Maybe it's the doom predictions some folks are fearing about the end of the Mayan calendar this year or maybe these guys are obsessed with old Bruce Willis movies. Either way a class of physics students from the University of Leicester decided to evaluate whether or not the premise of Willis' 1998 "Armageddon" movie -- where a group of oil drillers is sent by NASA to detonate nuclear devices on an asteroid that threatens to destroy Earth -- could actually happen.
In short - the students found that the device would need to be about a billion times stronger than the biggest bomb ever detonated on Earth -- the Soviet Union's 50 megaton hydrogen bomb "Big Ivan" -- in order to save the world the asteroid.
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According to the University, the students devised a formula to find the total amount of kinetic energy needed in relation to the volume of the asteroid pieces, their density, the clearance radius (which was taken as the radius of Earth plus 400 miles), the asteroid's pre-detonation velocity, and its distance from Earth at the point of detonation. Using the measurements and properties of the asteroid as stated in the film, the formula revealed that 800 trillion terajoules of energy would be required to split the asteroid in two with both pieces clearing the planet. However, the total energy output of Big Ivan "only comes to 418,000 terajoules."
"A series of assumptions must be made due to limited information in the film. First, the asteroid is approximated as a spherical object 1000km in diameter (the asteroid is quoted as being the size of Texas) that splits into two equal sized hemispheres. The asteroid in the film reaches a clearance either side of the Earth of 400 miles (640km) which is the assumed value for our calculation," according to the student paper "Could Bruce Willis Save the World?"
The students also said scientists would have to detect the asteroid much earlier if there were any real chance splitting the asteroid before it hit Earth. In the movie the explosions were to split the monster rock so it could pass around the Earth. On top of this, the asteroid would need to be split at almost the exact point that it could feasibly be detected at 8 billion miles, the students said.
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The papers, entitled "Could Bruce Willis Save the World?" and "Could Bruce Willis Predict the End of the World?" were published in the University of Leicester Journal of Special Physics Topics.
The papers come on the heels of a recent NASA report that said there are roughly 4,700 potentially hazardous asteroids, or as the agency calls them PHAs. NASA says these PHAs are a subset of a larger group of near-Earth asteroids but have the closest orbits to Earth's - passing within five million miles (or about eight million kilometers) and are big enough to survive passing through Earth's atmosphere and cause damage on a regional, or greater, scale
The numbers come from asteroid observations made by NASA's Wide-field Infrared Survey Explorer, (WISE) satellite which looked at the objects that orbit within 120 million miles of the of the sun into Earth's orbital vicinity, NASA said. Specifically NASA said NEOWISE sampled 107 PHAs to make predictions about the entire population as a whole. Findings indicate there are roughly 4,700 PHAs, plus or minus 1,500, with diameters larger than 330 feet (about 100 meters). So far, an estimated 20 to 30% of these objects have been found, NASA stated. Previous estimates of PHAs predicted similar numbers, they were rough approximations, NASA said.
MORE: The weirdest, wackiest and coolest sci/tech stories of 2012 (so far!)
Asteroids have also been in the news a lot lately. It has been widely reported that NASA could announce this month a manned project to land on an asteroid in the future. And in April Google executives Larry Page and Eric Schmidt and filmmaker James Cameron said they would bankroll a venture to survey and eventually extract precious metals and rare minerals from asteroids that orbit near Earth. Planetary Resources, based in Bellevue, Wash., initially will focus on developing and selling extremely low-cost robotic spacecraft for surveying missions.
And of course Doomsday 2012 scenarios have abounded in the news for a long time. NASA has spent some time shooting these theories down - including one of a world ending asteroid. "The Earth has always been subject to impacts by comets and asteroids, although big hits are very rare. The last big impact was 65 million years ago, and that led to the extinction of the dinosaurs. We have already determined that there are no threatening asteroids as large as the one that killed the dinosaurs. For any claims of disaster or dramatic changes in 2012, where is the science? Where is the evidence? There is none, and for all the fictional assertions, whether they are made in books, movies, documentaries or over the Internet, we cannot change that simple fact," NASA stated.
And of course Doomsday 2012 scenarios have abounded in the news for a long time. NASA has spent some time shooting these theories down - including one of a world ending asteroid. "The Earth has always been subject to impacts by comets and asteroids, although big hits are very rare. The last big impact was 65 million years ago, and that led to the extinction of the dinosaurs. We have already determined that there are no threatening asteroids as large as the one that killed the dinosaurs.
Do we know the dinosaurs were wiped out by an asteroid specifically, as opposed to a comet? And as far as comets go, we have no way of cataloguing what is out there. Its staggeringly improbable that there's a 1000km comet out there with a Near Earth Orbit -- that's the size of Ceres, it would be a dwarf planet -- but there could be all sorts of 20km comets out there with hazardous orbits and we just wouldn't know. So that statement is misleading.
I think they usually say it was an asteroid but I'm not sure. It seems more likely that the dinosaurs were wiped out by a combination of blows. Maybe the Earth was in a part of the galaxy with a lot of energetic activity, a star passing close to our solarsystem creating increased bombardment, the impact might have caused a supervolcano on the opposit side of the planet a few thousand years later and so on.
