Slashdot Mirror
Another Asteroid Close Call
james was one of a number of people that submitted the news that
the earth has had another near miss, this time with an asteroid. This particular one is thought to be about 300 meters in length, meaning that if it had struck the earth, it would have destroyed an area of say...South Africa. Not to mention the fall out. But
we don't need
a
better system
for watching the stars. Nope. Obviously not.
How do you calculate the damage? Do you use high school physics F=mdv/dt? Do you use university level physics? Anyone who knows how to calculate please show off.
Here's a list of PHAs (Potentially Hazardous Asteroids) and a simulation of the orbit of this particular asteriod.
Tired of being "punished" by the Slashdot $rtbl since 2002. I'm now over at http://soylentnews.org/ .
Opps, though it probably derives from misuse.
We are certainly in no position to prevent an impact with a large comet, meteor or asteroid. What we've learned from space observation in the last several decades is space is a very dangerous place.
Three million years ago, the Sun left one of the main arms of the galaxy. Scientists have found evidence of 27 distinct extinctions on the planet, all of them when we were in the arm. That means there have been more, many more, in the 4 billion year history of the planet. Currently, we are in a fairly quiet place, a little above the arm but not quite out of the galaxy.
25 million years from now, the orbit of our local group of stars will return back into the spiral arm. When we return back to the arm, where the star density is far higher than it is out in the boonies away from the arm, the odds of the earth not having a major impact event is nill. In fact, the odds of not having a major impact event between now and when we will be back in harms way is almost as small.
In the mean time, since it is likely that none of you will live to see the next impact event, don't worry about it. When it happens, enjoy the event from your spectacular view from Heaven itself, if that's where you end up. On the other hand, if you're stoking the fires of Hell, you'll be too busy to worry about it. I suggest, then, that you spend your time working to get into heaven and to avoiding hell. That's the only thing that you can control, through faith and good works.
Hi Guys,
1 02 .htm
Here in the UK it would appear that someone is talking note
http://www.nssc.co.uk/press/releases/2002/1/020
Now wait a minute. I remember about the time "Deep Impact" came out in the theaters, scientists assured us that the chances of a large asteroid hitting the earth were extremely remote. And now large asteroids are barely missing us? Have these assumptions been called into question?
How about this [pdf, 2M]. The main problem is early detection. Modifying the trajectory of any decent sized object is considerably more difficult the closer it gets to Earth. Why? Because more force is needed to alter the trajectory to eliminate the possibility of collision. If you can give a small nudge when the object is much farther away, this beats a huge nudge when it is close by. Not that we have any organized way to produce any kind of nudge right now.
I think...I think it's in my basement. Let me go upstairs and check. -M.C. Escher (1898-1972)
Wrong. We will have a means some day, in the meantime, it's important to start the funding process, then the building of the observatories, so we can start cataloging the asteroids which are candidates to wipe us out.
Doing nothing with the assumption we can never do anything is against all evidence of progress in our history...
From Nasa's FAQs About NEO Impacts:
How much warning will we have?
With at least half of even the larger NEOs remaining undiscovered, the most likely warning today would be zero -- the first indication of a collision would be the flash of light and the shaking of the ground as it hit. In contrast, if the current surveys actually discover a NEO on a collision course, we would expect many decades of warning. Any NEO that is going to hit the Earth will swing near our planet many times before it hits, and it should be discovered by comprehensive sky searches. This is the purpose of the Spaceguard Survey. In almost all cases, we will either have a long lead time or none at all.
I've never seen any missile defense plans that have anything to do with stopping an asteroid. Asteroids are much faster, coming from farther out and much bigger than rogue ICBMs. Every missile defense plan I've seen lacks both the range and firepower to make the least bit of difference to an object this size or bigger.
You mean to tell me that the people who couldn't figure out where the russian space station was going to crash into the earth, which was a CONTROLLED decent of an object of known mass, will be able to calculate where a giant rock that they don't know the shape or exact mass of, will land, when it's 30 days away?
I'm not trying to be a troll, but it does cite a past real world situation.
The previous has been a secret message to my comrades.
isaac asimov wrote a neat book called a choice of catastrophes he addresses being hit by an asteroid while it is statistically possible it is highly unlikely.
Remember, Asimov was writing (in 1980) before Gene Shoemaker's work from the 60s and after became fully accepted. It really wasn't until all the work identifying impact craters on the earth that was inspired at least in part by Shoemaker's work, and by the Alvarez hypothesis on the K-T extinction (i.e., the asteroid that killed the dinosaurs), got underway that astronomers and geologists took the idea of large impacts seriously (most scientists thought that Meteor Crater was an extinct caldera before Shoemaker, despite the name). Also, Sagan et al.'s work on sandstorms in the Martian atmosphere in the 1970s, which helped to provide a possible mechanism for global effects from local impacts, wouldn't have been completely digested by the time Asimov was writing. Though Asimov was right that overpopulation is the most serious of the issues he deals with in the book (and of course few countries outside Asia take the problem seriously), it would be foolish to dismiss the threat of an impact.
You need to define "large" and "barely missing", to even understand what those assumptions are saying.
First, we're doing pretty well at tracking the really large earth-grazing asteroids now - for rocks at least a kilometer in diameter (picture the "little guy" that hit at the end of Deep Impact) we're tracking an estimated ~90% instead of 10% of them now, and the big improvement has come in the last five years or so.
For the stuff smaller than a kilometer (which don't threaten civilization, but can still be large enough to make much of New York City a memory), I don't know that we're doing much tracking at all. So what's your definition of "large"? Thanks to the heavy ocean cover and relatively sparse city covering of the land, odds are we'll get hit in a nice relatively non-fatal location before a city-buster earns its name. And we'll get hundreds or thousands of near misses before then. What's your definition of "barely missing"? I've heard it to refer to anything passing inside the moon's orbit, which is a target with 3,600 times the cross section of Earth. That's a near miss on a cosmic scale, not on a human one.
It's hard to set odds on something like this, but the most informed I've seen would give us about even odds of having a populated area smashed up (damage as much as a trillion dollars) sometime in the next millenium. Not such bad odds that we want to start putting up an "asteroid defense shield", but bad enough that some other valuable activities (pointing more telescopes at the sky, cataloguing asteroids, improving launch vehicle technology) become more valuable for this secondary reason.
Feh.
Mass of spherical 300 meter diameter chondrite: ~4g/cc * 1.4E13cc ~= 5.6E10kg
Velocity: ~20000mps
Kinetic Energy of asteroid: 1.13E19 J
One megaton = 4.19E15 J
Energy of a 100 megaton bomb as a fraction of the kinetic energy of this asteroid: 1/27th
Hardly a bitch-slap. More of an abject whine.
Then there's the little matter of actually getting the Tsar Bomba to the asteroid. Hopefully in enough time to actually be able to steer the asteroid away, instead of fragmenting it into 5 chunks each of about 1E10 kg.
You also have to consider the fact that nuclear explosions in space behave differently than nuclear explosions in the Earth's atmosphere. A nuclear device is primarily a source of soft x-rays. Since the atmosphere is relatively opaque to soft x-rays, the energy is converted to thermal energy and visible light by absorption and re-emission. This produces the flash, blast wave and thermal pulse. In space, you get a burst of soft x-rays and little else. The nuclear device would have to be very close to the asteroid, so that the soft x-rays were absorbed by the surface of the asteroid and converted into thermal energy.
Mea navis aericumbens anguillis abundat