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On the other hand
Joined: 19 Apr 2003
Location: I walk along the avenue
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 Posted: Mon Dec 08, 2008 11:45 am Post subject: Does earth need an asteroid shield? |
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The risk is remote, but given what we think happened to the dinosaurs, the results of the loaded chamber coming up could be dire indeed.
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A group of the world's leading scientists has urged the United Nations to establish an international network to search the skies for asteroids on a collision course with Earth. The spaceguard system would also be responsible for deploying spacecraft that could destroy or deflect incoming objects.
The group - which includes the Royal Society president Lord Rees and environmentalist Crispin Tickell - said that the UN needed to act as a matter of urgency. Although an asteroid collision with the planet is a relatively remote risk, the consequences of a strike would be devastating.
An asteroid that struck the Earth 65 million years ago wiped out the dinosaurs and 70 per cent of the species then living on the planet. The destruction of the Tunguska region of Siberia in 1908 is known to have been caused by the impact of a large extraterrestrial object.
'The international community must begin work now on forging three impact prevention elements - warning, deflection technology and a decision-making process - into an effective defence against a future collision,' said the International Panel on Asteroid Threat Mitigation, which is chaired by former American astronaut Russell Schweickart. The panel made its presentation at the UN's building in Vienna.
The risk of a significantly sized asteroid - defined by the panel as being more than 45 metres in diameter - striking the Earth has been calculated at two or three such events every 1,000 years, a rare occurrence, though such a collision would dwarf all other natural disasters in recent history.
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http://tinyurl.com/6hh59y |
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seosan08
Joined: 10 Oct 2008
Location: Korea
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| Posted: Mon Dec 08, 2008 3:19 pm Post subject: |
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| Hell yeah! Ya never know when them homos will launch an attack! And ya know they will! |
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VanIslander
Joined: 18 Aug 2003
Location: Geoje, Hadong, Tongyeong,... now in a small coastal island town outside Gyeongsangnamdo!
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| Posted: Mon Dec 08, 2008 3:20 pm Post subject: |
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| so be it |
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OneWayTraffic
Joined: 14 Mar 2005
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| Posted: Mon Dec 08, 2008 4:47 pm Post subject: |
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While a building sized asteroid could certainly take out a city, it would have to be a direct hit. The chances of that are pretty slim. A larger asteroid could cause regional or global devastation but the odd get smaller as size increases.
For those interested, a incoming rock at 17km/s carries kinetic energy of 144 GJ per ton of mass. A cubic rock 45m in diameter would have roughly 46 million GJ of energy. That's roughly 11 megatons of TNT. More if the rock is iron, less if it's mainly water ice. A rock 45 kilometers across would carry a million times more energy- more than sufficient to wipe out most life on earth. The chances of this happening in any one year are far less than a million to one.
If one calculates the expected cost of these events, and multiplies by the small chance of occurance, then it's quite reasonable to invest a few million dollars each year in detection. |
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Jandar
Joined: 11 Jun 2008
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| Posted: Mon Dec 08, 2008 5:19 pm Post subject: |
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| Screw that, it would make much more sense to allow the asteroid impact. |
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mithridates
Joined: 03 Mar 2003
Location: President's office, Korean Space Agency
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| Posted: Mon Dec 08, 2008 5:46 pm Post subject: |
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Here's where you can find out the actual effects of an asteroid impact:
http://www.lpl.arizona.edu/impacteffects/
Asteroid 2008 BT18 was discovered in January and passed really close to the Earth in July. It turned out to be a binary asteroid as well (600 m and 200 m in diameter), but let's go with the first assumption that it was a single object and see what happens if it were to hit the Earth.
Here's what happens if it lands 500 km away in an ocean of 1000m depth:
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Your Inputs:
Distance from Impact: 500.00 km = 310.50 miles
Projectile Diameter: 800.00 m = 2624.00 ft = 0.50 miles
Projectile Density: 3000 kg/m3
Impact Velocity: 17.00 km/s = 10.56 miles/s
Impact Angle: 45 degrees
Target Density: 1000 kg/m3
Target Type: Liquid Water of depth 1000.00 meters, over typical rock.
Energy:
Energy before atmospheric entry: 1.16 x 1020 Joules = 2.78 x 104 MegaTons TNT
The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 2.9 x 105years
Atmospheric Entry:
The projectile begins to breakup at an altitude of 54000 meters = 177000 ft
The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 16.9 km/s = 10.5 miles/s
The impact energy is 1.14 x 1020 Joules = 2.73 x 104MegaTons.
The broken projectile fragments strike the ground in an ellipse of dimension 1.38 km by 0.979 km
Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.
The impact does not shift the Earth's orbit noticeably.
Crater Dimensions:
What does this mean?
The crater opened in the water has a diameter of 14.1 km = 8.77 miles
For the crater formed in the seafloor:
Crater shape is normal in spite of atmospheric crushing; fragments are not significantly dispersed.
Transient Crater Diameter: 6.14 km = 3.81 miles
Transient Crater Depth: 2.17 km = 1.35 miles
Final Crater Diameter: 7.81 km = 4.85 miles
Final Crater Depth: 0.55 km = 0.341 miles
The crater formed is a complex crater.
The volume of the target melted or vaporized is 0.152 km3 = 0.0366 miles3
Roughly half the melt remains in the crater , where its average thickness is 5.15 meters = 16.9 feet
Thermal Radiation:
What does this mean?
The fireball is below the horizon. There is no direct thermal radiation.
Seismic Effects:
What does this mean?
The major seismic shaking will arrive at approximately 100 seconds.
Richter Scale Magnitude: 7.1
Mercalli Scale Intensity at a distance of 500 km:
III. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck.
IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.
