What is up you guys? This is terrifying, I actually don't like public speaking, I usually say no, because it makes me nervous. So the idea of going live to some amount of subscribers or people I told them. I don't want to know how many people are on, because that would just freak me out more yeah, but it's good to be here I'll, tell you why I'm doing this in a little bit, but for today the question we're gon na answer is: why does helium Raise your voice, we all know. If I do this, this is live.

It breaks your voice. Go really high! Wait! A second! That's not right, because this is sulfur hexafluoride. It actually does the opposite of helium. It makes your voice low, so we're going to discuss that, and here it starts to wear off it's like still in my lungs.

Why does sulfur hexafluoride? Make your voice go view alone and yeah helium makes it go really hot what the heck is going on there. So today, we're gon na sort of these science sleuths and we're gon na figure this out. Okay - and this is like losing all the helium who cares get out here - we're live so the way that's gon na work is each class will start with. The question like I said, we'll go through the clues to answer it, so it's kind of gon na be like a magic trick.

I'm gon na take some negative information. That's in my brain and I'm gon na magically and wirelessly transfer it through that camera through your computer phone into your brain, all right and I'm kind of excited. This is like what gets me most pumped about science and education. Is these aha moments, so this is the first day of class, so I'm gon na start with a little bit of groundwork, a syllabus kind of to sort of tell you guys the structure of how I want to do these.

So, first of all, the question is like why the heck am i doing this well teaching high school physics is like my dream job. That's what I'm actually getting my teaching credentials right now, and so this is sort of an opportunity to just sort of jump in with two feet, and you know, probably not otherwise. It's thing the first time you like teach a class to do it to like some large number of people which I'm not letting them tell me how many are on all right, but right we're doing this thing. So, of course, she's like I have my videos.

Why do I need to do this, and the answer is: this is a little bit more personal, it's a little bit more fluid and a little bit more interactive. We have the chat over there. So, at the end, you guys can ask questions and I'll answer a couple questions at the end of every class, so each of these classes will be about 15 minutes long I'll. Do them like three times a week Monday, Wednesday Friday at 1:00 p.m.

and then the last five minutes will kind of be a QA, so questions you guys asked her in the chat, I'll look at them and I'll answer a couple of them. This won't be alike. I said each time also we'll have a question that we're ansel answer and we'll go through some cool physics, principles sort of stepping through together, so this won't be a replacement for your actual science class. Unfortunately, this is just you know, an opportunity for me to share my passion with you guys, but also it just felt with like, given everything that's going on right now and the uncertainty and the fact that you guys are home from school.

It didn't feel right to me to just put up like one ten minute video a month and that'd, be it I feel like at this moment more than any. We need a little bit more connection. So that's the goal here. You guys deserve some sense of normalcy.

So I'm gon na try and give you that three times a week - and I promise to do this for at least two weeks so six classes, and then we can see how it's going and sort of assess you guys are liking it and it's working and I Haven't made it on, like livestream, fails like more than four times I'll count that success and potentially we'll keep going with this. This also isn't going to be like a tip local science demo, where it's like, Oh Mentos and Coke or, like you know, elephant toothpaste. The same stuff, you see like the science expert go on the Today Show and they do the same thing over and over on all the shows I feel like those are exciting and cool to look at, but the science becomes sort of like an afterthought, and I Want the science to be more at like the heart of it, because you guys can understand that and it can be really exciting. So I think with that.

Oh, the other thing I do want to mention is that the challenge I have here today is like I've heard from five-year-olds who you know. Parents are like I'm so stoked to watch with my five-year-old. It's gon na be really exciting. I've also heard from dudes with PhDs, who are like, oh I'm so stoked this gon na, be really exciting.

That puts me in a challenging situation because, like where do I strike the balance right on what topics to hit? So my goal is to more like update your mental model. We're gon na talk generally about principles, less about specific facts to memorize and that's more helpful. Anyways for going out in the real world and applying these principles, so this is kind of gon na be high school physics level. But if you sort of understand the math or the science in my videos, it's gon na be about the same level, all right.

