The idea that a vote cast by a person remains the same after he submitted it is taken very seriously in any democracy. Voting is the right of the citizen, and it's how we choose the people who make important decisions on our behalf. When the security of the ballot is compromised, so, too, is the individual's right to choose his leaders.
Quantum Suicide Image Gallery
Fabrice Coffrini/AFP/Getty Images
Votes cast in the Swiss canton of Geneva were protected for the first time by quantum cryptography. See quantum suicide images.
There are plentiful examples of vote tampering throughout history in the United States and in other countries. Votes get lost, the dead manage to show up on the poll results, and sometimes votes are even changed when they're tallied.
But, hopefully, the days when paper ballots get lost on the back roads of Florida en route to be counted will soon be gone, and the hanging chad will become an obscure joke on sitcom reruns from the early 21st century. In other words, it's possible that the votes we cast will soon become much more secure.
One of the ways to safeguard votes is to limit access to them when they're being transferred from precincts to central polling stations where they're tallied. And this is just what the Swiss are looking into. The nation best known for its neutrality is on the cutting edge of research into quantum cryptography. But unlike traditional cryptology methods -- encoding and decoding information or messages -- quantum cryptology depends on physics, not mathematics.
Video Gallery: Wrangling Photons
Researchers at the University of Bath are pioneering the development of photonic crystal fibers. These fibers can transmit data through light, changing the way we use everyday tools from medical equipment to grocery store scanners.
U¬sing a machine developed by Swiss manufacturer Id Quantique, votes cast in the Swiss canton of Geneva during the October 2007 parliamentary elections were transmitted using a secure encryption encoded by a key generated using photons -- tiny, massless packets of light. Since this method uses physics instead of math to create the key used to encrypt the data, there's little chance it can be cracked using mathematics. In other words, the votes cast by citizens in Geneva are more protected than ever.
Id Quantiques' quantum encryption is the first public use of such a technique. What's more, it has catapulted the little-known world of quantum cryptology onto the world stage. So how does it work? Since it's based on quantum physics -- the smallest level of matter science has been able to detect -- it can seem a little confusing. But don't worry, even quantum physicists find quantum physics incredibly perplexing.
In this article, we'll get to the bottom of how quantum encryption works, and how it differs from modern cryptology. But first, we'll look at the uses and the limitations of traditional cryptology methods.
Traditional Cryptology
Photo courtesy NSA
A German Enigma machine
Privacy is paramount when communicating sensitive information, and humans have invented some unusual ways to encode their conversations. In World War II, for example, the Nazis created a bulky machine called the Enigma that resembles a typewriter on steroids. This machine created one of the most difficult ciphers (encoded messages) of the pre-computer age.
Even after Polish resistance fighters made knockoffs of the machines -- complete with instructions on how the Enigma worked -- decoding messages was still a constant struggle for the Allies [source: Cambridge University]. As the codes were deciphered, however, the secrets yielded by the Enigma machine were so helpful that many historians have credited the code breaking as a important factor in the Allies' victory in the war.
What the Enigma machine was used for is called cryptology. This is the process of encoding (cryptography) and decoding (cryptoanalysis) information or messages (called plaintext). All of these processes combined are cryptology. Until the 1990s, cryptology was based on algorithms -- a mathematical process or procedure. These algorithms are used in conjunction with a key, a collection of bits (usually numbers). Without the proper key, it's virtually impossible to decipher an encoded message, even if you know what algorithm to use.
There are limitless possibilities for keys used in cryptology. But there are only two widely used methods of employing keys: public-key cryptology and secret-key cryptology. In both of these methods (and in all cryptology), the sender (point A) is referred to as Alice. Point B is known as Bob.
In the public-key cryptology (PKC) method, a user chooses two interrelated keys. He lets anyone who wants to send him a message know how to encode it using one key. He makes this key public. The other key he keeps to himself. In this manner, anyone can send the user an encoded message, but only the recipient of the encoded message knows how to decode it. Even the person sending the message doesn't know what code the user employs to decode it.
PKC is often compared to a mailbox that uses two keys. One unlocks the front of the mailbox, allowing anyone with a key to deposit mail. But only the recipient holds the key that unlocks the back of the mailbox, allowing only him to retrieve the messages.
The other usual method of traditional cryptology is secret-key cryptology (SKC). In this method, only one key is used by both Bob and Alice. The same key is used to both encode and decode the plaintext. Even the algorithm used in the encoding and decoding process can be announced over an unsecured channel. The code will remain uncracked as long as the key used remains secret.
SKC is similar to feeding a message into a special mailbox that grinds it together with the key. Anyone can reach inside and grab the cipher, but without the key, he won't be able to decipher it. The same key used to encode the message is also the only one that can decode it, separating the key from the message.
Traditional cryptology is certainly clever, but as with all encoding methods in code-breaking history, it's being phased out. Find out why on the next page.
Both the secret-key and public-key methods of cryptology have unique flaws. Oddly enough, quantum physics can be used to either solve or expand these flaws.
Henkster/SXC
The keys used to encode messages are so long that it would take a trillion years to crack one using conventional computers.
The problem with public-key cryptology is that it's based on the staggering size of the numbers created by the combination of the key and the algorithm used to encode the message. These numbers can reach unbelievable proportions. What's more, they can be made so that in order to understand each bit of output data, you have to also understand every other bit as well. This means that to crack a 128-bit key, the possible numbers used can reach upward to the 1038 power [source: Dartmouth College]. That's a lot of possible numbers for the correct combination to the key.
The keys used in modern cryptography are so large, in fact, that a billion computers working in conjunction with each processing a billion calculations per second would still take a trillion years to definitively crack a key [source: Dartmouth College]. This isn't a problem now, but it soon will be. Current computers will be replaced in the near future with quantum computers, which exploit the properties of physics on the immensely small quantum scale. Since they can operate on the quantum level, these computers are expected to be able to perform calculations and operate at speeds no computer in use now could possibly achieve. So the codes that would take a trillion years to break with conventional computers could possibly be cracked in much less time with quantum computers. This means that secret-key cryptology (SKC) looks to be the preferred method of transferring ciphers in the future.
But SKC has its problems as well. The chief problem with SKC is how the two users agree on what secret key to use. If you live next door to the person with whom you exchange secret information, this isn't a problem. All you have to do is meet in person and agree on a key. But what if you live in another country? Sure, you could still meet, but if your key was ever compromised, then you would have to meet again and again.
