Welcome back to the final science class we are live. This is exciting. The way this works is you should know by now, as we start with the question, and then we have three clues to help answer that question. Today's question is: how do you survive a five-mile fall with no parachute and there's so much juicy science packed up into this, so we're going to get right into this first, a very quick announcement as to why this is my last class, because a lot of people Have asked - and I would say for starters, I wanted to do this class if we were lined for three reasons.

One teaching high school physics is my dream job, so I wanted to try it out and see if it really was cool. The second is, it gave me a chance for some mastery learning. I gave a TED talk on the SuperMario effect. I'm like I'm just gon na try this I'm a totally fail, but it'll be fun to get a little bit better and then the third is, I didn't, want to be completely absent during this whole thing, so just a way to be a little bit more present.

So addressing those three things, basically, I've loved it. It's been really fun. I still want to teach even more so now. The second thing I've learned a bunch.

Hopefully you look at the first class versus this class. This one should be a little bit smoother. I feel, like I've, learned a lot and then three things have stabilized a little bit with this whole crazy coronavirus situation, so I feel a little bit more comfortable pulling back. So why not keep doing it? The biggest thing is it just takes a lot of time.

I want to do it right. I want to give you guys something good, I'm still making my monthly videos. I've been getting up at 6 a.m. for the past two weeks, working on this next video, which is gon na, be really crazy and fun, and then it's just kind of like it's given me a new opportunity from teaching this class there's an opportunity.

I'm now working on in the background that has to do with teaching that all will be coming in the future at some point that you guys will be available to you guys and then the final thing is this has sort of been a bummer with the corona Virus, but the positive thing is my schedule is cleared and I really have enjoyed running time with my family and I didn't want this to be a situation where it just came and went, and I just felt like I packed my schedule with stuff like I usually Do I really want to take advantage of this so to be fair to my family and to me, and I'm really enjoying it? I just kind of want to pull back a little bit, but I'm doing great mental health. A lot of people are like. Are you? Okay, yes, I'm great, I'm doing all the things as much as possible to keep both my physical and mental health in a good spot, and I really hope you guys are too that's really important. You got to hang in there.

We can do this. Okay on to some science, how do you survive a five-mile fall with no parachute, I'm going to start with the riddle, you're an astronaut? Congratulations! I can do that. I worked for NASA, so I can just grant that you're an astronaut you're on the internal space station. Something needs to be fixed, someone hands you this hammer, you go out there, you're fixing it.

Suddenly. You realize you forgot to tie your cable to the space station and you're slowly drifting away. What should you do and if you're like? Oh, you should just do one of these things where you swim back to the space station that won't work, and let me show you why this is an astronaut. They've got him right in the middle and your center of mass.

It does not move. You have absolutely nothing to push against. You can't do anything, it's like being in the middle of a frozen lake right, no matter what he tries, there's nothing he could do. He could barely push against the air molecules which is like what he's trying to do.

But if you were actually outside the space station, you wouldn't be able to do that so remember, you're, holding this wrench and so holding this wrench. What can you do? Maybe you figure it out already. You want to throw it in the opposite direction. Why do you want to do that? Well, our buddy Newton came up with the law about this Newton's third law, equal and opposite reactions.

So, by throwing the wrench this way, that's gon na make you go back this way now the wrench will be going fast because it weighs less and you'll move back a little bit slower, but you actually will move back, which is why having a gun in space Is actually of useful, there are oxidizer, so it will fire and you fire it. You'll go the opposite direction. So if you wanted to go that way on the moon, you just like fire that way. You're like you just fly up so well a few weeks ago.

We talked about inertia which is like how much stuff a thing has right how hard it is to move a thing. So momentum is just that inertia in action that gives us our first clue. Maybe you've heard of this word before momentum. Oh yeah, I got ta, throw this momentum mass times, velocity, okay, it's like inertia, mass velocity, movin.

So there's this thing called conservation of momentum, which is really helpful. That's what's happening with the wrench and space momentum of that system is conserved. So, by definition, if you throw this - and you got ta move that back move back that way, so they kind of cancel each other out. This is true even with let's say you on the earth you're like yeah mark.

If I jump up technically, if I hit the ground, the earth should move down a little bit. If momentum is truly concerned and here's what's wild, it actually does the earth moves. The thing is, is you were such a tiny wrench compared to this big mass of Earth? It throws goes that way and it does move ever so slightly the other direction. So this is a true law that holds true everywhere.