So we're gon na we're just gon na give it a chance and and yeah. Let's see how it goes so helium it makes your voice go higher, but why - and I love love that word - why kids ask it a lot right because they're trying to understand the world around them and some people say you know if you know how photosynthesis works, It sort of takes the magic out of it, but I feel like it's the opposite like I can appreciate the beauty of a tree, but if I know and I'm looking at a massive redwood, it's beautiful visually. But if I also know that it's like dude those things power up their energy from the Sun, they use that photosynthesis. They take the carbon dioxide of the air.

They use that to rip it apart and that carbon that they steal out of the air is what makes them bigger their carbon vacuums. We've talked about that video, like that's beautiful and then when I look at a tree and I see holy crud, that's a look at all that carbon it sucked out of the air - and I know generally how that happens. That's like a dual level of understanding and and the beauty of nature around you, and if you could have that understanding about a lot of things, not just trees, the world is so much more of a cooler place. So that's what we're gon na try and do today, all right so helium our first clue to uncovering.

Why not just that helium makes your voice higher, but why is air the fluid? Alright, that's your first important mental model, and that seems weird. What do you mean? The ears are fluid, there's no fluid fluid is like water right. It is. It's just super, not dense.

Okay. So let me show you a video here and we're gon na switch over and by the way, this I'll get that in a second all right. So you see this ice tray right ice. The air around that is cold becomes more dense, it kind of sinks, and you see the soldering iron over there.

The air around that and never play that again is hot. It's less dense and it kind of floats. But look at this like this is usually schlieren imaging allows you kind of see the air currents. That's fascinating right! Here's another one from my buddy Destin from smarter every day.

This is a gun, that's firing in super slow motion. Those are pressure waves. You see. Doesn't that look just like a pebble going into a pond? You see it rippling out like that, so here's a demo, I've got we'll switch back live by the way.

This is going to be super rough with, like switching cameras like we forget, built this set in like 12 hours yesterday, so bear with us. Air is a fluid. So here's the sulfur hexafluoride check this out. Someone is like constructing something outside I'm gon na light, this flame upside down, which makes my finger real hot.

So I'm going to turn on the sulfur hexafluoride, and you can't see this. It's looking like nothing. What I'm doing right now is I'm filling this container with this heavy liquid right. It's happening, okay, so it's filling up this cup.

That might be good, I'm going to bring it over here and pour it into this cup. What do you think might happen whoo? It almost didn't go out. I was gon na have to blow it out and cheap. I did laughter all right, so, let's pull back wide.

So what the heck just happened there. What what happened is like this sulfur hexafluoride is a lack of oxygen. Fire needs oxygen. We poured that liquid into here, it filled this up, it's heavier than air, so pushed it out right in the same way, oil is heavier than water and it goes to the bottom and the water sinks up, so that starved the flame of oxygen and it died In fact, the biggest use for sulfur hexafluoride in industry is in really high voltage like control rooms so that it doesn't arc and and cause a spark.

So they put this stuff in those rooms to make it more safe. So you can't have an arc and a big explosion. All right air is a fluid, so think about what happens. If you drop a pebble in a pond, you see ripples right.

You see waves that go out so that brings us to our second clue. Sound travels through air in ways in the same way that you know if you drop a pebble in a pond, you see waves that go out from where you drop the pedal. So if I blow on the back of my hand right, I can feel that I feel the pressure on the back of my hand, a fun experiment. We didn't have time to said that we got a leaf blower here with parent's permission now, you're like stuck inside.

If you guys have a leaf blower blow that on your face film it in slow-mo with like your iPhone and play that back hours of fun, it's amazing that's! I would really feel the pressure from that air right. Well, your eardrums, which is simulated by this thing right here. They sense, like you, sense pressure on the back your hand from blowing on it. They sense pressure in the air like a million times more sensitive than the back, your hand, so little vibrations in the air.

