Following the Sun: Crash Course Kids #8.2 - By Crash Course Kids
Transcript
| 00:09 | have you ever noticed maybe on a nice summer evening | |
| 00:12 | and you're running around outside that your shadow looks super | |
| 00:15 | long . But then at other times of the day | |
| 00:17 | it's really short . What's up with that ? Does | |
| 00:19 | your shadow have a mind of its own like peter | |
| 00:22 | pants , nope . I mean I hope not . | |
| 00:24 | That would be strange to understand how shadows move over | |
| 00:27 | time . Let's talk about what a shadow is exactly | |
| 00:30 | . Mhm . Say you're standing outside in the sun | |
| 00:36 | and you spot your body shadow , your body is | |
| 00:38 | solid . That means it can block sunlight since sunlight | |
| 00:41 | can't pass through your body , it makes a dark | |
| 00:43 | area behind it opposite from the direction the sun is | |
| 00:46 | coming from . This dark part where the sunlight can't | |
| 00:48 | reach is your shadow . So why doesn't this dark | |
| 00:50 | patch stay in the same spot throughout the day ? | |
| 00:52 | Well for one thing you move so your shadow moves | |
| 00:55 | with you , but let's pretend you stand in the | |
| 00:57 | same spot all day long . No , wait , | |
| 01:00 | that sounds super boring . Just picture something that doesn't | |
| 01:03 | move around like a tree or a building . Its | |
| 01:05 | shadow would still move throughout the day . That's because | |
| 01:08 | the shadow is made by the light of the sun | |
| 01:10 | and the sun is constantly moving in the sky . | |
| 01:14 | Well , you know , it's not really the son | |
| 01:16 | that's moving . You should definitely check out our video | |
| 01:18 | about how the earth moves or rotates on its axis | |
| 01:21 | , making the sun appear to move across the sky | |
| 01:24 | , even though it constantly seems to be changing where | |
| 01:26 | it is in the sky . Some people know exactly | |
| 01:29 | where the sun is going to be at certain points | |
| 01:31 | during the day . In fact , ancient civilizations , | |
| 01:34 | thousands of years ago , use the sun like a | |
| 01:36 | giant clock . They could tell what time it was | |
| 01:38 | based on the sun's position in the sky , how | |
| 01:40 | they figure that out because the sun follows a certain | |
| 01:43 | pattern every day . These civilizations saw the sun rising | |
| 01:46 | in the east and setting in the west . Day | |
| 01:48 | after day . Soon they were able to guess what | |
| 01:50 | time it was based on where the sun was on | |
| 01:52 | its path from east to west . Cool . Huh | |
| 01:55 | . And since the movement of the sun follows patterns | |
| 01:57 | during the day , so does the movement of shadows | |
| 02:00 | . Any idea what those shadow patterns might look like | |
| 02:02 | ? Let's find out . We'll follow the sun for | |
| 02:08 | a day and see how it changes the shadow of | |
| 02:10 | a specific object . Then we can chart the length | |
| 02:13 | and the direction of the shadow from morning to evening | |
| 02:15 | to see which patterns we can spot first . Let's | |
| 02:18 | pick an object that stands still . Not running around | |
| 02:20 | all crazy like how about a lamppost ? Say one | |
| 02:23 | that's about four m tall . Now , let's start | |
| 02:25 | early in the morning . seven a.m. Son . Show | |
| 02:28 | us what you got . The lamppost has a pretty | |
| 02:30 | long shadow this early in the morning and it looks | |
| 02:32 | like it's extending to the west . What happens to | |
| 02:35 | the shadow if we fast forward to nine a.m. Interesting | |
| 02:38 | . The shadows still pretty long , but not quite | |
| 02:40 | as long as at seven a.m. And it's still stretching | |
| 02:43 | out towards the west . So let's see what happens | |
| 02:45 | at 11 a.m. Well , look at that , the | |
| 02:47 | shadows even shorter , but again still pointing westward . | |
| 02:50 | So in the morning it looks like the lamppost shadow | |
| 02:53 | starts out long and get shorter as we get closer | |
| 02:56 | to noon , but they all extend to the west | |
| 02:58 | . What happens at noon ? Hardly any shadow . | |
| 03:01 | The sun is high in the sky at noon , | |
| 03:03 | almost directly overhead . Depending on where on earth an | |
| 03:05 | object is . Its shadow will usually point north or | |
| 03:08 | south at noon rather than east or west . Let's | |
| 03:11 | see what happens to the shadow in the afternoon , | |
| 03:13 | jumping to two PM , looks like the shadows are | |
| 03:15 | getting a little bit longer again , now that the | |
| 03:17 | sun's going lower in the sky , but unlike in | |
| 03:20 | the morning , the shadow is now pointing east . | |
| 03:22 | Will the shadow continued to get longer ? At four | |
| 03:24 | PM , yep , it's definitely getting longer . Still | |
| 03:27 | pointing east to how about six p.m. The shadows about | |
| 03:30 | as long as it was in the morning . Right | |
| 03:32 | . But again , unlike in the morning , the | |
| 03:34 | shadow is stretching out towards the east . So what | |
| 03:37 | patterns did we see the lamppost shadow follow ? Let's | |
| 03:39 | look at these two bar graphs that recorded our observations | |
| 03:42 | in the first graph , we've charted the length of | |
| 03:44 | the lamppost shadows based on what we observed with the | |
| 03:47 | lamppost . The sun created long shadows in the morning | |
| 03:50 | when it was rising in the east when it was | |
| 03:52 | almost directly overhead . At noon the shadows were shorter | |
| 03:55 | . Then as the sun set in the west in | |
| 03:57 | the afternoon , the shadows got longer again . And | |
| 03:59 | what did we observe about the direction the shadows were | |
| 04:02 | going in at certain points of the day ? Well | |
| 04:04 | , like the second graph shows us . We saw | |
| 04:06 | that the shadows in the morning and afternoon faced two | |
| 04:08 | different directions in the mid day . Shadow was somewhere | |
| 04:11 | in between . So graph number one shows us that | |
| 04:13 | when the sun is low in the sky , shadows | |
| 04:15 | are long . When it's high in the sky , | |
| 04:17 | shadows are short . Graph number two shows us that | |
| 04:20 | whatever direction the sun is in the sky , the | |
| 04:22 | shadows it creates will point in the opposite direction . | |
| 04:29 | So now you know what a shadow is and that | |
| 04:31 | it changes in both length and direction during the day | |
| 04:34 | , depending on where the sun is in the sky | |
| 04:36 | . Basically , the sun is your shadows , boss | |
| 04:38 | ? Yes , son , no , son , whatever | |
| 04:40 | you say , son . |
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