169 FAQs about the Earth (The Astronomy Cafe)

View your home from space TerraServer , Your Longitude and Latitude

Basic statistics and facts: A NASA Data Book , NASA/NSSDC FactSheet

Today's earthquake live: US Geological Service Event List

Today's space weather forecast: NOAA Space Environment Center

Satellite Data Archive NASA CDAWeb , Dynamics Explorer

Geophysical data archive: National Geophysical Data Center , Real-time solar wind data

Introductory geophysics papers America Geophysics Union

When does Spring arrive?: Table of dates and times

 Back to the Astronomy Cafe - 365 of the most popular questions since 1996. Over 1 million page requests!

Beginner:
  1. [Updated]Did the Earth rotate faster in the past?
  2. [Updated]What is the current distance of the Earth from the Sun?
  3. [Updated]Will the Earth ever fall into the Sun?
  4. [Updated]Are we really alone in the universe?
  5. [Updated]How and why does Earth spin?
  6. [Updated]What is the speed of Earths rotation?
  7. [Updated]What does Earths core really look like?
  8. [Updated]Are there millions of mini-comets entering the atmosphere?
  9. [Updated]What does Earth look like from far away?
  10. [Updated]What are the 10 different ways Earth can come to an end?
  11. [Updated]When will the next Ice Age arrive?
  12. [Updated]Has there been any new research on the Tunguska Event in 1908?
  13. [Updated]What is the latest about the meteors that struck Greenland, Canada and Texas?
  14. Will Earth ever stop spinning?
  15. [Updated]Is there any truth to the idea that Earth is only 6,000 years old?
  16. [Updated]Where does the atmosphere end and space begin?
  17. [Updated]Are there any alternative theories about what causes the seasons on the Earth?
  18. [Updated]Does the Earth wobble as it spins?
  19. Where can I get a picture of the Earth and Moon as seen from millions of miles away?
  20. What would happen if the Earth stopped spinning?
  21. If the Earth stopped spinning would gravity stop?
  22. What will happen to the Earth when there is no sun?
  23. Where does oil come from?
  24. If I could float above the ground, would the Earth rotate underneath me?
  25. What would happen if you traveled through an aurora?
  26. On which day of the year is the Earth closest to the Sun?
  27. Why are there more than 12 hours of daylight on the Equinoxes?
  28. Can you slow Earth's rotation artificially?
  29. How much would we have weighed on Earth when its day was only 18 hours long?
  30. Has the Earth's rotation ever speeded up in the past?
  31. Where does the atmosphere end and outer space begin?
  32. What is the mass of the Earth?
  33. How quickly does the Earth move through space?
  34. What is the distance from the Sun to the Earth for each month of the year?
  35. How do you actually prove the Earth is not at the center of the solar system?
  36. When the Earth's magnetic field reverses, does its rotation also switch?
  37. Are auroras seen on other planets?
  38. Can you hear an aurora?
  39. How often are aurorae seen in the continental United States?
  40. What are some of the early theories about auroras?
  41. How long have auroras been observed?
  42. Is there a greater risk for solar radiation when taking the polar route by jet plane?
  43. Is it true that organic matter cannot pass through the van Allen radiation belts?
  44. Did the Earth gain a new van Allen radiation belt in 1998?
  45. What is the strongest magnetic field ever known?
  46. Do animals really use magnetism in any interesting way to navigate?
  47. Do magnets loose their magnetism in space when they are outside the earth's magnetosphere?
  48. Is there a monument to the Northern Lights somewhere?
  49. How much power do aurora produce and can we use it?
  50. When do auroras occur?
  51. What effects do auroras have on the Earth?
  52. How hot do auroras get?
  53. Did the asteroid that hit the Earth 65 million years ago affect the Earth's orbit?
  54. Could intelligent life have existed on Earth a billion years ago?
  55. Is the Earth really shrinking?
  56. How do you think the Earth will finally come to an end?
  57. How long will the Earth remain habitable?
  58. How do you account for life being so common, but no aliens visiting us here on Earth?
  59. Why haven't all chimps become humans, and why are there no Cro-Magnon people alive today if evolution is true?
  60. Are there more stars in the sky in the north or south hemispheres?
  61. How did the Earth get its name?
  62. Do planetary conjunctions have any effect on the Earth?
  63. Exactly how round is the Earth?
  64. How much of the earth's heat is produced by the Sun and internally?
  65. Has human activity altered the mass of the Earth?
  66. What did the Earth look like as it was forming?
  67. Do you weight differently at the North Pole than what you do at the equator?
  68. Exactly when is the earth nearest the sun?
  69. At what altitude would the Earth atmosphere have the same pressure as on Mars?
  70. Can you say more about the new moonlet discovered in orbit around the earth in 1997?
  71. What is the Earth's average temperature?
  72. How can I find out my exact geographic location?

