Tuesday, May 28, 2013
Post End of High School and Stuff
So this blog was originally created as part of an ongoing homework assignment in my Issues in Modern America class, but now the school year is over. Therefore this is no longer a place for homework and whatever, instead I will be using it off an on as my regular (regular as in not for school not as in regularly updated content) blog-ish type thing. Feel free to read by back entries they're still worthwhile, but subsequent entries won't always be on similar tangents. So without further ado; Welcome to my blog!
Wednesday, May 15, 2013
Rain of Iron and Ice #4
Now back to info about history as it relates to asteroid/meteorite impacts!
The space race is given (rather interestingly) a quick run-through that also manages to capture more info than I knew about it. Races to get probes to the Moon, Mars, and Venus are described and the successes and failures of both Russians and Americans were numerous. So it was very exciting when three American probes returned over 17000 images of the moon that depicted enormous craters to those less than a meter in size. These images also showed that these were all impact craters as evidence for volcanic activity was absent. However, the plethora of craters told scientists nothing about the frequency of their impacts because no data could yet be collected as to their age. The crater ages were later measured by Apollo space missions allowing for accurate calculations of cratering rates both on the Moon and the infall rate of asteroids and meteorites on Earth. The evidence collected by later spacecraft of Mars and Mercury showed that Earth was in prime impact real estate, but scientists were perplexed by an apparent lack of evidence and so a quest to find evidence of impacts on Earth began. And by 1962 more than 200 Earth craters had been identified and authenticated. The biggest of these was the 65 million year old, 200+ Km wide Yucatán Peninsula crater which is now believed to be evidence of the asteroid that wiped out the dinosaurs. Using all this data a variety of frequency estimates were made. It was approximated that hundred-megaton (about 5 times more powerful than a WWII nuke like the ones from Hiroshima or Nagasaki) impacts occurred every 1500 years, one gigaton impacts every 12000 years, teraton impacts every 800000 years and petaton (globally devastating) impacts every 100 million years (Lewis 74). Other, smaller impacts are more common but were harder to measure with the devices of the time.
In 1967 in response to the close approach of the asteroid Icarus (which had no chance of actually hitting Earth but created quite a stir due to the closeness of its approach) an M.I.T. class was tasked with creating a solution if it was discovered that Icarus was on a collision course with Earth. The end of the year presentation by students was attended by the M.I.T. community, and the press (who ended up circulating widely inflated reports about the circumstances of the asteroid's pass by the Earth). However, Icarus was nothing new to astronomers who had known about it since 1949 when it became the 13th body to have an orbit that brought it close to Earth.
I'm glad that I'm finally getting where I want to go with this book. The information about the relative frequency of asteroid/meteorite impacts on Earth is very intriguing as is the 1967 M.I.T. project which suggested one of the favorite methods in the case of imminent asteroid impact; use a satellite to slowly pull the asteroid out of an Earth-bound trajectory.
The space race is given (rather interestingly) a quick run-through that also manages to capture more info than I knew about it. Races to get probes to the Moon, Mars, and Venus are described and the successes and failures of both Russians and Americans were numerous. So it was very exciting when three American probes returned over 17000 images of the moon that depicted enormous craters to those less than a meter in size. These images also showed that these were all impact craters as evidence for volcanic activity was absent. However, the plethora of craters told scientists nothing about the frequency of their impacts because no data could yet be collected as to their age. The crater ages were later measured by Apollo space missions allowing for accurate calculations of cratering rates both on the Moon and the infall rate of asteroids and meteorites on Earth. The evidence collected by later spacecraft of Mars and Mercury showed that Earth was in prime impact real estate, but scientists were perplexed by an apparent lack of evidence and so a quest to find evidence of impacts on Earth began. And by 1962 more than 200 Earth craters had been identified and authenticated. The biggest of these was the 65 million year old, 200+ Km wide Yucatán Peninsula crater which is now believed to be evidence of the asteroid that wiped out the dinosaurs. Using all this data a variety of frequency estimates were made. It was approximated that hundred-megaton (about 5 times more powerful than a WWII nuke like the ones from Hiroshima or Nagasaki) impacts occurred every 1500 years, one gigaton impacts every 12000 years, teraton impacts every 800000 years and petaton (globally devastating) impacts every 100 million years (Lewis 74). Other, smaller impacts are more common but were harder to measure with the devices of the time.
