The Origin of the Universe

Unit: Life on EarthTopic 1: Understanding our UniverseBiology in Focus, Preliminary CourseGlenda Childrawi and Stephanie HollisIntroduction In order to fully understand life on Earth, we first must first understand a little bit about the formation of the universe, our solar system and ultimately our planet Earth. You would have studies this in year 9 and 10 but well quickly review now.

map.gsfc.nasa.govThe UniverseThe universe includes all of space and all of the known matter and energy. This includes millions of galaxies and the stars within. Galaxies can contain up to 100000 million stars!!

Where did all this come from???

The UniverseScientist currently believe that the Universe started as a Big Bang and is still expanding away from a central group of galaxies. They believe happened between 15-20 billion years ago (BYA).

The UniverseGalaxies are the largest structures in the Universe. They are made from stars, gas and dust and are named according to shape. What galaxy do we live in?

The UniverseLooking at the night sky, you can see the Milky Way. Its the part of the sky most densely populated by bright objects. This band of stars is the disc of our spiral galaxy.

The UniverseA solar system lies within a galaxy and is composed of planets, asteroids, comets and other objects that orbit a star or stars.

The UniverseA planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity.

The Formation of our Solar SystemThe creation of Earth is interlinked with the creation of our solar system. They began forming at the same time as a result of the same forces about 4.6 billion Years ago.

The Formation of our Solar SystemA large cloud of dust and gas (nebula) began to collapse onto itself. It is believed that this collapse may have been triggered by a shockwave from a supernova nearby. Video

Nebula Supernova

The Formation of our Solar SystemAs the pressure caused by the collapse increased, the central sphere became very hot and started to glow forming a protostar. A wide disk formed around its equator.

The Formation of our Solar SystemDue to gravity the nebula continued to collapse into a individual globular bodies and began to rotate. The Law of Conservation of Angular Momentum helps explain this phenomenon.

The Formation of our Solar SystemDebris within the disk began to gather into large clumps by the process of accretion (The gathering together of small bodies into larger ones by gravity). This process is responsible for the initial formation of the planets.

(Well come back to this in a second!)

The Formation of our Solar SystemDepending on how close the planetesimals were to the sun, different materials would not be able to condense because of the heat and would be blown away by solar radiation.

The Formation of our Solar SystemThis would explain the rocky inner planets and gaseous outer planets of our solar system.

Back to EarthThe first billion years of Earths life the planet was a relatively cool and homogenous (the same, uniform) mass of silicon compounds, iron and magnesium. These materials would have been distributed evenly throughout Earths interior.

Back to Earth As planet Earth grew in size and mass its gravity also increased attracting more and more meteorites and other objects floating around in the early formation of our solar system.

Accretion Under the force of gravity, the materials began to build upon each other increasing temperature and pressure. As temperature increased, rocks became molten and the process of differentiation began.

Earths Interior The Early differentiation of materials is preserved in the Earths layers today. But how do we know this? Scientists havent been able to drill through the Earths crust..

Earths Interior Scientists have been able to make inferences about Earths interior by studying the way earthquake waves (seismic waves) travel through Earths interior and by studying meteorites that have preserved the original ingredients of the solar system.

Earths Interior The internal structure of materials within the Earth is layered according to variations in density. The densest materials sink to the centre and form the core while the less dense materials float to the surface and form the crust.

Earths Interior Iron and nickel are the densest of the materials found on Earth and are therefore believed to be the main elements of the core.

Earths Interior Pyroxene and olivine are less dense and can be found in the layer above the core.

Earths Interior Granite and sandstone are the least dense and are found above the other two layers and form the outer layers which includes the crust.

HomeworkNone! Enjoy the free time!