#scriptdraft2

Title: Experimenting in the lab

[Title, music, cuts of me walking through the lab, putting on gloves, safety glasses, lab coat]

Welcome to The Lab! Let’s take a look at the materials for our experiment. [Camera pans around to lab bench]

[YouTube link on the bottle of H2O2] [Pick up the bottle of H2O2]  

This is hydrogen peroxide. You may recognize it from your first aid kit at home. If I left this bottle sitting here, the hydrogen peroxide would eventually break down into water and oxygen gas. This process - when you have chemical compounds that break apart to form smaller, simpler substances - is called decomposition. Since this is normally a slow process, it wouldn’t be very exciting for us to watch, right? We need to add something that will speed it up – a catalyst.

[Pan back around to lab bench and have YouTube link on the packet of yeast]

Here we go - yeast! Yeast produce an enzyme called catalase. Actually, your body has this enzyme, too! Organisms make this enzyme to protect against hydrogen peroxide damaging cells. This catalyst is the special sauce in our recipe. Catalase speeds up the decomposition of hydrogen peroxide into water and oxygen gas. But how does a catalyst speed it up? Picture this - I want to roll this ball down the hill to my friend at the bottom, but there is a big, tall rock in the way. I could get the ball over the big rock, but it would take a lot of time and energy. I look around and find a spot with smaller rocks that would be easier to get the ball over and down to my friend. For hydrogen peroxide under normal conditions, there is essentially a big rock in the way – so the breakdown is slow because it takes a larger amount of energy to get over the barrier. But with catalase, the rocks in the way are smaller. This different pathway doesn’t take as much energy so the reaction happens faster. We need to add one more thing to our experiment!

[Pan back around to lab bench and have YouTube link on the bottle of soap]

We are going to add some soap! The reaction is going to produce a lot of oxygen gas. This would normally be released out into the air, but by adding soap, the oxygen will get trapped in the soap bubbles instead. This foam is going to help us see what’s happening during the experiment.

We’re ready for the experiment! [Do one elephant toothpaste reaction] But wait… we’re not done yet. What would happen if we changed the recipe? Now that we know all the pieces of the reaction, we can play around with the recipe to try to better understand the factors that influence it. This is what a scientist does. So what are we playing around with when we change the recipe? Variables! There are three important variables to an experiment. Something that you change, or manipulate, is called the independent variable. After you change something, you then wait to see what happens to something else – the dependent variable. Everything else should stay the same because we want to be sure that the independent variable is causing the change in the dependent variable. Which variable should we change in our experiment?

[Hold up H2O2 and yeast - Viewer clicks to choose]

 [H2O2 script]

Let’s make a hypothesis! What do you think will happen if you change amount of H2O2? [Viewer chooses hypothesis]

If I increase the concentration of H2O2, then ______________.

[Focus group on Monday: get hypotheses from the kids]

[Experiment is the same for each hypothesis – just a different ending for the revisit]

Here we have four beakers filled hydrogen peroxide mixed with water. Each beaker has a different strength, or amount, of hydrogen peroxide: 5%, 10%, 15%, 30%. We only want to observe how the amount of hydrogen peroxide affects how much foam is made during the reaction. We don’t want to change anything else so we’ll use the same amount of yeast and soap each time. Let’s do the experiment and test your hypothesis.

[Camera frames H2O2 vials on bench - viewer chooses H2O2 concentrations to test] [Spontaneous dialogue during experiment]

[Next segment depends on hypothesis]

You predicted that _______.

[Correct] What we saw supports your hypothesis! But, remember, it’s not about being right or wrong, it’s about what we learned in the process.

[Incorrect] That’s not what we saw during the experiment. But, remember, it’s not about being right or wrong, it’s about what we learned in the process.

