Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Dangerous universe


Published on

Talk for public setting about various cosmic threats to life on Earth.

Published in: Education, Technology
  • Hi there! Get Your Professional Job-Winning Resume Here - Check our website!
    Are you sure you want to  Yes  No
    Your message goes here
  • Be the first to like this

Dangerous universe

  1. 1. Our Dangerous Universe! Dr. Brian Thomas Washburn University Topeka, KS Woodcut c. 1668 (comet) NASA image - GRB event NASA image – Solar Flare
  2. 2. We live in a BIG Universe… <ul><li>Our planet circles a star </li></ul><ul><ul><li>1 million times larger </li></ul></ul><ul><li>That star is one of 400 billion stars in the Milky Way Galaxy </li></ul><ul><ul><li>10 billion times larger than the solar system </li></ul></ul><ul><li>Our Galaxy is one of at least 100’s of billions in the universe </li></ul>
  3. 3. Relative Sizes
  4. 4. Our Galaxy in the Universe
  5. 5. Our Galaxy in the Universe
  6. 6. It’s BIG and DANGEROUS! <ul><li>We know of at least 5 mass extinctions in the Earth’s history </li></ul><ul><ul><li>At least one of these was caused by a cosmic event. </li></ul></ul>
  7. 7. Ancient History
  8. 8. Comets and Asteroids <ul><li>Have killed before and will again </li></ul><ul><ul><li>How often? Impossible to say (random), but maybe every 100 million years for major event? </li></ul></ul>
  9. 9. 2029 Close Approach <ul><li>April 13, 2029 - asteroid 2004 MN4 will come within 18,600 miles above the ground. </li></ul><ul><ul><li>Geosynchronous satellites orbit at 22,300 miles </li></ul></ul><ul><ul><li>Is 320 meters wide </li></ul></ul><ul><ul><li>Will be visible to the naked eye </li></ul></ul><ul><li> </li></ul>
  10. 10. Other Random Events… <ul><li>In order of increasing energy and decreasing frequency: </li></ul><ul><li>Solar flares </li></ul><ul><ul><li>250 million megatons, a few per decade </li></ul></ul><ul><li>“ Superflares” </li></ul><ul><ul><li>2500 trillion megatons, rate uncertain </li></ul></ul><ul><li>Supernovae </li></ul><ul><ul><li>10 30 megatons, one @ 3 light years per Gy </li></ul></ul><ul><li>Gamma-Ray Bursts </li></ul><ul><ul><li>10 31 megatons, one @ 6500 light years per Gy </li></ul></ul>
  11. 11. Solar Flares <ul><li>Magnetic fields on the Sun get wound up and then “break” </li></ul><ul><ul><li>Releases lots of energy in photons (x-rays, UV) and charge particles </li></ul></ul><ul><ul><li>Can affect the Earth if we’re in the right place. </li></ul></ul><ul><li>1859 flare started fires in telegraph offices, depleted ozone over the poles. </li></ul>
  12. 12. Supernovae <ul><li>2 main types: </li></ul><ul><ul><li>“ Core collapse” of a massive star </li></ul></ul><ul><ul><li>Explosion of a “white dwarf” star </li></ul></ul>
  13. 13. Gamma-Ray Burst <ul><li>2 kinds – “short” and “long” (duration) </li></ul><ul><ul><li>Long: special case of a particular type of core collapse supernova </li></ul></ul><ul><ul><li>Short: maybe neutron stars colliding </li></ul></ul>
  14. 14. What happens on Earth? <ul><li>Gamma-rays, x-rays and cosmic rays (charged particles) enter atmosphere </li></ul><ul><ul><li>All absorbed, but break up molecules </li></ul></ul><ul><ul><li>Chemistry happens and Ozone is depleted </li></ul></ul><ul><ul><ul><li>Like the Antarctic ozone hole today </li></ul></ul></ul><ul><li>Less ozone – more UV </li></ul><ul><ul><li>Sunburns, DNA damage for simpler life </li></ul></ul><ul><li>Nitrogen dioxide “smog” could darken the sky, bad for plants </li></ul>
  15. 15. Astronomy Magazine, Oct. 2005
  16. 16. Global View Relative DNA damage over about 2 years after a GRB
  17. 17. A GRB may have helped start the Late Ordovician Mass Extinction ~ 440 million years ago 2nd largest mass extinction known Primarily shallow-sea life at this time. No known land life.
  18. 18. Guaranteed Bad Days <ul><li>Our Sun is aging. </li></ul><ul><ul><li>Currently ~ 5 billion years old, with a total life span of ~ 10 billion years. </li></ul></ul><ul><li>As it ages, the Sun’s heat output slowly increases. </li></ul><ul><ul><li>Within 2 billion years it will be hot enough to boil off the Earth’s oceans </li></ul></ul><ul><li>Finally, the Sun will expand to a red giant, its surface will reach the Earth. </li></ul>
  19. 19. The Long Run <ul><li>Yes, the universe is out to get you, and eventually it will win. </li></ul><ul><li>As Maynard Keynes said: </li></ul><ul><ul><li>“ In the long run, we’re all dead!” </li></ul></ul>