143 FAQs about Astrophysics (The Astronomy Cafe)

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

Beginner:

  1. Where can I learn more about anti-matter?
  2. If I point my laser pointer at the Moon, why don't I see a spot?
  3. How does it feel to be weightless?
  4. How do sound waves travel through outer space?
  5. Can gravity be shielded?
  6. Could a marshmallow traveling at the speed of light knock the Earth out of orbit?
  7. How fast is the force of gravity?
  8. Why do things rotate?
  9. How long can a person survive at 95 and 105 degrees F?
  10. Where do the neutrinos go that are made by humans?
  11. On which asteroids could you jump into orbit?
  12. Is the photon that reaches your eye from a distant galaxy the very same one that started its journey across intergalactic space?
  13. How the ding dang was the Astronomical Unit determined?
  14. What is the difference between a gamma-ray and a cosmic ray?
  15. If you took a vacuum cleaner into space, what would happen?
  16. Is there really sound in space?
  17. What is a plasma?
  18. What caused the flag to wave on the Moon during the Apollo 17 mission?
  19. If scientists always seem to be 'proving wrong' the current favorite theory, what is the point of all this research if in the end we never establish anything as being True?
  20. Does light have mass?

Intermediate:

  1. Do anti-particles produce anti-gravity?
  2. What is energy?
  3. How does the photoelectric effect support the idea that light is a particle?
  4. How much of a charge excess would be needed in the universe to produce detectable non-gravitational motions?
  5. Is there only one kind of atom with 106 protons?
  6. Have scientists confirmed the spontaneous creation of matter from the vacuum?
  7. When two laser beams interfere with each other, what happens to the energy?
  8. Do we really know how gravity and magnetism operate?
  9. Does everything in the universe consist of energy?
  10. If the force of gravity were reduced 50 percent, how would this change stars and the universe?
  11. Does time stop at Absolute Zero?
  12. What do absolute space and time mean?
  13. What exactly is the Pauli Principle?
  14. Does light have anything to do with the 5th dimension?
  15. Does gravity produce gravity?
  16. Can gravity be shielded?
  17. Could you give a technical explanation of the 'Slingshot' maneuver?
  18. Do other dimensions exist?
  19. What happens to matter at Absolute Zero?
  20. How are tachyons supposed to work?
  21. What is a boson?
  22. Can elementary particles be split?
  23. How does the gravitational 'slingshot' maneuver work?
  24. Can sub-atomic particles be infinitely compressed?
  25. Is the empty space inside particles the same kind as there is inside atoms?
  26. Where do the neutrinos go that are made by humans?
  27. What would the predicted properties of Element 115 be?
  28. At what distance from the Earth do astronauts experience weightlessness?
  29. Are quarks really considered fundamental particles?
  30. Would a person tan or burn more quickly at high altitude than at sea level?
  31. how does a magnetic field differ from a gravitational field?
  32. What does it mean to travel to another dimension?
  33. Does anti-matter fall faster than normal matter?
  34. Have either amino acids or nucleic acids been detected in interstellar space?
  35. Are quarks really the smallest particles next to electrons?
  36. Is there any evidence that the Laws of Nature change over time, or in different regions of the universe?
  37. Is anti-gravity possible?
  38. How pervasive is the role of chaos in astrophysics?
  39. Is there an Absolute Highest Temperature opposite to Absolute Zero?
  40. Does data ever become obsolete before it can be properly interpreted?
  41. How close can the moon come to the earth before disrupting?
  42. Can radioactive decay be influenced by exposure to oscillating electromagnetic fields?
  43. Can gravity be simulated using electromagnetic forces?
  44. What is the most energetic form of light that astronomers have ever seen?
  45. If a chemical in a candle flame produces different colors, why not stars?
  46. Can astronomers tell whether stars and galaxies are made of anti-matter?
  47. Are there any particles smaller than quarks inside quarks?
  48. Will the laws of physics change in the future?
  49. Why is physics so complicated?
  50. How do you reconcile Zeno's paradox with modern physics?
  51. Why is the sky blue?
  52. What are the different types of electromagnetic radiation?
  53. Can things be infinitely small?
  54. Why was there a slight imbalance between matter and antimatter just after the Big Bang?
  55. What is the cosmological significance of neutrinos having a small, but non-zero, mass?
  56. Is there a connection between the laws of the microcosm and the structure of the universe?
  57. Could our universe be a quark in another, bigger universe?
  58. Does chaos really occur or exist in nature?
  59. Do magnetic fields exist throughout space?
  60. How is a stellar parallax used to determine the distance to stars?
  61. How is it possible for physicists to slow light down to 38 miles/hour?
  62. Is there such a things as 'pure energy'?
  63. What is 'quantum foam'?
  64. Why can't we find 'dark matter' inside the solar system?
  65. How is the vacuum contained in space?
  66. Why do we need a Unified Theory of Everything?
  67. Will Theory of Everything predict exactly what will happen tomorrow?
  68. Are photons, gravitons and neutrinos really massless?
  69. Has the decay of the proton been detected yet?
  70. How would the existence of a 4th neutrino affect cosmology?
  71. What is the 'darkness' that you see between the stars in the sky?
  72. Why does mathematics work so well in understanding the physical world?
  73. What is the coldest temperature recorded in space or in nature?
  74. Exactly what is gravity?
  75. What is hyperspace?
  76. What are the '10 dimensions' that physicists are always talking about?
  77. Is light conducted by space, or does it travel through it?
  78. What are quarks and gluons?
  79. What is anti-matter?
  80. Is there anything that is 'something' that is not matter?
  81. In which part of the electromagnetic spectrum is the sky brightest?
  82. How do scientists define time?
  83. How can one particle emit enough gravitons...or whatever...to affect all other particles in the universe?
  84. Have gravitons been detected yet?
  85. What is time?