As we increased the H2O2 concentration, we saw more foam formation. But why? Let’s look at the chemical reaction: 2 H2O2 -> 2 H2O + O2. H2O2 is a reactant and water and oxygen are products.  When 2 molecules of H2O2 decompose, one molecule of oxygen is formed. So by increasing the amount of H2O2, the amount of oxygen formed through the catalyzed decomposition reaction also increases. More oxygen results in more foam!

You just learned about a cool reaction, but more importantly, today, you were a scientist! Scientists don’t have a recipe book to follow, so this process of experimentation is how scientists approach solving problems. Just like the scientists that study new materials for solar cells to power your home, or research a cure for cancer, you can be a scientist by following the scientific method. 

Ask questions, make predictions, experiment, observe and measure, analyze data, formulate conclusions, and always ask new questions.

Now, go experiment!

[Link to click to experiment with the other variable.]

 [Yeast script]

Let’s make a hypothesis! What do you think will happen if you change the amount of yeast?

[Viewer chooses hypothesis]

If I increase the amount of yeast, then ______________.

[Focus group on Monday: get hypotheses from the kids]

[Experiment is the same for each hypothesis – just a different ending for the revisit]

Here we have four beakers with different amounts of yeast: ½ packet, 1 packet, 2 packets, 3 packets. We only want to observe how the amount of yeast affects how fast the foam is made. We don’t want to change anything else so we’ll use the same amount of hydrogen peroxide and soap each time. Let’s do the experiment and test your hypothesis.

[Camera frames yeast on bench - viewer chooses beakers with yeast to test] [Spontaneous dialogue during experiment]

[Next segment depends on hypothesis]

You predicted that _______.

[Correct] What we saw supports your hypothesis! But, remember, it’s not about being right or wrong, it’s about what we learned in the process.

[Incorrect] That’s not what we saw during the experiment. But, remember, it’s not about being right or wrong, it’s about what we learned in the process.

As we increased the amount of yeast, we saw the foam was formed faster. But why? In each experiment, the amount of hydrogen peroxide was the same. Chemical reactions have fixed stoichiometry. This means that every two molecules of H2O2 breaks down into two molecules of water and one molecule of oxygen. This doesn’t change, even with a catalyst, so each reaction we did produces the same amount of oxygen. But, this is a catalyzed reaction. When we increase the amount of yeast present, there is more catalase enzyme hanging around to break down the H2O2. So when the extra catalase gets through the stock of H2O2 faster, oxygen is also released (and foam formed) faster.

You just learned about a cool reaction, but more importantly, today, you were a scientist! Scientists don’t have a recipe book to follow, so this process of experimentation is how scientists approach solving problems. Just like the scientists that study new materials for solar cells to power your home, or research a cure for cancer, you can be a scientist by following the scientific method.

Ask questions, make predictions, experiment/observe/measure, analyze data, formulate conclusions, and ask new questions.

Now, go experiment!

Why do we laugh?

 What is the similarity between laughing and fighting? We can find out by taking a look at our facial expressions.

We first squint, so the skin on our cheek could pad and protect our eyes. We also lift the upper lip to expose our teeth, especially showing our sharp canines in preparation for an attack. Another similarity is that we produce a loud and explosive sound. This not only threatens the opponent, but controls our breathing to lower our heart rate and blood pressure that prepares us for the fight.

 This seems so irrational – why is laughing similar to a defensive fight? If we laugh to show friendliness and happiness, what is the purpose of sharp teeth and threatening sound?

 One theory suggests us to look at play fights. For many mammals, including human ancestors, play-fighting is an important part of development, because it trains our basic skills. However, play-fighting usually carries a high risk of injury, so it needs to be carefully controlled.

In a play fight between Ape A and B, success means breaking the defense, and making direct contact with the opponent’s vulnerable body part. For example, Ape A may succeed in a play-fight against Ape B by getting its fingers on to the stomach of Ape B.

Now, Ape A’s body is getting ready for a fight – its eyes squint, teeth exposed, and breath controlled. The signal means, ‘You’re getting through my defense.’

