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Old February 18 2013, 04:30 PM   #76
FordSVT
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Re: Russia reports amazing meteorite strike

bigdaddy wrote: View Post
It was the number one story on NBC Nightly News!

"The Russian meter, the close comet, the California light, are we safe? ARe you going to die? Is the end near?! We will ask some dumbass who can't read the script! Then have more on Dateline!"

As a child I saw a massive comet in the sky, it didn't explode, then when I was hiking in 2002 there was a massive boom, then an Earthquake. They claimed it was a meteorite that crashed in upstate NY, but they never found the crash site. These things happen. The Russian one is scary, but rocks ht the Earth every day, most we don't need to worry about.
This is one of those cases where I approve of wild over-reaction on the part of the public. Our governments need to spend more time and more money on NEO detection and a bunch of people freaking out might nudge the right people to pay attention to this subject.

If this thing had been 2-3 times as massive, we still wouldn't have detected it, and it could have killed a lot of people. If it had been 5-10 times more massive, we'd be talking about how Russia was going to recover after losing a city of a couple million people.
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Old February 18 2013, 04:43 PM   #77
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Re: Russia reports amazing meteorite strike

^Absolutely. This was a much-needed wake-up call for the public and the world's governments about the threat from NEOs, and we're quite lucky that it was a much gentler wake-up call than the one posited in Arthur C. Clarke's Rendezvous with Rama, in which humanity didn't begin monitoring space for incoming asteroids until after an impact that killed 600,000 people and wiped out Padua, Verona, and Venice. (Unnervingly, the date of that event in the book was September 11, 2077.)
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Old February 18 2013, 06:43 PM   #78
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Re: Russia reports amazing meteorite strike

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This isn't a situation where brute force is the optimal solution. You can't really blow up an asteroid like in the movies -- and if you could, it could actually make things worse, because all that mass would still be on the same collision course for Earth, and it would come down spread out far more widely. The only real solution is to divert the asteroid so it misses the planet. Which isn't that hard to do. It only takes the Earth about 7 minutes to traverse its own diameter as it moves through its orbit, so you just need to change the asteroid's course or speed a tiny bit so it crosses our orbit a few minutes later or earlier. This is the benefit of detection systems, because the earlier we find these objects, the easier it is to deflect them; not only do you have more time to alter an asteroid's course, but the farther away it is, the less of a course change you need to impart to get it to miss.
I have to add to my comments above, since I wasn't completely right. When dealing with objects of a few dozen to a few hundred meters across -- potential city-killers like the Chelyabinsk object rather than planet-killers -- it could be viable to vaporize them completely given enough advance warning. There's a proposed laser system that would do just that, discussed in this Centauri Dreams post (which happens to make the same Rendezvous with Rama reference I made just above).

Although I have to question whether it would be necessary to use the lasers to vaporize them completely, when it would be more efficient just to nudge them off course. Maybe the idea is to prevent them from ever being threats again?
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Old February 19 2013, 12:54 AM   #79
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Re: Russia reports amazing meteorite strike

This will be forgotten about pretty soon. It's not a wake up call.
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Old February 19 2013, 03:05 AM   #80
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Re: Russia reports amazing meteorite strike

It's more like that first alarm that you hit the snooze button on then roll back over.
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Old February 19 2013, 03:13 AM   #81
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Re: Russia reports amazing meteorite strike

It's like when the "low fuel" idiot light comes on on the dash and you don't go directly to a station because you know you can get another 50 miles before you're really out of gas.
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Old February 19 2013, 06:25 PM   #82
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Re: Russia reports amazing meteorite strike

A projection of the impactor's estimated orbit has been released:

http://www.esa.int/Our_Activities/Op...and_assessment

Its elliptical orbit extended well past the orbit of Mars, suggesting it may have originated in the Main Asteroid Belt. Further proof that it had nothing to do with the asteroid 2012 DA14, which is a Near-Earth Object that orbits between Venus and Earth.
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Old February 19 2013, 09:39 PM   #83
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Re: Russia reports amazing meteorite strike

Christopher wrote: View Post
A projection of the impactor's estimated orbit has been released:

http://www.esa.int/Our_Activities/Op...and_assessment

Its elliptical orbit extended well past the orbit of Mars, suggesting it may have originated in the Main Asteroid Belt. Further proof that it had nothing to do with the asteroid 2012 DA14, which is a Near-Earth Object that orbits between Venus and Earth.
There you go, letting the facts get in the way of a good story.
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Old February 20 2013, 05:29 AM   #84
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Re: Russia reports amazing meteorite strike