It's possible to send a message concerning which key a user would like to use, but shouldn't that message be encoded, too? And how do the users agree on what secret key to use to encode the message about what secret key to use for the original message? The problem with secret-key cryptology is that there's almost always a place for an unwanted third party to listen in and gain information the users don't want that person to have. This is known in cryptology as the key distribution problem.
It's one of the great challenges of cryptology: To keep unwanted parties -- or eavesdroppers -- from learning of sensitive information. After all, if it was OK for just anyone to hear, there would be no need to encrypt a message.
Quantum physics has provided a way around this problem. By harnessing the unpredictable nature of matter at the quantum level, physicists have figured out a way to exchange information on secret keys. Coming up, we'll find out how quantum physics has revolutionized cryptology. But first, a bit on photons.
Photon Properties
Photons are some pretty amazing particles. They have no mass, they're the smallest measure of light, and they can exist in all of their possible states at once, called the wave function. This means that whatever direction a photon can spin in -- say, diagonally, vertically and horizontally -- it does all at once. Light in this state is called unpolarized. This is exactly the same as if you constantly moved east, west, north, south, and up-and-down at the same time. Mind-boggling? You bet. But don't let this throw you off; even quantum physicists are grappling with the implications of the wave function.
The foundation of quantum physics is the unpredictability factor. This unpredictability is pretty much defined by Heisenberg's Uncertainty Principle. This principle says, essentially, that it's impossible to know both an object's position and velocity -- at the same time.
But when dealing with photons for encryption, Heisenberg's principle can be used to our advantage. To create a photon, quantum cryptographers use LEDs -- light emitting diodes, a source of unpolarized light. LEDs are capable of creating just one photon at a time, which is how a string of photons can be created, rather than a wild burst. Through the use of polarization filters, we can force the photon to take one state or another -- or polarize it. If we use a vertical polarizing filter situated beyond a LED, we can polarize the photons that emerge: The photons that aren't absorbed will emerge on the other side with a vertical spin ( ).
The thing about photons is that once they're polarized, they can't be accurately measured again, except by a filter like the one that initially produced their current spin. So if a photon with a vertical spin is measured through a diagonal filter, either the photon won't pass through the filter or the filter will affect the photon's behavior, causing it to take a diagonal spin. In this sense, the information on the photon's original polarization is lost, and so, too, is any information attached to the photon's spin.
So how do you attach information to a photon's spin? That's the essence of quantum cryptography. Read the next page to find out how quantum cryptography works.
Using Quantum Cryptology
Quantum cryptography uses photons to transmit a key. Once the key is transmitted, coding and encoding using the normal secret-key method can take place. But how does a photon become a key? How do you attach information to a photon's spin?
This is where binary code comes into play. Each type of a photon's spin represents one piece of information -- usually a 1 or a 0, for binary code. This code uses strings of 1s and 0s to create a coherent message. For example, 11100100110 could correspond with h-e-l-l-o. So a binary code can be assigned to each photon -- for example, a photon that has a vertical spin ( ) can be assigned a 1. Alice can send her photons through randomly chosen filters and record the polarization of each photon. She will then know what photon polarizations Bob should receive.
When Alice sends Bob her photons using an LED, she'll randomly polarize them through either the X or the + filters, so that each polarized photon has one of four possible states: (), (--), (/) or ( ) [source: Vittorio]. As Bob receives these photons, he decides whether to measure each with either his + or X filter -- he can't use both filters together. Keep in mind, Bob has no idea what filter to use for each photon, he's guessing for each one. After the entire transmission, Bob and Alice have a non-encrypted discussion about the transmission.
The reason this conversation can be public is because of the way it's carried out. Bob calls Alice and tells her which filter he used for each photon, and she tells him whether it was the correct or incorrect filter to use. Their conversation may sound a little like this:
• Bob: Plus
Alice: Correct
• Bob: Plus
Alice: Incorrect
• Bob: X
Alice: Correct
Since Bob isn't saying what his measurements are -- only the type of filter he used -- a third party listening in on their conversation can't determine what the actual photon sequence is.
Here's an example. Say Alice sent one photon as a ( / ) and Bob says he used a + filter to measure it. Alice will say "incorrect" to Bob. But if Bob says he used an X filter to measure that particular photon, Alice will say "correct." A person listening will only know that that particular photon could be either a ( / ) or a ( ), but not which one definitively. Bob will know that his measurements are correct, because a (--) photon traveling through a + filter will remain polarized as a (--) photon after it passes through the filter.
After their odd conversation, Alice and Bob both throw out the results from Bob's incorrect guesses. This leaves Alice and Bob with identical strings of polarized protons. It my look a little like this: -- / / -- -- -- / … and so on. To Alice and Bob, this is a meaningless string of photons. But once binary code is applied, the photons become a message. Bob and Alice can agree on binary assignments, say 1 for photons polarized as ( ) and ( -- ) and 0 for photons polarized like ( / ) and ( ).
This means that their string of photons now looks like this: 11110000011110001010. Which can in turn be translated into English, Spanish, Navajo, prime numbers or anything else the Bob and Alice use as codes for the keys used in their encryption.
Introducing Eve
The goal of quantum cryptology is to thwart attempts by a third party to eavesdrop on the encrypted message. In cryptology, an eavesdropper is referred to as Eve.
In modern cryptology, Eve (E) can passively intercept Alice and Bob's encrypted message -- she can get her hands on the encrypted message and work to decode it without Bob and Alice knowing she has their message. Eve can accomplish this in different ways, such as wiretapping Bob or Alice's phone or reading their secure e-mails.
Quantum cryptology is the first cryptology that safeguards against passive interception. Since we can't measure a photon without affecting its behavior, Heisenberg's Uncertainty Principle emerges when Eve makes her own eavesdrop measurements.
Here's an example. If Alice sends Bob a series of polarized photons, and Eve has set up a filter of her own to intercept the photons, Eve is in the same boat as Bob: Neither has any idea what the polarizations of the photons Alice sent are. Like Bob, Eve can only guess which filter orientation (for example an X filter or a + filter) she should use to measure the photons.
After Eve has measured the photons by randomly selecting filters to determine their spin, she will pass them down the line to Bob using her own LED with a filter set to the alignment she chose to measure the original photon. She does to cover up her presence and the fact that she intercepted the photon message. But due to the Heisenberg Uncertainty Principle, Eve's presence will be detected. By measuring the photons, Eve inevitably altered some of them.