But if the play fight stays as a harmless play, the defensive Ape will turn its halfway exposed teeth into a smile-like expression, and produce the ‘ha-ha’ sound to suggest a ‘false alarm’.

This is also why we laugh when being tickled – when we sense the touch at our vulnerable stomach, our body is ready to stop the attack. But if it is done by someone we trust, we will turn the defense into laughter. The trust factor is important, because we usually don’t laugh when tickled by a creepy stranger.

 There is a ‘Benign-Violation’ theory that summarizes the reasons why we laugh. Benign means the action is harmless, and violation refers to the unexpected threat. When both happens at the same time, we laugh.

As humans evolved, the types of violation expanded from simple physical threats. It could be violation of linguistic norms, like the unusual accents [insert video]. It may also be social norm violation, like this high-five [insert video]. It could even be violation of moral norms, like this [insert video or screenshot].

Anything that threatens our sense of how things “should be” is humorous, so long as the threatening situation also seems benign.

Link at https://docs.google.com/document/d/1NBZ4wuyE1eUyZd3XXUo3Z7M4R87DULnHqpfHMxs1S3g/edit?usp=sharing

Kenneth: Once upon a time (in the year 2009), Stephen Hawking held a party with all the usuals, wine, hors d’oeuvres, and yet, no one turned up! <Show party setting> You’d thought that he’d be upset  <show stephen hawking with sad face>  But it turns out that he was far from it <show sad face turning into smiling> He had in fact only sent out the invitations to the party after the party, and had addressed it to all time travelers of the future. He did so in an attempt to prove his own theory, that

TIME TRAVEL WAS NOT POSSIBLE!

No party-goers, meant no travelling back in time!

Or were people of the future just too cold for Hawkings?

 Is time travel possible then? What exactly is time travelling?

When we think about it, we’re all actually time travelling, but not in the manner you might be thinking of.

What we are doing, is to time travel at a rate of 1hour/hour, which means that for every 1 hour we experience, 1 hour passes around us! In the year 1905, Einstein proposed that when we travel at extreme speeds, time around us actually slows down, and that we could experience time at an “accelerated” rate. In other words, when we are travelling at a high speed for an hour, the world around us could be experiencing time at a much faster rate, for e.g. 7 hours could have passed.

This has been seen in many modern sci-fi movies, the most recent of which would be in Interstellar, where Anne Hathaway and Matthew McConaghey’s character descends to a planet where time passes a lot slower than the rest of the universe around them. Based on some of Einstein’s math, if we travel at a speed of approximately 90% the speed of light (number appears on screen), a year to us would seem like 2.3 years to the rest of the world. This means that should we invent a space ship which could travel at a speed of 0.9c, when we take a year trip in it, all your friends and family would have aged 2.3 years in that period! <insert little animation of a space ship taking off and coming back, to see a infant turning a toddler on earth, while an infant maybe remains as an infant on the ship) Travelling at 0.99c, this number becomes 7 years. In fact, the faster you travel, the slower time around you would slow down. This is probably not the idea of time travelling we often have, but you are travelling through time at a different speed from what we would normally do, and so it might be possible to travel forward through time should we attain high enough speeds! What about travelling back in time? Can we run backwards with incredible speeds to be able to go back in time? Doesn’t sound really possible does it? <flash the FLASH running backwards across the screen>

How about, travelling faster than the speed of light? In fact, that’s one of the possible theories of reverse time travelling, that we would need to travel faster than the speed of light. Part of einstein’s initial proposal when he talked about time dilation (which is travelling a high speeds to slow down time around us), was that it was not possible for us to travel at speeds faster than the speed of light.

Why?

