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Constellation Fornax, EXtreme Deep Field.jpgConstellation Fornax, EXtreme Deep Field (cropped).jpg
The Cosmology Portal


The Hubble eXtreme Deep Field (XDF) was completed in September 2012 and shows the farthest galaxies ever photographed. Except for the few stars in the foreground (which are bright and easily recognizable because only they have diffraction spikes), every speck of light in the photo is an individual galaxy, some of them as old as 13.2 billion years; the observable universe is estimated to contain more than 2 trillion galaxies.

Cosmology (from the Greek κόσμος, kosmos "world" and -λογία, -logia "study of") is the study of the origin, evolution, and eventual fate of the universe. Physical cosmology is the scientific study of the universe's origin, its large-scale structures and dynamics, and its ultimate fate, as well as the scientific laws that govern these areas.

The term cosmology was first used in English in 1656 in Thomas Blount's Glossographia, and in 1731 taken up in Latin by German philosopher Christian Wolff, in Cosmologia Generalis.

Religious or mythological cosmology is a body of beliefs based on mythological, religious, and esoteric literature and traditions of creation myths and eschatology.

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In physical cosmology and astronomy, dark energy is an unknown form of energy which permeates all of space and tends to accelerate the expansion of the universe. Dark energy is the most accepted hypothesis to explain the observations since the 1990s indicating that the universe is expanding at an accelerating rate. According to the Planck mission team, and based on the standard model of cosmology, on a mass–energy equivalence basis, the observable universe contains 26.8% dark matter, 68.3% dark energy (for a total of 95.1%) and 4.9% ordinary matter. Again on a mass–energy equivalence basis, the density of dark energy (6.91 × 10−27 kg/m3) is very low: in the solar system, it is estimated only 6 tons of dark energy would be found within the radius of Pluto's orbit. However, it comes to dominate the mass–energy of the universe because it is uniform across space.


Did you know...

  • ... that space is flexible, and has been expanding at a measurable rate since the beginning of time?
  • ... that most of the atoms in our bodies were created in stars through fusion?
  • ... that the Earth isn't flat, but the universe is? Based on Einstein’s Theory of General Relativity, there are three possible shapes that the Universe may take: open, closed, and flat. Once again, measurements by WMAP on the CMBR have revealed a monumental confirmation – the Universe is flat.
  • ... that the average density of visible matter in the universe is about 10−30 g/cm3?
  • ... that the Earth is neither the center of the Universe nor the galaxy, because the universe has no center?
  • ... that considering only the largest structures, the Universe is made up of filaments, voids, superclusters, galaxy groups and clusters? By combining galaxy groups and clusters, we come up with superclusters. Some superclusters in turn form part of walls, which are also parts of filaments.



Edwin Powell Hubble was an American astronomer who played a crucial role in establishing the field of extragalactic astronomy and is generally regarded as one of the most important observational cosmologists of the 20th century. Hubble is known for showing that the recessional velocity of a galaxy increases with its distance from the earth, implying the universe is expanding. Known as "Hubble's law", this relation had been discovered previously by Georges Lemaître, a Belgian priest/astronomer who published his work in a less visible journal. There is still much controversy surrounding the issue, and some argue that it should be referred to as "Lemaître's law", although this change has not taken hold in the astronomy community.

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