Here's an interesting story in the Gray Lady this morning:

Most astronomers doubt that any large comets or asteroids have crashed into the Earth in the last 10,000 years. But the self-described “band of misfits” that make up the two-year-old Holocene Impact Working Group say that astronomers simply have not known how or where to look for evidence of such impacts along the world’s shorelines and in the deep ocean.

Scientists in the working group say the evidence for such impacts during the last 10,000 years, known as the Holocene epoch, is strong enough to overturn current estimates of how often the Earth suffers a violent impact on the order of a 10-megaton explosion. Instead of once in 500,000 to one million years, as astronomers now calculate, catastrophic impacts could happen every few thousand years.

If an asteroid or comet hit the Indian ocean five thousand years ago, and caused a megatsunami, as the article points out, this could provide an explanation for the almost-universal flood myths of ancient times.

But it also means that we have to continue to look out for these things, and become sufficiently spacefaring to manage them. Unfortunately, NASA's current plans are just the opposite. But then, I'm not sure that protecting us from asteroids is in NASA's current charter. I certainly wouldn't trust them with the job.

Not in terms of this holocene doohickey, but Couldn't those massive impacts also explain all of the stories about the great plains of the US being an inland ocean, because of all of the sea creatures in the strata?

Just saying cuz I never thought of it like that before.

Sorry, accidentaly deleted a part of the first sentence. "I'm not speaking in terms of this holocene. . . ." Is what I meant. Sorry.

"but Couldn't those massive impacts also explain all of the stories about the great plains of the US being an inland ocean, because of all of the sea creatures in the strata"

The deposition of sediment and plate tectonics explains that. Uplift, Erosion, Uplift, Erosion....Rinse, Lather Repeat.

I meant Another explanation, sorry. 50 million years is a long time ago for life, but not for tectonics, I was just thinking that a flooded greatplains for millenia could be explained by being a giant oceanic flood basin.

Interesting, indeed. The last word on impact frequency has not been written. As a general rule, geologic data beats calculations from a limited data set, or simplistic physical theory. We'll need to see whether the geologic data is consistent with the cosmic impact interpretation exclusively. It would not be surprising to see the impact frequency estimates revised upward by a factor of two, but a factor of ten would be surprising.

You are correct,NASA has no mandate to defend the Earth from cosmic impact.

What we need is some big telescopes located 2-3+ AU out of the plane of the elliptic. As it is, lighting conditions mean that there are some trajectories we don't see until it is too late.

DocBrown?

I swear that was exactly what Arthur C. Clarke described in "Hammer of God."

Also, wouldn't making a hardy space telescope that could mantain position opposite the sun in the orbit of venus do the trick of tracking the leading and trailing earth asteroids?

For that matter, couldn't a pair of less hardy, but more powerful space telescopes orbing mars, observe the leading and trailing asteroid groupings of earth without solar interference, as well as provide eas tracking for precise location?

I'm prolly wrong about both, but when you are talking about space, and enough room for a whole solar system, then there are a lot of ninjafied ways of tracking the asteroids we are supposedly worried about.

Though I think this was about commets, which seems to me, should require a LOT! of telescopes with very good resolution to be able to look all the way out to the. sgadlrfhen belt.

ORT CLOUD!!!

I did not look it up, I remembered. Is that right? thats where the comets are?

huh? huh? huh?

really, I know I'm dumb on this stuff, but can I get a biscuit for this?

I think the purpose of putting the out of the plane of the ecliptic is to prevent the sun from masking stuff coming in at highly inclined orbits.

"almost-universal flood myths of ancient times."

Wrong thread for a debate, so I'll say nothing for now...

A debate about what? Whether or not there are flood myths? (Note: in the anthropological sense, "myth" doesn't necessarily imply that it isn't true.)

See also A Hit, A Very Palpable Hit (remove the extra space between "blog" and "spot" to make that link work); Australia and New Zealand may have gotten clobbered by a 150-200 meter tsunami caused by an impact in 1500 AD.

Note also that asteroid sizes follow a power-law distribution such that for every asteroid 3 km in diameter, there are 200 of them 300 meters in diameter -- and 40,000 of them 30 meters in diameter (source -- remove the extra space, yadda yadda). So for every impact the size of the one in the Indian Ocean, there could be hundreds capable of destroying a city -- or that look awfully similar to a nuclear explosion. The real risk is geopolitical.