Another effect of Einstein’s theory of relativity (where all of this is under), is that when we travel at high enough speeds, time and space aren’t the only thing around us that changes. One other factor which changes with high speed, is the mass of the object! With more mass, it takes a lot more energy to move the object at the same speed, and as we approach the speed of light, the amount of energy required would be wayyyyy too great

Hi all, I have placed the script in a Google doc for comments (feel free to comment and provide feedback as much as you want!! :)

https://docs.google.com/document/d/16WoV6ygmprXA0dgz8_NEA5wlj3XZwCY8_JztuZU8Rwg/edit?usp=sharing

Why can’t I find my stuff?

Narrator:

It’s winter time and I’m getting dressed to go outside. But every time I start putting on layers after layers of clothes, I always can’t seem to find my gloves. (location in the dorm; scene of me putting on layers of clothes and discovering in horror that I lost my gloves) Are they in the kitchen? On my bed? On the couch? Oh dear, I seem to have a problem. Why can’t I find my stuff? Is it because I have a lot of stuff that makes it so hard to remember?

Well, Google stores about 45 billion index pages of information. If each page of information was a sheet of paper (host holds up a piece of paper) and if we stack them all together, we would create a tower of paper 610 times taller than Mount Everest! (camera men on the sides dump a mountain of papers on the host, causing him/her to comically fall over)

So how can a search engine like Google find your search results so quickly while I find it so difficult to find a pair of gloves? It’s like finding a needle in haystack; so how’s it done? (a camera closeup while the host hold up in his/her hand a needle and casually throws it in the stack of papers)

Well, it turns out that searching on the Internet is kinda like looking for a person in a hotel room. (*change scene: a sonorous “ding!” sound of a hotel lift, a pan shot of the interior of Hyatt Regency Cambridge hotel)

Here’s James and he is going to hide in his hotel room. But we want to find where is James.

The simplest way would be to run through every room nearest to you and keep finding. But that would take a long time.

Is there a better way I can find James? Hmmm.. (rub chin and raise one eyebrow)

Well, it turns out that there’s a better way known as Binary Search.

(*The keywords “Binary Search” flashes over the host’s hands)

Let’s say the people were arranged in alphabetical order in increasing numbers of the hotel rooms. We could run to the room in the middle and check if the name of the person in the room is James. And then if the person starts with a smaller alphabet than James, we head to the left. If not we head to the rooms to the right. We then head off to the middle room of the newly sectioned area. And we rinse and repeat. Eventually we will find James just like the first method. But we find James at a much much shorter time.

(The above scene would be done with simple animation drawing over my head with the host talking below on the camera)

How much shorter would that be? Well, that depends on number of people staying at the hotel. Let’s say it takes 10 seconds to knock on each hotel door and there’s 500 people, it would take about 80 minutes for the first method and 1.5 minutes for Binary Search. If there were a thousand people in the hotel, it would take 160 minutes for the first method and only 1.6 minutes for Binary Search. Now that’s a whole lot of difference.

(I suspect there might be a better way of illustrating this point that a slightly better algorithm make a huge difference when dealing with large problems)

Is finding James such a big deal? Well, yes! Finding James faster means getting your results on Google faster. Because finding James is like searching a keyword term on Google. And that means less waiting time for all of us.

So how does any of what we just learned help us to find things better at home? Noticed how the people in the hotel were arranged in rooms numbers based on alphabetical order? So the location of each person in a different hotel room depends on the alphabetical relationship of their names. So we don’t need to remember which person is in which room, we just need to remember the alphabetical relationship that all the people have with each other.

In the same way, simply by placing your home items in locations where they have a natural relationship to makes it easier for us to find them. The TV remote goes near the TV, the shoes go to the shoe rack, the coats go into the cupboard and the the winter gloves goes in the winter jacket.

(location is back in the dorm *Finds gloves in the jacket)

Aha! So that’s where my gloves are!

Pitch: Repeating patterns called fractals are present in every facet of our existence, and are indispensable in nature research, medicine, and technology. In that way, mathematics helps us explore and understand the world around us.

(Camera zooms into host standing by the Charles River, talking on a cell phone; when camera is close, the host acknowledges it)

What do a cellphone, a river, and a cancer cell have in common?