Christopher wrote: View Post
Gary7 wrote:
They may be able to predict if it will bend it in such a way as to bring it closer or further away on the next pass, but I don't believe they can make an accurate estimate on the exact distance it will pass next time.
Yes, they can, within an accuracy of plus or minus about 20,000 kilometers. Heck, NASA's already done calculations for not just the next pass, but the next 25 passes going up to 2137, and you can see for yourself how detailed the calculations are. This is the only pass prior to 2087 when it has any prospect of coming closer to Earth than a hundredth of an AU (1.5 million kilometers).
I can appreciate NASA's ability to create precise estimates on the distances and paths of celestial objects, but I'm mystified as to how they could possibly determine mass. Wouldn't they need to be able to penetrate the object with some kind of sensor to determine density and composition, and in multiple places throughout the object (because density and composition vary from spot to spot)? Not having a precise measurement of mass will skew calculations of gravitational effects, which ultimately affects the trajectory.
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Old February 20 2013, 05:53 AM   #85
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Re: Russia reports amazing meteorite strike

Gary7 wrote: View Post
Christopher wrote: View Post
Gary7 wrote:
They may be able to predict if it will bend it in such a way as to bring it closer or further away on the next pass, but I don't believe they can make an accurate estimate on the exact distance it will pass next time.
Yes, they can, within an accuracy of plus or minus about 20,000 kilometers. Heck, NASA's already done calculations for not just the next pass, but the next 25 passes going up to 2137, and you can see for yourself how detailed the calculations are. This is the only pass prior to 2087 when it has any prospect of coming closer to Earth than a hundredth of an AU (1.5 million kilometers).
I can appreciate NASA's ability to create precise estimates on the distances and paths of celestial objects, but I'm mystified as to how they could possibly determine mass. Wouldn't they need to be able to penetrate the object with some kind of sensor to determine density and composition, and in multiple places throughout the object (because density and composition vary from spot to spot)? Not having a precise measurement of mass will skew calculations of gravitational effects, which ultimately affects the trajectory.
The longer you track an object the more precisely you can estimate its mass.

In addition, an asteroid's mass is much smaller than the masses of the objects deflecting them. The Earth and the Moon are each deflected almost nothing by a near-miss asteroid, and Jupiter and the Sun even less. Since inertial mass and gravitational mass are equal, the asteroid is accelerated gravitationally by other objects an amount that is independent of its mass. Therefore, to a high order of accuracy, the mass of the asteroid is irrelevant.
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Old February 20 2013, 03:06 PM   #86
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Re: Russia reports amazing meteorite strike

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The thing is we CAN see half-mile wide asteroids. Granted we're not tracking everything out there. This rock was nothing to be concerned about and NASA would be wasting time looking for stuff like this. We get hit by this kind of thing all of the time this one just happened to happen over a populated area.
You missed my point, one of these smaller ones that fly under the radar could strike a bigger one that we think will miss us and change its trajectory slightly to a trajectory that would not be conducive to the survival of the human race. That is why developing new tech to track these little guys along with better computers to look at the course of all the space rocks in our solar system matters in the coming decades.

This isn't a situation where brute force is the optimal solution. You can't really blow up an asteroid like in the movies -- and if you could, it could actually make things worse, because all that mass would still be on the same collision course for Earth, and it would come down spread out far more widely.
Given we don't have anti matter weapons yet or anything that can explode in the 200 gigaton range its a bit speculative as to if the pieces left would be small enough to wipe out life on Earth and as I made clear such an weapon would only make sense assuming we only figure out the rock is headed toward Earth at the last minute and can't organize anything else in time or everything we organize fails to work.

Even if it doesn't work all that well I would rather let the atmosphere work its thing on tens of thousands of pieces of rock instead of dealing with just one half mile wide rock.

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Old February 20 2013, 04:32 PM   #87
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Re: Russia reports amazing meteorite strike

Gary7 wrote: View Post
I can appreciate NASA's ability to create precise estimates on the distances and paths of celestial objects, but I'm mystified as to how they could possibly determine mass. Wouldn't they need to be able to penetrate the object with some kind of sensor to determine density and composition, and in multiple places throughout the object (because density and composition vary from spot to spot)? Not having a precise measurement of mass will skew calculations of gravitational effects, which ultimately affects the trajectory.
Generally it'd work the other way around -- if you observe how two objects interact gravitationally, how they affect each other's motion, you can calculate both their masses using simple Newtonian physics. And there are other ways. Taking a spectroscopic reading of an object can tell you something about its composition, and you can compare it to other objects that are better understood, all of which can help you estimate density.

