Earth 101 | National Geographic — Transcript

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1. 0:02- [Narrator] Earth, the only planet known to maintain life.
2. 0:06A product of scientific phenomena and sheer chance.
3. 0:10This blue speck in space holds the past,
4. 0:13present, and future, of our very existence.
5. 0:17(instrumental music)
6. 0:19Approximately 4.5 billion years ago,
7. 0:22the Earth formed from particles left over
8. 0:24from the creation of our sun.
9. 0:27Gravity drew these particles together
10. 0:29to form pebbles which then formed boulders,
11. 0:31and eventually, the Earth.
12. 0:34At its heart is a solid inner core
13. 0:37covered by a liquid outer core.
14. 0:39Above this sits the mantle, made of flowing silicate rocks,
15. 0:42and a rocky crust.
16. 0:45This rocky mass is the third planet from the sun,
17. 0:49orbiting the star from an average distance
18. 0:51of about 93 million miles.
19. 0:55It's close enough to the sun to be warm
20. 0:57unlike the cold gas giants.
21. 0:59But not so close that its surface
22. 1:01is exposed to extreme heat and solar radiation
23. 1:04as is the case with Mercury.
24. 1:07Earth's unique position in the solar system
25. 1:09allows it to house phenomena
26. 1:11yet to be found anywhere else in the universe,
27. 1:14particularly liquid surface water and life.
28. 1:19According to one theory, much of Earth's water
29. 1:22is as old as its rocks, both of which having formed
30. 1:25during the Earth's earliest days.
31. 1:28Because of Earth's unique distance from the sun,
32. 1:31the planet is able to contain water
33. 1:33in all of its forms, liquid, ice and gas
34. 1:36rather than have them permanently frozen
35. 1:39or evaporated into space.
36. 1:43But Earth is the only known place in the universe
37. 1:46with liquid water on the surface,
38. 1:48thereby having unique cascading effects on the planet.
39. 1:52It hydrates the land helping create nutrient rich soil.
40. 1:56It collects and pools to form oceans and freshwater systems.
41. 2:01And it cycles upward to add moisture
42. 2:03to Earth's protective atmosphere.
43. 2:06And where there is liquid water, there is life.
44. 2:13About 3.8 billion years ago in Earth's oceans
45. 2:17primitive life existed in the form of microbial organisms.
46. 2:21They and the ensuing billions of years
47. 2:23gave rise to a range of more advanced life forms
48. 2:27that survived in Earth's seas, lands and skies.
49. 2:34As the only world known to harbor life,
50. 2:37Earth's biodiversity is expansive in nature.
51. 2:41An estimated 1.5 million species of plants,
52. 2:45animals, bacteria, fungi and others
53. 2:49have been cataloged with potentially millions,
54. 2:51if not billions more yet to be discovered.
55. 2:57Home to life and fueled by water,
56. 3:00Earth houses a unique global ecosystem
57. 3:03as curious and as grand as the astronomical events
58. 3:06that made them possible.