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A depiction of the earth in orbit about the sun, also showing the orbits of: mercury, venus, and mars.

In science, earth (TR:835) (LH:25) (TL:860|#29) is the planet on which humans reside, located between the orbits of Venus and Mars, and the third planet closest to the sun.


The following (see: large) shows the history of earth, with respect to continental drift events, the origin of animate things, the five main mass extinctions:[1]

History of earth 1.jpg


The following shows the main periods or eras, according to fossil record, of the earth; wherein, the first human, as distinct species, formed 150K years ago, in the location of the East African Rift Valle, during the Pleistocene era, and the homo-lineage, e.g. homo habilis (2.4M) and homo erectus (1.8M), forming (see: evolution timeline)[2] during the Pliocene era, branching off from the ape branch of evolution, in respect to last common ancestor, about 5M years ago:[3]

Earth (periods).png


The following are quotes:

“At the macroscopic level the earth is a thermodynamic entity. Life is sustained on it because of the temperature gradient maintained by the net energy balance between the energy that comes from the sun and the energy that leaves the earth. At the microscopic level, i.e. the level of the individual person or animal, living organisms are also thermodynamic structures exhibiting energy exchanges between themselves and the environment.”
— Nigel Mason (2001), Introduction to Environmental Physics (pg. 17) [4]

End matter


  1. (a) Reader, John. (1986). The Rise of Life. Roxby.
    (b) Lutgens, Fredrick K. (2006). Essentials of Geology. Pearson.
    (c) Ledo, W.; Martinez, J.D.; Ramos, C.; Saab, Z. (2013). “History of Life: as We Know It” (image). Pacific Rubiales Energy Corp.
  2. Evolution timeline – Hmolpedia 2020.
  3. Anon. (2017). “Lecture 10: History of Life on Earth”, Evolution and Biodiversity, BIL 160, University of Miami.
  4. Mason, Nigel; Hughes, Peter; and McMullan, Randall. (2001). Introduction to Environmental Physics (ch. 2: The Human Environment, pgs. 17-55). Taylor and Francis.

External links

  • Earth – Hmolpedia 2020.
Theta Delta ics T2.jpg