I've done some study on flood myths. My impression was that early humans, who were not then experts in irrigation, settled close to the water. Whenever there was a flood greater and faster than normal, there was a problem. Flood stories were passed down to warn the next generation to watch out for the next one.

But no, now it's meteors. Back around Y2k it was the Black Sea flood. In 1987 I remember reading speculations on cyclones at the Sumerian coast. :^)

There is no need for any of these hypotheses to explain such a basic fact of Stone-to-Chalcolithic Age life. Occam's Razor, laddie.

But in order to combat asteroids. We'd have to put weapons in space! *GASP!*

Josh, not if you use that gravity tractor idea.

Josh, not if you use that gravity tractor idea.

If sizes of these objects actually obey a power law (seems reasonable), note that the most recent nontrivial impact we know of (Tunguska) was less than 100 years ago. Those two facts together would seem to indicate that signifant impacts every 10k+ years is pretty reasonable, yes?

Bill, if you can perturb asteroids so they don't hit Earth, you have a weapon in space since that implies you can then perturb that orbit to hit things you don't like. Another reason down the road to get into space. After all, any spacecraft or orbit colony, even a several miles long O'Neill style colony can dodge large asteroids a lot better than a planet can. OTOH, they aren't quite as padded.

Mike, part of the problem caused by the Tungusta impact is that if it had happened a couple hundred years earlier it might not have left enough of an impact in the geologic record to have been noticed by scientists today. In fact, it boggles the mind that the discovery Jay Manifold mentioned, and the other two impacts mentioned in the article, hit the ocean around Australia in the last 1200 years without being noticed by us until the last five years or so.

(BTW, Jay, could you post those links in a form in which I can read? For some strange reason, my browser isn't showing the url's so I can edit them.)

I've done some study on flood myths. My impression was that early humans, who were not then experts in irrigation, settled close to the water. Whenever there was a flood greater and faster than normal, there was a problem. Flood stories were passed down to warn the next generation to watch out for the next one.

But no, now it's meteors. Back around Y2k it was the Black Sea flood. In 1987 I remember reading speculations on cyclones at the Sumerian coast. :^)

There is no need for any of these hypotheses to explain such a basic fact of Stone-to-Chalcolithic Age life. Occam's Razor, laddie.

If the geology says the Black Sea flood, and the other impacts described in the article, and the one Jay talked about, happened, then they happened, regardless of whether you think they're compatible with occam's razor or not.

If they happened, they would have produced physical effects that would have wrecked human populations on coastlines nearby. There's nothing "magic" to stop the tsunamis. And no point in discussing human history as if it could be divorced from something we now know happened.

I'm no expert, but if true, does this mean that the power-law multiplier is greater by the same factor? In other words, is an impact of any given size now ten times more likely?

If so, then we are even more overdue for another Dinosaur Killer, and protection against this threat is even more important. If so, the risk of dying in an extinction-level event is the greatest accidental risk.

Maybe the reason why politicians don't take this seriously is that if it happens there won't be any people around to blame them. To get lynched (better than most politicos and bureaucrats deserve) there has to be someone to do the lynching.

"There are some things out there so dangerous that the only defense is not to be there when they happen".

"If so, then we are even more overdue for another Dinosaur Killer, and protection against this threat is even more important. If so, the risk of dying in an extinction-level event is the greatest accidental risk."

Proabilities do not work that way. ELE's are not like milk deliveries. You are, for all intents and purposes, just as likely to get hit the year after an ELE as you are 50 million years later.

The only think to microscopically change the odds is 50 million years later a small number of those rocks have had their wanderings terminated by impact with another celestial body, likely Jupiter and are therefore no longer available to impact Earth.

Responding to Phil's request ... remove the space, etc:

http://avoyagetoarcturus.blog spot.com/2004_03_01_avoyagetoarcturus_archive.html#107896989558519610

http://avoyagetoarcturus.blog spot.com/2002_09_01_avoyagetoarcturus_archive.html#85481271

Thanks, Rand, for clarifying "myth". My mistake and misreading.

GBuc

Rand, is it possible that one time you could make a blog post without taking the opportunity to talk shit about NASA?

Rand, is it possible that one time you could make a blog post without taking the opportunity to talk shit about NASA?

Is it possible that you could work on your reading comprehension? I do so every day, even when I put up posts about space.

I see why you call yourself dense.

"Josh, not if you use that gravity tractor idea"

But couldn't that idea be adapted to disrupt the orbital trajectories of other countries satellites?