is the same principle that gives rise to sound channels. Is this incorrect? I am only 16 so i have by no means set my mind on the idea. I just learned it in a Berkley physics lecture that i found on youtube.
jakevikoren 1 year ago
@jakevikoren Yes, it is correct. But Fermat talked about the path that takes the least time compared to nearby paths---the physics is the same as Huygens principle (the idea you state) but the mental picture is quite different. Roger Bowley
MrOldprof 1 year ago
I wish my high school teachers went as in depth as this. They explain things so simply, and sometimes that complicates the theory because its not explained properly :/ I love watching these videos especially the ones related to my school topics because it helps a lot ! Thanks !
BenPsOhYeah 1 year ago
I wouldn't say that light takes the quickest road, but that it uses the path of least resistance, which means the path that requires the least amount of energy to go. And that makes total sense in a world of inanimate objects, because they don't 'want' to go a certain way and thus go where they are pushed or drawn the most easily by their own energy or by outside influences.
janeyanna 1 year ago
I cant help but offer another analogy to the viewers, this time explaining the principle of least time (I love explaining things!). Here goes!
Imagine you are at a distance away from a river bank, and a ways downstream you see a lovely damsel in distress having trouble staying afloat in the river. To reach her you have a few options as to which path you can take.
You could run in a straight line, directly to said damsel, minimizing the distance traveled.
JimmyFatz 1 year ago
...You might alternatively decide to run directly to the river bank, then swim diagonally to the lady in peril.
...or why not run diagonally to the bank and swim directly, after all, you can run much faster than you can swim, and with this path you minimize the swimming distance.
However, the best path you can choose is the one that minimizes the amount of time it takes to save m'lady :), where both your running and swimming paths are angled.
JimmyFatz 1 year ago
In the example, the starting point is analogous to an object emitting light, and the damsel is you observing the object. The river bank and the river itself represent two separate mediums the emitted light travels through (air and water for example)
The principle of least time states that light will always take this shortest time path to travel to the observer.
JimmyFatz 1 year ago
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JimmyFatz 1 year ago
So this is just a silly question from a non-physicist...but if you took a laser with a visible beam, would you see it bending as part of the mirage? I know the curvature would be pretty small, but I was just curious.
And I'll agree with the other comments - the refraction model makes much more intuitive sense than the "path of least resistance" explanation we see here.
kubicam 1 year ago
"imagine this is the sky, actually it's just my filing cabinet" thnx for that ;) also i was taught that light only reflects in away as that the index of incidence is = to the index of refraction are you saying that it doesn't always reflect that way however the equilateral way is most likely ? just seems the more out of highschool science i get the more i realise almost everthing i learned was wrong jsut so they could simplify a concept.
derickhaywood 1 year ago
"imagine this is the sky, actually it's just my filing cabinate" thnx for that ;)
derickhaywood 1 year ago
Uh... weren't we tought in physics class that the changing density of the hot air on the road actually directly bends the light due to refraction? This shortest path thing is rather odd, I've heard it before but what is wrong with the classical photons-as-particles model in this case?
8DX 1 year ago
@8DX Agreed. A changing index of refraction is a much simpler and richer explanation. This video seems to contrived, making it harder to understand by trying to oversimplify it.
HiAdrian 1 year ago
@HiAdrian - harder to understand - and also in my mind just giving a completely incorrect idea of light as something that "knows" the shortest route, or "choosing" the quickest route.
8DX 1 year ago
Wow i loved the last explanation! I understand it a bit better now.
samipso 1 year ago
this is amazing!!! why does the marage act like a mirror though? by that i mean, why does it invert the image???
martindm 1 year ago
To answer an earlier question about the relationship between mirages and hallucinations of an oasis, keep in mind that the mirage would be of the sky, which would be blue, which would look like water.
A mirage is not a hallucination, but a person prone to hallucinate would be more likely to do so if they saw a mirage.
Spudtion 1 year ago
From wikipedia:
Cold air is denser than warm air and has therefore a greater refractive index. As light passes from colder air across a sharp boundary to significantly warmer air, the light rays bend away from the direction of the temperature gradient. When light rays pass from hotter to colder, they bend toward the direction of the gradient. If the air near the ground is warmer than that higher up, the light ray bends in a concave, upward trajectory.