The answer is… (black screen with the word animated on it, framed with images) fractals.

(back to Charles River, host drawing repeating pattern with chalk while talking)

Fractals in mathematics are never-ending patterns.

(change setting: now in a room with a blank wall and computer; show animation of Sierpinski triangle while talking on screen)

Scientists can program these infinite patterns by repeating a simple mathematical process over and over. So, if you zoom in, you’ll see the same shape again and again and again... (show making sierpinski).

Similarly, a tree grows by repetitive branching. Just like our fractal, a tree extends its branches, one smaller than the other, but similar.

Of course, a tree can’t grow as far and precisely as a “truly mathematical” fractal, but parts of it show enough like properties that we can study nature in terms of fractals.

In fact, so many things in nature have these pattern properties  (show snowflake and seashell, fill screen with others -- fern, water spinning out of tap; somehow zoom in or show similar parts), it sometimes feels like the world itself is one giant fractal! (fill the screen with patterned shapes until it’s too much)

SO MANY FRACTALS!!! (head spin)

A bit overwhelming, right? Well, one way to explain this abundance of patterns is the fact that nature is just great at reusing efficient mechanisms.

Rivers of the planet flow like the “rivers of blood” in our bodies. Lightning bolts become electrifying rivers of the sky. And just look at this honey!

Here’s something even wackier: a brain fractal shaped forest!

Whew, that’s enough fractals to make my fractal brain hurt.

Luckily, mathematicians have found a way to describe the wacky structures. They’ve accepted that clouds are not spheres and bark is not smooth... But, with fractal geometry, we can mathematically explore them!

In the 1970’s, a mathematician named Benoit Mandelbrot was hired to investigate noise in telephone lines. Now, Mandelbrot loved connecting images with numbers, so he immediately looked at the noise in terms of the shapes it created. And he came up with this: (show Mandelbrot  set and talk over it)

At first, the image didn’t look too special. In fact, it kinda resembled a turtle with a giant head (show turtle).

It wasn’t until nighttime that Mandelbrot looked closer. He zoomed in once, and found a smaller turtle latched on to the original one. And an even smaller turtle on that one. Mandelbrot kept zooming and zooming and the turtles kept shrinking and shrinking, but they were still all the same shape!

Mandelbrot was convinced he’d seen a nightmare! But when the shape remained on the screen the next day, Mandelbrot knew he was onto something huge. A simple equation, applied repeatedly, carried incredible properties.

What if, thought he, you could create such expressions for other natural phenomena?

And that’s exactly what mathematicians do today. Fractal geometry allows them to model, say, mountain ranges (animate from fractal triangles), and then use the models to study earthquakes or create realistic special effects for our favorite movies (Star Wars battle/death scene; pause, then show me looking disturbed).

In healthier news, fractals may also help doctors diagnose cancer faster and more accurately. They can study the edges of various cells in our bodies using fractal geometry. Here, the cell on the right is more jagged and repeating than that on the left, which means it’s the more aggressive, faster-growing cancer cell. This way of discovering cancer can be about 10 times more effective than the current methods!

So that’s how cancer cells and rivers relate. But what about cell phones? They aren’t really a part of nature.

Well, in the 90’s, a radio astronomer by the name of Nathan Cohen was having troubles with his landlord. The man wouldn’t let him put a radio antenna on the roof! So, Cohen decided to make a more compact, fractal radio antenna instead (Koch)

The landlord didn’t notice it, and it worked better than the ones before!

Working further, Cohen designed a new version, this time using a shape called “the Menger Sponge” (voiceover over animation of traveling through the Menger Sponge). The fractal’s infinite “sponginess” allowed the antennae to receive multiple different signals.

(soapy sponge used as prop; maybe host is in shower?)