In 1967 in response to the close approach of the asteroid Icarus (which had no chance of actually hitting Earth but created quite a stir due to the closeness of its approach) an M.I.T. class was tasked with creating a solution if it was discovered that Icarus was on a collision course with Earth. The end of the year presentation by students was attended by the M.I.T. community, and the press (who ended up circulating widely inflated reports about the circumstances of the asteroid's pass by the Earth). However, Icarus was nothing new to astronomers who had known about it since 1949 when it became the 13th body to have an orbit that brought it close to Earth.
I'm glad that I'm finally getting where I want to go with this book. The information about the relative frequency of asteroid/meteorite impacts on Earth is very intriguing as is the 1967 M.I.T. project which suggested one of the favorite methods in the case of imminent asteroid impact; use a satellite to slowly pull the asteroid out of an Earth-bound trajectory.
Rain of Iron and Ice #3
How meteorite impacts work:
This section begins by differentiating meteors from meteorites. If a meteor doesn't complete its fall to Earth, if it burns up on the way, it remains a meteor. If a meteor falls from the sky and hits the Earth it becomes a meteorite.
As a meteor enters the Earth's atmosphere it begins to be ablated (the name for the process in which a projectile melts and vaporizes) and the rate at which this occurs is based on the density of the air in which the meteor is traveling (which doubles every 5K) and how fast the object is going. This means that a faster moving object will penetrate to a lesser depth into the Earth's atmosphere than a slow moving object.
The book brings up that since asteroids and meteorites regularly impact the Earth or other planets, if they weren't replenished there would be no more and meteor showers would stop. However this isn't the case so scientists came up with some hypotheses: 1, that Jupiter's gravity acts on harmonically orbiting asteroids slowly pulling their orbit away from normal sending them on tracks through the inner solar system or 2, that comets with long orbits are disturbed by Jupiter's gravity and sent on shorter orbits through the central solar system. Astronomers then calculated the approximate number of asteroids and meteors that are created and how many each hypothesis would produce and the numbers suggest that both hypotheses are correct, about 50% of newly created Near Earth Asteroids come from bodies dislodged from the Asteroid Belt by Jupiter and the other 50% come from comets that Jupiter's gravity effects in such a way to have them orbit by the Earth too. This is relevant because comets and asteroids have different chemical makeups and so they'll do different things when they come into contact with the Earth's atmosphere.
Not all impacts leave lasting evidence. Since they are random the vast majority will land in the ocean and disappear without a trace. Additionally events like the Tunguska meteorite occur with unknown frequency. The meteorite exploded with great force, but because it didn't create a crater the evidence of felled trees would only last 100 years or so. Despite not impacting the Earth the Tunguska meteorite could still have caused plenty of damage if it had come only minutes or hours later and exploded over a populated city. The only evidence that will remain of the Tunguska event will be small spheres of magnetite which no one will be looking for because there isn't a crater.