Spudtion 1 year ago
The mirror example confused me. The angle of incidence equals the angle of reflection; the only path that light can take from a source (in this case the person on the right) that ends up reaching the left person's eyes is the symmetrical one because that is the only way that light reflects off a mirror.
socer777 1 year ago
@socer777 correct.
Spudtion 1 year ago
His explanation is wrong. If the blue car's light would only take the path that was fastest, we would not see the blue car directly at all, only its mirage.
hikergate 1 year ago
@hikergate "His explanation is wrong... we would not see the blue car directly at all, only its mirage."
The key is 'local' paths.
If you listen, he is always careful to state that it is the local shortest path. Think of a very lumpy hill side: There is a top to the hill. But also there are the lumps on the side of the hill. The top of any lump is a local peak because every direction goes down _locally_.
Similarly light has local shortest paths where all adjacent paths take longer.
chrisofnottingham 1 year ago
Argh my brain!
Abengoshis 1 year ago
I can't see how anyone could think this explanation doesn't make sense...it seems to me that light, like water and electricity, follows the path of least resistance.
Naddig74 1 year ago
But by the classical laws, this would mean that the light would need to be sentient -aware of its surroundings so as to know that there was a shorter path. Electricity is different in that the resistance is a property of the medium through which it travels, but the light has the "choice" of continuing in what we perceive to be a straight line, or changing its direction (without being steered by wires) to a shorter path.
TheZefMan 1 year ago
@TheZefMan That makes no sense at all. Are you suggesting that water and electricity _are_ sentient?
Naddig74 1 year ago
@Naddig74 The thing is this explanation is incorrect as far as I can see (please correct me if I am wrong). Light follows all possible paths, not the fastest one. However, even though light follows all possible paths, we only see the photons that travel in the direction that our eyes are located at.
socer777 1 year ago
@socer777 First, your use of the word photon is indecorous; second, light does follow all possible paths, but we can only see the light waves that are traveling at the lowest energy state, viz. the point of reflection that demands the shortest distance for the light wave to travel to the reflection point and from that point to your eye i.e. the single symmetrical point between you and the object you see in the reflection. Any asymmetrical points, e.g. all other paths, are unseen,
fcdog555 1 year ago
@fcdog555 The only problem with using the word photon is that refraction is a property of waves, so 'light beam' would be a bit better. Photon is still accurate.
Second, light does follow all possible paths, but it is important to note that not all paths are possible. In the drawing with the mirror, only the symmetric path is possible. The others are impossible and terribly misleading.
Spudtion 1 year ago
@Spudtion Well here is a simple experiment to prove you wrong that all of the shown paths are possible, but only one is visible. Okay, so set a long mirror on the floor; place some to stand ahead of the mirror the the mirror is closer; now walk towards the person, as you get closer the line of symmetry will move up the mirror; the only way this could make sense is if light traveled in all possible paths.
fcdog555 1 year ago
@fcdog555 You're proving the wrong thing. The light does bounce from the source to all points on the mirror (assuming a diffuse source), but not all of those rays will then bounce from the mirror to one particular observer location - as shown in the diagram.
Spudtion 1 year ago
@Spudtion hmmm well considering you did say that only the symmetric point is possible, I actually just proved that wrong:p
fcdog555 1 year ago
@fcdog555 If you get to be obtuse, so do I.
My statement was that 'in the drawing with the mirror, only the symmetric path is possible'. The other paths that were drawn are indeed impossible. There are infinitely many other paths that aren't drawn though, which would be possible. These are the superset of the ones you would explore in your experiment, and they would all be symmetrical.
Spudtion 1 year ago
@Spudtion hmm what exactly do you mean they are impossible? You are being kind of vague. If you mean they are impossible to see, well then duh. If you are saying they are impossible for light then travel, then you are wrong.
fcdog555 1 year ago
@fcdog555 I mean they are quite literally impossible. Your experiment is entirely irrelevant and I think you're still hung up on the concept of there being unseen paths. There ARE unseen paths. They simply aren't seen because the position of the observer is not in the path. There are NOT 'unseeable' paths caused by different energy states.