The Menger Sponge is not really the sponge you’d be scrubbing your back with, but you can still think of it like that. Imagine both water and soap getting through your sponge’s holes, except the water is Wi Fi and the soap is, say, Bluetooth. Without Cohen’s “sponge,” your cell phone would have to look something like a giraffe to receive both those signals (illustrate: phone with antennas glued on for those two signals). Not quite as handy, is it?

(closing statement delivered at original Charles River location)

Fractals are already very common, yet we are still searching for more applications, asking questions, building new patterns and exploring nature’s best. Here at MIT (move camera from host and Charles river to MIT dome right across) and everywhere in the world.

Look around you. What beautiful patterns do you see?

Why do some people handle cold better than others? Why is it that some are so fearful of the cold; they’d rather die than be caught outside without all the winter gear on, mask and all, while others can wear one layer for a morning jog? What makes all the difference?

  Imagine a giant furnace, to generate more heat we need to burn more coal.  Now imagine your body as this giant furnace, our metabolism is the fire and sugars are the coals. To generate more heat for warmth, our bodies’ burn more sugars. This is the first way we deal with cold.

  Our blood circulatory system acts like highways to the different organs, imagine our blood as trucks carrying oxygen and heat to the organs. As the speed of the trucks are higher, more heat falls out and is lost to the surroundings. Hence our body slows down the flow of blood by tightening up the blood vessels. This is the same as squeezing a lane on the highway.

  It turns out that our bodies aren’t always equally created. Some just have better genetic makeup than others, and are able to produce more heat from the same amount of sugars. Much like how some people never fatten up no matter how much they eat!

  Contrary to belief, size DOES matter, and so does body type! For one, smaller bodies have more surface area to volume ratio and hence more areas to lose heat. Secondly, bodies with stockier frames and shorter arms mean less distance for blood to travel. Lastly, people with a “healthy bulge” have an extra layer of “insulation” from the cold!

  But thankfully there is one way to increase our tolerance to cold: meditation!

Introducing “Wim Hof” from the Netherlands, In 2009, he completed a full marathon in temperatures below -20 degrees celcius dressed in nothing but his shorts. Wow. I’d probably not last 100metres. Wim Hof is aptly nicknamed “Iceman” for his ability to withstand extreme cold conditions by “turning up” his internal thermostat with his “mind”. Wim Hof practices meditation that allows his body to produce more heat than an average person, as well as shut down certain proteins to slow heat loss to surroundings.

In 2011, he spent 1hr 52mins standing fully immersed in ice. Now that’s just crazy!

  After understanding all this knowledge about withstanding the cold… perhaps there are mutants around us? These would be people that have evolved to better survive the cold.

Why can’t I find my stuff?

Narrator:

It’s winter time and I’m getting dressed to go outside. But every time I start putting on layers after layers of clothes, I always can’t seem to find my gloves. Are they in the kitchen? On my bed? On the couch? Oh dear, I seem to have a problem. Why can’t I find my stuff? Is it because I have a lot of stuff that makes it so hard to remember?

  Well, Google stores about 45 billion index pages of information. If each page of information was a sheet of paper and if we stack them all together, we would create a tower of paper 610 times taller than Mount Everest!

  So how can a search engine like Google find your search results so quickly while I find it so difficult to find a pair of gloves? It’s like finding a needle in haystack; so how’s it done?

  Well, it turns out that searching on the Internet is kinda like looking for a person in a hotel room. Here’s James and he is going to hide in his hotel room. But we want to find where is James.

  The simplest way would be to run through every room nearest to you and keep finding. But that would take a long time.

  Is there a better way I can find James? Hmmm.. (rub chin and raise one eyebrow)

  Well, it turns out that there’s a better way known as Binary Search.

  Let’s say the people were arranged in alphabetical order in increasing numbers of the hotel rooms. We could run to the room in the middle and check if the name of the person in the room is James. And then if the person starts with a smaller alphabet than James, we head to the left. If not we head to the rooms to the right. We then head off to the middle room of the newly sectioned area. And we rinse and repeat. Eventually we will find James just like the first method. But we find James at a much much shorter time.