Now, where else is this used balloons? You've blown one of these up before so you should know very well, what's gon na happen. If I let this go, I'm gon na do my best to hit the camera. I was before a job. Oh balloon! You have a list pressure.

It's pushing air molecules out that way, and so, by definition, hammer out the back. The balloon conservation conservation momentum has to go the other way. This is how Rockets work you can't use a propeller in space. There's nothing to push against so rockets are literally throwing hammers out in the back of a rocket, and that makes the rocket go in the other direction.

Of course, there it's, a chemical combustion, and you have gases that are expanding and moving out that way and by definition the Rockets got ta go the other way, so there's even an engine and by the way, in a second we're gon na get to this thing. Where I'm breaking all these glasses with the co2 cartridge right after this next stop we're gon na do that, which is probably gon na, be a bad idea, but we're gon na try it anyways, they even have ion engines and ion engines, are something we use in Space you're freakin, throwing electrons, they don't weigh very much, but you have so many and you're putting them out so fast because of conservation momentum. It moves this thing forward. Some of our farthest space path, spacecraft, like dawn, are being propelled by ion engines, it's literally electrons.

Being shot out now, do you know the farthest object? Man-Made object in the whole solar system? It's actually something called Voyager. This came from JPL, it is 13 million miles away and if you're like me, 13 million miles doesn't mean it's moving 11 miles per second by the way, just fast think of something 11 miles away in a second. It moves that fast. It's the farthest man-made object.

Ever to help you get a sense of scale of what that means. If the Sun were a soccer, ball like this and the earth were a BB, and that is the correct scale. How far out do you think the earth orbits around that Sun? I asked a bunch of people, this question and in general I got answers about like this or this maybe some like this: it's not their fault, because that's kind of how they're drawn on these scales of a solar system. So I actually did a video about this.

I'm gon na show you a clip from this video to help us appreciate how far away voyager is. So, if you retain nothing else from this video. Just remember that earth is the head of a pin and it's at the 26-yard line and as the final rocky planet we have Mars at the 40-yard line, also a pleco pepper, and now we start to see bigger gaps and more than a football field away from Our Sun we have Jupiter, which is the scaled size of a grape. So then, eventually, I kind of summarize.

I went through all the planets with scales. Here's the summary, which is also the sizes of Neptune and orbits around our Sun, the size of a soccer ball. Nearly eight football field, so there in the distance you can see the soccer for this view should help. You appreciate the difficulty in accurately, representing both the size and distance between the planets in a single image.

Okay, so before we get to the new ninth planet - let's recap so: we've got a pepper flake at the 10-yard line for mercury and then a pinhead at the 18-yard line for Venus and then another pinhead for Earth at the 26-yard line, and then a pepper flake. For Mars, at about the 40 and then of course, the asteroid belt, and then we make it to Jupiter, which is a grape at about 135 yards. Then we cross the street to get to Saturn, which is a grape that orbits at about two and a half football fields around our soccer ball. Sun.

Then we double our distance from the Sun to get to the seventh planet, which is a pea at five football fields away and finally, at nearly eight football fields away from our Sun. We have another P, which is Neptune and now we've laid the framework for understand. So that Voyager spacecraft, I told you about which is using normal proportion, its propulsion - it's not actually using ion engines. But the point is it's really far away it? Is you see this distance here, it's five times the distance of Neptune to the Sun.

So, on this scale, it's like two and a half miles away five times this gap right here is how far we've sent it and, what's so, cool about it. This is a picture of it when it was flying by Jupiter, obviously an artist rendition. This was made at JPL, which is really cool on it. We have something called the Golden Record and on that it has instructions on how to play this record.

There's a needle enclosed in this here's directions to where we are in our solar system. It has some basic information about atoms and then on the back. It has sounds of the earth and in here you could decode it and there's pictures of the earth has music. It's really cool Carl Sagan.

Had this to say, he said, the launching of this bottle into the cosmic ocean says something very hopeful about life on this planet. If you need a good science hero, Carl Sagan's, your guy, what's also cool about that, is even at the speed it's traveling at 11 miles a second it'll take 40,000 years before that little message in the bottle is to our nearest neighbor. So, 40,000 years from now, someone may find that and be like wow. This is so cool, it's a record of our civilization, no matter what happens here.

Okay, let's do something super, not advised in a live class. Let me tell you the setup we've got here. Things are about to get real. This is a co2 cartridge.