Advanced:

  1. Does the physical vacuum produce a pressure that can be measured?
  2. Are all particles and fields just vibrations in an energy field?
  3. What is the substance of gravity?
  4. Why do bodies have gravitational fields?
  5. What is the minimum mass of a cloud that can gravitationally collapse?
  6. How does the size of a crater depend on the size of the meteorite?
  7. Would space be totally empty and non-existent without virtual particles?
  8. What is the Roche Limit and who discovered it?
  9. What is the role of time in the so-called Theory of Everything?
  10. What is the relationship between electromagnetic fields, gravitational fields and space-time?
  11. What is a cosmic string?
  12. How are tachyons supposed to work?
  13. Where does the energy come from that produces virtual particles?
  14. Can events be truly random if cause and effect holds for all physical phenomena?
  15. Can the structure we see in the physical world be simply a projection of how our brains work?
  16. What is infinity?
  17. Since the field around a planet is constant, why does the 'slingshot' effect work?
  18. What exactly is a sub-atomic particles structure like?
  19. So, is Schroedinger's cat alive or dead?
  20. How is Zeno's Paradox resolved in physics?
  21. How does energy flow in those other dimensions to space-time outside the standard four?
  22. Are quantum uncertainty and the existence of compact dimensions to space-time related?
  23. What is Grand Unification Theory?
  24. Is there a 'smallest possible size' to space beyond which it cannot be further divided?
  25. What is the Everett-Wheeler Theory of quantum mechanics?
  26. How do you calculate centrifugal forces in a rotating space station?
  27. Can electrons really be in two places at once?
  28. How did 'hidden variables' theory get put to rest in quantum mechanics?
  29. Is the blue color of a flame caused by continuum or line emission?
  30. What is the latest on the nature and existence of 'dark matter'?
  31. Could you tell me what the arrows of time are in relation to cosmology?
  32. Can virtual particles still be created in a vacuum where the temperature is absolute zero?
  33. What are the 'infinities' that physicists keep finding in their theories?
  34. What is gravity really like?
  35. Where does gravity actually come from?
  36. What exactly is Zero-Point energy?
  37. What exactly is the Higgs field supposed to be?
  38. What are the main ideas behind superstring theory?
  39. What is the Casimir Effect?
  40. What is hyperspace?
  41. Given that the vacuum is filled with virtual quantum particles, is there really such a thing as Nothingness?

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