now let's go to an even less complicated one so again when we were talking about the things that the spectrum can tell us in my opinion um well where did it go in my opinion composition was really complicated temperature was pretty complicated but this last one is easier to understand it doesn't take as much to explain although it is still a little weird okay so let's set up this last one i won't tell you what it is yet we're gonna figure out what this last thing is okay so here we go and this is the last thing we're gonna be talking about today okay so there's not too much more here all right let's get into it so let's say there's a light bulb let me draw a little light bulb right here let's say that's a light bulb okay let me zoom this in a little bit there we go and let's say that light bulb is a green light bulb like it's got green glass on it or something it's just it's a green light bulb okay nope that's not a mushroom that is a light bulb that's the best i can do don't make fun of my don't make fun of my my light bulb oh it's okay it's perfect it's now oh i have an idea it's okay all right now let's say you and your friend are looking at that light bulb and you're standing here let me see here let's say you are right here here's you that's that's you whatever i guess you're a ninja you're a ninja because i can't draw a pace okay um and over here here's your friend over there your friend is looking at apparently your friend's like a pac-man ghost or something whatever you guys are looking at this light bulb okay now don't overthink this don't overthink this this light bulb is sending off green light in every direction so there's some green light coming this way and there's some green light coming this way my pen is not cooperating there we go whatever i didn't draw that very well but uh don't overthink this here's a hard question what color are you and your friend gonna see what color are you and your friend gonna see yeah you're gonna see green right you're just gonna see green it's not gonna it's not complicated it's just it's just green right good job now on the other hand let's say we change the situation a little bit okay so this is like situation one up here let's say we change the situation just a little bit we got the exact same light bulb light bulb not mushroom you're standing in the exact same place and your friend is standing in the exact same place but this time this time instead of uh the light bulb just sitting there you guys are looking at it while it is moving okay and let's say that that light bulb is moving towards you which means it's moving away from your friend okay now what is that going to do if the light bulb is moving this way then the wave in front of it is going to end up getting bunched up because the light is moving into sorry because the bulb is moving into its own beam of light the peaks will end up being closer together because it's emitting them closer and closer and closer to you okay can you figure out what's going to happen to the light behind the light bulb what's going to happen to the light on this side if the light over here is getting bunched up because the light bulb is moving into its own light what might happen to the light back here just take a guess give you guys a second not quite it's stretched it gets stretched out you can almost think of this as kind of like a slinky okay you can almost think of that beam of light as kind of like a slinky so when you move into your own light that you're giving off you're gonna squish it up but when the light bulb moves away from the uh the source it's going to end up stretching out okay now this changes what your friend and you see what's gonna change about what you guys are seeing and i just threw my pen across the room what's gonna change about what you guys see i don't need specifics but what kind of thing is gonna change it's oh it's not gonna change how bright the object looks but it's gonna change it's kind of weird it's gonna change the color you see it's gonna change the color you see because uh remember our eyes see wavelength as color right our eyes see wavelength as color so because uh same thing we could think of it as frequency also um because this light got squished up what happened to the wavelength on this side did the wavelength right here get shorter or longer is this wavelength shorter or longer than the real color that the light bulb's trying to give off that's shorter and over here on the other side it looks longer right on the other side it looks longer so because it's altering what gets to our eyes it's gonna alter the colors you see and in fact you and your friend are gonna see different colors okay and in fact the faster this thing moves the wronger the colors you will guys will see because it's always actually a green light bulb it's always trying to make green light but the faster it moves the more this is going to get bunched up and the more that's going to get stretched out and so that means that the colors you guys sees will be more and more wrong okay if something is moving really slow you're not going to notice its color change so everybody check it out check this out watch my hand watch my hand did my hand change color for you guys it didn't change color for me right it i didn't see my hand change color and that is because my hand is not moving very fast but if i could move my hand at like close to the speed of light when i shoved it in at you you would actually be able to see its color physics look like it changes right now how does it change um well check it out here we go here we go if this is a green light and let's say it moves towards you very fast what's the next color along the rainbow that's a little bit shorter than green light if we made this light a little bit shorter wavelength think about the rainbow roy g biv what's the next color that's a little bit shorter than uh green it's blue so if this light bulb if this green light bulb came at you fast enough it will look blue and that's where this process gets its name if that object is coming at you and the color you're seeing is shorter than the real color we call it a blue shift a blue shift on the other hand if you were your friend your friend wouldn't see blue because they're not seeing a shorter color let's say that this green light bulb moves away from you very very very very very fast so that it stretches out to the longest color we could possibly see what color would this person see if they're seeing now the longest possible color yeah as it went away from them faster and faster first it would look yellow and then if it went faster it would look orange and then if it went even faster it would eventually learn look red that's correct um so um we could have called named this after any of those colors it would make sense to say it was a yellow shift right um but we actually call it a red shift because if you got it moving fast enough you would see a fake red color coming off of it okay so if something is coming towards you it's gonna have what we call a blue shift and when if something is going away from you we call that a red shift okay so let's put this together if you compare the color you see to the real color what could you learn about this object what would you learn about this object if you compare the fake color you're seeing to the real color it's trying to give off what could you figure out about that object what is all of this telling us here's a hint what was the object doing it's yeah it's it's the movement it's how fast it moves that's good it's the speed we can learn the speed of this object by how strong this effect is okay so let's add that as the third thing the spectrum can tell us okay the third thing that we can learn from the spectrum is the speed towards or away it tells us the speed towards or away from us so yeah we can figure out if a star out there is coming at us or moving away from us and how fast it's going okay um how do we do that well again um the color is shifting here kind of like with temperature but here the color shifts without getting hotter so this graph would shift left or right without getting taller okay and i'll show you what that looks like in a second um but uh essentially again if we're seeing a shorter color than the real color then we know the objects coming towards us and if we're seeing a longer color than the real color we know the objects moving away from us and the bigger the difference between what we see and the real color on either side tells us how fast it's doing that okay and it only works for towards or away because it only squishes the light if it's coming towards us and it only stretches the light if it's moving away from us right if this object were moving up and down you wouldn't get that effect okay oh and by the way all together this is called the doppler effect have any of you guys ever heard of the doppler effect yes or no have you ever heard this term doppler effect that's okay um sometimes they mention it if you pay really close attention to the to the weather um you might sometimes hear the weather person say uh like doppler radar um or something like that um this is something we use to track clouds okay doppler radar in weather is is basically what we do we take a a a light of known wavelength and bounce it off of a cloud and if the clouds coming towards us when that light reflects back to us um we can uh it'll get squished up and we know that that cloud is coming at us but if the cloud was moving away uh the the light that bounces back will be stretched out and we'll know that the cloud is going away um that's actually how radar in general works that's how we're able to track other planes uh we can track their speed and direction by looking at light bouncing off of them if it gets squished up we know it's coming this way if it's stretched out we know it's going away from us right