When light bounces off a reflective surface the angles between the rays of light and the normal to the surface at that point will be exactly the same.
Spudtion 1 year ago
@Spudtion Okay, well here is an experiment: Lay a mirror down; place a light bulb ahead of it; stand in front of the mirror; turn light bulb on; now you are trying to tell me that even though this light source is producing light in ever direction possible (ignoring the dark spot that would be underneath the light of course), there are still paths in which no light can travel?
fcdog555 1 year ago
@fcdog555 ok. In your example, assume the source and the observer are at the same height and the same distance from the mirror. Light will go from the source to a point on the mirror 1/4 of the way from the source to the observer. It will not, however, go from that point on the mirror to the observer. Yes, there are impossible paths.
Spudtion 1 year ago
another of my questions answered
I'm starting to like this
XManXHunterX 1 year ago
I remember once, on a very hot day, I walked along a very hot tarmac road.. I was probably 16 at the time.. one of those dream summers.
mirages and fields, it was like catcher on the rye.
my sandals picked up literally 2 inches of melted tarmac on the soles, it stayed there for as long as i had the sandals, best sandals in the world IMO at the time.
Ah those summers of youth.. how wonderful they seem now.
yet knowing what mirages are now is even more wonderful.
marsCubed 2 years ago
niiice :D that really good
Wiggyify 2 years ago
i think this explains how people see the flying dutchman
wiremodmangarry 2 years ago 17
@wiremodmangarry I won't let you steal my dreams. The Dutchman is real I say, REAL!
gfdriver 7 months ago
so why does the change in the speed of light change its direction?
p.s. is light effected by magnetism?
robertwc82 2 years ago
Ye I was thinking about the same thing. Could it be a bit like what we experience when looking from air into water? The refractive index of hot air is smaller than that of colder air but because the edge is not absolutely sharp like with water it bends instead of making a sharp angle. The effect however is the same, we see the image in a different place than it should be.
omegavalerius 2 years ago
He only explained about mirrors not mirages right?
paronfisk 2 years ago
no he explained how hot air bends light
AlphaMark3 2 years ago
No matter where i stand in a room, i can see a small beam of light, which is reflecting off a wall caused by a lazer. My question is... How come i can see it from anywhere in the room.
coogiewoogie 2 years ago
@coogiewoogie
I understand what your trying to say.
why does it reflect in all directions?
hmmm Im not sure bye
G3org3Master 2 years ago
@G3org3Master
maybe not why but, how.
coogiewoogie 2 years ago
@coogiewoogie
ok il try and answer now:
Mirros dont absorb and colour, they reflect it all. (Non-mirror) walls absorb most of the light from a lazer or lightbulb etc and so if the red lazer hits the wall, a lot of red is absobd at that spot, the red is then refrcted or emmited from the wll outward in any direction.
I hope this helps.
G3org3Master 2 years ago
@G3org3Master
Mirrors dont absorb any colour*
G3org3Master 2 years ago
haha. The fact that there is little reflection, or mainly absorption, makes this even more fascinating. if only a small amount of the original light source is reflected due to absorption, its amazing that still in almost any point in a room if you stare at the dot on the wall, you can see it clearly. but more than that, the room itself does not appear to have been lit. I love science.
coogiewoogie 2 years ago
see what, the beam or the projection of the beam on the wall or the reflected beam?
robertwc82 2 years ago
@robertwc82
I was thinking of the image produced 'on' the wall. Just because, I know it is more in line with how i was thinking originally. I know, you can only see a lazer, if you look down the beam to its origin, or see the photons reflecting off a particle in the air. But this is not really what i am asking.
coogiewoogie 2 years ago
i guess when it hits the wall it bounces of in many directions, its a good question, its making my brain strain thinking about it.
robertwc82 2 years ago
@coogiewoogie
Just the like the proff in the video explained, the light reflects in all directions, but not all of the reflecting rays contribute to the image at the same time. So depending on where you stand in the room, all you're doing as an observer is changing the angle b/w you and the original beam of light as it reflects from the wall, and since it reflects in all directions, you will be able to see it from anywhere in the room, unless the path is blocked by something in the way.
