Day dot

The universe is a massive 13.7billion years old. In the first few minutes of the formation of the universe was the big bang, an explosion that produced most of the Earth's Hydrogen and Helium we have today! The Stella fusion in stars makes other light elements through their fusion and the heavier elements were created during supernova nucleosynthesis events.

With all these explosions in the early times of the universe it was a whole heap of dust and particles that eventually formed our solar system through the Nebular Hypothesis. The theory is that a rotating disk of dust formed and the concentrated centre became our sun. As the dust and particles started to collide when rotating around the sun they accreted into planetesimals. The heavier elements were brought to the centre by the force of gravity and accreted to form the first four planets, Mercury, Venus, Mars and Earth. These planets are the terrestrial planets and are characterized by a metallic core surrounded by a rocky shell. An asteroid belt separates the terrestrial planets and the juvian planets. The juvian planets were formed by the lighter elements and these are, Jupiter, Saturn, Uranus and Neptune. They are made up of volatile gasses, not unlike our sun, however the internal pressure of these planets is too low for nucleosynthesis to occur.

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Now let’s take a focus on our planet, Earth, which was formed as described above approximately 4.6 billion years ago. Early earth was bombarded with many asteroids which provided us with the iron-nickel rich core we have today. But if they hit the surface of this rocky planet, how did the iron nickel end up in the core? At the time when these asteroids hit the Earth was, essentially, one hot mess! This was called Hadean Earth. At this time the rock was still molten and the stratification of the Earth was able to occur. The heaviest elements (like iron) simply sank to the Earth's centre. These iron-rich minerals in the core explain Earth’s magnetic field, which has reversals every so often, which is most likely due to the currents of the iron rich liquid changing. The magnetic field is responsible for deflecting most of the solar wind from around the Earth, and therefore allows life on Earth! 

Early Earth had a faint young sun and nowhere near as much solar radiation was put out as there is today. The Earth would have frozen over if it weren't for the very rich CO2 atmosphere that it had causing a greenhouse and the lack of vegetation to uptake CO2. Once Earth’s crust solidified, around 4.4 billion years ago, it was surprisingly similar to what the Earth looks like today (geologically so there were oceans and continents, plants and animals had not arrived yet - thats for a later blog!). However there was a lack of oxygen and a CO2 rich atmosphere, but we believe that the ocean mass was approximately the same. How do we know this? Zircons! If dogs are a mans best friend, Zircons must be a Geologists best friend because they will always be there for you! From jack hills in WA zircon crystals have been found and dated back to 4.38 billion years ago. Zircon has uranium in its lattice which decays to lead at a precise age and it is because of this long time span that scientists are able to date rocks with Zircon present. 

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So there you have it, the universe was created around 13.7 billion years ago, and Earth about 4.6 billion years ago... feeling youthful? 

Thanks for reading, 

Rach