Joe: A chance yes, a certainty no. There may be one strike in some centuries and more than one in other centuries, even a string of dry centuries for no apparent reason. The nature of the events are unrelated. There is no convention of Tunguska size objects where they all decide whose turn it is to smack into earth. They don't have calendars. It's a myth imposed by people's expectations. And of course you can sell a lot of papers if you suceed in frightening a lot of people, or in a more modern example, drive up the hit rate on a conspiracy theory website and your advertisers will give you more money. But the truth lies elswhere. DT --- On Thu, 7/23/09, Joe Bauman <josephmbauman@yahoo.com> wrote:
From: Joe Bauman <josephmbauman@yahoo.com> Subject: Re: [Utah-astronomy] Statistical mythbusting. To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Date: Thursday, July 23, 2009, 6:22 PM Hi Daniel, But isn't it true that in the situation you site, say the chance is one in 100, that in a century there's a good chance it will happen? To turn your example around, I'd be willing to bet you won't flip 10 heads in a row. Thanks, Joe
--- On Thu, 7/23/09, daniel turner <outwest112@yahoo.com> wrote:
From: daniel turner <outwest112@yahoo.com> Subject: [Utah-astronomy] Statistical mythbusting. To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Date: Thursday, July 23, 2009, 7:16 PM
Kim recently was brave enough to take on a common misconception about the concept of what is normal. More of this needs to be done and I hope that no one becomes offended.
I would like to address the concept that the earth is "due" for a Tunguska size impact event. Frontrunner train arrivals can be considered to be "due" because each train is part of a coordinated system of schedules and operators communicating with a central dispatcher who keeps things running as expected.
Impact events are not subject to a dispatcher with a schedule to keep, they are independent events. Let's assume that the odds of getting hit are once every 100 years. Then the olds of a hit during any one year are 1 in 100. That is true for all years; the year before Tunguska, the year after Tunguska, the year OF Tunguska, and this year, more than a century after Tunguska. The odds on each year are the same: 1 in 100. That's the way statistical odds work for unrelated events.
In a coin flip example, if you happen to toss heads three times in a row the odds of doing so on the next flip is 50%. If you manage to toss 10 consecutive heads in a row, the odds on the next flip are still 50%. That's because the coin is just a lump of metal without any memory of recent events or expectations of future events.
So as far as Tunguska is concerned, you should go out and buy a bunch of green bananas with the full confidence that you have plenty of time for them to ripen. Impact events are never "due".
DT
--- On Thu, 7/23/09, Chuck Hards <chuck.hards@gmail.com> wrote:
From: Chuck Hards <chuck.hards@gmail.com> Subject: Re: [Utah-astronomy] Asteroid or Comet Collision With Earth Probability To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Date: Thursday, July 23, 2009, 5:21 PM BTW, for the worriers among us, some scientists feel that the earth is overdue for a "nuclear" sized impact; one big enough to cause major disruptions or even mass extinction. Thus the current emphasis on finding and cataloging objects that cross earth's orbit. (Get busy, Patrick!) ;o)
Combat soldiers are fond of saying that you never hear the one (bullet) that gets you... _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
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