  How much shorter would that be? Well, that depends on number of people staying at the hotel. Let’s say it takes 10 seconds to knock on each hotel door and there’s 500 people, it would take about 80 minutes for the first method and 1.5 minutes for Binary Search. If there were a thousand people in the hotel, it would take 160 minutes for the first method and only 1.6 minutes for Binary Search. Now that’s a whole lot of difference.

  Is finding James such a big deal? Well, yes! Finding James faster means getting your results on Google faster. Because finding James is like searching a keyword term on Google. And that means less waiting time for all of us.

  So how does any of what we just learned help us to find things better at home? Noticed how the people in the hotel were arranged in rooms numbers based on alphabetical order? So the location of each person in a different hotel room depends on the alphabetical relationship of their names. So we don’t need to remember which person is in which room, we just need to remember the alphabetical relationship that all the people have with each other.

  In the same way, simply by placing your home items in locations where they have a natural relationship to makes it easier for us to find them. The TV remote goes near the TV, the shoes go to the shoe rack, the coats go into the cupboard and the the winter gloves goes in the winter jacket.

 *Finds gloves in the jacket

Aha! So that’s where my gloves are!

Andrea bites into an apple

 Mmmm, delicious!

Eating foods is one of the great pleasures of life. And to enjoy foods like apples, carrots,  or almonds, or even  snack foods like a chocolate bar, or tortilla chips, we rely on one part of our bodies to repeatedly withstand as forces as high as 225 pounds: our teeth. That’s like having a mountain goat jump up and down on our teeth (silly - show).

Teeth are the hardest exposed substance in our bodies – even harder than our bones! On the Mohs scale, which rates minerals in terms of hardness, with talc at the low end and diamonds at the top,  Human teeth rate 5 on a scale of 10. That’s harder than iron or steel!

 Each one of your teeth sits in a little pocket in your gums.  Your gums cover your jawbone, which has a hole where this pocket sits. The roots of your tooth project into this hole to act like an anchor to secure your teeth in the jawbone. But your tooth doesn’t actually come into direct contact with the jawbone - that would be painful every time you bit down to chew.

 As you chew food, your teeth actually move a little bit, but why don’t they actually fall out?  It turns out they are anchored in the jawbone by a piece of specialized tissue called the periodontal ligament, or PDL. The PDL acts as a kind of cushion between the jawbone and the tooth. The PDL can easily absorb the normal forces that a tooth experiences when we chew, say, an apple. 

Inside the PDL, there are all kinds of specialized types of cells.  One type, called mechanoreceptors, sense forces of movement or pressure applied to the tooth.  If the force is large enough, such as biting into a hard shell, these receptors tell your brain – hey stop biting down!

But sometimes, we need to apply large forces to the tooth to get them to move, like when you have braces.  What does the PDL do then?

As the tooth moves in its pocket, the PDL is squeezed in one direction and stretched in the other. Your PDL’s job is the keep your tooth cushioned.  The part of the PDL that is being squeezed against the bone needs to create more space in your jaw, so it can feel comfortable again.

So what actually needs to happen is that a little part of your jaw needs to be dissolved away so the PDL can feel like that nice fat cushion.  The body contains cells called osteoclasts that come in and literally dissolve a little bit of the bone. This takes about 2-5 days.

 But what happens to the part of the PDL cushion that got stretched?

Another kind of cell called an osteoblast comes in a builds up the jawbone, so the PDL cushion can get back into its proper shape. As the bone is built up, this is what holds your tooth in its new position.  This process takes about 15-30 days.  

Once that has happened, it’s time to go back in for another adjustment, and starts the process all over again.

Cut to image of entire body with skeleton highlighted.

Voiceover: Your jaw isn’t the only place where these osteoclasts and osteoblasts alter your bone structure.  In fact, this process of bony remodeling is happening throughout your body.