Say Alice sent to Bob one photon polarized to a ( -- ) spin, and Eve intercepts the photon. But Eve has incorrectly chosen to use an X filter to measure the photon. If Bob randomly (and correctly) chooses to use a + filter to measure the original photon, he will find it's polarized in either a ( / ) or ( ) position. Bob will believe he chose incorrectly until he has his conversation with Alice about the filter choice.
After all of the photons are received by Bob, and he and Alice have their conversation about the filters used to determine the polarizations, discrepancies will emerge if Eve has intercepted the message. In the example of the ( -- ) photon that Alice sent, Bob will tell her that he used a + filter. Alice will tell him this is correct, but Bob will know that the photon he received didn't measure as ( -- ) or ( ). Due to this discrepancy, Bob and Alice will know that their photon has been measured by a third party, who inadvertently altered it.
Alice and Bob can further protect their transmission by discussing some of the exact correct results after they've discarded the incorrect measurements. This is called a parity check. If the chosen examples of Bob's measurements are all correct -- meaning the pairs of Alice's transmitted photons and Bob's received photons all match up -- then their message is secure.
Bob and Alice can then discard these discussed measurements and use the remaining secret measurements as their key. If discrepancies are found, they should occur in 50 percent of the parity checks. Since Eve will have altered about 25 percent of the photons through her measurements, Bob and Alice can reduce the likelihood that Eve has the remaining correct information down to a one-in-a-million chance by conducting 20 parity checks [source: Vittorio].
In the next section, we'll look at some of the problems of quantum cryptology.
Quantum Cryptology Problems
Despite all of the security it offers, quantum cryptology also has a few fundamental flaws. Chief among these flaws is the length under which the system will work: It’s too short.
The original quantum cryptography system, built in 1989 by Charles Bennett, Gilles Brassard and John Smolin, sent a key over a distance of 36 centimeters [source: Scientific American]. Since then, newer models have reached a distance of 150 kilometers (about 93 miles). But this is still far short of the distance requirements needed to transmit information with modern computer and telecommunication systems.
The reason why the length of quantum cryptology capability is so short is because of interference. A photon’s spin can be changed when it bounces off other particles, and so when it's received, it may no longer be polarized the way it was originally intended to be. This means that a 1 may come through as a 0 -- this is the probability factor at work in quantum physics. As the distance a photon must travel to carry its binary message is increased, so, too, is the chance that it will meet other particles and be influenced by them.
One group of Austrian researchers may have solved this problem. This team used what Albert Einstein called “spooky action at a distance.” This observation of quantum physics is based on the entanglement of photons. At the quantum level, photons can come to depend on one another after undergoing some particle reactions, and their states become entangled. This entanglement doesn’t mean that the two photons are physically connected, but they become connected in a way that physicists still don't understand. In entangled pairs, each photon has the opposite spin of the other -- for example, ( / ) and ( ). If the spin of one is measured, the spin of the other can be deduced. What’s strange (or “spooky”) about the entangled pairs is that they remain entangled, even when they’re separated at a distance.
The Austrian team put a photon from an entangled pair at each end of a fiber optic cable. When one photon was measured in one polarization, its entangled counterpart took the opposite polarization, meaning the polarization the other photon would take could be predicted. It transmitted its information to its entangled partner. This could solve the distance problem of quantum cryptography, since there is now a method to help predict the actions of entangled photons.
Even though it’s existed just a few years so far, quantum cryptography may have already been cracked. A group of researchers from Massachusetts Institute of Technology took advantage of another property of entanglement. In this form, two states of a single photon become related, rather than the properties of two separate photons. By entangling the photons the team intercepted, they were able to measure one property of the photon and make an educated guess of what the measurement of another property -- like its spin -- would be. By not measuring the photon’s spin, they were able to identify its direction without affecting it. So the photon traveled down the line to its intended recipient none the wiser.
The MIT researchers admit that their eavesdropping method may not hold up to other systems, but that with a little more research, it could be perfected. Hopefully, quantum cryptology will be able to stay one step ahead as decoding methods continue to advance.
Source:www.howstuffworks.com
Tuesday, December 11, 2007
Saturday, November 24, 2007
Can the dodo be resurrected/
Resurrecting the Dodo and Other Extinct Creatures
Though some experts contend that it will never be possible, a great debate is underway in science about whether it's ethical to bring an extinct species back to life. Some animals are driven to extinction by human action, but others simply can't survive in their natural habitat or because of a major change in climate. Earth has gone through several mass extinctions, and bringing back many of these creatures could throw the world's ecosystem into chaos.
There's the question of where these creatures would go, especially since many extinct creatures would have no natural predators, except for humans. Would putting a saber-tooth tiger in the Siberian tundra disrupt the local food chain (in addition to terrorizing locals)? The alternative is keeping recreated species in a "Jurassic Park"-like zoo or nature preserve, which is exactly what a group of Japanese scientists proposed in 2005.
Image courtesy Andreas Meyer DreamstimeScientists believe that up to 10 million mammoths may be buried under the permafrost of the vast Siberian tundra. Some scientists to advocate cloning the animals.
In July 2007, a very well preserved woolly mammoth carcass was discovered in Siberia, reinvigorating debate about trying to resurrect the species. Some scientists contend that resurrecting extinct species may be easier with frozen animals. Sperm from mice frozen for 15 years have been used to inseminate living mice. The contention is that a female elephant could be inseminated with recovered mammoth sperm to create an elephant-mammoth hybrid. But dodos only lived in the warm climate of Mauritius and the surrounding islands -- the likelihood of finding a frozen one is slim to say the least -- so scientists would have to turn to other means to bring them back to life.
Another possibility proposed for mammoths is to remove DNA from an elephant egg and fuse it with the cell of a mammoth. That would create a creature that's 100 percent mammoth. A similar technique could conceivably be tried with a dodo, perhaps using a Nicobar pigeon, the dodo's closest non-extinct relative. But the cloned embryo would still have to be implanted into a living creature that can carry it to term (or until the egg is laid, in the case of the pigeon).
And yet another proposed method would be to use DNA from an extinct animal, like a dodo or mammoth, as a model. A living relative would then be genetically engineered to give birth to offspring that are essentially the model animal.
