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Date posted: December 29th 2016

Book Title: Cosmos (notes)


  1. “Nothing exists, but atoms and the void” -  Democritus
  2. “The universe seems neither benign nor hostile, merely indifferent to the concerns of such puny creatures as we” - Carl Sagan
  3. “Knowing a great deal is not the same as being smart; intelligence is not information alone but also judgement, the manner in which information is coordinated and used” - Carl Sagan
  4. “Books are like seeds. They can lie dormant for centuries and then flower in the most unpromising soil” - Carl Sagan
  5. “The world is my country, science is my religion” - Christiaan Huygens
  6. “Today there are hundreds of millions of books out there, the trick is to know which ones to read” - Carl Sagan
  7. “Quick decipherment is very important to avoid the systematic errors which invariably arise from prolonged reflection” Jean Francois Champollion
  8. “War is an illness of childhood” Albert Einstein
  9. “The percent likelihood of a society becoming physically violent if it is physically affectionate to towards its infants and tolerant of premarital sexual behavior is 2 percent” - Carl Sagan
  10. “[Aggression, territoriality, ritual and social hierarchy seem to be results of individuals (or societies) who have been deprived of the pleasures of the body. This is not very clear yet but] – Meanwhile we can each make a personal and non controversial contribution to the future of the world by hugging our infants tenderly” - Carl Sagan

Fun facts to remember

  1. There are a 400 billion stars in the galaxy, and 100 billion galaxies in the universe.
  2. The universe is 13.85 billion years old.
  3. The Earth and the Sun are 4.5 billion years old.
  4. Proxima Centauri is 4.2 light years from Earth.
  5. Alpha Centauri is a group of three stars, two binary stars orbiting each other and Proxima Centauri a little closer to us. The two first ones are 4.3 light years from Earth.
  6. The Sun is 40,000 light years from the center of the galaxy.
  7. Eratosthenes first realized the Earth wasn't flat in 300 BCE.
  8. Life seems to have originated 4 billion years ago.
  9. The Cambrian explosion didn’t happen until 600 million years ago.
  10. The first human-like creatures appeared 10 million years ago.
  11. Homoerectus evolved in Africa and migrated to other continents about 1.3 million years ago.
  12. 65 million years ago the last of the non-avian dinosaurs went extinct.
  13. With our bare eyes we only see 5 planets: Mercury, Venus, Mars, Jupiter, and Saturn.
  14. In Ptolemy’s model there were actually 9 “heavens”, Earth, moon, Mercury, Venus, Sun, Mars, Saturn, Jupiter and Stars
  15. Pythagoreans and later defenders of Ptolemy’s model thought there was a planet (not counting Earth) for each perfect solid. Mercury, Mars, Venus, Jupiter, and Saturn. There are only 5 perfect solids and this is why they got so pissed when Uranus was discovered.
  16. Mars has the most elliptic orbit of all the planets.
  17. The Sun is not located at the center of the orbits but at the focus of the elliptical orbit.
  18. Meteor showers are rock and ice (remnants from the passing of a comet) that burn up as they enter Earth’s atmosphere.
  19. A meteorite is a meteor that has made it through the atmosphere and landed on Earth without disintegrating.
  20. In 1908 a chunk of comet Encke entered Earth’s atmosphere in Siberia. This was called the Tunguska event.
  21. Venus and Uranus are the only planets that rotate counter-clockwise (as seen from above the north pole).
  22. Uranus is laying on its side so it’s rotational axis is on the plane of the orbit.
  23. A day in Venus is longer than a year.
  24. The atmosphere of Venus is around 480°C and its pressure is 90 times higher than Earth.
  25. Mars has a 24 hour and 40 minute day.
  26. Mars has the same surface area as the land on Earth.
  27. Leeuwenhoek was the inventor of the microscope.
  28. The moon landing happened in 1969.
  29. Venera (USSR) went to Venus in ‘75, the Vikings (USA) went to Mars in ‘76, the Voyagers (USA) sailed out in ‘77 and the Pioneers (USA) went to Venus in ‘78. The 70s were the golden decade of space exploration.
  30. A day in Jupiter lasts 9 hours and 56 minutes. In Saturn lasts 10 hours and 42 minutes.
  31. Jupiter’s moons are all in tidal lock, meaning the same side is always pointing towards Jupiter. Just like our moon is with Earth.
  32. Jupiter has an enormous magnetic field possibly because of superconducting metallic Hydrogen in its core.
  33. Thales of Miletus was one of the first Ionian scientists.
  34. Democritus came up with the concept of atom (which is greek for unable to cut). “Nothing exists” he used to say “but atoms and the void”.
  35. Ernest Rutherford discovered the nucleus in 1909.
  36. The number 10^100 was named by Edward Kasner’s nephew as Googol. (Edward was an American mathematician).
  37. Helium was detected in the Sun before it was found on Earth, hence its name from the greek god of the Sun, Helios.
  38. Photons are born in the fusion event in the star’s core, and it takes them millions of years to reach the surface because they collide all over the place with the Sun's atoms
  39. A binary star system composed of a white dwarf and a red giant produces several Nova explosions.
  40. A supernova leaves a neutron star (or pulsar) behind. It also leaves a nebulae behind.
  41. Smaller stars and planets can be born from nebulae.
  42. A small star usually dies by turning into a red giant, then a white dwarf and then a black dwarf.
  43. Andromeda (or M31) is 2.5 million light years away.
  44. The Milky Way rotates every quarter billion years, meaning that throughout its life (13.2 billion years) it has rotated around 52 times.
  45. The sequoia trees are the largest living beings on Earth.
  46. Blue whales are much larger than any dinosaur.
  47. The R-complex is the reptilian part of our brain and it evolved hundreds of millions of years ago.
  48. The Limbic system is the mammalian brain and it evolved tens of millions of years ago.
  49. Mammals characteristically nuzzle, fondle, hug, caress, pet, groom and love their young, behavior essentially unknown among reptiles.
  50. The percent likelihood of a society becoming physically violent if it is physically affectionate to towards its infants and tolerant of premarital sexual behavior is 2 percent.