I've got a. It goes on this little track right here, we've put a nail on the front: it's gon na hit these glasses. We're gon na see how many glasses we could break and at the back we've got duct tape. Kilt Ken here he's got the view of the house he's coming back for a guest appearance in the last one.

Now, why am I doing this? Well? This is jet propulsion, this rocketry. This is conservation of momentum. There's all this pressurized gas in here. It's gon na shoot out the back hammers in space right.

It's gon na throw some hammers we're just going to move this in the opposite direction, potentially very quickly because it's lightweight compared to all the particles that it's going to be shooting out with the pressurized air. Okay. So so much could go wrong here. Let's just see what we can do all right, so I'm gon na count down three two one.

Then I'm gon na hit this little nail, which should puncture the back of the co2 cartridge and send it that way. I might flinch, we'll see. Okay. Here we go three two one, I'm terrified that didn't work.

Okay, sometimes it takes a couple tries here we go three two one all right again, it's sort of bit my nail hold on check the alignment. Okay, I just need to hit it harder. I think. Okay, try it one more time.

Three, two one give me another nail all right. I do have footage from this morning when we tried this out. Do we have the replacement? Now we don't have a replacement nail? Okay, where did I just throw that one? I will show the footage: let me try we're gon na try it once more. With this current nail hold on okay, all right, I'm not giving up okay line it up.

Here we go, I'm really gon na go for it. Now, three, two one! Oh, we actually did puncture the back. It must be a bad cartridge huh. Do you give me a new one, we'll get this? If you have a new cartridge here, we'll try it once more I'll, try it this one just wasn't full.

So I was concerned that maybe they were old alright here we go we're gon na give it over try. Otherwise I'll show you the video of how we did it this morning. Let's see if I can puncture this kind of bent the nail alright. Well: here's what we're gon na do we're gon na move this out of the way we might try, bringing it back at the very end.

I'm gon na have my buddy Josh here, try and fix it and we'll see. If maybe at the end, we could get it going in the meantime, I will show you what happened and the face of my reaction when we tried it this morning. Here we go. Let's see, actually not this one right here.

This is science, okay, a punctured and the reaction so, like I said it can be dangerous. We did modify the system, so this is what we changed it to here we go. Is there sound Alex? So that could be what happened? We made some changes to make it go even faster, which hopefully will really show right in the very end. But okay, here we go we're live well, that's actually, probably not such a bad thing, because it was gon na make a lot of glass.

So if all the glass comes at the end, that may work better okay, so you have this momentum right, something's, moving fast. How do you stop it or even get it going now? That's a fancy! Word oops! That's a fancy word called impulse impulse is Force Times time or it's it's the change in momentum. Basically, right now, that's gon na sound a little fancy. Don't worry about that! Here's! Here's the demo we're gon na do now we're gon na bring this sheet in.

If you can help us out Josh, I've got an egg here right and I'm gon na try two things: one: I'm gon na throw this egg against this wall and then, after that, I'm gon na strode. It gets the sheet and I want you a different egg, because foreshadowing it may not survive the wall in physics terms, I want you to tell me the difference between these two things. Okay, you ready here. We go now make a hypothesis on.

What's about to happen, I can throw this in maybe 30 miles an hour here we go it broke. Okay, keep that in your brain. We're gon na do another one right here here we go! I'm gon na move this here. Okay, all right, I'm gon na get another egg.

Clearly this isn't a different egg. All right, you can see me here. We go, I'm gon na, throw it right here, same speed, okay, didn't break physics! All right help me move this out. Josh and you're kind of like all right, big whoop, and I threw that pretty hard.

I could throw that as hard as I want it wouldn't break in the sheet in physics terms, what do you think is the difference between those two. It's the same speed. Well, the difference is in one. The time was very short against the wall, whereas in the other one the time was big and therefore the force was small.

These are indirectly proportional turns. So if one goes big, the others got to go small. If one goes small. The others got to go big in the case of the egg hitting the wall.

What was small, the thing that was small was my time and therefore force had to be big in the case of the sheet. The thing that was big longer was the time. Therefore, the force was smaller. Here's another way to think about this.

You can see right here. I've got this little stick. Let's say that represents the force of the molecules holding this egg shell together right. This is the impulse.