Extracting and decoding the DNA is the fundamental challenge. Cells break down over time, even in well preserved or frozen specimens. Gaps in DNA mean that piecing together the full genetic map of a creature may be impossible. Gaps can lead to birth defects or unviable offspring. Some scientists also believe that sperm frozen for tens, or even hundreds, of thousands of years won't be usable. Yet things that seemed impossible a decade or two ago are now happening thanks to the rapid pace of genetics research. Scientists have produced full genetic maps of several living species, including humans and dogs, and have even recreated the 1918 influenza virus that killed millions.
Image used in Public DomainThe dodo is commonly found in popular culture, sometimes representing stupidity or something going extinct or out of fashion.However, it’s also used on the official coat of arms for Mauritius.
However, even if better DNA samples, improved genome-decoding techniques and more knowledge of cloning eventually make it possible, do we want revived dodos or woolly mammoths lumbering around? Proponents of the process contend that much could be learned from bringing back these animals, while critics say that the process could quickly get out of control. For example, researchers believe that it's possible to fully map the Neanderthal genome, which should teach us more about the relationship between modern humans and our ancient forebears. But is it ethical and wise to take the next great leap by cloning a Neanderthal? Perhaps they learned nothing from the movie "Encino Man."
Source:http://www.howstuffworks.com
Though some experts contend that it will never be possible, a great debate is underway in science about whether it's ethical to bring an extinct species back to life. Some animals are driven to extinction by human action, but others simply can't survive in their natural habitat or because of a major change in climate. Earth has gone through several mass extinctions, and bringing back many of these creatures could throw the world's ecosystem into chaos.
There's the question of where these creatures would go, especially since many extinct creatures would have no natural predators, except for humans. Would putting a saber-tooth tiger in the Siberian tundra disrupt the local food chain (in addition to terrorizing locals)? The alternative is keeping recreated species in a "Jurassic Park"-like zoo or nature preserve, which is exactly what a group of Japanese scientists proposed in 2005.
Image courtesy Andreas Meyer DreamstimeScientists believe that up to 10 million mammoths may be buried under the permafrost of the vast Siberian tundra. Some scientists to advocate cloning the animals.
In July 2007, a very well preserved woolly mammoth carcass was discovered in Siberia, reinvigorating debate about trying to resurrect the species. Some scientists contend that resurrecting extinct species may be easier with frozen animals. Sperm from mice frozen for 15 years have been used to inseminate living mice. The contention is that a female elephant could be inseminated with recovered mammoth sperm to create an elephant-mammoth hybrid. But dodos only lived in the warm climate of Mauritius and the surrounding islands -- the likelihood of finding a frozen one is slim to say the least -- so scientists would have to turn to other means to bring them back to life.
Another possibility proposed for mammoths is to remove DNA from an elephant egg and fuse it with the cell of a mammoth. That would create a creature that's 100 percent mammoth. A similar technique could conceivably be tried with a dodo, perhaps using a Nicobar pigeon, the dodo's closest non-extinct relative. But the cloned embryo would still have to be implanted into a living creature that can carry it to term (or until the egg is laid, in the case of the pigeon).
And yet another proposed method would be to use DNA from an extinct animal, like a dodo or mammoth, as a model. A living relative would then be genetically engineered to give birth to offspring that are essentially the model animal.
Extracting and decoding the DNA is the fundamental challenge. Cells break down over time, even in well preserved or frozen specimens. Gaps in DNA mean that piecing together the full genetic map of a creature may be impossible. Gaps can lead to birth defects or unviable offspring. Some scientists also believe that sperm frozen for tens, or even hundreds, of thousands of years won't be usable. Yet things that seemed impossible a decade or two ago are now happening thanks to the rapid pace of genetics research. Scientists have produced full genetic maps of several living species, including humans and dogs, and have even recreated the 1918 influenza virus that killed millions.
Image used in Public DomainThe dodo is commonly found in popular culture, sometimes representing stupidity or something going extinct or out of fashion.However, it’s also used on the official coat of arms for Mauritius.
However, even if better DNA samples, improved genome-decoding techniques and more knowledge of cloning eventually make it possible, do we want revived dodos or woolly mammoths lumbering around? Proponents of the process contend that much could be learned from bringing back these animals, while critics say that the process could quickly get out of control. For example, researchers believe that it's possible to fully map the Neanderthal genome, which should teach us more about the relationship between modern humans and our ancient forebears. But is it ethical and wise to take the next great leap by cloning a Neanderthal? Perhaps they learned nothing from the movie "Encino Man."
Source:http://www.howstuffworks.com
Sunday, October 7, 2007
MRI
On July 3, 1977, an event took place that would forever alter the landscape of modern medicine. Outside the medical research community, this event made scarcely a ripple at first. This event was the first MRI exam ever performed on a human being.
It took almost five hours to produce one image. The images were, by today's standards, quite ugly. Dr. Raymond Damadian, a physician and scientist, along with colleagues Dr. Larry Minkoff and Dr. Michael Goldsmith, labored tirelessly for seven long years to reach this point. They named their original machine "Indomitable" to capture the spirit of their struggle to do what many said could not be done.
This machine is now in the Smithsonian Institution. As late as 1982, there were but a handful of MRI scanners in the entire United States. Today there are thousands. We can image in seconds what used to take hours.
MRI is a very complicated technology not well understood by many. In this article, you'll learn all about how a huge, noisy MRI machine actually works. What is happening to your body while you are in the machine? What can we see with an MRI and why do you have to hold so still during your exam? These questions and many more are answered here, so let's get started!
MRI scan
If you have ever seen an MRI machine, you know that the basic design used in most is a giant cube. The cube in a typical system might be 7 feet tall by 7 feet wide by 10 feet long (2 m by 2 m by 3 m), although new models are rapidly shrinking. There is a horizontal tube running through the magnet from front to back. This tube is known as the bore of the magnet. The patient, lying on his or her back, slides into the bore on a special table. Whether or not the patient goes in head first or feet first, as well as how far in the magnet they will go, is determined by the type of exam to be performed. MRI scanners vary in size and shape, and newer models have some degree of openness around the sides, but the basic design is the same. Once the body part to be scanned is in the exact center or isocenter of the magnetic field, the scan can begin.
In conjunction with radio wave pulses of energy, the MRI scanner can pick out a very small point inside the patient's body and ask it, essentially, "What type of tissue are you?" The point might be a cube that is half a millimeter on each side. The MRI system goes through the patient's body point by point, building up a 2-D or 3-D map of tissue types. It then integrates all of this information together to create 2-D images or 3-D models.
