okay so these are the three main effects of general relativity or results of general relativity MASP in space and that creates gravity mass bends time and that slows time down and gravity makes the wavelength of all light that comes away from the object longer okay so let's apply everything that we've learned to the black hole situation we want to know what happens to somebody if they were to fall into a black hole and once we put all this together then we'll be done talking about this so here we go let's put it all together let me get a black hole on here there we go okay oops we zoom out a little bit there we go and let's say that way over here I'll focus this in one second way over here we got our spaceship there we go focus focus focus there we go so we're set up just like in the movie interstellar the spaceship is far enough away from the black hole that it's not gonna feel very strong effects from it it's basically way off in space but I take I finally take that guy we kidnapped like one of them and I put him in a box there we go I put him in a box and for the purposes of this this experiment I've spray-painted this box blue it's a blue box and right now because he's closer to the black hole than us he's gonna feel a little bit more gravity than us okay now here we go let's call this the Box point of view and this the spaceship point of view okay because what happens to this guy as he falls in is going to be different from different points of view what the people in the spaceship see happen to the person in the box is going to be a little different than what he experiences from his point of view in the box because anything that was a result of relativity is relative we're going to have different points of view on the effects of relativity here okay now it looks like there's a question yeah yeah sorry about our mad scientist character here he is kind of a jerk he's done with his test experiment so he's kind of tossing it now check this out here we go the first thing I want to talk about though is not an effect of relativity so this effect is gonna happen from everybody's point of view everybody's gonna see this happen to the guy in the box okay so first of all he's gonna fall towards the black hole so as he gets closer and closer to the black hole what happens to the amount of gravity he feels as he gets closer to the black hole what happens to the amount of gravity he feels is it more or less more yes it's more it's more and okay okay let's call this the front of the box I'll put a little F there for front and let's call this the back so front of the box back of the box which part of the box is gonna feel the most gravity from the black hole the front or the back the front and as he falls towards the black hole the difference in what the front feels from the back will increase so as he gets closer to the black hole the front the front will feel more and more gravity than the back and this situation should look familiar to you we've seen this situation play out a lot in this course what is that gonna cause to tap up somebody even just guessed it before I even asked yes this is going to cause the box to stretch okay as the box gets closer to the black hole it's going to stretch out and the closer he gets to the black hole the more it will stretch so this is a tidal effect it's a tidal effect but it's more extreme than any tidal effect we have seen so if this box was just like a normal sized box compared to his body right here by the time he gets really close to the black hole he could stretch over several miles now can the human body survive this can the human body survive this extreme stretching here's a picture from your book that is kind of also explaining what would happen to him as he goes towards the black hole he would get more and more stretched out and thinner and thinner and thinner this extreme gravity gravity effect is bad for the human body because the human body is not very stretchy so what would end up happening to his body and the box before they ever got to the black hole what would happen to them you're gonna die you'll die from this tidal effect right here your body will be stretched out over potentially hundreds and hundreds of miles and the but human body is not stretchy so you'll be ripped into bits you'll just be ripped into a whole ton of bits kind of like a large rock getting ripped into little bits to become a ring that's your body now yay and what is this giant strong tidal effect called this extreme tidal effect around a black hole is called spaghettification yay and that is an actual technical term for this spaghettification is the extreme tidal effect near a black hole so if this person died from this and there was an afterlife or something if there was like a heaven or something and he was in heaven and people are asking hey how did you die and people are like oh you know murder somebody murdered me oh I fell down some stairs this guy would be able to say I died from spaghettification yes based on the word spaghetti yes spaghettification there we go now here we go so here's an important thing though spaghettification has nothing to do with relativity so who sees it happen if this is not a relativity thing who sees it happen just the guy in the box just the spaceship or both who sees this happen to the guy in the box well the box dude definitely sees it happen to himself he's not going to be happy about this it's not gonna happen to the spaceship as long as it flip flies away but it they will see it happened to the guy in the box so spaghettification happens to the box from everybody's point of view it's not a relativity thing okay but everything else I'm about to mention is a relativity thing so it's gonna depend on your point of view okay so number one let's first talk about the Space Station's point of view okay it's the Space Station's point of view what do these people see happen to the box well they see the spaghettification we already said that what's gonna happen to the color of the box as it goes towards the black hole what's gonna happen to the color of the box yeah it'll actually go through the whole rainbow in the red direction it starts off blue eventually it'll turn green and then yellow and then orange and then red and then after that after red what's gonna happen if it stretches that light if it red shifts that light anymore after the box turns red what's gonna happen it'll go infrared and then microwave and then radio so to the human eye it would look like the Box disappeared when the red shift happened too much but we would still be able to track it all the way up to the event horizon if we had like a infrared telescope or a radio telescope but we would have to look through those telescopes in order to see the box when it turned invisible right you wouldn't be able to see it with your own eyes okay so there's gonna be an extreme redshift what's gonna happen to time inside the box from the spaceships