Cosmology: A Time Trek of the Universe

NASA (National Aeronautics and Space Administration) defines cosmology as “the scientific study of the large scale properties of the universe as a whole” from its birth to its death. Theoretical astrophysicist David Spergel described cosmology as a “historical science” as “when we look out in space, we look back in time”. Astronomy, in contrast deals with individual celestial objects. Most cosmology knowledge is based off observational data and computer simulations. 

Albert Einstein paved the way to cosmology through his Theories of Relativity, whereby to any observer the speed of an object depends on their time frame. If you were in a garden with your running sibling and a plane flew over at the same time, different speeds would be witnessed by you and the plane. Neither of these speeds are less accurate compared to the other but the difference is explained with the varied frames of reference the observer is in.  

This underpinned our understanding of the Big Bang, the expansion of the universe, which is relative to the observers position in the Universe. The Universe originated 13.6 billion years ago and the elementary particles (photons, quarks, neutrinos and electrons) appeared 1/1,000,000 seconds later. Evidence of the Big Bang was shown by the Cosmic Microwave Background (CMB) radiation leftover from the Big Bang. This was found by accident by Arno Penzias and Robert Wilson who were later attributed a Nobel Prize in Physics in 1978. 

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The first full-sky map came from NASA’s Cosmic Background Explorer mission and through this cosmologists learnt about the origins of galaxies. The Big Bang also explains the formation of the first objects summarised in a simplified timeline:

  • 13.7 billion years ago: Big Bang occurred while the first particles formed after milliseconds 
  • 13.4 billion years ago: the first generation of stars were formed
  • 13.2 billion years ago: the second generation of stars were formed with no planets around them yet. The stars began to ignite as the universe expanded 
  • 12.6 billion years ago: Appearance of the first elements CHON (carbon, hydrogen, oxygen and nitrogen) abundant in life at least on planet Earth. Carbon (CO2) and Oxygen (O2) is necessary for water formation (H2O).
  • 11.5 billion years ago: the largest structures in the Universe appeared with the formation of galaxy clusters such as our very own Milky Way galaxy.
  • 4.5 billion years ago: Formation of planets for example our planet Earth where the impacting comets and asteroids created the Earth’s atmosphere 
  • 4 billion years ago: Appearance of key building blocks needed for life (DNA as the basis of hereditary information, amino acids for proteins etc)