The total number of blocks can't change. It's the same at any point, if you spike above this line, the molecules that the force is holding out of the eggshell you're gon na break the eggshell okay. But what you can do is, if you can flatten the curve along. This axis is time.

If I can take, I take those same amount of blocks. I can't get rid of blocks, but I can take them if I rearrange them so now. The event just takes longer. Look what happens.

I'm underneath this line now right. I stay beneath that curve. I flatten to the curve and, as a result, the egg survives there's no moment where it spikes up and gets bigger, okay, we're kind of narrowing in on what the answer is. So then, why the heck do we have airbags and cars right? Keep this in mind.

What do airbags and cars do well, they extend to the top it takes for you to stop, as opposed to hitting the steering we're really fast. Therefore, what happens longer time you flatten the curve you stretch this out. The force is gon na be less right. Where else do you see this long jumpers when they're jumping, do they land in asphalt? No, what do they land in sand? Well, what's the deal with sand? Well, all sand does.

Is it lengthens the time stretches it out of the event, the change of momentum, the impulse to happen to go from moving fast to stopped right? How about with your phone, even the difference of dropping your phone. Unlike a wooden floor versus a marble floor which is gon na break more well going back to this right here, this is the the strength of your iPhone of the phone's glass holding it together on marble. You're just gon na get this spike. It's gon na.

It's gon na happen shorter because it's harder, whereas even wood floor, which seems pretty hard it's enough of a difference, fractions of a millisecond that keep it below the line and it won't break parkour right people do parkour. They jump off crazy things. What do they do? They roll what does rolling do well. That extends the time for which you stop versus just stopping yourself.

In fact, if you bend your knees versus locking your knees, it's like 10 to 20 times less force, just by bending your knees, jumping off something versus keeping them locked check out. This clip right here of this guy jumping off this roof. That seems insane right thinking about it. You see here he ripped his pants a little bit, but what was the trick to making that happen time? He slid down the roof which allowed him to lengthen the time for the event to occur even cars.

They used the thought was like. Oh, we should make these as strong as rigid as possible. Really rigid, like steel, don't bend at all turns out. That's the wrong thing, because the time is then short and it's like you hit really hard.

Now cars are designed to actually crumple, they crumple and crush all it's doing extending the time and as a result, so many more people lived through car accidents than they used to okay. What about this principle in the opposite? Where's the case where you might want to have a high force, how about with karate', if you're, breaking a wood board. This is why you shouldn't chicken out, if you're, trying to break a wood board - and you should follow through because you want to hit this spike as quickly as possible, because if you do that and you break the board, there's nothing left. You actually get a cheat and not have these there.

You have a momentarily. You know it hurts your hand just for a second, but once you break it, there's nothing left right. The worst thing you can do in that situation is chicken out. So you get right up to this line and then you stay underneath it because then it's like, oh all, that energy is going to your hand where, if you do just committed to it, you could really quickly broken it and be done with it.

Another example: here's a rubber hammer versus a metal hammer and you wouldn't think it makes such a big difference, but this is more effective at hammering in nails, except from in the case mine, because it's harder, so it's a shorter time, bigger force. You want to use the rubber nail if you don't want to like damage something as little as that seems to make a difference that tiny little difference in stiffness means that the length is just a little bit longer. What if you want to increase your momentum right? So, let's say you're hunting or whatever a bow and arrow target. If you pull it back just a little bit, you really want the more time as possible Force Times.

Time equals your change in momentum. That's why pulling it back is better! You have more time for it to be under force of the string. You're gon na have more momentum for your arrow same with. Like a gun, a longer barrel means it will go faster because it just has more time to be under the force of the gasses.

Coming out and a rifle goes faster than a handgun yeah, also with sports golf tennis. Whatever the reason you follow through is you want to extend the time you have against the force so anyways I could go on. But the point is, I love this when one little nugget one little equation, just one little, you know mental model to have in your brain can explain so many things in the real world. So clue 3.

It's all about time, and that's what I want you to remember this right. It's about the time it takes for the event to be slowed down is proportional to how much it hurts. So, when we're talking about how to survive a 5-mile fall with no parachute. What are you thinking just somehow? You don't want that to be an instantaneous end.

How can you lengthen out the time? Well, this actually happened. A dude fell from 2,000 feet. His parachute failed. This is him right here.