MRI provides an unparalleled view inside the human body. The level of detail we can see is extraordinary compared with any other imaging modality. MRI is the method of choice for the diagnosis of many types of injuries and conditions because of the incredible ability to tailor the exam to the particular medical question being asked. By changing exam parameters, the MRI system can cause tissues in the body to take on different appearances. This is very helpful to the radiologist (who reads the MRI) in determining if something seen is normal or not. We know that when we do "A," normal tissue will look like "B" -- if it doesn't, there might be an abnormality. MRI systems can also image flowing blood in virtually any part of the body. This allows us to perform studies that show the arterial system in the body, but not the tissue around it. In many cases, the MRI system can do this without a contrast injection, which is required in vascular radiology.
Magnetic resonance-
To understand how MRI works, let's start by focusing on the "magnetic" in MRI. The biggest and most important component in an MRI system is the magnet. The magnet in an MRI system is rated using a unit of measure known as a tesla. Another unit of measure commonly used with magnets is the gauss (1 tesla = 10,000 gauss). The magnets in use today in MRI are in the 0.5-tesla to 2.0-tesla range, or 5,000 to 20,000 gauss. Magnetic fields greater than 2 tesla have not been approved for use in medical imaging, though much more powerful magnets -- up to 60 tesla -- are used in research. Compared with the Earth's 0.5-gauss magnetic field, you can see how incredibly powerful these magnets are.
Numbers like that help provide an intellectual understanding of the magnetic strength, but everyday examples are also helpful. The MRI suite can be a very dangerous place if strict precautions are not observed. Metal objects can become dangerous projectiles if they are taken into the scan room. For example, paperclips, pens, keys, scissors, hemostats, stethoscopes and any other small objects can be pulled out of pockets and off the body without warning, at which point they fly toward the opening of the magnet (where the patient is placed) at very high speeds, posing a threat to everyone in the room. Credit cards, bank cards and anything else with magnetic encoding will be erased by most MRI systems.
The magnetic force exerted on an object increases exponentially as it nears the magnet. Imagine standing 15 feet (4.6 m) away from the magnet with a large pipe wrench in your hand. You might feel a slight pull. Take a couple of steps closer and that pull is much stronger. When you get to within 3 feet (1 meter) of the magnet, the wrench likely is pulled from your grasp. The more mass an object has, the more dangerous it can be -- the force with which it is attracted to the magnet is much stronger. Mop buckets, vacuum cleaners, IV poles, oxygen tanks, patient stretchers, heart monitors and countless other objects have all been pulled into the magnetic fields of MRI machines. The largest object I know of being pulled into a magnet is a fully loaded pallet jack (see below). Smaller objects can usually be pulled free of the magnet by hand. Large ones may have to be pulled away with a winch, or the magnetic field may even have to be shut down.
In this photograph, you can see a fully loaded pallet jack that has been sucked into the bore of an MRI system.
MRI safety-
Prior to allowing a patient or support staff member into the scan room, he or she is thoroughly screened for metal objects. Up to this point, we have only talked about external objects. Often however, patients have implants inside them that make it very dangerous for them to be in the presence of a strong magnetic field. Metallic fragments in the eye are very dangerous because moving those fragments could cause eye damage or blindness. Your eyes do not form scar tissue as the rest of your body does. A fragment of metal in your eye that has been there for 25 years is just as dangerous today as it was then -- there is no scar tissue to hold it in place. People with pacemakers cannot be scanned or even go near the scanner because the magnet can cause the pacemaker to malfunction. Aneurysm clips in the brain can be very dangerous as the magnet can move them, causing them to tear the very artery they were placed on to repair. Some dental implants are magnetic. Most orthopedic implants, even though they may be ferromagnetic, are fine because they are firmly embedded in bone. Even metal staples in most parts of the body are fine -- once they have been in a patient for a few weeks (usually six weeks), enough scar tissue has formed to hold them in place. Each time we encounter patients with an implant or metallic object inside their body, we investigate thoroughly to make sure it is safe to scan them. Some patients are turned away because it is too dangerous. When this happens, there is usually an alternative method of imaging that can help them.
Photo courtesy NASAThis image set is comparing a young individual (left) with an athletic male in his 80's (center) and with a person of similar age having Alzheimer's Disease (right), all imaged at the same level.
There are no known biological hazards to humans from being exposed to magnetic fields of the strength used in medical imaging today. Most facilities prefer not to image pregnant women. This is due to the fact that there has not been much research done in the area of biological effects on a developing fetus. The first trimester in a pregnancy is the most critical because that is the time of the most rapid cellular reproduction and division. The decision of whether or not to scan a pregnant patient is made on a case-by-case basis with consultation between the MRI radiologist and the patient's obstetrician. The benefit of performing the scan must outweigh the risk, however small, to the fetus and mother. Pregnant MRI technologists can still work in the department. In most cases, they are simply kept out of the actual scan room during their pregnancy.
MRI magnet-
There are three basic types of magnets used in MRI systems:
· Resistive magnets consist of many windings or coils of wire wrapped around a cylinder or bore through which an electric current is passed. This causes a magnetic field to be generated. If the electricity is turned off, the magnetic field dies out. These magnets are lower in cost to construct than a superconducting magnet (see below), but require huge amounts of electricity (up to 50 kilowatts) to operate because of the natural resistance in the wire. To operate this type of magnet above about the 0.3-tesla level would be prohibitively expensive.
· A permanent magnet is just that -- permanent. Its magnetic field is always there and always on full strength, so it costs nothing to maintain the field. The major drawback is that these magnets are extremely heavy: They weigh many, many tons at the 0.4-tesla level. A stronger field would require a magnet so heavy it would be difficult to construct. Permanent magnets are getting smaller, but are still limited to low field strengths.
· Superconducting magnets are by far the most commonly used. A superconducting magnet is somewhat similar to a resistive magnet -- coils or windings of wire through which a current of electricity is passed create the magnetic field. The important difference is that the wire is continually bathed in liquid helium at 452.4 degrees below zero. Yes, when you are inside the MRI machine, you are surrounded by a substance that is that cold! But don't worry, it is very well insulated by a vacuum in a manner identical to that used in a vacuum flask. This almost unimaginable cold causes the resistance in the wire to drop to zero, reducing the electrical requirement for the system dramatically and making it much more economical to operate. Superconductive systems are still very expensive, but they can easily generate 0.5-tesla to 2.0-tesla fields, allowing for much higher-quality imaging.