Spetsop 1 year ago
so light is lazy?
paronfisk 2 years ago
@paronfisk Hmm...more like efficient.
Skywatcher17 2 years ago
So if the light wave in a mirage is following the path of a parabola; at what point does the image flip upside down? Are superior mirages usually black mirages or darker in appearance, or is that photonic cancelation? How does a mirage differ from gravitional lensing?
Why do mirages cause hallucinations in the desert? Can a mirage be a rainbow? I think a lot more is involved than just temperature inversions. Demonstrate some mirages and reftaction in the laboratory!!
kimbob99 2 years ago
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kimbob99 2 years ago
i was tracking until you started drawing the pictures, now i'm a little confused. i'll have to research this a little more, but thanks for the quick lesson! i understand it better than before now :)
lucilombardo 2 years ago
another great video, thanks for the quick overview of mirage.
just to clarify - is it that light itself doesn't find the quickest path, rather light takes the multiple paths and we only see the one that reaches as first?
chentiangemalc 2 years ago 2
i never knew there was a school of einstiens in the world
now i know
zeratul575 2 years ago
Oh ... Thanks for understand about this.
I was 7 years old in 1973, We traveled to Southern Cross on Great Eastern Highway ( WA) , I saw this road, like that.
john1966elliott 2 years ago
Very good
The part about why we don't see 1,000,000 reflections in a mirror answered something that has bugged me for ages!
Thank you.
Mopperty 2 years ago 8
anyone heard of the tumbling toast theory?
cookiecamp 2 years ago
cookiecamp:
as far as i know it has been experimentally disproven. also, it doesnt fulfill the requirements of a theory. also, it has nothing to do with this video.
kurtilein3 2 years ago
It's a confusing concept as I always thought light will travel in straight lines and yet there is talk about the bending of a lightwave. I thought bending of a light wave would only happen near something as insane as a black hole.
Although truly fascinating and worth a big pile of brain thinking stuff time.
johnmacward 2 years ago
You should read about the concept of refraction.
eltotoX 2 years ago
I shall, I'll try and dig it out of that brain that learnt about it about a million years (5 years) ago and didn't give a crap then.
johnmacward 2 years ago
wow very cool. but how can it change speed light was constant and cant change speed. maybe im misunderstanding
mccutcheogeoff 2 years ago
the speed of light is only constant in a vacuum, it slows down when it enters water or say a diamond, or in this case speeds up as enters less dense air.
I'm not sure how this would affect the theory of relativity,
would be interesting to find out
iwan0t0smith 2 years ago
Also, the shimmering effect is where hot air meets colder air, two different densities blend so the photons path of travel is chaotic.
I get the same effect while diving, warm surface water meets colder bottom water = oil and water mixture looking really blurry.
Paxmax 2 years ago
whoa...
culwin 2 years ago
I remember learning this in my freshmen physics class :-) Glad to see I do know what I'm talking about when I explain it to others lol.
Chipsonfire 2 years ago
Is the path there really a parabola? Do/can people have an equation for that path?
colinstu 2 years ago
Wait a minute...isn't the speed of light Constant? Wasn't that the big thing with Einstein's Relativity, E=mc^2? Is this mirage thing to keep things constant?
JimPrower 2 years ago
jimprower:
its constant in a vacuum. in a medium, the local speed of light is lower.
thats why you see the blue glow when you look down into the water at a nuclear reactor. electrons are being accellerated close to the actual, constant speed of light, which is much higher than the speed of light in water. and that causes something like the light-equivalent to the sonic boom, each particle leaves behind a wave of photons travelling in a conical shape. its the only way to detect neutrionos.
kurtilein3 2 years ago
wow. Thanks thelleht and kurtlein3. I did not know this. That's incredibly fascinating!
JimPrower 2 years ago
5.00 mins The laws of snell What are they? Never even heard of them.