point of view as the box gets closer and closer to the black hole what's gonna happen to time inside the box as it gets close it slows down it slows down and as they get closer and closer and closer it goes more and more and more slow-motion and we would not be able to see it after it passed through the event horizon because no light can come out but we can calculate what would happen to his time as the gravity goes more and more and more towards infinity how fast would time be moving at the actual singularity if gravity goes to infinity there how fast will time be moving right there it would just stop it would not be moving it turns out the singularity itself does not experience time time does not move in a black hole there is no time so that would be another reason that it would be hard to figure out what a black if you wanted to go visit one if you somehow didn't die from the spaghettification that's gonna be freaky right now check this out check this out though that means from our point of view this box slowly turns into spaghetti its time slows down and it gradually turns invisible and then that spaghetti would just get slurped into the black hole and freeze in time frozen in time literally forever that's the spaceships point of view okay now what about the box's point of view what about box guy he does feel himself spaghettify and see himself spaghettify as he falls into the black hole but will yeah that's a good one time will feel normal to him okay time will feel normal to him so he would not experience his time slowing down but if he looked back at the spaceship what would it seem like time was happy what was happening to time in the spaceship from this guy's point of view as he falls into the black hole remember the spaceship has less and less gravity than him so it would yeah time would be look like it's speeding up out there in the spaceship so that would mean as he falls more and more towards the black hole the people in the spaceship would speed up more and more and more and more and because of the gravity being so high at the black hole when he gets really close to it he might be able to see thousands of years go by out here that's how fast time could be moving out here compared to his point of view would he be able to tell what was happening if things were going that fast probably not because things would be just like my blur but he would technically be able to see tons of time go by that doesn't really help him though cuz he's gonna fall into the black hole now here's the next question would his box change color from his point of view would his box change color from his point of view no because that's an effect of relativity he's moving with the light source the light source gets more and more stretched as it goes away from the object but because he's at the light source it hasn't had a chance to stretch much at all yet so it's going to be blue just always remember if it's on our general relativity list it's different from different points of view cool all right so he falls into the event horizon he falls into the event horizon technically his pieces fall into the event horizon he would still not be able to see the singularity if he looks back out if he's in the event horizon and somehow not dead and somehow his brain was still working would he be able to see out yes or no would he be able to see out of the event horizon yes so here's the thing in the event horizon you have to go faster than the speed of light to do what in the event horizon you have to go faster than the speed of light to do what leave or escape right leave or an escape so if you're in the event horizon let me zoom in here a little bit you have to go faster than the speed of light to go this way right but if there's a person in here if they're looking out they are looking at light that comes this way and there's no restriction on going that way I'm zooming come on focus there we go there's no restriction on going in he was able to go in lights able to go in it just can't leave so if he goes in the event horizon he won't even know he went in the event horizon because light is still coming in from outside he would be able to see out away from the black hole if he turned around and tried to look at the black hole he wouldn't be able to see that because light can't go this way so basically if you're falling into the black hole it would look like the event horizon got smaller and smaller and smaller but really you've already passed through it you can't you can see out you just can't see in and so he would be able to see our time go faster and faster and faster as he fell in until he got slurped into the singularity and crushed infinitely forever and ever yay so let me woah woah woah woah let me put that all together so review from the spaceships point of view from the spaceships point of view what happens to somebody as they fall into a black hole is they get spaghettified their color red shifts until they become invisible to the human eye it eventually becomes radio and their time would go slower and slower and slower and slower and then stop when they enter the black hole that's the spaceships point of view from the box's point of view from the point of view of somebody actually falling into the black hole they are spaghettified so that kills you know you're you're out of luck that's not a relativity thing but it won't be in slow motion it'll be normal to you because your time is always normal to yourself when you look back at the spaceship you see their time speed up and your spaceship stays the regular color all the way in very so your box stays the regular color all the way in okay okay don't visit a black hole in spoilers in interstellar at the end of the movie he goat the main character goes and enters into the black hole uh all of that was was BS okay all of that was BS there that's not gonna happen that way because he didn't get spaghettified in the movie the end of the interstellar should have been his body ripping apart and then all of all of the all of his should have fallen into the black hole and that would have been the end of the movie but yeah so parts of that movie are good parts of the movie or bad should have been and should have been a bad ending now somebody was asking about test questions just like the special relativity stuff I'm going to ask very basic type of questions about this kind of thing on the test so what I could ask is I could say you know here's the situation here's the situation if you're in the spaceship and you watched the box as it falls in what will happen to the time in the box from the spaceships point of view and you would answer if that was the question you would say the time in the box slows down so as long as you remember these effects I'm not gonna ask it's like oh I'm not gonna give you like a crazy crazy situation it's just gonna be a situation similar to this and I'll ask about what the spaceship sees and what the box seats