Cosmology

 

Hubble eXtreme Deep Field

With a combined 23-day exposure taken by the Hubble Space Telescope over a period of 10 years, the Hubble eXtreme Deep Field is the deepest image of the sky ever obtained, featuring galaxies just half a billion years after the Big Bang (click the image to enlarge)     [Source]

“Where did we come from?” This represents one of the most fundamental questions humankind has had, a topic philosophers and religious peoples have grappled with for millennia. Taking a stab at this question with the scientific method in mind, cosmology not only seeks to study the Universe’s origins, but its evolution and eventual fate as well.

The physics of the Universe can be explained back no further than the first 10-43 of a second (the amount of time it takes light to travel one Planck length) following the Big Bang, which by itself is still pretty impressive. Only before this point does our understanding of physics completely break down, as the four fundamental forces of the Universe would have to have been united during this extremely brief instant. We currently lack a reconciliation of quantum mechanics and general relativity—our models for the Grand Unified Theory (GUT) force (the unity of the three non-gravitational forces) and the force of gravity, respectively—to explain this period known as the “Planck epoch”. Regardless, evidence is beginning to suggest that a theory of quantum gravity is necessary.

Formation of filaments.gif

A simulation depicting the formation of clusters and large-scale filaments in the Universe     [Source]

Cosmology examines large-scale structures in order to understand the dynamics of the Universe as a whole. On a large enough scale, the distribution of ordinary matter in the Universe appears essentially homogeneous (uniformly spread) and isotropic (the same in every direction), a deduction known as the cosmological principle. Along with the principle of equivalence and the principle of relativity (touched upon in the “Special Relativity” page), these three notions are what govern our current understanding of the fundamental nature of the Universe.

Cosmology is filled with several major unsolved problems: dark matter, the accelerated expansion of the Universe, and the anisotropy of the cosmic microwave background each epitomizing prime examples. Part of the extensive mystery is for many, including myself, what makes this field so fascinating!

 


Pages on Cosmology:

  • Olbers’ paradox  (coming soon!)
  • Expansion of the Universe  (coming soon!)
  • The Big Bang  (coming soon!)
  • The Cosmic Microwave Background  (coming soon!)
  • Dark matter  (coming soon!)
  • Dark energy  (coming soon!)