Future of MRI-
The future of MRI seems limited only by our imagination. This technology is still in its infancy, comparatively speaking. It has been in widespread use for less than 20 years (compared with over 100 years for X-rays).
Very small scanners for imaging specific body parts are being developed. For instance, a scanner that you simply place your arm, knee or foot in are currently in use in some areas. Our ability to visualize the arterial and venous system is improving all the time. Functional brain mapping (scanning a person's brain while he or she is performing a certain physical task such as squeezing a ball, or looking at a particular type of picture) is helping researchers better understand how the brain works. Research is under way in a few institutions to image the ventilation dynamics of the lungs through the use of hyperpolarized helium-3 gas. The development of new, improved ways to image strokes in their earliest stages is ongoing.
Predicting the future of MRI is speculative at best, but I have no doubt it will be exciting for those of us in the field, and very beneficial to the patients we care for. MRI is a field with a virtually limitless future, and I hope this article has helped you better understand the basics of how it all works!
It took almost five hours to produce one image. The images were, by today's standards, quite ugly. Dr. Raymond Damadian, a physician and scientist, along with colleagues Dr. Larry Minkoff and Dr. Michael Goldsmith, labored tirelessly for seven long years to reach this point. They named their original machine "Indomitable" to capture the spirit of their struggle to do what many said could not be done.
This machine is now in the Smithsonian Institution. As late as 1982, there were but a handful of MRI scanners in the entire United States. Today there are thousands. We can image in seconds what used to take hours.
MRI is a very complicated technology not well understood by many. In this article, you'll learn all about how a huge, noisy MRI machine actually works. What is happening to your body while you are in the machine? What can we see with an MRI and why do you have to hold so still during your exam? These questions and many more are answered here, so let's get started!
MRI scan
If you have ever seen an MRI machine, you know that the basic design used in most is a giant cube. The cube in a typical system might be 7 feet tall by 7 feet wide by 10 feet long (2 m by 2 m by 3 m), although new models are rapidly shrinking. There is a horizontal tube running through the magnet from front to back. This tube is known as the bore of the magnet. The patient, lying on his or her back, slides into the bore on a special table. Whether or not the patient goes in head first or feet first, as well as how far in the magnet they will go, is determined by the type of exam to be performed. MRI scanners vary in size and shape, and newer models have some degree of openness around the sides, but the basic design is the same. Once the body part to be scanned is in the exact center or isocenter of the magnetic field, the scan can begin.
In conjunction with radio wave pulses of energy, the MRI scanner can pick out a very small point inside the patient's body and ask it, essentially, "What type of tissue are you?" The point might be a cube that is half a millimeter on each side. The MRI system goes through the patient's body point by point, building up a 2-D or 3-D map of tissue types. It then integrates all of this information together to create 2-D images or 3-D models.
MRI provides an unparalleled view inside the human body. The level of detail we can see is extraordinary compared with any other imaging modality. MRI is the method of choice for the diagnosis of many types of injuries and conditions because of the incredible ability to tailor the exam to the particular medical question being asked. By changing exam parameters, the MRI system can cause tissues in the body to take on different appearances. This is very helpful to the radiologist (who reads the MRI) in determining if something seen is normal or not. We know that when we do "A," normal tissue will look like "B" -- if it doesn't, there might be an abnormality. MRI systems can also image flowing blood in virtually any part of the body. This allows us to perform studies that show the arterial system in the body, but not the tissue around it. In many cases, the MRI system can do this without a contrast injection, which is required in vascular radiology.
Magnetic resonance-
To understand how MRI works, let's start by focusing on the "magnetic" in MRI. The biggest and most important component in an MRI system is the magnet. The magnet in an MRI system is rated using a unit of measure known as a tesla. Another unit of measure commonly used with magnets is the gauss (1 tesla = 10,000 gauss). The magnets in use today in MRI are in the 0.5-tesla to 2.0-tesla range, or 5,000 to 20,000 gauss. Magnetic fields greater than 2 tesla have not been approved for use in medical imaging, though much more powerful magnets -- up to 60 tesla -- are used in research. Compared with the Earth's 0.5-gauss magnetic field, you can see how incredibly powerful these magnets are.
Numbers like that help provide an intellectual understanding of the magnetic strength, but everyday examples are also helpful. The MRI suite can be a very dangerous place if strict precautions are not observed. Metal objects can become dangerous projectiles if they are taken into the scan room. For example, paperclips, pens, keys, scissors, hemostats, stethoscopes and any other small objects can be pulled out of pockets and off the body without warning, at which point they fly toward the opening of the magnet (where the patient is placed) at very high speeds, posing a threat to everyone in the room. Credit cards, bank cards and anything else with magnetic encoding will be erased by most MRI systems.
The magnetic force exerted on an object increases exponentially as it nears the magnet. Imagine standing 15 feet (4.6 m) away from the magnet with a large pipe wrench in your hand. You might feel a slight pull. Take a couple of steps closer and that pull is much stronger. When you get to within 3 feet (1 meter) of the magnet, the wrench likely is pulled from your grasp. The more mass an object has, the more dangerous it can be -- the force with which it is attracted to the magnet is much stronger. Mop buckets, vacuum cleaners, IV poles, oxygen tanks, patient stretchers, heart monitors and countless other objects have all been pulled into the magnetic fields of MRI machines. The largest object I know of being pulled into a magnet is a fully loaded pallet jack (see below). Smaller objects can usually be pulled free of the magnet by hand. Large ones may have to be pulled away with a winch, or the magnetic field may even have to be shut down.
In this photograph, you can see a fully loaded pallet jack that has been sucked into the bore of an MRI system.
MRI safety-
Prior to allowing a patient or support staff member into the scan room, he or she is thoroughly screened for metal objects. Up to this point, we have only talked about external objects. Often however, patients have implants inside them that make it very dangerous for them to be in the presence of a strong magnetic field. Metallic fragments in the eye are very dangerous because moving those fragments could cause eye damage or blindness. Your eyes do not form scar tissue as the rest of your body does. A fragment of metal in your eye that has been there for 25 years is just as dangerous today as it was then -- there is no scar tissue to hold it in place. People with pacemakers cannot be scanned or even go near the scanner because the magnet can cause the pacemaker to malfunction. Aneurysm clips in the brain can be very dangerous as the magnet can move them, causing them to tear the very artery they were placed on to repair. Some dental implants are magnetic. Most orthopedic implants, even though they may be ferromagnetic, are fine because they are firmly embedded in bone. Even metal staples in most parts of the body are fine -- once they have been in a patient for a few weeks (usually six weeks), enough scar tissue has formed to hold them in place. Each time we encounter patients with an implant or metallic object inside their body, we investigate thoroughly to make sure it is safe to scan them. Some patients are turned away because it is too dangerous. When this happens, there is usually an alternative method of imaging that can help them.
