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Russ
2002-Aug-19, 05:01 PM
On the CNN site here;
http://www.cnn.com/2002/TECH/space/08/16/asteroid.encounter/index.html
They say this: " The space rock, 2002 NY40, is not to be mistaken for 2002 NT7, another newly discovered asteroid that generated headlines weeks ago when scientists briefly mused that it would smack into our planet in 2019.

Then they says this: "Flybys like this happen every 50 years or so," said NASA's Don Yeomans, who manages the space agency's Near-Earth Object Program at the Jet Propulsion Laboratory in Pasadena, California.

They open the article saying that we have one now and one in the pipe for 17 years from now. Then they say this happens about every 50 years. By my rounded off math, that's 20 years boys. Further IIRC, these NEA's have been popping up about 2 a year since we started looking with any seriousness.

Go figure!? /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_razz.gif /phpBB/images/smiles/icon_lol.gif

The Bad Astronomer
2002-Aug-19, 07:47 PM
Well, the 50 year figure is quoted from Don Yeomans, so it's not really CNN saying it.

Russ
2002-Aug-19, 08:32 PM
On 2002-08-19 15:47, The Bad Astronomer wrote:
Well, the 50 year figure is quoted from Don Yeomans, so it's not really CNN saying it.

I'll grant you that but you'd think they'd comment on the difference or get Don to explain the discrepancy. I mean, come on! They are supposed to be professional journalists. If the reporter didn't catch it the editor should. Somebody at CNN should be able to do 6th grade arithmatic. /phpBB/images/smiles/icon_rolleyes.gif /phpBB/images/smiles/icon_lol.gif

beskeptical
2002-Aug-20, 08:14 AM
This case isn't toooo bothersome but I agree with Russ about reporters not often seeming to ask any questions about the facts they are fed.

Donnie B.
2002-Aug-20, 07:39 PM
That would probably be every 50 years, give or take an order of magnitude.

Ilya
2002-Aug-21, 09:22 PM
A lot of things in astronomy, especially statistical ones, are so approximate that getting within correct order of magnitude is considered sufficient.

In other words, "in astrophysics, 1 is approximately equal to 9" (Lorenz and Mitton, Lifting Titan's Veil (http://www.amazon.com/exec/obidos/tg/detail/-/0521793483/qid=1029964572/sr=8-1/ref=sr_8_1/102-0067998-3450548?s=books)

David Hall
2002-Aug-22, 09:19 AM
Yes, I would agree. When I something like this, I don't get very upset about them. 50 years is an average number only; you also have to realize that the phenomenon itself is fairly random. You may get 2 in one year and then nothing for a hundred. That averages to 50 years doesn't it?

But in any case, it does seem to me that the average as given is too low. I think they are more frequent than that. My guess is that this guy is using a figure he's been quoting for years, before all these new NEA discoveries started being made. It probably was thought to be about once in 50 years for a long time.

Russ
2002-Aug-22, 09:13 PM
On 2002-08-22 05:19, David Hall wrote:
Yes, I would agree. When I something like this, I don't get very upset about them. 50 years is an average number only; you also have to realize that the phenomenon itself is fairly random. You may get 2 in one year and then nothing for a hundred. That averages to 50 years doesn't it?

But in any case, it does seem to me that the average as given is too low. I think they are more frequent than that. My guess is that this guy is using a figure he's been quoting for years, before all these new NEA discoveries started being made. It probably was thought to be about once in 50 years for a long time.

I'll grant all of you that these numbers are ...thumbnail... at best but the average Joe-On-The-Street doesn't know that. I suspect that even the average Joe-On-The-Beat CNN reporter doesn't know either. But you'd think as they read through what was written that they'd notice that one paragraph says 20 the other 50 and ask a question.

My personal belief (unscientific) about the situation is; we've got these things whizzzzing close by (>100Kkm) at 2-3 per year and we just don't see them bucause they are on the Sun side.

I think Gene Shoemaker had it right. He said something to the effect that: "We'll know when we're about to be hit when the object enters the admosphere." /phpBB/images/smiles/icon_lol.gif

GrapesOfWrath
2002-Aug-23, 11:05 AM
On 2002-08-22 17:13, Russ wrote:
But you'd think as they read through what was written that they'd notice that one paragraph says 20 the other 50 and ask a question.

Maybe they did, and got the same answer.

Russ
2002-Aug-23, 03:14 PM
On 2002-08-23 07:05, GrapesOfWrath wrote:


On 2002-08-22 17:13, Russ wrote:
But you'd think as they read through what was written that they'd notice that one paragraph says 20 the other 50 and ask a question.

Maybe they did, and got the same answer.

I suppose that's possible. But I know that there can be BIG difference between possible and probable. /phpBB/images/smiles/icon_lol.gif

Cloudy
2002-Sep-06, 03:48 AM
The "50 year" prediction is based on probability. On the average, there will be 20 such asteroids every 1000 or so years.
2000 every 100,000 years etc.

Of course we could then have had one today and one twenty years from now. Just like you could get a royal flush today playing poker and then get one again tomorow. And get one 100 days later. The average would then be one every 33 or so days. Getting a flush today has no effect on getting the same result tommorow.

Another illustration of this common falacy -
"The chances of their being two bombs aboard a plane is a heck of allot less then their being only one. So next time you fly, bring a bomb." /phpBB/images/smiles/icon_smile.gif






<font size=-1>[ This Message was edited by: Cloudy on 2002-09-05 23:49 ]</font>

Russ
2002-Sep-11, 10:11 PM
On 2002-09-05 23:48, Cloudy wrote:
The "50 year" prediction is based on probability. On the average, there will be 20 such asteroids every 1000 or so years.
2000 every 100,000 years etc.

Of course we could then have had one today and one twenty years from now. Just like you could get a royal flush today playing poker and then get one again tomorow. And get one 100 days later. The average would then be one every 33 or so days. Getting a flush today has no effect on getting the same result tommorow.

Another illustration of this common falacy -
"The chances of their being two bombs aboard a plane is a heck of allot less then their being only one. So next time you fly, bring a bomb." /phpBB/images/smiles/icon_smile.gif

<font size=-1>[ This Message was edited by: Cloudy on 2002-09-05 23:49 ]</font>


Hey Cloudy:

Thanks for the statistics refresher. It's my observation that it is reasoning like this that keeps the lights lit in Las Vegas. /phpBB/images/smiles/icon_lol.gif It is also my expectation (sense of the force) /phpBB/images/smiles/icon_wink.gif that we have a lot more of these NEA's whizzing by than is currently acknowledged by the professional astronomy community. Not that they're hiding anything, it's just, being scientists, they don't acknowledge what hasn't been measured & cataloged.

If we ever launch a satalite that looks back our direction from say Venus' orbit, I think we'll get a cold chill down our collective spine knowing just how much danger we're really in. /phpBB/images/smiles/icon_smile.gif /phpBB/images/smiles/icon_biggrin.gif