## NASA Downgrades Asteroid-Earth Collision Risk 244

Posted
by
timothy

from the elephant-detector-working-fine dept.

from the elephant-detector-working-fine dept.

coondoggie writes

*"NASA scientists have recalculated the path of a large asteroid known as Apophis and now say it has only a very slim chance of banging into Earth.. The Apophis asteroid is approximately the size of two-and-a-half football fields, and updated computational techniques and newly available data indicate the probability of an Earth encounter on April 13, 2036 for Apophis has dropped from one-in-45,000 to about four-in-a million, NASA stated."*
## four in a million? (Score:5, Insightful)

Isn't four in a million the same as one in 250,000 ?

## Comparing different ratios... (Score:2, Insightful)

## Re:four in a million? (Score:2, Insightful)

Well yes, but "million"

soundsmore impressive.## Four in a million, huh? (Score:4, Insightful)

And "two football fields" doesn't tell us much about the thing's actual size. Besides "football" having two different meanings, one of which has multiple field sizes, what kind of volume are we looking at here?

## Uh oh... (Score:3, Insightful)

## Check my Numbers... (Score:1, Insightful)

## Soothsaying (Score:3, Insightful)

Clearly 4 in a *million* must be a very very small number, not like 1 in 250000 - which has thousands on the right-hand side, so that can't be good.

In an attempt to make a new probability "less scary" the authors (or summary writers) also commit a specific error - there is only ONE asteroid so any probability related to it is ALWAYS 1 in something. It can never be 4 in something because there is only once chance of collision.

## Re:Comparing different ratios... (Score:3, Insightful)

Yes, but can we get this in a real world equivalent. Something like 1200 words out of a library of congress?

## Re:four in a million? (Score:4, Insightful)

Yes, but four-in-a-million is only five syllables, and thus much more useful.

Four in a million

NASA says we might survive

with hyperbole

## Re:Four in a million, huh? (Score:3, Insightful)

Yes, I get upset when they compare objects (where the important dimension is mass (weight) and maybe volume,) to something that is clearly a measure of area at best.

Similarly hail should not be sized by coins.

## Re:How useful is this, really? (Score:4, Insightful)

What is the real use in this? When, within reasonable (I'm not a scientist, but lets use an 85% confidence interval) levels of knowing, would we be able to determine that in fact, yes, this thing is or is not going to hit us?How's a 99.9996% confidence interval? Not the most obvious way to word it and it doesn't strictly apply, but you could say that in the population of hypothetical asteroid trajectories, 99.9996% of them don't hit earth. More study of its orbit is probably going to increase that number.

Not sure how saying it's odds of hitting us is 1 in 250,000 is less useful than saying it's :)

definitelynot going to hit us (with 85% certainty).The article states that they aren't being given the funding to further fund research centers for adequate testing. Politics aside - is there any funding (and more importantly, scientific viability) for preventative action for any of this, or are we just providing confidence intervals of our ultimate doom?Sadly, no in terms of funding. Even the agencies who could conceivably cobble together something at the last minute aren't getting enough funding. We aren't funding the finding of these object to see if we even need preventative action.

As far as viability... there are quite a few things that would work quite easily with today's technology. But it would take time to actually construct the solution. And they all take time. Virtually none of them would work with only a year before the impact. Even ignoring the silliness of the Armageddon Solution blowing apart a Texas-sized meteor with a nuke, all it would mean is that two California-sized meteors hit the earth instead. The solutions most likely to work are ones where we slowly push (or pull) it out of the way over the course of years.

I'm not really worried about an asteroid that we know about, and are tracking, that looks very unlikely to hit the earth. I'm much more worried about all the objects we

don'tknow about, so we have no idea how likely they are to hit us. My biggest concern is that we discover an object that has a high probability of hitting earth in only a year or two.More funding for finding and tracking, pls k thx.

## Re:four in a million? (Score:1, Insightful)

Having Col Carter around makes it 1 in a billion anyway.

## Re:NASA and risk... (Score:5, Insightful)

This kind of uncertainty is much easier to derive with fewer question marks than deriving the risk of catastrophic failure in a complex machine.

Basically what this implies is that taking new measurements, we have an improved estimate of the position of the asteroid at the current time, and the risk of impact is taken by projecting those into the future using well known and tested dynamic estimation methods. Current uncertainty is easily defined as a 6x6 covariance matrix (for the 6 state variables), and this matrix can be determined using a good least-squares estimation method and published measurement numbers.

In other words I give these numbers a lot more credence than risk numbers on the space shuttle. Theres a lot more science and lot fewer assumptions.

Also I would be careful comparing practices in the huge human-spaceflight program, centered at JSC and KSC with those of smaller planetery exploration programs from places like JPL and Ames. They have amazingly different cultures and practices -- NASA is in no way a monolithic entity.

## Re:Oh god (Score:3, Insightful)

Yes, we are. Eventually. Might as well get it over with, eh?

Besides, you all are such pessimists. I like to think of it like this. If it hits us, dying will be the one thing that mankind finally comes together and actually achieves, something that everyone, everywhere can be a part of.