Photo courtesy NASAThis image set is comparing a young individual (left) with an athletic male in his 80's (center) and with a person of similar age having Alzheimer's Disease (right), all imaged at the same level.
There are no known biological hazards to humans from being exposed to magnetic fields of the strength used in medical imaging today. Most facilities prefer not to image pregnant women. This is due to the fact that there has not been much research done in the area of biological effects on a developing fetus. The first trimester in a pregnancy is the most critical because that is the time of the most rapid cellular reproduction and division. The decision of whether or not to scan a pregnant patient is made on a case-by-case basis with consultation between the MRI radiologist and the patient's obstetrician. The benefit of performing the scan must outweigh the risk, however small, to the fetus and mother. Pregnant MRI technologists can still work in the department. In most cases, they are simply kept out of the actual scan room during their pregnancy.
MRI magnet-
There are three basic types of magnets used in MRI systems:
· Resistive magnets consist of many windings or coils of wire wrapped around a cylinder or bore through which an electric current is passed. This causes a magnetic field to be generated. If the electricity is turned off, the magnetic field dies out. These magnets are lower in cost to construct than a superconducting magnet (see below), but require huge amounts of electricity (up to 50 kilowatts) to operate because of the natural resistance in the wire. To operate this type of magnet above about the 0.3-tesla level would be prohibitively expensive.
· A permanent magnet is just that -- permanent. Its magnetic field is always there and always on full strength, so it costs nothing to maintain the field. The major drawback is that these magnets are extremely heavy: They weigh many, many tons at the 0.4-tesla level. A stronger field would require a magnet so heavy it would be difficult to construct. Permanent magnets are getting smaller, but are still limited to low field strengths.
· Superconducting magnets are by far the most commonly used. A superconducting magnet is somewhat similar to a resistive magnet -- coils or windings of wire through which a current of electricity is passed create the magnetic field. The important difference is that the wire is continually bathed in liquid helium at 452.4 degrees below zero. Yes, when you are inside the MRI machine, you are surrounded by a substance that is that cold! But don't worry, it is very well insulated by a vacuum in a manner identical to that used in a vacuum flask. This almost unimaginable cold causes the resistance in the wire to drop to zero, reducing the electrical requirement for the system dramatically and making it much more economical to operate. Superconductive systems are still very expensive, but they can easily generate 0.5-tesla to 2.0-tesla fields, allowing for much higher-quality imaging.
Future of MRI-
The future of MRI seems limited only by our imagination. This technology is still in its infancy, comparatively speaking. It has been in widespread use for less than 20 years (compared with over 100 years for X-rays).
Very small scanners for imaging specific body parts are being developed. For instance, a scanner that you simply place your arm, knee or foot in are currently in use in some areas. Our ability to visualize the arterial and venous system is improving all the time. Functional brain mapping (scanning a person's brain while he or she is performing a certain physical task such as squeezing a ball, or looking at a particular type of picture) is helping researchers better understand how the brain works. Research is under way in a few institutions to image the ventilation dynamics of the lungs through the use of hyperpolarized helium-3 gas. The development of new, improved ways to image strokes in their earliest stages is ongoing.
Predicting the future of MRI is speculative at best, but I have no doubt it will be exciting for those of us in the field, and very beneficial to the patients we care for. MRI is a field with a virtually limitless future, and I hope this article has helped you better understand the basics of how it all works!
Thursday, June 28, 2007
C-4 Explosives
Dear Readers,
Here is some information on C-4 explosives:
Twenty years ago, most people didn't have any idea what C-4 was. Recently, it has become an all-too-familiar term, popping up in newspapers and on television all the time. In October 2000, terrorists used C-4 to attack the U.S.S. Cole, killing 17 sailors. In 1996, terrorists used C-4 to blow up the Khobar Towers U.S. military housing complex in Saudi Arabia. In December 2001, a man smuggled similar material, hidden in his shoes, onto a commercial airliner. C-4 has also been used in many of the Palestinian suicide bombings in Israel and the Israeli-occupied territories.
In this article, we'll find out what this powerful material is and see how it can wreak such destruction.
Basics of explosive:
The fundamental concept behind explosives is very simple. At the most basic level, an explosive is just something that burns or decomposes very quickly, producing a lot of heat and gas in a short amount of time.
Photo courtesy U.S. Department of DefenseSoldiers set off two C-4 charges on an air base runway during a training operation. Like other high explosives, C-4's destructive power comes from rapidly expanding hot gas.
A typical explosive consists of some explosive material, some sort of detonation device and, typically, some sort of housing. The explosive material undergoes a rapid chemical reaction, either a combustion or decomposition reaction, when triggered by heat or shock energy from the detonator.
In the chemical reaction, compounds break down to form various gases. The reactants (the original chemical compounds) have a lot of energy stored up as chemical bonds between different atoms. When the compound molecules break apart, the products (the resulting gases) may use some of this energy to form new bonds, but not all of it. Most of the "leftover" energy takes the form of extreme heat.
The concentrated gases are under very high pressure, so they expand rapidly. The heat speeds up the individual gas particles, boosting the pressure even higher. In a high explosive, the gas pressure is strong enough to destroy structures and injure and kill people. If the gas expands faster than the speed of sound, it generates a powerful shock wave. The pressure can also push pieces of solid material outward at great speed, causing them to hit people or structures with a lot of force.
C-4 is a high explosive designed for military use. In the next section, we'll find out what sets it apart from other explosives.
High and Low
In low explosives, such as the propellant in a bullet cartridge, the reaction occurs relatively slowly and the pressure isn't as damaging. The expanding gases only serve to push a small object. High explosives, such as C-4 and TNT, expand more rapidly, generating much greater pressure. Explosives experts refer to rapid explosive reactions as detonation and slower explosive reactions as deflagration.
What is C-4?
C-4, or composition 4, is one variety of plastic explosive. The basic idea of plastic explosives, also called plastic bonded explosives (PBX), is to combine explosive chemicals with a plastic binder material. The binder has two important jobs:
It coats the explosive material, so it's less sensitive to shock and heat. This makes it relatively safe to handle the explosive.
