oceang - origins

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School

Cornell University *

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1540

Subject

Astronomy

Date

Oct 30, 2023

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pdf

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Uploaded by UltraSeaLion3766

Origins of stars, earth, moon, oceans and life The universe is about 14 billion years old Our solar system is about 4,5 billion years old Starts started to form from reionization and ignition of hydrogen and helium, and only after the universe became transparent to visible light 1> When the Big Bang happened there was only hydrogen (and a little helium) in the universe Gravity pulled hydrogen together and caused thermonuclear fusion - lighter elements formed heavier Our sun is the 3d generation star (first two blew up) Inner planets are rocky, and outer are gas giants A star explodes > particles from it get spread around (nebulae/clouds of dust) ours contains oxygen and silica, and carbon) > All of them started to get pulled together by gravity (in spirals) “build by stardust and assembled by gravity” Earth used to be a sterile ball of minerals and rocks > but then a huge ball of hydrogen started to fuse and lit the sun up (ignition)> all the remaining gas is now on the outskirts of the solar system (it was “blown” away) 1. Big Bang Happened About 14 Billion Years Ago: All the mass of the universe expanded outward from a single point — hydrogen atoms formed as the universe began to cool. There was only hydrogen (and some helium) in the universe at this early stage. 2. Hydrogen gas was pulled together by gravity into large dense clouds • Temperature and pressure in the core of large dense hydrogen clouds increases due to compressional heating • When core temperatures reach 10 million degrees Kelvin, thermonuclear-fusion begins to form heavier elements - plus heat and visible light (among other types of radiation) 3. The only place in the universe where elements heavier than hydrogen or helium can be created is inside of stars where nuclear fusion of lighter elements creates heavier elements such as carbon (with atomic number 12) and on up to iron (atomic number 26). And elements heavier than iron are only formed when the largest stars explode. 4. New star formation continues today. We live in the age of stars! 5. When large stars explode, they form nebular clouds of gas and dust containing a mix of light and heavy elements that are available to be pulled back together by gravity to form new stars and new planets and new us! 6. Every single carbon atom making up YOUR physical body today was, at one point in the past, sitting in the center of a boiling hot star!!! You very truly are made of star dust!!!

1. Our Sun is 4.5 billions years old and in about 4 more billion years the sun will run out of hydrogen fuel and die. 2. But before the sun dies, it will expand in size beyond the orbit of earth and in so doing will vaporize the earth. 3. This is not a matter of maybe — this is an absolute certainty! All stars eventually run out of hydrogen fuel and our sun is no exception. 4. The full arc of earth history, from its initial formation through the evolution of all life, is at its midlife. —Eventually all of earth, and all of life on earth, will end – for certain! 5. But all the vaporized atoms that were once part of the sun and earth, and make up our bodies today, will eventually contract back to make new stars and new planets — and maybe even new life!

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