Intermediate:
  1. [Updated]If the Earth left the Sun's orbit, would we be able to tell immediately?
  2. [Updated]Why does the earliest sunset occur almost 2 weeks before the December solstice?
  3. [Updated]Why doesn't the longest night of the year have the earliest sunset or the latest sunrise?
  4. [Updated]If the day is 23 hours and 56 minutes long and we use 24-hour clocks, where do the extra 4 minutes go?
  5. [Updated]Was the tilt of the Earth's axis ever larger than 23 1/2 degrees in the past?
  6. [Updated]Has El Nino really slowed down the rotation of the Earth?
  7. [Updated]Why is the sky blue?
  8. [Updated]Are there differences in gravity from one place on the Earth to another?
  9. [Updated]How is the Earth-Sun distance determined?
  10. [Updated]Is the Earth about to reverse its magnetic field?
  11. [Updated]How are auroras produced?
  12. [Updated]If auroras didn't exist how would the Earth be affected?
  13. [Updated]How much mass does the Earth gain from the solar wind?
  14. [Updated]What do we know about Earth's ancient magnetic field?
  15. [Updated]What is the maximum and minimum distance for the Earth that is compatible with life?
  16. [Updated]What is your opinion about how life started on the Earth?
  17. [Updated]How did the Earth's atmosphere get to be so rich in nitrogen and not carbon dioxide?
  18. [Updated]If the Moon vanished, what would happen to the Earth?
  19. [Updated]Does the motion of the Earth around its barycenter cause the core of the Earth to slosh around?
  20. What is the South Atlantic Anomaly?
  21. What would happen if the magnetic field of the Earth suddenly changed?
  22. What effects do sunspots have on the Earth?
  23. What conditions are required for starting life on Earth?
  24. What would happen if the rotation axis of the Earth suddenly changes?
  25. What would happen to your weight if you traveled to the center of the Earth?
  26. If the Sun mysteriously vanished, what would happen to the Earth?
  27. What would happen if the Earth were suddenly stopped in its orbit?
  28. If the Sun suddenly became a black hole, what would happen to the Earth's orbit?
  29. By how much does the axis of the Earth shift when it wobbles?
  30. What kinds of things cause the Earth to wobble?
  31. Why isn't the length of day symmetric about the noon hour?
  32. How can I find the Sidereal Time for my location?
  33. Why do we have to add an extra day in February every 4 years?
  34. What are the dates in March for equal day/night durations from pole to pole?
  35. Do the perihelion and aphelion times for the Earth correspond to the solstice dates?
  36. Why does the first day of summer arrive on December 1 and not December 21 in the southern hemisphere?
  37. Why is the tilt of the Earth's axis 23 1/2 degrees?
  38. Does the rotation of the Earth affect the way water goes down a drain in the North and South Hemispheres?
  39. How old is the Earth?
  40. Is the Earth's pole shifting?
  41. How is the mass of the Earth determined?
  42. If the universe is mostly hydrogen and helium, why isn't the Earth composed the same way?
  43. Is the Earth's atmosphere thicker at the equator due to rotation?
  44. Where can I get info about the amount of oxygen in the atmosphere at various altitudes?
  45. What are 'red lightning' or 'sprites' seen in thunderstorms?
  46. What causes auroras to have different colors?
  47. Is the Earth's magnetic field changing?
  48. Why don't auroras happen near the equator?
  49. How do auroras affect the Earth?
  50. Do aurora give off heat?
  51. Will there be a 'restructuring' of the Earth's magnetic field in the year 2013 that will end the Earth?
  52. Can you store and extract energy from a magnetic field?
  53. Does Earth's magnetic field or solar activity influence the El Nino cycle?
  54. Why does the magnetic pole of the Earth flip?
  55. Who discovered the reversal of the Earth's magnetic field?
  56. Can aurora or the Earth's magnetic field be harnessed to make energy?
  57. How can you artificially create aurora?
  58. I recently heard a high-pitched hum while watching an aurora from British Columbia, was I imagining it?
  59. What does the solar activity cycle have to do with auroral activity?
  60. What happened to the carbon dioxide in the Earth's early atmosphere?
  61. Why did the dinosaurs have to go extinct before humans could evolve?
  62. What effect did the Moon have on the Earth 900 million years ago when it was 21,250 miles closer?
  63. Does the presence of oxygen in an atmosphere always mean that life must exist there?
  64. What causes the 'sprites' seen in certain weather phenomena?
  65. What is the 'Tree of Life' and how many species of life are there on Earth?
  66. Why does the wavelength response of the human eye match the atmospheric transmission window in the visual range so well?
  67. Can the Earth be destroyed by a neutrino belt or a photon storm?
  68. What aspects of astronomy influence the weather?
  69. What is the ionosphere composed of?
  70. Where are the Van Allen radiation belts and are they important to life?
  71. Exactly when is the earth nearest the sun?
  72. What is the maximum mass of an object that can be in geosynchronous orbit around the Earth?

Advanced:

  1. If the Sun stopped shining, how long would the Earth cool to Absolute Zero in a few days?
  2. Do the precession of the equinoxes, and the Earth's orbital eccentricity affect weather?
  3. Will the equinoxes and solstices switch places in 13,000 years because of the precession of the Earth's rotation axis?
  4. Can you explain the various cycles produced by the earth's orbit/rotation?
  5. What things influence the wobble of the earth's axis?
  6. How much energy would it take to explode the Earth?
  7. How do you actually prove the Earth is not at the center of the solar system?
  8. Is there any gravity at the center of the Earth?
  9. How does lightning work?
  10. Where did the Earth's second atmosphere of methane and ammonia come from?
  11. What was the atmosphere of the Earth like after the sun went through the T-Tauri stage?
  12. Why are the atmospheres of Venus and Earth so different?
  13. Does the reversal of the Sun's magnetic field have any effect on the Earth?
  14. Why does the Earth have radiation belts?
  15. Does the Earth have more than two magnetic poles?
  16. Is there a relationship between Earth's rotation and its magnetic field?
  17. What is a Schumann Resonance?

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