They can sense. So when you talk what's happening, is your vocal cords? Are they punch into the air into your throat and then it hits the air molecules in your throat and then all the way up and a chain reaction, all the way to the person across the room. Those air molecules are crashing into each other and their eardrum moves and the louder. It is the more it moves in if you are saying talking or singing in a high frequency like ah right versus low higher frequency, higher pitch just means.

Those vibrations are happening more frequently so about a hundred and eighty times a second with a high pitch, maybe a hundred times a second for a low pitch. I'm gon na show you this demo right here to help. You understand this a little bit better. So this on the screen is a longitudinal wave, and what you can see here is that these follow one individual particle just like if you drop a pebble in a pond, the water molecule.

Next to that rock, doesn't go shooting across the top of the water. Think if you see a piece of wood floating on top of a pond and a pebble hits it that individual piece of wood moves a little bit, but it doesn't fly across the pond right. It's the same thing here, so the air molecules kind of stay where they're at they just crash into each other and then, if they crash so here's that determines the wavelengths, where you kind of see that the tops of those waves right and so again, if that Thing on the left was moving quicker. Those wavelengths would be closer.

That's a higher frequency, okay. So the next thing we'll kind of discuss, then, is I'll. Just go straight to this. You can see on the computer, so this is.

I made the world's largest air horn with Lincoln and Dan from what's inside, and this is how we intro to it. Ignore it it's that behind you now you can look okay, so here is, we could say on this demo or on this screen. In that same video, I sort of explained what I just talked about, so here's me kind of reviewing the same concept just in a little different words. I use jello too.

Of course, let's say this: jello block represents a volume of air molecules. If that horn diaphragm hits the jello molecules over here, there's a chain reaction of jello molecules crashing into each other. Until, finally, you see movement on the other side of the jello block, and this is where your eardrum is, so it moves back and forth. At the same rate as the horn diaphragm, because of all of these collisions of the jello molecules in between this is called a pressure wave and it's how sound travels through air.

And so if the horn diaphragm is heating. The air molecules at a high frequency, or very frequently our brain decodes, that of a high punch, but if the crashes are happening at a low frequency or less frequently than our brain decodes that as a low pitch. So we had with that big horn. We had it like two and a half miles away and I'll show that clip in a second and we had walkie talkies and we said okay can fire the horn.

What do you think happened? Maybe if you've seen the video you remember, but the sound didn't come to us right away. Why is that? Well should make more sense right now right because you have these molecules crashing together. This is why sound travels slower than light, because sound actually needs things just crash into each other before it reaches you and the greater the distance. The more that's exacerbated so here's what actually happened.

This should make a little bit more sense. Now that you've got a little bit of an updated mental model on sound, so the horn is now super far away. I literally can't see it with my naked eye. It's so far away.

I can barely see it it's right at the crest of the hill. There's a little tiny speck and it's right there, we're gon na do an experiment and we're gon na test the speed of sound. We should hear it on this walkie-talkie and then some amount of time later we might be able to hear it from this distance. Lincoln's gon na measure the time on his stopwatch, and then we should be able to calculate from there what the Veta sound is we're ready when you are crazy.

It took 11 seconds for the sound of the horn to get here. It's so clear, like I feel like we can go 10 miles further. Think about what this means. It took an unbroken chain of two and half miles of air molecules 11 seconds to all collide with each other until they made it all the way down here and bumped into the air molecules in our ear canals which then bumped into our eardrums.

I just like that end part there with Lincoln that's funny so now, with this mental model, now think about lightning and thunder. Well, why is it you see lightning and the Thunder is delayed. Well, first of all, thunder is frickin. Amazing, because did you know that's a sonic boom Thunder is a sonic boom.

Basically, the air around the lightning bolt becomes so hot and superheated that it expands super fast. It goes faster than the speed of sound, which is, by definition, a sonic boom. So that's what you hear the reason: there's a delay: it's like five seconds for every mile or something in freedom units. I know it is in kilometers.

America is because the sound needs to crash into each other right. The light you see immediately electromagnetic waves. It comes to your light speed of light, much quicker right, so this mental model will also help you understand the Doppler effect. Have you heard of the Doppler effect well, this is when you kind of a siren goes by and it's one pitch coming at you and when it leaves it's a different pitch now think about which should be the higher frequency in the lower frequency.

