1 00:00:00,000 --> 00:00:01,760 Thirsty? 2 00:00:01,760 --> 00:00:13,970 How about a nice cold glass of dinosaur pee? 3 00:00:13,970 --> 00:00:26,660 Ah, so refreshing. 4 00:00:26,660 --> 00:00:27,660 Let me explain. 5 00:00:27,660 --> 00:00:30,660 Last time we learned all about the water cycle. 6 00:00:30,660 --> 00:00:33,659 Water circulates around the Earth going from a liquid to a gas, 7 00:00:33,659 --> 00:00:36,659 and occasionally to a solid, over and over again. 8 00:00:36,659 --> 00:00:40,659 And while I was babbling on about the water cycle, you may have noticed something. 9 00:00:40,659 --> 00:00:44,659 Water never leaves the system, and new water never comes in. 10 00:00:44,659 --> 00:00:46,659 That makes water a limited resource. 11 00:00:46,659 --> 00:00:47,659 resource. 12 00:00:47,659 --> 00:00:52,600 There's only a certain amount of it on Earth, no more and no less, and that amount never 13 00:00:52,600 --> 00:00:53,600 changes. 14 00:00:53,600 --> 00:01:01,810 So, what does it mean when we say that water is a limited resource? 15 00:01:01,810 --> 00:01:06,010 Remember that water is matter, and matter is made up of particles. 16 00:01:06,010 --> 00:01:09,890 As we've learned, the particles can move around, changing states, buddying up with 17 00:01:09,890 --> 00:01:13,930 other particle friends, but new particles can't be created from nothing, and they 18 00:01:13,930 --> 00:01:15,969 can't be totally destroyed. 19 00:01:15,969 --> 00:01:18,329 This is called the conservation of matter. 20 00:01:18,329 --> 00:01:23,269 Since water keeps cycling over and over again on our planet without adding or removing matter, 21 00:01:23,269 --> 00:01:25,010 we say it's a closed system. 22 00:01:25,010 --> 00:01:27,329 Well, it's a mostly closed system. 23 00:01:27,329 --> 00:01:30,549 Teensy amounts can leak out into space and whatnot. 24 00:01:30,549 --> 00:01:33,569 But for our purposes, let's assume it's closed. 25 00:01:33,569 --> 00:01:37,870 Now, if you were paying super close attention last time, you may have noticed that we only 26 00:01:37,870 --> 00:01:40,909 talked about three of the Earth's four spheres. 27 00:01:40,909 --> 00:01:45,390 We talked about how water, the hydrosphere, interacts with the geosphere in liquid form 28 00:01:45,390 --> 00:01:47,329 and the atmosphere in vapor form. 29 00:01:47,329 --> 00:01:48,709 Can you tell which one we missed? 30 00:01:48,709 --> 00:01:49,709 You're looking at it. 31 00:01:49,709 --> 00:01:50,709 Me. 32 00:01:50,709 --> 00:01:51,709 And you. 33 00:01:51,709 --> 00:01:52,709 And us. 34 00:01:52,709 --> 00:01:54,329 We're both members of the biosphere. 35 00:01:54,329 --> 00:01:58,530 That means me, and you, and my cat in this tree, and that triceratops that lived a long 36 00:01:58,530 --> 00:02:01,769 time ago, were all part of the water cycle too. 37 00:02:01,769 --> 00:02:04,129 And that leads to some pretty crazy ideas. 38 00:02:04,129 --> 00:02:07,290 This is where science can get kind of...gross. 39 00:02:07,290 --> 00:02:09,530 Let's look at the water cycle over time. 40 00:02:09,530 --> 00:02:13,629 Hmm. 41 00:02:13,629 --> 00:02:17,310 Water has been on the Earth almost as long as there has been an Earth. 42 00:02:17,310 --> 00:02:21,370 Scientists aren't sure how it got here in the first place, but we know that it's here, 43 00:02:21,370 --> 00:02:22,930 and it's not going anywhere. 