Here is what happens when there is an impact explosion: the kinetic energy of the object is almost immediately converted into heat which produces a small, exceedingly hot fireball of vast energy and pressure. The fireball briefly reaches temperatures of several hundreds of thousands of degrees and the energy released is significantly greater than that of the Sun before expanding faster than the speed of sound and producing high amounts of x-rays. The fireball will continue to expand until its pressure is equal to that of the surrounding atmosphere. At this point the fireball, which is still ridiculously hot, will begin to rise from the burning remnants of whatever was on the ground and allowing the relatively cold surrounding air to rush in. These winds can reach hurricane speeds and serve to fan the blaze around ground zero. The fireball may release so much energy that surfaces illuminated by it can spontaneously burst into flame while anything within the range of the fireball is vaporized (this can occur even with relatively small explosions like the one in Halifax, Nova Scotia on December 6th 1917 during which many people were never found having been consumed by the explosion). Due to the forces involved the volume of matter excavated by the explosion will usually be about one hundred times greater than that of the impacting body (Lewis 59). The rapid excavation creates a shock wave both in the air and in the ground causing buildings several kilometers away from the explosion to have the ground beneath them pushed outwards. The glass in these buildings will shatter and then accelerate to near the speed of sound becoming deadly projectiles directed at the people who may be unfortunate enough to be around (or in the case of the recent Russian meteor, the people who went to their windows to see what had happened). Aerial explosions typically effect a larger area less severely and impacts or explosions in water will have a similar effect except that the water will rush in to fill the gap left by the explosion, rising up in the center before splashing down again (this process can repeat several times). Such an initial explosion and the splashing that follows will often create tidal waves or tsunamis that will devastate shorelines nearby.
This is the kind of thing that some sort of prevention strategy would try to... well... prevent, and why shooting a rocket at an asteroid is usually a bad idea. If a rocket were to hit an asteroid and blow it up, usually the asteroid would simply be in many smaller pieces and these pieces could each go through the process described above. Fun stuff.
This section begins by differentiating meteors from meteorites. If a meteor doesn't complete its fall to Earth, if it burns up on the way, it remains a meteor. If a meteor falls from the sky and hits the Earth it becomes a meteorite.
As a meteor enters the Earth's atmosphere it begins to be ablated (the name for the process in which a projectile melts and vaporizes) and the rate at which this occurs is based on the density of the air in which the meteor is traveling (which doubles every 5K) and how fast the object is going. This means that a faster moving object will penetrate to a lesser depth into the Earth's atmosphere than a slow moving object.
The book brings up that since asteroids and meteorites regularly impact the Earth or other planets, if they weren't replenished there would be no more and meteor showers would stop. However this isn't the case so scientists came up with some hypotheses: 1, that Jupiter's gravity acts on harmonically orbiting asteroids slowly pulling their orbit away from normal sending them on tracks through the inner solar system or 2, that comets with long orbits are disturbed by Jupiter's gravity and sent on shorter orbits through the central solar system. Astronomers then calculated the approximate number of asteroids and meteors that are created and how many each hypothesis would produce and the numbers suggest that both hypotheses are correct, about 50% of newly created Near Earth Asteroids come from bodies dislodged from the Asteroid Belt by Jupiter and the other 50% come from comets that Jupiter's gravity effects in such a way to have them orbit by the Earth too. This is relevant because comets and asteroids have different chemical makeups and so they'll do different things when they come into contact with the Earth's atmosphere.
Not all impacts leave lasting evidence. Since they are random the vast majority will land in the ocean and disappear without a trace. Additionally events like the Tunguska meteorite occur with unknown frequency. The meteorite exploded with great force, but because it didn't create a crater the evidence of felled trees would only last 100 years or so. Despite not impacting the Earth the Tunguska meteorite could still have caused plenty of damage if it had come only minutes or hours later and exploded over a populated city. The only evidence that will remain of the Tunguska event will be small spheres of magnetite which no one will be looking for because there isn't a crater.
