Harnessing the Sun - By MITK12Videos
Transcript
| 00:11 | the sun , the main source of life on earth | |
| 00:16 | . Why is the sun so important ? It gives | |
| 00:21 | us energy . Plants use this energy to grow and | |
| 00:26 | we use solar cells to convert energy from sunlight to | |
| 00:30 | electricity . How else can we harness the power of | |
| 00:33 | the sun ? One way we can harness the sun's | |
| 00:38 | power is through heat . We know that light from | |
| 00:41 | the sun carries energy to the earth because when you | |
| 00:45 | stand in the sun you feel warmer and when you | |
| 00:49 | leave things out in the sun , oh no , | |
| 00:53 | they can get hot . We can use sunlight to | |
| 00:56 | make things even warmer . If we either trap it | |
| 00:59 | or focus it , let's look at ways . We | |
| 01:04 | can trap sunlight . Some ways are very old , | |
| 01:10 | even hundreds of years ago . People use greenhouses to | |
| 01:13 | keep plants warm . A greenhouse is a building with | |
| 01:17 | a big glass windows , sunlight passes through the glass | |
| 01:21 | and heats up the plants and air inside . The | |
| 01:26 | hot air is trapped inside by the glass so the | |
| 01:29 | plants stay warmer than if they were outside . The | |
| 01:31 | greenhouse greenhouses were used by gardeners of the roman Emperor | |
| 01:36 | Tiberius so he could eat his favorite veggies year round | |
| 01:41 | and they're still used today . We can use the | |
| 01:45 | same idea to build a solar oven so you can | |
| 01:48 | cook using just sunlight . If you take a box | |
| 01:53 | , line it with aluminum foil and cover the top | |
| 01:56 | with saran wrap , you've just made a solar oven | |
| 02:00 | . Light heats up your food through the saran wrap | |
| 02:04 | and once inside the heat is trapped . Mm delicious | |
| 02:09 | smores . Unfortunately , this heating effect isn't always a | |
| 02:16 | good thing on earth . The atmosphere is like a | |
| 02:20 | window that lets sunlight in and then traps heat . | |
| 02:24 | When cars and factories pollute , it makes the window | |
| 02:28 | of the atmosphere thicker , so more heat gets trapped | |
| 02:33 | . This trap heat is responsible for global warming and | |
| 02:38 | the earth is slowly getting warmer on average as we | |
| 02:41 | pollute more global warming melts glaciers and disrupt habitat . | |
| 02:47 | This is why it's so important that we pollute less | |
| 02:50 | . Going into the future , trapping sunlight is one | |
| 02:54 | way to harness the power of the sun . Another | |
| 02:57 | way is to focus it here . Sunlight is being | |
| 03:01 | focused with the lens . The illuminated water droplets show | |
| 03:05 | where the light is focused . If you can take | |
| 03:08 | the energy of sunlight spread out over a large area | |
| 03:12 | and concentrated onto a small area , you'll heat it | |
| 03:16 | up much more Arquimedes . An ancient greek scientist tried | |
| 03:21 | to use this principle to build a weapon to burn | |
| 03:24 | ships . He had many small mirrors which reflected sunlight | |
| 03:30 | onto a single point . That point was so hot | |
| 03:35 | that it could set wood on fire . It's debatable | |
| 03:40 | whether such a weapon would work with ancient technology , | |
| 03:44 | but it is a fascinating idea . Nonetheless . We | |
| 03:48 | can use the same idea today to start a campfire | |
| 03:52 | with the lens . Light can be focused from a | |
| 03:56 | wide area to a small point with all that sunlight | |
| 04:01 | focused on a small spot , that heat is enough | |
| 04:05 | to start a fire . Remember kids don't do this | |
| 04:08 | without an adult mm marshmallows . This same focusing idea | |
| 04:15 | is used in much more advanced technology today as well | |
| 04:20 | . Instead of sunlight , a laser cutting machine generates | |
| 04:25 | a laser beam , which is another type of light | |
| 04:28 | and focuses it to a tiny point in order to | |
| 04:32 | burn through material . There are lots of other ways | |
| 04:35 | that you can use energy from sunlight besides trapping it | |
| 04:39 | or by focusing it to do something useful . Can | |
| 04:42 | you think of any ? Mhm . |
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Harnessing the Sun is a free educational video by MITK12Videos.
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