In this video #neildegrassetyson explains how we have a misunderstanding of planet Earth.
Earth is the third planet from the Sun and the only astronomical object known to harbor life. This is enabled by Earth being a water world, the only one in the Solar System sustaining liquid surface water. Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's surface. The remaining 29.2% of Earth's surface is land, most of which is located in the form of continental landmasses within one hemisphere, Earth's land hemisphere. Most of Earth's land is somewhat humid and covered by vegetation, while large sheets of ice at Earth's polar deserts retain more water than Earth's groundwater, lakes, rivers and atmospheric water combined. Earth's land is part of Earth's crust, consisting of several slowly moving tectonic plates, which interact to produce mountain ranges, volcanoes, and earthquakes. Earth has a liquid outer core that generates a magnetosphere capable of deflecting most of the destructive solar winds and cosmic radiation.
Earth has a dynamic atmosphere, which sustains Earth's surface conditions and protects it from most meteoroids and UV-light at entry. It has a composition of primarily nitrogen and oxygen. Water vapor is widely present in the atmosphere, forming clouds that cover most of the planet. The water vapor acts as a greenhouse gas and, together with other greenhouse gases in the atmosphere, particularly carbon dioxide (CO2), creates the conditions for both liquid surface water and water vapor to persist via the capturing of energy from the Sun's light. This process maintains the current average surface temperature of 14.76 °C, at which water is liquid under atmospheric pressure. Differences in the amount of captured energy between geographic regions (as with the equatorial region receiving more sunlight than the polar regions) drive atmospheric and ocean currents, producing a global climate system with different climate regions, and a range of weather phenomena such as precipitation, allowing components such as nitrogen to cycle.
Earth is rounded into an ellipsoid with a circumference of about 40,000 km. It is the densest planet in the Solar System. Of the four rocky planets, it is the largest and most massive. Earth is about eight light-minutes away from the Sun and orbits it, taking a year (about 365.25 days) to complete one revolution. Earth rotates around its own axis in slightly less than a day (in about 23 hours and 56 minutes). Earth's axis of rotation is tilted with respect to the perpendicular to its orbital plane around the Sun, producing seasons. Earth is orbited by one permanent natural satellite, the Moon, which orbits Earth at 384,400 km (1.28 light seconds) and is roughly a quarter as wide as Earth. Through tidal locking, the Moon always faces Earth with the same side, which causes tides, stabilizes Earth's axis, and gradually slows its rotation.
Neil deGrasse Tyson (US: /dəˈɡræs/ də-GRASS or UK: /dəˈɡrɑːs/ də-GRAHSS; born October 5, 1958) is an American astrophysicist, author, and science communicator. Tyson studied at Harvard University, the University of Texas at Austin, and Columbia University. From 1991 to 1994, he was a postdoctoral research associate at Princeton University. In 1994, he joined the Hayden Planetarium as a staff scientist and the Princeton faculty as a visiting research scientist and lecturer. In 1996, he became director of the planetarium and oversaw its $210 million reconstruction project, which was completed in 2000. Since 1996, he has been the director of the Hayden Planetarium at the Rose Center for Earth and Space in New York City. The center is part of the American Museum of Natural History, where Tyson founded the Department of Astrophysics in 1997 and has been a research associate in the department since 2003.
From 1995 to 2005, Tyson wrote monthly essays in the "Universe" column for Natural History magazine, some of which were later published in his books Death by Black Hole (2007) and Astrophysics for People in a Hurry (2017). During the same period, he wrote a monthly column in StarDate magazine, answering questions about the universe under the pen name "Merlin". Material from the column appeared in his books Merlin's Tour of the Universe (1998) and Just Visiting This Planet (1998). Tyson served on a 2001 government commission on the future of the U.S. aerospace industry and on the 2004 Moon, Mars and Beyond commission. He was awarded the NASA Distinguished Public Service Medal in the same year. From 2006 to 2011, he hosted the television show NOVA ScienceNow on PBS. Since 2009, Tyson has hosted the weekly podcast StarTalk. A spin-off, also called StarTalk, began airing on National Geographic in 2015. In 2014, he hosted the television series Cosmos: A Spacetime Odyssey, a successor to Carl Sagan's 1980 series Cosmos: A Personal Voyage.
