Earth’s Place in the Earth’s Place in the UniverseUniverse

CosmologyCosmology

Simply put, the study of the Universe (and Simply put, the study of the Universe (and everything in it… including us), its origin, everything in it… including us), its origin, present state, and its future can all be present state, and its future can all be defined as defined as CosmologyCosmology. .

The Big BangThe Big Bang

• Most scientists believe in Most scientists believe in the theory that the Earth, the theory that the Earth, our Solar System, our our Solar System, our Galaxy, and the entire Galaxy, and the entire Universe began at one Universe began at one defining moment known as defining moment known as the Big Bang. the Big Bang.

• This doesn’t mean that this This doesn’t mean that this is the ONLY possibility, but is the ONLY possibility, but it is the scientific theory it is the scientific theory that as the strongest that as the strongest evidence and the most evidence and the most support amongst the support amongst the scientific community.scientific community.

Big Bang Continued…Big Bang Continued…

• From this moment From this moment on, matter has on, matter has been expanding been expanding outward for the last outward for the last 13.7 billion years.13.7 billion years.

The Big Bang Cont…The Big Bang Cont…

• As gravity began to As gravity began to condense small condense small amounts of amounts of matter/gas matter/gas together…together…– Galaxies formed Galaxies formed

and “clumped” and “clumped” togethertogether

– Stars turned onStars turned on– Planets formedPlanets formed

Cosmic Background RadiationCosmic Background Radiation

• Most of what we “think” Most of what we “think” we know about the we know about the beginning of the beginning of the universe and the Big universe and the Big Bang came from the Bang came from the study of study of Cosmic Cosmic Background Background RadiationRadiation..– Discovered in 1965Discovered in 1965– A persistent radio hiss A persistent radio hiss

(white noise) coming from (white noise) coming from all directions in space. all directions in space.

– This tells us that radiation This tells us that radiation from the Big Bang has from the Big Bang has been cooling and moving been cooling and moving outward in all directionsoutward in all directions

GalaxiesGalaxies• In the universe, there are In the universe, there are

estimated to be between estimated to be between 50 billion and 100 billion 50 billion and 100 billion galaxiesgalaxies

• Our sun is one of about Our sun is one of about 400 billion other stars in a 400 billion other stars in a spiral-shaped galaxy we spiral-shaped galaxy we call the Milky Way. call the Milky Way.

• We are located about half-We are located about half-way down one of the arms. way down one of the arms.

• Our galaxy is moving away Our galaxy is moving away from all other galaxies, from all other galaxies, except our nearest except our nearest neighboring galaxy, neighboring galaxy, Andromeda, which we are Andromeda, which we are actually moving toward actually moving toward (gravity). (gravity).

• Andromeda is about 2.5 Andromeda is about 2.5 million light years away.million light years away.

The Milky WayThe Milky Way

Solar SystemSolar System• About 5 billion years ago, About 5 billion years ago,

our solar system formed our solar system formed when Hydrogen and when Hydrogen and Helium gas began to Helium gas began to condense around a condense around a common center of gravity. common center of gravity.

• When temperature and When temperature and pressure became high pressure became high enough, fusion began and enough, fusion began and the sun “turned on”. the sun “turned on”.

• The “shock wave” from The “shock wave” from this event blew lighter this event blew lighter elements further out into elements further out into the solar system.the solar system.

Solar System Continued…Solar System Continued…

• The strong pull of gravity The strong pull of gravity from the sun pulled from the sun pulled heavier elements like iron heavier elements like iron and nickel (metals) closer and nickel (metals) closer toward the center, toward the center, forming the small, rocky forming the small, rocky inner planets that we call inner planets that we call the Terrestrial planets. the Terrestrial planets.

• The lighter elements such The lighter elements such as hydrogen and helium as hydrogen and helium found their place a little found their place a little further out, forming the further out, forming the larger outer planets that larger outer planets that we call the Gas we call the Gas Giant/Jovian planets. Giant/Jovian planets.

• The left-over “stuff” The left-over “stuff” formed asteroids, comets, formed asteroids, comets, meteors, dwarf planets, meteors, dwarf planets, etc…etc…

The Solar SystemThe Solar System(distance not to scale)(distance not to scale)

EarthEarth• Around 4.6 billion years Around 4.6 billion years

ago, at a distance of ago, at a distance of about 93 million miles, about 93 million miles, the Earth formed from the Earth formed from the heavier elements the heavier elements floating around in floating around in space… such as iron, space… such as iron, nickel, silicon and nickel, silicon and oxygen.oxygen.

• This material collected, This material collected, forming a sphere about forming a sphere about 8,000 miles in diameter. 8,000 miles in diameter. In the beginning, the In the beginning, the Earth was a giant ball Earth was a giant ball of…of…

“ “liquid hot magma”liquid hot magma”..

The CoreThe Core• Heavier elements like Heavier elements like

Iron and Nickel Iron and Nickel compressed to form compressed to form the core, while lighter the core, while lighter elements like oxygen elements like oxygen and silicon “floated” and silicon “floated” to the surface to to the surface to create the rocky crust create the rocky crust (rocks are largely (rocks are largely composed of oxygen composed of oxygen and silicon)and silicon)

• This Iron/Nickel core This Iron/Nickel core spins in the molten spins in the molten material beneath the material beneath the surface, generating a surface, generating a magnetic field around magnetic field around the planet called the the planet called the “Magnetosphere” “Magnetosphere”

Earth Continued…Earth Continued…

• But space is cold and the But space is cold and the Earth began to cool. As it Earth began to cool. As it cooled, the outer layer cooled, the outer layer solidified and formed a thin solidified and formed a thin shell of rock we call the shell of rock we call the surface (thinner than the surface (thinner than the shell of an egg, in respect). shell of an egg, in respect).

• Inside, the magma was still Inside, the magma was still really hot, and that heat really hot, and that heat began to escape through began to escape through holes in the crust, creating holes in the crust, creating volcanoesvolcanoes

• For million and millions of For million and millions of years, volcanoes spewed gas years, volcanoes spewed gas and water vapor into space.and water vapor into space.

Earth Continued…Earth Continued…

• Earth’s gravity was strong Earth’s gravity was strong enough to hold these gases enough to hold these gases close to the surface, close to the surface, eventually creating a blanket eventually creating a blanket of gas surrounding our planet of gas surrounding our planet that we call the atmosphere. that we call the atmosphere.

• As more and more water As more and more water vapor was added, clouds and vapor was added, clouds and weather began to form. weather began to form. Eventually enough rain fell to Eventually enough rain fell to fill all of Earth’s low spots, fill all of Earth’s low spots, creating our oceans.creating our oceans.

• Comets may have also Comets may have also helped to add water to our helped to add water to our oceans.oceans.

• Without this blanket of gas, Without this blanket of gas, life on Earth COULD NOT life on Earth COULD NOT EXIST. EXIST.

Earth’s Internal Heat SourceEarth’s Internal Heat Source

• While the core of While the core of the planet has been the planet has been cooling for billions cooling for billions of years, it is of years, it is cooling slowly.cooling slowly.

• The decay of The decay of radioactive radioactive elements (and the elements (and the heat that they heat that they produce) is the produce) is the mainmain source of source of internal heat/energy internal heat/energy