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Earth impact

  1. Jul 13, 2004 #1
    Is it true I have more chance of expiring from a global cotastrophe in the next 50 years as a result of a terestrial object from outer space colliding with Earth than winning the powerball with a $1 ticket.
     
  2. jcsd
  3. Jul 14, 2004 #2

    Chronos

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    The odds are favorable. Catastrophic global events [according to geologists] only occur about one time every 50-100 million years. Keep buying those lotto tickets.
     
  4. Jul 16, 2004 #3

    Phobos

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    actually...

    1 YEAR PROBABILITY FOR ALL AMERICANS...

    1 in 5,200,000 - - win Megabucks (1 play) (Massachusetts Lottery Commission, 2001)
    1 in 600,000 - - 1 km asteroid or larger hits Earth – causes global havoc & kills billions (reported in Scientific American Nov 2003)
    1 in 100,000 - - win Megabucks (play once a week) (M.L.C.)
    1 in 5,000 - - small asteroid destroys a city/causes major tsunami (Sci. Am.)

    city-destroying asteroids hit once every 200-300 years...the last one was in 1908 (Tunguska) which fortunately hit in a remote region of Siberia

    the impact magnitude that Chronos mentions (like the K-T event) does occur once every 100 million years, but it take a lot less than that to cause a global catastrophe
     
    Last edited: Jul 16, 2004
  5. Jul 16, 2004 #4

    selfAdjoint

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    In recent years I haven't had much respect for Scientific American, these silly probabilities lower it still more. 1 in 600,00 for a global catastophe asteroid hit means we should see something of that magnitude every 600,000 years, almost twice a megayear. At that rate the earth would be covered with big craters, erosion and mountain building wouldn't have had time to diguise them.
     
  6. Jul 19, 2004 #5

    Phobos

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    Certainly the odds are tricky to calculate, but the order of magnitude matches other sources...

    A September 2000 United Kingdom report on Potentially Hazardous Near Earth Objects says that a 1.7 km object hits the Earth once every 250,000 years. The results are:
    recently reported by Reuters...
    and from the Feb 2004 planetary defense conference in Orange County...
    This may be a biased source (from the UK government folks trying to study the asteroid threat), but interesting nonetheless...
     
  7. Jul 19, 2004 #6

    Phobos

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    any insights into this? (mountain building/erosion rates, number of visible craters now, etc.)
     
  8. Jul 19, 2004 #7

    selfAdjoint

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    Well that's 5 KT level events in the last 3 million years (give or take 1 for distribution). Great 5 wipe outs of species, and still visible craters miles across, like Chixalub (sp?). I give you no recorded disaster like this to the Pleistocene fauna, and no such craters. Unless you say they all fell on the glaciers, so that "absence of evidence is not evidence of absence".
     
  9. Jul 19, 2004 #8
    ok there is no question that we do face risk from a major impact whether it be from small area destruction to widespread global destruction. The question is do we have the facilities to guage fair notice as to whether an object is going to collide with the Earth and can we ultimately prevent it from striking our planet.
     
  10. Jul 20, 2004 #9

    Chronos

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    The chances of seeing it coming more than a week or so in advance are almost zero. The chance of us being able to do anything about it are about the same. Fortunately, the odds of it happening are pretty low. In the early solar system, calamity was a frequent occurence. These days, massive orbital bodies are pretty much set in their ways. Most collision courses have already ran their routes. We owe a big thanks to Jupiter for that.
     
  11. Jul 20, 2004 #10

    Phobos

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    Ok, there's the confusion. The KT event was from a 10 km asteroid (or comet), not a 1 km asteroid. That UK report estimates the frequency of a 10 km object impact more on the order of once every 100 million years.
     
  12. Jul 20, 2004 #11

    Phobos

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    As Chronos said, it's tough, but not impossible.

    We have the technology to find the asteroids. Now we just need to devote the time & money to do so. We (humans) are spending a few million dollars per year looking for the larger (> 1 km) near-earth asteroids. Check recent news stories & you'll see that some scientists & politicians are asking for more funding on this.

    We also have the technology to deflect asteroids...given enough lead time. If we detect an incoming object with 1 weeks notice, then forget it. Duck and cover. If we detect it with a few years notice, well then we have a chance.
     
  13. Jul 20, 2004 #12
    oh dear its as bad as that huh

    ok lets say an asteroid with say a diameter of 2km hit 'say for sakes of arguments' a sparse area in Arizona what effect would it have ?
     
  14. Jul 21, 2004 #13

    Phobos

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    Well, it can get complex, but simply put, the more lead time, the better off we will be. Smaller objects require less lead time than more massive ones. And then there's the type of asteroid/comet...deflecting a solid rock has different challenges than deflecting a gravel heap.

    But it's at least good news that astronomers are looking for near earth asteroids & comets and that NASA (and others) are investigating ways to deflect them. We may not be doing a lot, but at least we're not ignoring it. And the odds are low for anything hitting in the near-future, so we hopefully have plenty of time to deal with this.

    see my previous post (quoted text for a 1.7 km object impact)
     
    Last edited: Jul 21, 2004
  15. Jul 21, 2004 #14

    Njorl

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    I'm sure if I won the lotto, I'd get hit with an asteroid the same day.

    That reminds me of a joke:


    Everyday a guy stops in his local church and prays, "Please God, let me win the lottery. Please, please PLEASE!"

    After a year of this, with no results, the lights of the church dim, a heavenly beam of light falls upon him, and a booming voices states, "WOULD YOU AT LEAST MEET ME HALF-WAY AND BUY A DAMN TICKET!"

    Njorl
     
  16. Jul 21, 2004 #15

    Nereid

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    This site provides a good overview of the general issue (the only thing it doesn't really cover is the risks from 'new' comets), and has an up-to-date page with links to news items. Note that only one PHA is rated above zero on the Torino scale.
     
  17. Jul 22, 2004 #16

    Chronos

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    I haven't won the lottery yet. So my guess is the odds are pretty good that the people who have are pretty safe for next few million years. The early solar system was a very violent place. Many collisions, moon formation and an unstable sun trying to reach thermal equilibrium. My best guess is we now live in a more stable system than the past. Most orbital bodies have found stable orbits and prefer to remain there. I would, however, like to see a timeline for crater formation on the moon to support that theory.
     
    Last edited: Jul 22, 2004
  18. Jul 22, 2004 #17

    russ_watters

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    HERE is an interesting site:

     
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