Ejecta:
What does this mean?
The ejecta will arrive approximately 334 seconds after the impact.
At your position there is a fine dusting of ejecta with occasional larger fragments
Average Ejecta Thickness: 101 micrometers = 3.99 1/1000 of an inch
Mean Fragment Diameter: 688 micrometers = 27.1 1/1000 of an inch
Air Blast:
What does this mean?
The air blast will arrive at approximately 1520 seconds.
Peak Overpressure: 4290 Pa = 0.0429 bars = 0.609 psi
Max wind velocity: 9.93 m/s = 22.2 mph
Sound Intensity: 73 dB (Loud as heavy traffic) |
Now, an asteroid like this was discovered just six months before it passed by the Earth, and until the last few days we thought it was a single object instead of two. It's doubtful that we could have been able to stop it even if we had found out that it was on a direct collision course in January. |
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Gopher
Joined: 04 Jun 2005
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| Posted: Mon Dec 08, 2008 6:33 pm Post subject: |
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| The answer is not to transform the Earth into a fortress but to explore and colonize space -- diversify our holdings, so to speak. |
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Jandar
Joined: 11 Jun 2008
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| Posted: Mon Dec 08, 2008 6:36 pm Post subject: |
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| The answer is to have an impact and cull the species. |
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PeteJB
Joined: 06 Jul 2007
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| Posted: Mon Dec 08, 2008 8:31 pm Post subject: |
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| The odds may be low, but the odds of winning the lottery are even worse. |
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yawarakaijin
Joined: 08 Aug 2006
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| Posted: Mon Dec 08, 2008 8:48 pm Post subject: |
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| PeteJB wrote: |
| The odds may be low, but the odds of winning the lottery are even worse. |
That analogy only holds true if there are hundreds of millions of objects that are on a near earth orbit. Millions and millions of people play the lottery, thats why it is always won by somebody.
To my knowledge there aren't millions and millions of asteroids out there big enough and with a near enough orbit to be of much concern. If there was only a total pool of say 1000 people playing the lottery what are the chances of any one of those 1000 people getting the right numbers?
The universe is infinitely vast and the distances between objects are mindboggling, I very much doubt we will be around to ever be hit again. The one that wiped out the dinosaurs was a fluke. I can't say I see lightning striking twice.
If it does we will be long dead or long gone, having colonized other worlds, before another one strikes. |
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mithridates
Joined: 03 Mar 2003
Location: President's office, Korean Space Agency
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| Posted: Mon Dec 08, 2008 9:04 pm Post subject: |
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| yawarakaijin wrote: |
| PeteJB wrote: |
| The odds may be low, but the odds of winning the lottery are even worse. |
That analogy only holds true if there are hundreds of millions of objects that are on a near earth orbit. Millions and millions of people play the lottery, thats why it is always won by somebody.
To my knowledge there aren't millions and millions of asteroids out there big enough and with a near enough orbit to be of much concern. If there was only a total pool of say 1000 people playing the lottery what are the chances of any one of those 1000 people getting the right numbers?
The universe is infinitely vast and the distances between objects are mindboggling, I very much doubt we will be around to ever be hit again. The one that wiped out the dinosaurs was a fluke. I can't say I see lightning striking twice.
If it does we will be long dead or long gone, having colonized other worlds, before another one strikes. |
There was a fairly big explosion just 100 years ago that wiped out quite a large piece of land in Siberia. Here it is recreated by a supercomputer:
http://ngm.nationalgeographic.com/2008/08/earth-scars/blast-interactive
http://en.wikipedia.org/wiki/Tunguska_event |
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Gopher
Joined: 04 Jun 2005
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| Posted: Mon Dec 08, 2008 9:17 pm Post subject: |
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| yawarakaijin wrote: |
| I can't say I see lightning striking twice... |
Your thinking is good, especially on vast spaces. But given enough time, yes, asteroids will strike the Earth again and again...
Ever look at the Moon's surface? |
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yawarakaijin
Joined: 08 Aug 2006
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| Posted: Mon Dec 08, 2008 9:34 pm Post subject: |
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| Gopher wrote: |
| yawarakaijin wrote: |
| I can't say I see lightning striking twice... |
Your thinking is good, especially on vast spaces. But given enough time, yes, asteroids will strike the Earth again and again...
Ever look at the Moon's surface? |
That's the other problem with the universe! It simply lasts too long! 
No doubt the earth will be struck again but I don't think we will have a civilization ending asteroid impact bewteen now and the time we leave or bite the dust in a far more mundane manner. |
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ernie
Joined: 05 Aug 2006
Location: asdfghjk
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| Posted: Mon Dec 08, 2008 9:55 pm Post subject: |
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| i'm pretty sure we'll either blow ourselves up or poison our air and water first. sounds like another make work project to me. |
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sojourner1
Joined: 17 Apr 2007
Location: Where meggi swim and 2 wheeled tractors go sput put chug alugg pug pug
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| Posted: Mon Dec 08, 2008 10:25 pm Post subject: |
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| ernie wrote: |
| i'm pretty sure we'll either blow ourselves up or poison our air and water first. sounds like another make work project to me. |
I agree. We need to be responsible caretakers of the Earth on the ground level before we try to do it from space. Would any responsible caretaker build nuclear bombs capable of destroying the Earth many times over and allow companies to release terrible pollution into the environment just to make money? Here we are sending rockets up to study other planets to better understand our own by learning how different the others are and yet it's so obvious what is going wrong with our world. Most individuals know what is right, but the super powerful rich billionairs don't want it that way. It's obvious to almost everyone we're getting it all wrong, particularly with awful pollution and habitat destruction.
Why can't we, "make work," with projects focusing on fixing our sick world? |
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