His name is Paul Lewis. This is in 2009. He landed on the roof, his parachute failed, he landed on the roof of an airplane hangar and was one of those metal really flexi roofs and he ran in and in just the right spot, and the time was long enough for the deceleration that he didn't even Break any bones he he did say after that he wasn't gon na go skydiving again, which I really can't blame him and then specifically for our answer. There was actually a guy who fell from five miles, and this is the clip right here.

Five miles up he's got no parachute check out what and the crowd on the ground looking up. They have a visual on him right now, he's in and he's kicking and moving from here and look perfect you just so he used the net, but you really could have. You could have used anything right. You could have used a platform with rockets.

You could add rockets on his back. You know that's where people do use packing peanuts, anything to just extend the time for him to land. He chose to use in that. So if you want to know how to survive with no parachute, just figure out some way to extend the time, maybe take a big big, big bucket of packing peanuts.

Okay, so I'm gon na leave you with the final thought. Alright, this is it and it's to stay curious. Before I get into this final thought, though, you can come back to me, Alex we're gon na try this one more time. I've been informed for my massive quarantine level crew here of three of us, that we may be in good shape again, so we're just go.

Try it if it doesn't work, just know that I still love you, but if it does, then it'll be heroic. Okay. Here we go alright, so let's just see what happens, all right don't be mad at me. If this doesn't work, this is live.

This is what you get is what you pay for here. We go three, I'm waiting for the camera guy over here. Okay, here we go ready, Josh, good, okay, three two! Oh, I glasses with safety. First, okay, three two one: there you go boom, what a way to end science class and for the record duct tape killed Ken this looking great is, is kill, fell down a little in the back, but other than that yeah we're in good shape.

Dr. croquette. That was a PC. My part is totally racing.

Oh yeah, my final thought is to stay curious. Okay, we will have science class here, but every day can be a science class for you all right. The key to that is observation. If you're observing the world around you and just makes you thinking about things and wondering and asking questions, you have Google, you can answer these questions.

I love to think of things to talk with with my friends who loved and talked about these types of things as well just random questions. So if you don't have someone to find your tribe isn't online find people who like to talk about this stuff, especially science stuff. I just want to give you an example of this. I've got driving in the car.

I have my laptop down here because I knew a good glass on it. We can go to the laptop screen Alex so driving in the car. I here are a couple questions you know I was just thinking. What's an example, what I mean by stay curious? Let me just give you some questions that I've thought of in the scenario of being in my car all right: what why do these rail? Why do you signs like this? Have these holes at the bottom? You ever thought about that.

Have you ever even seen that right so step, one of the scientific method is observing? Why is that they have to do with crashes? I'm not going to tell you the answer these. I want you to wonder yourself. Why do some of these trucks have these little doors on the back? What's the purpose of those cute little doors I'll, give you a clue that tends to be refrigerated trucks? What's the purpose of these things? Have you ever even noticed them before they're, actually pretty common? They go around the nuts. What might those before again, this is sort of a safety thing that makes visually useful safety check.

How do people, how do they know and people when cars are at lice, someone told me once they have scales and that never made sense to me. I don't think scales, there's a different way. Maybe you've seen these cuts in the concrete have to do with induction and wires of current magnetic fields. How are things reflective? A normal sign is on the left, but just with your headlights, these signs becomes so they almost like shine back at you completely passive passes with a retroreflection, so all of these things are like Google Bowl.

Hopefully, some of these get your heart pump and you're like yeah. These are good questions. What's the purpose of these things, this actually has a lot to do with our class today, right here. Okay, clue is that they're filled a lot of times with water or sand.

So I'm gon na leave you guys with that. I will say for me per like even with my wife she's, an English major, so we make a great combo and you know a lot of times I'll be like. Have you ever wondered? Why she's? Like? Oh boy, here we go again right. So when we spend like a certain amount of time talking about nerdy stuff, we got to talk about like feelings and stuff to keep it balanced conservation of conversation.

That's one of Newton's fourth principle I think but yeah or sometimes we'll just be like hugging or whatever we'll be like talking and they'll, be like a lull in the conversation she'd be like. Are you thinking about like your next video and you know sometimes I'm guilty like I give these things in my head and I'm stoked about them and I think about them, and it's just like a great rewarding way to with live life where you're curious about the Natural world around you and you try and find the answers. So, even though we won't have science class here, you have science class in your heart forever more and hopefully, what we've done here has helped instill that passion within you so be good. Prioritize.

Your physical and your mental health and I'll see you guys around on the Internet and, as always, thanks for watching.