(0:00) (Crash Course Intro Plays)

You know who we haven't hung out with in a while? This guy. What's up sun? You remember that the sun provides the earth with energy, or warmth. And you know that the Earth's surface is made up of different types of land and water. Now, it would probably make sense that these different landforms and bodies of water absorb - or soak up - the sun's heat at different rates, right? 

Well, you're right! It does. Which one absorbs more of the sun's energy: land or water? And more importantly, why? 

(0:37) Let's start with a refresher course on the sun. We know the sun is the star at the center of our 8 planet solar system that provides us with heat. We also know that heat is a kind of energy that warms things. This energy starts in the sun's core, it travels very slowly to the sun's surface before it takes a super speedy trip to Earth in the form of light and heat. 

(0:58) You and I can see and feel that heat as sunlight. But how much of all of that energy that the sun cooks up actually makes it to us, the land, and the water on Earth? I know what will help us figure this out. A delicious pie graph. 

Essentially 100% of the energy that warms the Earth comes from the sun. About 20% of that energy is absorbed by the Earth's atmosphere and clouds. Nearly 30% never makes it into the Earth's surface and is instead bounced back out to space by clouds and different gases and particles in the atmosphere. But about half of the sun's incoming energy, just over 50%, is absorbed by the Earth's surface, that is, its land and water. 

(1:32) Well, when that 50% of sunlight gets to Earth, the land and water absorb, or soak up, its warmth. But, like I mentioned before, they absorb this heat at different rates. So, which one absorbs more of this heat? It's time to play land vs. water! 

Okay, let's think of a place somewhere on Earth where land meets water. Is anyone else thinking - beach? Let's take a look at how the sun's energy is absorbed by both the land and the water on our little beach. 

(1:59) The land is all the sand you see, right up until the shoreline starts. And the water is the shoreline and all of the ocean behind it. So, what happens when the sun's energy hits the land? Well, the sunlight is absorbed by the sand, making the sand warm or even hot to the touch. The longer the sand is exposed to the sun, the more heat it absorbs. Now, let's take a close look at the land. It is a darker color than the water, and generally darker colored objects absorb more heat than lighter colored objects. 

(2:25) So, when the same sunlight that warms the sand hits the water next to it on our little beach, the water doesn't soak up quite as much of that energy as the land did. Instead, that water reflects more of it. 

Reflection is the opposite of absorption. Instead of being absorbed by the water, some of the sun's energy is bounced, or reflected off the water in a different direction. And lighter colored things tend to reflect more heat than lighter colored things. This is why the water that's been under the same sun as the sand all day doesn't feel quite as hot as the sand. So, when you get hot after playing around on the sand all afternoon, and I really hope you've been wearing sunscreen, you can wade off in the water to cool off. That's what the beach is all about, right? 

(3:00) So, it looks like team land wins, by which I mean it absorbs more of the sun's energy. The land absorbs more energy because darker colored objects absorb more heat than lighter colored objects. And light colored things, like the water, reflect more of the sun's energy. Hey, where'd the sun go? Oh right, outside. Sounds like a plan to me. 

(Crash Course Outro Plays)