In this case, we're talking about an object in a fairly circular orbit between Earth and Venus. The circularity tells us it isn't a recent capture that came in from further out; it's been in the inner system for a long time, long enough for its orbit to circularize. And that means it can't be an icy body, since any volatiles would've vaporized long ago. So it must be rocky or metallic. Spectral readings show it's a subclass of S-type, silicate, asteroid. We know the density of silicate rock, because, hey, it's what most of the Earth's crust is made of. And we've studied plenty of other similar asteroids.

And like I said, it's not like we're not going to keep watching the damn thing. If our current estimates of its mass are wrong, then further observations of its trajectory will diverge from our estimates and we will correct our estimates!


jmc247 wrote: View Post
You missed my point, one of these smaller ones that fly under the radar could strike a bigger one that we think will miss us and change its trajectory slightly to a trajectory that would not be conducive to the survival of the human race.
Maybe once every few million years, sure. You're talking about an immensely low-probability event. Even with all the debris out there, space is still huge and empty. That's why Earth gets hit by large objects so rarely even though there are so many of them out there.

Not to mention that you're talking about a hell of a sweet spot there -- hit by something large enough to change its course significantly within our lifetimes or that of our civilization, yet small enough not to shatter it? That makes it even more vanishingly improbable. Your odds of being struck by lightning are considerably higher. Hell, your odds of dying in a traffic accident are immensely higher.


That is why developing new tech to track these little guys along with better computers to look at the course of all the space rocks in our solar system matters in the coming decades.
Exactly. We've already found this one, and we're not going to stop tracking it. And the events of this past week are already goading politicians to pay more attention to the need for better spacewatch systems, so hopefully they'll finally get more funding.



Given we don't have anti matter weapons yet or anything that can explode in the 200 gigaton range its a bit speculative as to if the pieces left would be small enough to wipe out life on Earth...
Nonsense. The whole reason the laws of physics exist is to let us extrapolate the outcomes of events that have not been directly observed. We know the conversion rate of matter to energy -- it's E=mc^2. We've synthesized and observed small quantities of antimatter for decades and we can extrapolate upward. We can calculate how much energy it would take to vaporize an object of a given composition. We can calculate how much energy would be imparted to the Earth by an impactor of a given mass and velocity. All of this is quite easily done with a little physics. That's what it's for!

Of course, there is a margin for uncertainty, a range of error, so there's always the possibility that an object wouldn't be completely vaporized -- which is why the far saner and more practical approach is to deflect rather than destroy. And that's why we should put our effort into detection first and foremost, to ensure we have plenty of advance warning, rather than taking our asteroid-defense philosophy from Michael Bay.


Even if it doesn't work all that well I would rather let the atmosphere work its thing on tens of thousands of pieces of rock instead of dealing with just one half mile wide rock.
That's because you're not considering the physics of it. Remember that huge, 500-kiloton explosion over Chelyabinsk five days ago? That wasn't the meteoroid that exploded -- it was the air in front of it. As the impactor broke up in the atmosphere and was decelerated, it transferred its immense kinetic energy to the atmosphere in front of it in the form of immense heat, resulting in a fireball nearly 30 times more powerful than the Hiroshima bomb and a shock wave that caused serious damage to the city below and injured over a thousand people. Now imagine that happening tens of thousands of times all over the Earth within the span of a few minutes or hours. All that heat getting dumped into the atmosphere all at once, the equivalent of thousands of nuclear bombs detonating in the air all over the world.

Mass and energy can't be destroyed, only redistributed. So if the mass of that asteroid hits the Earth, it doesn't matter much whether it does so in one single clump or in thousands of separate pieces. You're still imparting the same amount of total kinetic energy to the Earth. Spreading it out over space and time might change the way it does damage, but it wouldn't have that much effect on the total amount of damage. It would still be a planetary catastrophe either way.
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Old February 20 2013, 06:42 PM   #88
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Re: Russia reports amazing meteorite strike

Indeed, this meteorite did a good dose of damage and no meaningful piece of hit a populated area.

All of the damage and injuries were simply caused by the simple presence of it in the air.

The Daily Show's "report" on the incident:

How I Meteored Your Motherland
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