Roger: There may be a common factor relating volcanic erruption events to a schedule, like it takes a certain amount of time to load the canon for the next shot, but this isn't true for asteroid impacts. Meteor showers are related events tied to the orbit of a parent comet or asteroid. Tunguska events are not so related. Their parent bodies were disrupted so long ago that their orbits are fully random as far as we can determine. DT --- On Thu, 7/23/09, Rodger C. Fry <rcfry@comcast.net> wrote:
From: Rodger C. Fry <rcfry@comcast.net> Subject: Re: [Utah-astronomy] Statistical mythbusting. To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Date: Thursday, July 23, 2009, 6:39 PM Daniel, I totally agree with your appraisal. Statistics may show the number of significant astroid impacts per hundred years. But a period of lower than average doesn't mean a higher than average frequency of impacts anytime soon.
But looking at this as applied to Joe Bauman's comment about the Yellowstone Super Volcano this are a bit different. It is well documented that the YSV has a periocity rate of about 620K years. I believe that the last major event was about 620-640K years ago. Based on this, it is quite likely that the YSV will blow it's stack in the near geologic future. Probably not in our lifetime but perhaps in the next 5K years and almost certainly within the next 50K years.
Just a thought.
Rodger Fry ----- Original Message ----- From: "Joe Bauman" <josephmbauman@yahoo.com> To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Sent: Thursday, July 23, 2009 7:22 PM Subject: Re: [Utah-astronomy] Statistical mythbusting.
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)
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