Modax wrote:Do we know the dinosaurs were wiped out by an asteroid specifically, as opposed to a comet? And as far as comets go, we have no way of cataloguing what is out there. Its staggeringly improbable that there's a 1000km comet out there with a Near Earth Orbit -- that's the size of Ceres, it would be a dwarf planet -- but there could be all sorts of 20km comets out there with hazardous orbits and we just wouldn't know. So that statement is misleading.
It generally assumed due to the make up of the 'boundary formerly know as K-T'. Comets usually do not carry enough iridium contamination to create such a global layer. Other trace elements in the boundary also point towards a chondritic origin. http://en.wikipedia.org/wiki/Alvarez_hypothesis
A minute's thought suggests that the very idea of this is stupid. A more detailed examination raises the possibility that it might be an answer to the question "how could the Germans win the war after the US gets involved?" - Captain Seafort, in a thread proposing a 1942 'D-Day' in Quiberon Bay
Modax wrote:Do we know the dinosaurs were wiped out by an asteroid specifically, as opposed to a comet? And as far as comets go, we have no way of cataloguing what is out there. Its staggeringly improbable that there's a 1000km comet out there with a Near Earth Orbit -- that's the size of Ceres, it would be a dwarf planet -- but there could be all sorts of 20km comets out there with hazardous orbits and we just wouldn't know. So that statement is misleading.
Comets are made of (dirty) ice, that does not like reentry. Not just the heat, but the shock of slamming into atmosphere. Asteoids with a relatively solid metal core stand a far better chance of surviving both and slamming on the ground.
I'm nobody. Nobody at all. But the secrets of the universe don't mind. They reveal themselves to nobodies who care. -- Stereotypical spacecraft are pressurized. Less realistic spacecraft are pressurized to hold breathing atmosphere. Realistic spacecraft are pressurized because they are flying propellant tanks. -Isaac Kuo -- Good art has function as well as form. I hesitate to spend more than $50 on decorations of any kind unless they can be used to pummel an intruder into submission. -Sriad
someone_else wrote:Comets are made of (dirty) ice, that does not like reentry. Not just the heat, but the shock of slamming into atmosphere. Asteoids with a relatively solid metal core stand a far better chance of surviving both and slamming on the ground.
A few tens of million tons of dirty ice burning up in the atmosphere wouldn't be a lot better, at least as far as human civilisation is concerned.
There are hardly any excesses of the most crazed psychopath that cannot easily be duplicated by a normal kindly family man who just comes in to work every day and has a job to do.
-- (Terry Pratchett, Small Gods)
Replace "ginger" with "n*gger," and suddenly it become a lot less funny, doesn't it?
-- fgalkin
Yeah, just saying that to do the same degree of damage of an asteroid you need a far bigger comet or one on a pretty funky course since the thing is likely going to blow up like a firecracker when slamming on high atmosphere at their usual speeds in excess of 50 km/s at Earth due to their highly elliptic orbits.
NEO Asteroids instead have orbital speeds (and orbits) more similar to Earth so the speed of impact with the atmosphere is likely much less (i.e. they have far more chances of not breaking up too much even before you factor a solid-ish metal core).
So if you have to do a crapshoot and try to guess who killed off dinosaurs, an asteroid is much more likely.
I'm nobody. Nobody at all. But the secrets of the universe don't mind. They reveal themselves to nobodies who care. -- Stereotypical spacecraft are pressurized. Less realistic spacecraft are pressurized to hold breathing atmosphere. Realistic spacecraft are pressurized because they are flying propellant tanks. -Isaac Kuo -- Good art has function as well as form. I hesitate to spend more than $50 on decorations of any kind unless they can be used to pummel an intruder into submission. -Sriad
Blowing up won't help much; all the debris is still smashing into the atmosphere and releasing its energy there.
What's really significant, I think, is the iridium layer at the K-T boundary- a comet just shouldn't contain that much iridium unless it's the size of a small moon, in which case it should have done enough damage to... I'd expect something like that to significantly rearrange plate tectonics, let alone cause an extinction event by global climate change.
Ehm, you mean massive reentry heating boiling off stuff? I never thought it was an issue.
The issue is if it goes in sea and causes massive tsunamis or hits dry land where there is something of interest. The smaller the chunks the less the overall damage.
You're turning a mass-extintion into a "we just lost California/everything a few km from West Coast, President".
I'm nobody. Nobody at all. But the secrets of the universe don't mind. They reveal themselves to nobodies who care. -- Stereotypical spacecraft are pressurized. Less realistic spacecraft are pressurized to hold breathing atmosphere. Realistic spacecraft are pressurized because they are flying propellant tanks. -Isaac Kuo -- Good art has function as well as form. I hesitate to spend more than $50 on decorations of any kind unless they can be used to pummel an intruder into submission. -Sriad
It's the other way round: instead of having a (somewhat) local impact, you shower a whole hemisphere with debris. Since you seem to be talking about a sub global extiction size asteroid, that is prefarable.
This is pre-WWII. You can sort of tell from the sketch style, from thee way it refers to Japan (Japan in the 1950s was still rebuilding from WWII), the spelling of Tokyo, lots of details. Nothing obvious... except that the upper right hand corner of the page reads "November 1931." --- Simon_Jester
I never thought it was an issue.