Remember the car was stationary and honked his horn, it wouldn't matter, but the fact that the car is moving. What does that do with the weight? Here's a really good video that helps explain that. So. First of all, here's an example.

So it starts at a high pitch and moves to a lower pitch, even though from the drivers perspective of the horn is playing the same pitch the entire time. So, what's going on as the vehicles coming towards you, the sound waves that it's a meeting bunch up, and so I delivered to you at a frequency which you interpret as a higher pitch, because the frequency of sound waves is pitch and then, when the vehicle passes, You and is moving away from you. The sound waves spread out, and so you hear them at a lower frequency, a lower pitch all right. So what's cool about this, that should hopefully make sense right because the cars moving the waves on the front are more compressed.

They're happening more frequently higher frequency higher pitch the waves on the back are more spaced apart. Lower frequency lower pitch right. What's really cool about that, this isn't just true for sound. It's also true for light, which is one of the main reasons.

We know that the Big Bang occurred is because, when we look at all the stars, they should be a certain color, but they're all shifted. The frequency is a little bit lower than what they should be, which means everything is moving away from us. And now you might being like whoa hold on everything's moving away from us. Does that mean we're at the center of the universe, a good mental model, for that is like no, it just means everything's expanding.

I just put this black dot on this balloon from the reference point of that black dot. When I blow up that balloon, everything is moving away from that dot. So that's the same thing. This universe is getting bigger and bigger expanding expanding.

We know that, because all the stars are red shifted red is a frequency that is lower, which means everything is moving away from us, which is super cool. Okay. This is the juicy part all right. If, if I've lost you somehow, this is where it all comes together, and just it's beautiful for us answering.

Why does helium raise your voice now that you've got rating the right mental model? Okay, heavier things are harder to lose wow. This is really heavy all right. Now this is a big shocker right. If I want to move this as fast as I can using the muslim' arm, I can move it about that past.

This hammer is a lot lighter, see how much faster I can move that same muscle same force. It just goes faster because it's lighter okay, I promise we won't do a lot of equations, but here's one if you're in physics, you know this force equals mass times acceleration. Those are fancy words. You don't need to really know it that much.

But if your force is the same, okay same size F and I make that time, the eggs got ta get really big right to stay balanced. You can think of this. Like a teeter totter, you have an eighth grader on one side and two third graders on the other side, if you swap one of those third graders for seventh grader, it's gon na weigh more well to keep that teeter totter balanced. You got to swap that other thirty Gator for like a kindergartener right, so both these things are true.

Do you want us the equation to stay balanced? If you make the M really big, the a the accelerations got to get tiny. All that's to say this equation is basically explaining this. The force is the same the muscles in my arm. If you make the mass way bigger how much I can accelerate this goes down accelerate.

It means just like making something move. Have a change in velocity. If you make the mass smaller look, how fast I can move that okay here we go we're getting to the punchline. This is exciting.

I have three balloons here. I want you to guess, which is filled with which okay, we'll start with the easy one. The fact that this is taped should give you a clue. Hopefully this doesn't break in my break.

I'm just gon na pull the tape off. Okay, we get into the good part. Okay, what's gon na happen here, peace out balloon that was the helium what's gon na happen here that could put in the normal balloon and, let's see, whoa, look at this thing. Doesn't that look funny? It's cuz! This has the sulfur hexafluoride in it.

If I can put the camera, which I won't, the helium is up there, this is the sulfur hexafluoride, which is heavier. The sulfur hexafluoride is heavier it's heavier than normal air check. This out ready one two see how much quicker that fell and the helium you know is lighter. It went up.

So what's your brain thinking, you put it all together, you have all the pieces at this point. The mental model should be there. What happens is because the helium weighs less, you put it into your throat and it's right there and you speak and your vocal cords push against it. They're, like I got this same vocal cord same.