Bluebuthappy182 2 years ago
I honestly thought that it was a reflection of light on the hot air. I was completely wrong. Excellent explanation! :)
redone632 2 years ago
redone632:
when you see a reflection inside an aquarium, on the inside between water and glass, its a similar kind of reflection. so these mirages still are a kind of reflection. its a reflection along a surface that seperates two different densities, and an area inbetween where it is mixed and you have a continuum doesnt matter.
kurtilein3 2 years ago
light doesn't 'know' where to go, it just conserves energy
SkyBlue222222 2 years ago 3
I always wondered about this!
Still don't get how light "knows" where to go though.
DeoMachina 2 years ago
That's the thing, it just does it. As the professor explained, the concept itself sounds stupid and makes no sense, but works out every time when you actually apply it.
prisoner1138 2 years ago
prisoner1138:
it does make sense, if you consider this:
the light still travels along all the other paths, its just that those dont lead to your eye. if the path _would be_ a little slower, it doesnt mean that no light travels there, it just hits your nose or eyebrow. you can still see it by moving your eye to where the slightly off path is the shortest one.
so it doesnt require any cleverness or foreshadowing of events by the photons. its just how the ones you see seperate from the rest.
kurtilein3 2 years ago
Think of it like this, you have a small flow of water and you place an obstacle in front of it, like a ball of cotton, the water will divert around the obstacle even though the shortest path matematically is to go straight through the obstacle, the water will eventually seep through the ball of cotton but it in slower amount and it will take longer.
Jokker88 2 years ago
Light continuously bounces and scatters off molecules in the air, when it hits a gradient of cold and hot air a smaller amount of light will penetrate the denser cold air compared to the hot air and will take a longer time to do so. It's simple statistics, when looking into the mirage you will mostly see light which traveled through the hot area.
Jokker88 2 years ago
jokker: if your assertions about how light travels through air would be correct, air would not be transparent.
therefore i conclude that you pulled your assertions out of thin air.
kurtilein3 2 years ago
jokker88:
nope.
water follows gravity until it hits the object, then changes path, flows around, and resumes following gravity. LIGHT NEVER DOES ANYTHING REMOTELY LIKE THAT. so your explanation is incorrect. light will move the path that will be the shortest right from the beginning. water never does anything like that, it doesnt start flowing where no obstacles will be before reaching them.
wrong explanations only add to confusion. dont use analogies if they just dont work.
kurtilein3 2 years ago
He should have replaced water with electrons, and that would have been a better analogy.
jalexoid 2 years ago
deomachina:
simple, it doesnt. the light travelling on slightly longer paths just hits your nose or eyebrows...
the light that follows all the other paths its still there, it just doesnt hit your eyes. and light, viewed from the side, is invisible. but it allows the person standing next to you to see what you do.
so the photons dont need to be clever.
kurtilein3 2 years ago
I think in an old textbook in school it said that it was from air refracting as it went from cooler to warmer (or vice versa).
sporkafife 2 years ago
sporkafife:
its still correct. refraction requires a surface that seperates two mediums of different densities.
now there may be a continuum between those two mediums/materials inbetween. it doesnt matter, you still get the same effect. some optical glass fibers have a continuum between high density and low density glass, some have smooth surfaces, it doesnt matter both kinds work well.
kurtilein3 2 years ago
.Kthxbai.
1trip711 2 years ago
Richard Feynman gave a great lecture about mirrors and about how light travels through all possible paths and we see the sum of all possible paths. The more I learn about nature the more amazing this universe seems to be.
joyork 2 years ago 22
excellent as always
888Xenon 2 years ago 11
Learning new things all the time, thanks Sixty Symbols! :)
KimCarlsson 2 years ago 3
Oh dear! I thought I vaguely understood mirrors, now it turns out that I don't have a clue :)
chrisofnottingham 2 years ago
Quel homme ce Fermat!
xlrv1 2 years ago
I remember learning that in Physics in high school, but it was one thing I just could 'not' wrap my head around. But, once he said symmetry from Snell's Law, it made a little more sense, but not full sense.
Doogeedoo12 2 years ago 2