Here is what happens when there is an impact explosion: the kinetic energy of the object is almost immediately converted into heat which produces a small, exceedingly hot fireball of vast energy and pressure. The fireball briefly reaches temperatures of several hundreds of thousands of degrees and the energy released is significantly greater than that of the Sun before expanding faster than the speed of sound and producing high amounts of x-rays. The fireball will continue to expand until its pressure is equal to that of the surrounding atmosphere. At this point the fireball, which is still ridiculously hot, will begin to rise from the burning remnants of whatever was on the ground and allowing the relatively cold surrounding air to rush in. These winds can reach hurricane speeds and serve to fan the blaze around ground zero. The fireball may release so much energy that surfaces illuminated by it can spontaneously burst into flame while anything within the range of the fireball is vaporized (this can occur even with relatively small explosions like the one in Halifax, Nova Scotia on December 6th 1917 during which many people were never found having been consumed by the explosion). Due to the forces involved the volume of matter excavated by the explosion will usually be about one hundred times greater than that of the impacting body (Lewis 59). The rapid excavation creates a shock wave both in the air and in the ground causing buildings several kilometers away from the explosion to have the ground beneath them pushed outwards. The glass in these buildings will shatter and then accelerate to near the speed of sound becoming deadly projectiles directed at the people who may be unfortunate enough to be around (or in the case of the recent Russian meteor, the people who went to their windows to see what had happened). Aerial explosions typically effect a larger area less severely and impacts or explosions in water will have a similar effect except that the water will rush in to fill the gap left by the explosion, rising up in the center before splashing down again (this process can repeat several times). Such an initial explosion and the splashing that follows will often create tidal waves or tsunamis that will devastate shorelines nearby.
This is the kind of thing that some sort of prevention strategy would try to... well... prevent, and why shooting a rocket at an asteroid is usually a bad idea. If a rocket were to hit an asteroid and blow it up, usually the asteroid would simply be in many smaller pieces and these pieces could each go through the process described above. Fun stuff.
Tuesday, May 14, 2013
Rain of Iron and Ice #2
Rain of Iron and Ice continues to discuss the issues with proving that meteors were not heavenly bodies (or that they existed at all). Lewis brings up the issue that despite people finding a variety of strange iron deposits around the Earth they couldn't be confirmed as meteorites because there wasn't an observed fall to coincide with the found object. It wasn't until the late 1600's that scientists from the Royal Society of London or the Société Royale decided that uncivilized hicks might have something to offer. As science developed, our world view changed and more data came in about meteorites so that by 1759 the French Academy could editorialize that, "these meteors are not rare," which says a lot about how much danger we might be in. While it suggests that meteor impacts happen often, it also suggests that they aren't extraordinarily catastrophic since the world didn't end over and over again.
The first solid evidence for meteorites extraterrestrial origin came in 1800 and 1801 when E.C. Howard found chemical similarities in the compositions of meteors that were markedly different from local rocks. This difference in chemical makeup is the first indicator that meteors were, in fact, meteors and not random terrestrial rocks. France took slightly longer to confirm Howard's discoveries. It wasn't until 1803 that Antione-François de Fourcroy performed similar research to reach the same conclusion before commenting on the value of eye-witness accounts. He said, "I could distrust the imagination of a learned man, but I would place all my faith in the testimony of an ignorant person, because, by nature, the ignorant person has no imagination." Which is a rather back-handed compliment if you ask me. The book then continues into how people were unable to process the idea that rocks fell from the sky, so they simply ignored it.
Now we finally get to some good interesting info about the meteorites themselves. The book describes three types of meteors, Irons, Stones, and Stony-Irons (basically chocolate, vanilla, and swirl). With the Irons being able to easily pass through the atmosphere and the Stones usually having quite a bit more trouble.
There was a push against the idea that craters could be the result of the impacts of such bodies because hundreds of years earlier geologists had come to the conclusion that because Earth was so old catastrophic events would have no effect and have never happened. These impact craters would blow massive holes in a defining theory of geology and so many educated people resisted the idea, but when, in the early to mid 1900's the evidence became irrefutable, many more craters were found all over the world.
And I have finally found where the book begins to talk about how asteroid/meteorite impacts work!
The first solid evidence for meteorites extraterrestrial origin came in 1800 and 1801 when E.C. Howard found chemical similarities in the compositions of meteors that were markedly different from local rocks. This difference in chemical makeup is the first indicator that meteors were, in fact, meteors and not random terrestrial rocks. France took slightly longer to confirm Howard's discoveries. It wasn't until 1803 that Antione-François de Fourcroy performed similar research to reach the same conclusion before commenting on the value of eye-witness accounts. He said, "I could distrust the imagination of a learned man, but I would place all my faith in the testimony of an ignorant person, because, by nature, the ignorant person has no imagination." Which is a rather back-handed compliment if you ask me. The book then continues into how people were unable to process the idea that rocks fell from the sky, so they simply ignored it.
