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← Adventures of an asteroid hunter

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Showing Revision 12 created 03/14/2017 by Brian Greene.

  1. I am holding something remarkably old.
  2. It is older than any human artifact,
  3. older than life on Earth,
  4. older than the continents
    and the oceans between them.
  5. This was formed
    over four billion years ago
  6. in the earliest days of the solar system
  7. while the planets were still forming.
  8. This rusty lump of nickel and iron
    may not appear special,
  9. but when it is cut open ...
  10. you can see that it is different
    from earthly metals.
  11. This pattern reveals metallic crystals
    that can only form out in space
  12. where molten metal
    can cool extremely slowly,
  13. a few degrees every million years.
  14. This was once part
    of a much larger object,
  15. one of millions left over
    after the planets formed.
  16. We call these objects asteroids.
  17. Asteroids are our oldest
    and most numerous cosmic neighbors.

  18. This graphic shows near-Earth asteroids
    orbiting around the Sun,
  19. shown in yellow,
  20. and swinging close to the Earth's orbit,
  21. shown in blue.
  22. The sizes of the Earth, Sun and asteroids
    have been greatly exaggerated
  23. so you can see them clearly.
  24. Teams of scientists across the globe
    are searching for these objects,
  25. discovering new ones every day,
  26. steadily mapping near-Earth space.
  27. Much of this work is funded by NASA.
  28. I think of the search for these asteroids
    as a giant public works project,
  29. but instead of building a highway,
    we're charting outer space,
  30. building an archive
    that will last for generations.
  31. These are the 1,556 near-Earth asteroids
    discovered just last year.

  32. And these are all of the known
    near-Earth asteroids,
  33. which at last count was 13,733.
  34. Each one has been imaged, cataloged
  35. and had its path
    around the Sun determined.
  36. Although it varies
    from asteroid to asteroid,
  37. the paths of most asteroids
    can be predicted for dozens of years.
  38. And the paths of some asteroids can be
    predicted with incredible precision.
  39. For example, scientists
    at the Jet Propulsion Laboratory
  40. predicted where the asteroid Toutatis
    was going to be four years in advance
  41. to within 30 kilometers.
  42. In those four years,
  43. Toutatis traveled 8.5 billion kilometers.
  44. That's a fractional precision
  45. of 0.000000004.
  46. (Laughter)

  47. Now, the reason I have
    this beautiful asteroid fragment

  48. is because, like all neighbors,
  49. asteroids sometimes drop by unexpectedly.
  50. (Laughter)

  51. Three years ago today,

  52. a small asteroid exploded
    over the city of Chelyabinsk, Russia.
  53. That object was about 19 meters across,
  54. or about as big as a convenience store.
  55. Objects of this size hit the Earth
    every 50 years or so.
  56. 66 million years ago,

  57. a much larger object hit the Earth,
  58. causing a massive extinction.
  59. 75 percent of plant
    and animal species were lost,
  60. including, sadly, the dinosaurs.
  61. That object was
    about 10 kilometers across,
  62. and 10 kilometers is roughly
    the cruising altitude of a 747 jet.
  63. So the next time you're in an airplane,
  64. snag a window seat, look out
    and imagine a rock so enormous
  65. that resting on the ground,
  66. it just grazes your wingtip.
  67. It's so wide that it takes your plane
    one full minute to fly past it.
  68. That's the size of the asteroid
    that hit the Earth.
  69. It has only been within my lifetime

  70. that asteroids have been considered
    a credible threat to our planet.
  71. And since then, there's been
    a focused effort underway
  72. to discover and catalog these objects.
  73. I am lucky enough
    to be part of this effort.
  74. I'm part of a team of scientists
    that use NASA's NEOWISE telescope.
  75. Now, NEOWISE was not
    designed to find asteroids.
  76. It was designed to orbit the earth
    and look far beyond our solar system
  77. to seek out the coldest stars
    and the most luminous galaxies.
  78. And it did that very well
    for its designed lifetime of seven months.
  79. But today, six years later,
    it's still going.
  80. We've repurposed it
    to discover and study asteroids.
  81. And although it's
    a wonderful little space robot,
  82. these days it's kind of like a used car.
  83. The cryogen that used to refrigerate
    its sensors is long gone,
  84. so we joke that
    its air-conditioning is broken.
  85. It's got 920 million miles
    on the odometer,
  86. but it still runs great
  87. and reliably takes a photograph
    of the sky every 11 seconds.
  88. It's taken 23 photos
    since I began speaking to you.
  89. One of the reasons NEOWISE is so valuable

  90. is that it sees the sky
    in the thermal infrared.
  91. That means that instead of seeing
    the sunlight that asteroids reflect,
  92. NEOWISE sees the heat that they emit.
  93. This is a vital capability
    since some asteroids are as dark as coal
  94. and can be difficult or impossible
    to spot with other telescopes.
  95. But all asteroids, light or dark,
    shine brightly for NEOWISE.
  96. Astronomers are using
    every technique at their disposal

  97. to discover and study asteroids.
  98. In 2010, a historic milestone was reached.
  99. The community, together, discovered
    over 90 percent of asteroids
  100. bigger than one kilometer across --
  101. objects capable
    of massive destruction to Earth.
  102. But the job's not done yet.
  103. An object 140 meters or bigger
    could decimate a medium-sized country.
  104. So far, we've only found
    25 percent of those.
  105. We must keep searching the sky
    for near-Earth asteroids.

  106. We are the only species
    able to understand calculus
  107. or build telescopes.
  108. We know how to find these objects.
  109. This is our responsibility.
  110. If we found a hazardous asteroid
    with significant early warning,
  111. we could nudge it out of the way.
  112. Unlike earthquakes, hurricanes
    or volcanic eruptions,
  113. an asteroid impact
    can be precisely predicted
  114. and prevented.
  115. What we need to do now
    is map near-Earth space.
  116. We must keep searching the sky.
  117. Thank you.

  118. (Applause)