This is my vocal cord same force. It can move it back and forth really fast, really frequently higher frequency higher pitch. Conversely, with this over hexafluoride, here's your vocal cords same force they're like dude. This is what I've got.

I'm doing my most muscles heavier thing. Acceleration goes down. It moves those back and forth and pushes on them less frequency, lower frequency, lower pitch mic drop science y'all. That's exciting, that's cool! So now that you guys have this mental model, it's gon na.

Allow you to understand things. The fact we know air is a fluid means. The Doppler effect can make more sense, means thunder and lightning makes more sense means. Now you can explain to everyone else and impress them that you know that helium, I'm out of breath makes your voice higher.

My sulfur hexafluoride would go, make it go lower. Ultimately, it comes down to those molecules are just lighter for helium, so your vocal cords could push push on them really fast, lighter things are easier to move just like harder. Things are hard to move higher frequency higher pitch alright, so that's kind of where we are. What just happened? There was a magic trick, the best kind of magic trick, a negative knowledge for my brain, just widely transferred through the camera into your brain, and you have a better understanding of what happening you need to watch some of that back, that's cool, even if you only Stood part of it, that's cool too.

We planted the seed, so don't get discouraged, if not all that made sense. Ok, so I'm gon na end with these things with the question from the next class, so you guys can start thinking about it. In fact, I'll probably have some prizes for people who can answer the question right, but before I do that, let's see hold on so the Horde. Sorry, let's not show that screen yet.

Okay, before I do that, I just want to end with something actually don't go to this computer you're, not on this computer right, there's a surprise. I don't want you guys to see it. Can you hear the audio all right, Rhianna, I'm gon na end with this thought, so you got to do the typical marker over this now feels like a marker over video right feeling it okay, you guys feeling this like. This is like a live.

Video, a big part of what I'm doing this is you guys are like the future of our country of the world. You are future scientists and engineers and doctors and artists - and this is tough like I get how this would be really tough right now and so, with everything going on, I felt like it was the least I could do to kind of check in and make sure That you guys we're doing okay a little bit weird. I totally get that so I kind of want to be here more often so I was thinking like three times a week would feel about right. I want you guys to know that, like I'm taking this very seriously social distancing stuff, this is the real deal.

However, having said that, like it's going to be bumpy, but I know that we'll get through this and that as a global community, I said this in my last video we're gon na come out stronger, we're gon na be better for having gone through this. The most successful people, I know are those that can take their life challenges and see them as opportunities. So do me a favor and find out how you are gon na freakin punch coronavirus in the face. What are you doing to friggin? Take this opportunity and just take control of it right for me, that meant, you know, I'm ditching the once a month format this may totally bomb my channel and kill in the algorithm, but I don't care.

This is a cool opportunity to learn to teach we a couple buddies helped me set this set up yesterday in like six hours. This is really rough. This was brutal, wasn't super smooth, but you know what I'm doing what I can. Maybe you wanted to learn to play the guitar or learn a new language right, what an opportunity you've got on top of doing your school work to try something like that.

Maybe you have anxiety right. Mental health is a very real thing. It's just as important as physical health, so maybe for you that just means you've got to get through every day, one foot in front of the other, but this gives you an opportunity to practice some of those coping skills. You shouldn't be ashamed.

Maybe it's! You know. My dad told me he was out for a walk. He's got a little bit of gray hair, an older gentleman. He saw someone loading groceries into the car and they turned to him and they're, like you know, do you do you want me to get you for some groceries right? Okay, I can't get emotional, you guys cannot.

I don't want to become a meme on my first last year. They offered to get him groceries right because they didn't want him to have to risk himself total stranger, that's punching coronavirus in the face. What can you do to step it up and to go above and beyond and be you know a source of light for someone else so take this seriously, there's no need to panic. We totally got this together.

We got this. We can do this all right. So with that, I'm gon na show you the last question. In fact, part of this is I want to sort of give a shout out to other youtubers.

