[♪ INTRO]
Hi Squeaks, are you all ready for our winter walk?
I can’t wait to go snowshoeing with you!
Yeah, it is cold out there, but look how beautiful it is!
All the snow, the air and…oh, Squeaks!
I bet the Fort’s pond will be completely frozen over!
Ice skating would be really fun! But our pond’s probably a little too small for that.
But we might be able to slide around on it a little if we’re careful.
Before you ever go out onto something like a frozen lake or pond,
even if it looks solid, check with your grownups to make sure it’s safe!
Sometimes, there’s only a thin layer of ice on top
with really cold liquid water underneath.
Will the ice crack? That’s a great question, Squeaks.
Well, it depends…
It’s not exactly about being too heavy, although that’s part of it.
The real reason that the ice might crack is that
our bodies would apply too much pressure to it.
Sure, I can explain what pressure is, Squeaks.
But to do that, I first have to explain what a force is.
No, not the Force from Star Wars.
But forces in the real world are still super awesome.
And they are all around us, all the time.
They’re acting on our table, and the whole Fort, and even you and me!
If I were to take a step onto the ice, the weight of my body
would push down on the surface, or top, of the ice.
And because the ice doesn’t move,
that surface pushes back up on me with the exact same strength.
Those two pushes are examples of a force.
Forces are how much two things push or pull on each other when they meet.
And pressure tells us how much pushing or pulling is being done in a certain area.
For example, if I stepped out onto the ice and just stood there,
all of my weight…and all of my force…is pushing down on an area
that’s the size of the bottom of my shoes.
My feet are pretty small, so that's a lot of force pushing down on a little area.
And that creates a lot of pressure!
And too much pressure on ice can be a very bad thing. It can make the ice crack!
But if I were lying down, the pressure would be a lot lower because my weight…
my force…spreads out from just my tiny feet to my belly,
and my arms, and my legs.
That’s right! Just like a polar bear!
If a polar bear finds themselves on ice that’s too thin, they’ll will slide on its belly.
That spreads its weight out so it doesn’t put too much pressure in one spot!
And then the bear can cross the ice without breaking it.
Oh, no. Don’t worry. There are no polar bears near the Fort!
We are too far south for them.
But there are smaller animals here that use the
same strategies to get around in the winter.
Have you ever seen the feet of a lynx or a snowshoe hare?
They have big, wide paws and can spread their toes out.
Their feet let them spread their weight over a larger area
so they create less pressure on the ground when they walk.
This means they can walk over the snow without falling in.
That’s exactly right, Squeaks; that’s how snowshoes work.
Do you want to play make believe lynx and hare on our walk?
And maybe if the pond looks safe, we could pretend to be polar bears!
Yeah, ice can be super slippery! It’s another reason to be careful
when you’re walking or skating on ice. But it can be fun, too!
Do you know why ice is slippery?
You’re right - friction! Squeaks remembered the fun we had with water slides,
when we learned about friction.
Friction is also a kind of force.
And it’s made whenever two things rub up against each other.
The rougher the two things rubbing against each other,
the more friction there is between them. The smoother they are, the less fiction.
It’s like when you walk barefoot on a smooth floor,
your feet are just a little rough and keep you from slipping around.
But if you go running in with socks on, you slip and slide.
Just like on ice, that’s right Squeaks!
But that doesn’t completely explain why ice is so slippery.
If you rub your hands together quickly,
you’ll see that friction can cause things to heat up. Try it with me!
Here, feel my hands now! They're warm!
So as you move along the ice, scientists think you create
just enough warmth to melt the top layer of the ice,.
Ice is liquid water that has been frozen solid.
When it melts, it turns back into liquid water. And liquid water is very slippery.
It creates less friction than solid ice does.
That makes it easier to glide around,
whether you’re wearing shoes or skates, or lynx paws.
But do you want to hear something even cooler about ice?
Hey, when you have the chance to make a good ice pun,
snow way I'm gonna miss that!
Some scientists also think that the top layer of ice
isn’t even fully solid or fully liquid. It might be something in-between.
Now, that layer of "kinda-solid, kinda-liquid water" water is so thin
you’d need a super powerful microscope to see it.
But it’s enough to make ice just a little bit slippery from the get-go.
Before friction can come along and do any melting
that makes ice even more slippery.
Well, Squeaks, you can avoid falling over by keeping track of your belly button.
And whatever the rest of your body is doing,
keep your belly button directly above where your feet are.
That always helps me keep my balance. Just…like…so.
Oops, I guess robot rats don't really have belly buttons!
But if you did have one, it would be right…there!"
We might have to do a little experimenting before we go on the ice
to figure out the best way for you to find your balance, Squeaks.
Let’s practice a little more and then head out!
Thanks for joining Squeaks and me, today.
You can join us back at the Fort for more winter fun next week!
[♪ OUTRO]