Now we finally get to some good interesting info about the meteorites themselves. The book describes three types of meteors, Irons, Stones, and Stony-Irons (basically chocolate, vanilla, and swirl). With the Irons being able to easily pass through the atmosphere and the Stones usually having quite a bit more trouble.
There was a push against the idea that craters could be the result of the impacts of such bodies because hundreds of years earlier geologists had come to the conclusion that because Earth was so old catastrophic events would have no effect and have never happened. These impact craters would blow massive holes in a defining theory of geology and so many educated people resisted the idea, but when, in the early to mid 1900's the evidence became irrefutable, many more craters were found all over the world.
And I have finally found where the book begins to talk about how asteroid/meteorite impacts work!
Rain of Iron and Ice by John S. Lewis #1
Rain of Iron and Ice by John S. Lewis is a book about the history of asteroid and comet impacts on Earth and the dangers they present. The book opens with a recreation of "events in Constantinople, A.D. 472" (1). It describes what people would have seen and their likely reactions to a fiery explosion, thinking that the world would end. The book continues by describing the early history of recording asteroid impacts. This was especially difficult in Europe because the people most likely to observe asteroid impacts were 'lowly uneducated peasants' and they're claims weren't taken seriously by 'educated' people from the Church or a university. Therefore most data about asteroid impacts during the Middle Ages and earlier come from the eastern societies like China or the Middle East. It wasn't until after the plague that a schism appeared in Europe between Science and the Church which allowed ideas based on observation instead of theology to prosper.
All the info about why there isn't much data about asteroid impacts is interesting, but because I chose this book hoping it had relevant info for my Marketplace of Ideas project, it is at this point proving somewhat disappointing. However I am certain (based on the cover) that after Lewis covers the basic history he will progress into the effects of asteroid impacts etc.
All the info about why there isn't much data about asteroid impacts is interesting, but because I chose this book hoping it had relevant info for my Marketplace of Ideas project, it is at this point proving somewhat disappointing. However I am certain (based on the cover) that after Lewis covers the basic history he will progress into the effects of asteroid impacts etc.
Thursday, May 2, 2013
Marketplace of Ideas
Started working on my Marketplace of Ideas project. I was basically inspired to do something with defending Earth from collisions with near Earth objects (asteroids, meteors, etc) after watching astrophysicist and director of the Hayden Planetarium, Neil DeGrasse Tyson talk about the asteroid Apophis which is a large asteroid projected to come extremely close to Earth on 4/13/2029 (coincidentally a Friday) and depending on its path at that time, it may hit Earth seven years later. I think this also ties in nicely to the recent meteor explosion over Russia back in February.
I've got a cool game planned that I think aptly shows how unequipped we (the people of Earth) are to defend ourselves in the case of a potential asteroid impact. In the first scenario the player would have to try to fit a square block into a round hole. Naturally this is impossible and represents what we could do if we were in danger of being impacted by an asteroid. Then the player would have to opportunity to try and fit a block of clay into a round hole. Something they'd be able to do with the tools I'd provide, representing what we could do (survive/not be impacted) should we find ourselves in danger of being impacted.
I've got a cool game planned that I think aptly shows how unequipped we (the people of Earth) are to defend ourselves in the case of a potential asteroid impact. In the first scenario the player would have to try to fit a square block into a round hole. Naturally this is impossible and represents what we could do if we were in danger of being impacted by an asteroid. Then the player would have to opportunity to try and fit a block of clay into a round hole. Something they'd be able to do with the tools I'd provide, representing what we could do (survive/not be impacted) should we find ourselves in danger of being impacted.
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