So every week the person who's gon na introduce the next question is sort of an up-and-coming youtuber or someone who maybe you've never heard of that. I think you should see their channel. So here's the channel of someone probably haven't heard of him, but you should give his channel a try. What's up students, i'm mr.

Bies, this is my partner in crime Chandler and my buddy mark Grover. You know we did TVs together. He asked me to give you a question for your next class. So here's my question, I thought long and hard and this is it okay mark.

If I fart, do I lose weight, or do I gamely what happens like generally, you know what happens to my weight when I fart, I want to yep Chandler thought about whatever I'll see you guys in the next class, all right, mr. V's, fine, maybe you've heard So that's what we're gon na talk about next week. Right! That's the question! I want you guys to think about that. In the same, just like this week, I'm gon na give you three clues.

We're gon na update our mental models of the world and you're gon na be able to answer that question and everyone's gon na love you cuz, you're gon na, be so smart. So with that there'll be a link in this video once it's uploaded, you can click on that and you can answer you can take a guess at this question I'll pick, someone who I feel like gives the best most concise answer we may be. Having surprises both talked about having like headphones, I could give out to people who get it right each week or each three times a week. So officially with that, thank you guys.

So much for attending I'll, say class is dismissed if you want to stick around after the bell, I'm gon na do just a few minutes of Q & A so. This is a chance each time. I generally don't do a lot of interaction. So this is your guys opportunity to ask me questions and all and I'll answer them.

So thank you so much for attending a little bit of QA you're, officially dismissed. You won't get in trouble if you leave right now and yeah. This is great. Okay, so okay for Michael Garvey, he asked is sulfur hexafluoride toxic and the answer is no it's hard to get if you're like.

Oh, I want to get some of that, because this is like a cool party trick. It's harder to get a bottle like this. Is I don't know a couple hundred bucks or something it lasts a long time? It's totally not toxic. Just like helium isn't the danger is it goes in your lungs and it's heavier than air, so it can stay in your lungs.

So if you did a bunch in and you're breathing in you're, not gon na get as much air. So in worst case scenario, you turn yourself upside down and literally pour that gas out of your lungs because it's magical but yeah. Otherwise, it's fine! Then why do people have different sounding voices, says tuk soo? Ah no. We, I feel like just like a substitute teacher.

How many pronounce names here T lead, then why do people voices? Let me ask you that tealy. Why do you think people have different sounding voices? Guess right now in the chat, if you think the answer is remember, I said this is my muscle. These are my vocal cords. Well, the bigger your muscles.

I don't have very big muscles, but my man Luke over here running camera, he's got big muscles. He could push this hammer faster than I could right. He could push this heavy thing faster than I could so it's a function of just your vocal cords and how those push air right and a bunch of other things, but simply put that's just the fact that you're pushing air in a little bit different speed than Someone else, okay, last question from penguin nation. I feel like you're like pranking the sub and I have to say penguin nation.

Now I guess that's your screen name, penguin nation. Why can't my friend hear me when I'm a mile away? In other words, why does it not travel further great question so because this is actually a mechanical thing and things are colliding right? Think if you had a bunch of billiard balls, you hit the first billiard ball hits the first one. It is the second one. It hits the third one at some point.

It makes sense. Those would stop colliding. Why? Well, you probably say there's friction on the table. It's felt mark obviously, and their sound or and there's you know, you're losing energy technically to heat, and so that's it.

It's just like a non-conservative system, so each of these collisions gives off some energy and so eventually there's no more energy for the sound anticipate. In addition, there's sort of an inverse square law rule thing where the further you are away from me, the less of a percentage you're getting of that energy right. If you're really close, if you get all this the further you go away, this is a really big thing: you're getting a smaller sliver right. This is why it's harder to kick a field goal from really far away versus really close.

The further you are that angle gets right, so that's kind of the concept, it's those two things, but basically I think the bigger driver is just see how all these collisions and you're losing energy so good questions. This was so fun. This is exciting. We did it.

We made it through. I don't think I didn't think I did well beyond lifestream fails, so that's a win in my book class is officially dismissed. I will see you guys next Wednesday same time find out if farting makes you a less.