74 Comments

  • CiszHelion

    Um, but the water is darker, look at sattelite or aerial photos.

    And the water is moving and spreading the heat, while the sand only gets warm on top.

    This seems wrong.

  • Freakazette

    I'm curious what grade level these are for? When I saw the title I was expecting more explanation than just "darker objects absorb light and lighter ones reflect it" like other properties that factor into reflectivity, the ocean's constant movement, and percentage of surface area for land and water. I don't think this is definitive at all, since the ocean is constantly dissipating the energy it absorbs, and it's temperature varies greatly dependent on location (like the Atlantic Ocean is generally warmer than the Pacific)

  • Zoe Li

    Nice fox shirt! I'm guessing you filmed the past 6 episodes on the same day?

    (not like there's anything wrong with that, because I absolutely love the content!)

  • 1234kalmar

    Imagine. 50% of a tiny fraction of the sun's full output hits us, and it's still immensely much energy. Amazing.

  • Matthew Prorok

    I'm not sure about this one, maybe you'll clear it up in an upcoming episode, but there's a degree to which this is misleading.  It's true that land reflects less light than water, and thus if you have equal areas of land and water, the land will be heated more.  But the Earth doesn't have equal areas of land and water.  Its surface is 70% water.  The majority of heat transfer to the Earth as a whole goes to the oceans, largely because there's just a lot more ocean than land.

  • Jalopy Math

    Yes people, 8 planets! Come on, get over it! Wait a minute… Wrong audience… Ok, forget what I just said.

  • Adam Read

    If darker colored objects pick up more of the Sun's heat, does that mean people of color get hotter than white people?

  • Aubrey Nelson

    I am a science teacher, and I'm confused by this explanation of why the water is cooler, as according to the climatology class I took, sand actually has higher albedo (reflects more sunlight), at 30-35%, than water, especially with high solar altitude (which has albedo of only 3-10%). I was under the impression that water doesn't heat up as quickly, not because of its color (which is often dark blue, as opposed to light yellow like sand), but because it has very high specific heat– it takes more energy to raise its temperature. Also, because solar radiation penetrates water, and water circulates, the absorbed energy is more evenly spread in water, so that the surface of water doesn't get as hot as it does with sand, but the sand beneath the surface stays cool. I know this is for young kids, and so "specific heat" might not be something you want to address yet, but, while simplified explanations are much appreciated (and I love Crash Course videos for this purpose), I don't think this is accurate. (My sources: Moran, Joseph M. Climate Studies: Introduction to Climate Science. American Meteorological Society, Boston, MA. 2010. Chapter 3 and 4, albedo chart on page 84). Thank you!

  • Jessica Wall

    +Aubrey Nelson I am also a science teacher. I teach 6th grade science in Georgia, so this is a topic I am teaching my students. I am not going to show them this video, although I am very disappointed because I love Crash Course, and really hoped that Crash Course Kids would have the same caliber. I don't know much about specific heat and all that, but I know that the color of the land and water have very little to do with this unequal heating. The textbook doesn't even go into why it happens, but I'm guessing its a solid vs. liquid issue. Land is more molecularly dense, and therefore the energy is absorbed faster, which is why it also looses heat more quickly (also not addressed in this video). I may be wrong, but it makes way more sense than what this video says.

  • A Person

    The water of the beach is not dark because sunlight is able to reach the bottom making it able to see trough but the deeper the water is the less sun it gets so it turns darker

  • Chloé Daisy Winant

    The reasoning in this video is incorrect. Water acts as a heat reservoir – it absorbs and holds onto heat energy more efficiently than land and (and the air above land). Water has more molecules in the same amount of space as air, so the air will absorb then release heat energy more quickly than water since the air molecules have more space to vibrate. (This is the real reason land/air heat up more quickly, not their color or albedo). The bonds between the hydrogen and oxygen in water are also very flexible and able to hold onto that heat energy for a longer period of time, causing the air temperature above the ocean to stay consistent day and night relative to the air that heats up and cools very rapidly in a 24 hour period.

  • Valerie Armstrong

    This video does not give the correct scientific reason for the unequal heating of land and water. I'm a middle-school science teacher, and I generally love Crash Course. Sadly, I won't be using this video. I have made plenty of mistakes myself, so I'm not judging, but I hope that Crash Course will re-make this video with the correct explanation. The main reasons for the uneven heating of land and water are 1-the different specific heats of water and sand and 2-the transparency of water vs. the opacity of sand, and 3-The differnt movements of solid and liquid particles. 1: The specific heat of water is 4,182 joules/kilogram, while the specific heat of quartz sand is only 830 j/kg. That means it takes almost 5 times the amount of energy to heat up 1 kg of water as it does to heat up 1kg of sand by the same amount. (For equal volumes, it's still going to take more than 3 times the energy to heat water.) 2-Since sand is opaque (light can't pass through it), any energy that is not reflected is absorbed by the surface only. That means that the energy that is absorbed is concentrated in the upper layers. Since water is transparent, some of the energy is absorbed at the surface, but much energy passes further down and is absorbed by water below the surface. 3-Since sand is a solid, its particles only vibrate in place, while molecules in liquid water can and do flow around each other. That means that the heat absorbed by the surface layer of sand can only be transferred by conduction to the sand just below it or to the atmosphere just above it. As you know from digging your feet down into the sand at the beach, the energy doesn't get too deep into the sand. On the other hand, since water molecules move around each other, they spread the heat more evenly through the water (though it's still not even as you know from floating near the surface of a lake and then diving down deep into it).

  • N. P.

    During exams, it makes me so happy to see a crash course vid on a topic I'm having trouble on. It's such a pain to go through a million others just to check whether what I wrote was correct or not.

  • Commandobolt

    0:59 no matteR CAN TRAVEL faster than light, and since you showed matter is traveling at light, your wrong

  • Lee Adrianson

    Yeah—usually I love using the Crash Course for Kids videos in my 5th and 6th grade classes, but this one seems a little off the mark. I don't think that your reasoning is sound or complete. There are several variables that figure into why water and sand would heat at different rates. I would love to see you redo this episode with a bit more research.
    Thanks for all you do to help kids learn!

  • Marina Martinez

    🌊🌄🌅I love water and land.🌎🌏🌍🌊🌊🌄🌅🌎🌅🌊🗻🏄🚣🚵🚤🔥💦(^'^)😸😺😹😻😽😿😽😸😸😺😼😸😹🙀😾

  • David Faubion

    You said, "Lighter colored things tend to reflect light more than darker colored things." That is a statement contrary to physics.

  • Arizza Ferreras

    Isn’t the fact that solids (land) have tightly-packed molecules than liquids (water) a better explanation why it heats up faster? Because heat causes the molecules to move/vibrate and since the solids are tightly packed, when one molecule moves the other molecules also move causing heat to pass around them.

  • Arizza Ferreras

    Isn’t the fact that solids (land) have tightly-packed molecules than liquids (water) a better explanation why it heats up faster? Heat causes the molecules to move/vibrate. Since the solids are tightly packed, when one molecule moves, the other molecules also move causing heat to pass around them.

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