44 00:02:22,930 --> 00:02:26,289 That means the water coming out of your faucet is old. 45 00:02:26,289 --> 00:02:27,289 Really old. 46 00:02:27,289 --> 00:02:30,469 I'm talking older than dinosaurs old. 47 00:02:30,469 --> 00:02:33,009 Take this thirsty brachiosaurus over here. 48 00:02:33,009 --> 00:02:35,250 He stops at a stream for a long drink. 49 00:02:35,250 --> 00:02:40,250 He moves about his day, doing dinosaur things, hanging out with his dinosaur friends, until 50 00:02:40,250 --> 00:02:41,250 nature calls. 51 00:02:41,250 --> 00:02:42,729 He's gotta go. 52 00:02:42,729 --> 00:02:47,449 The brachiosaurus pea hits the ground, and pea is, well, mostly water. 53 00:02:47,449 --> 00:02:52,490 The sun shines down and evaporates that water in the pea, turning it into water vapor, while 54 00:02:52,490 --> 00:02:55,509 the salt and other minerals are left behind on the soil. 55 00:02:55,509 --> 00:03:00,330 The water vapor rises into the atmosphere, mixes with other water vapor, and cools enough 56 00:03:00,330 --> 00:03:02,490 to condense into a cloud. 57 00:03:02,490 --> 00:03:05,969 Then the wind may move the cloud to a whole different part of the world. 58 00:03:05,969 --> 00:03:10,210 Eventually, gravity will pull the water back to the ground as precipitation. 59 00:03:10,210 --> 00:03:15,250 Keep in mind, the dinosaur pee, just like all matter, is made up of lots of particles. 60 00:03:15,250 --> 00:03:18,909 As they move together through the water cycle, the particles that were all together in our 61 00:03:18,909 --> 00:03:23,150 brachiosaurus pee get all mixed up with other water particles that have been on different 62 00:03:23,150 --> 00:03:24,150 journeys. 63 00:03:24,150 --> 00:03:28,469 But since the Earth only has a limited number of total water particles, these little guys 64 00:03:28,469 --> 00:03:31,409 move through the water cycle again and again. 65 00:03:31,409 --> 00:03:36,610 So some of the dinosaur pee water particles might have spent thousands of years locked 66 00:03:36,610 --> 00:03:37,789 in glacier ice. 67 00:03:37,789 --> 00:03:40,090 Some of them passed through many more dinosaurs. 68 00:03:40,090 --> 00:03:44,789 Some flowed through the Nile River as the ancient Egyptians were building the pyramids. 69 00:03:44,789 --> 00:03:47,150 Some hydrated a giant redwood tree. 70 00:03:47,150 --> 00:03:50,090 Some quenched the thirst of George Washington. 71 00:03:50,090 --> 00:03:55,110 And some of those particles eventually became, you guessed it, his pee. 72 00:03:55,110 --> 00:03:58,210 You could be drinking George Washington's pee. 73 00:03:58,210 --> 00:03:59,310 Or his sweat. 74 00:03:59,310 --> 00:04:00,310 Or his tears. 75 00:04:00,310 --> 00:04:05,129 The good news, though, is that as water moves through the cycle, nature cleans it. 76 00:04:05,129 --> 00:04:09,889 The water cycle takes salty, undrinkable water from the ocean and turns it into the glorious 77 00:04:09,889 --> 00:04:12,770 refreshing drinkable drink we all enjoy. 78 00:04:12,770 --> 00:04:15,569 That's because when water is evaporated from the ocean, 79 00:04:15,569 --> 00:04:17,170 or from a puddle of pee, 80 00:04:17,170 --> 00:04:19,730 the salt and other impurities get left behind. 81 00:04:23,879 --> 00:04:28,600 The particles in your drinking water would have some crazy stories to tell. 82 00:04:28,600 --> 00:04:30,120 But one thing's for certain. 83 00:04:30,120 --> 00:04:33,240 Since water is a limited resource in a closed system, 84 00:04:33,240 --> 00:04:39,000 some of the particles definitely pass through a dinosaur.