It makes the explosive material highly malleable. You can mold it into different shapes to change the direction of the explosion.
C-4 Ingredients
RDX - 91 percent
Di(2-ethylhexyl) sebacate - 5.3 percent
Polyisobutylene - 2.1 percent
Motor oil - 1.6 percent
The explosive material in C-4 is cyclotrimethylene-trinitramine (C3H6N6O6), commonly called RDX (which stands for "royal demolition explosive" or "research development explosive"). The additive material is made up of polyisobutylene, the binder, and di(2-ethylhexyl) sebacate, the plasticizer (the element that makes the material malleable). It also contains a small amount of motor oil and some 2, 3-dimethyl-2, 3-dinitrobutane (DMDNB), which functions as a chemical marker for security forces.
To make C-4 blocks, explosives manufacturers take RDX in powder form and mix it with water to form a slurry. They then add the binder material, dissolved in a solvent, and mix the materials with an agitator. They remove the solvent through distillation, and remove the water through drying and filtering. The result is a relatively stable, solid explosive with a consistency similar to modelling clay.
Just as with other explosives, you need to apply some energy to C-4 to kick off the chemical reaction. Because of the stabilizer elements, it takes a considerable shock to set off this reaction; lighting the C-4 with a match will just make it burn slowly, like a piece of wood (in Vietnam, soldiers actually burned C-4 as an improvised cooking fire). Even shooting the explosive with a rifle won't trigger the reaction. Only a detonator, or blasting cap will do the job properly.
Photo courtesy U.S. Department of DefenseA U.S. Army unit detonated C-4 explosives inside this Serbian battle tank during Operation Joint Guard.
A detonator is just a smaller explosive that's relatively easy to set off. An electrical detonator, for example, uses a brief charge to set off a small amount of explosive material. When somebody triggers the detonator (by transmitting the charge through detonator cord to a blasting cap, for example), the explosion applies a powerful shock that triggers the C-4 explosive material.
When the chemical reaction begins, the C-4 decomposes to release a variety of gases (notably, nitrogen and carbon oxides). The gases initially expand at about 26,400 feet per second (8,050 meters per second), applying a huge amount of force to everything in the surrounding area. At this expansion rate, it is totally impossible to outrun the explosion like they do in dozens of action movies. To the observer, the explosion is nearly instantaneous -- one second, everything's normal, and the next it's totally destroyed.
The explosion actually has two phases. The initial expansion inflicts most of the damage. It also creates a very low-pressure area around the explosion's origin -- the gases are moving outward so rapidly that they suck most of the gas out from the "middle" of the explosion. After the outward blast, gases rush back in to the partial vacuum, creating a second, less-destructive inward energy wave.
A small amount of C-4 packs a pretty big punch. Less than a pound of C-4 could potentially kill several people, and several military issue M112 blocks of C-4, weighing about 1.25 pounds (half a kilogram) each, could potentially demolish a truck. Demolition experts typically use a good amount of C-4 in order to do a job properly. To take out one 8-inch (20.3-centimeter) square steel beam, for example, they would probably use 8 to 10 pounds (3.6 to 4.5 kilograms) of C-4.
People apply C-4's explosive power toward all kinds of destruction. One common application is military demolition -- soldiers pack it into cracks and crevices to blow up heavy walls. It has also been widely used as an anti-personnel weapon, in battle and in terrorist attacks. In Vietnam, for example, soldiers used a number of C-4-based bombs and grenades. One notable weapon, the claymore mine, consisted of a C-4 block with several embedded ball bearings. When the C-4 was detonated, the ball bearings became deadly flying shrapnel (this sort of weapon was also featured in the movie Swordfish).
Unfortunately, C-4 will keep making headlines for years to come. Because of its stability and sheer destructive power, C-4 has attracted the attention of terrorists and guerilla fighters all over the world. A small amount of C-4 can do a lot of damage, and it's fairly easy to smuggle the explosive past light security forces. The U.S. military is the primary manufacturer of C-4, and it tightly guards its supply, but there are a number of other sources for similar explosive material (including Iran, which has a history of conflict with the United States). As long as it is readily accessible, C-4 will continue to be a primary weapon in the terrorist arsenal.
Source:
www.howstuffworks.com
Here is some information on C-4 explosives:
Twenty years ago, most people didn't have any idea what C-4 was. Recently, it has become an all-too-familiar term, popping up in newspapers and on television all the time. In October 2000, terrorists used C-4 to attack the U.S.S. Cole, killing 17 sailors. In 1996, terrorists used C-4 to blow up the Khobar Towers U.S. military housing complex in Saudi Arabia. In December 2001, a man smuggled similar material, hidden in his shoes, onto a commercial airliner. C-4 has also been used in many of the Palestinian suicide bombings in Israel and the Israeli-occupied territories.
In this article, we'll find out what this powerful material is and see how it can wreak such destruction.
Basics of explosive:
The fundamental concept behind explosives is very simple. At the most basic level, an explosive is just something that burns or decomposes very quickly, producing a lot of heat and gas in a short amount of time.
Photo courtesy U.S. Department of DefenseSoldiers set off two C-4 charges on an air base runway during a training operation. Like other high explosives, C-4's destructive power comes from rapidly expanding hot gas.
A typical explosive consists of some explosive material, some sort of detonation device and, typically, some sort of housing. The explosive material undergoes a rapid chemical reaction, either a combustion or decomposition reaction, when triggered by heat or shock energy from the detonator.
In the chemical reaction, compounds break down to form various gases. The reactants (the original chemical compounds) have a lot of energy stored up as chemical bonds between different atoms. When the compound molecules break apart, the products (the resulting gases) may use some of this energy to form new bonds, but not all of it. Most of the "leftover" energy takes the form of extreme heat.
The concentrated gases are under very high pressure, so they expand rapidly. The heat speeds up the individual gas particles, boosting the pressure even higher. In a high explosive, the gas pressure is strong enough to destroy structures and injure and kill people. If the gas expands faster than the speed of sound, it generates a powerful shock wave. The pressure can also push pieces of solid material outward at great speed, causing them to hit people or structures with a lot of force.
C-4 is a high explosive designed for military use. In the next section, we'll find out what sets it apart from other explosives.
High and Low
In low explosives, such as the propellant in a bullet cartridge, the reaction occurs relatively slowly and the pressure isn't as damaging. The expanding gases only serve to push a small object. High explosives, such as C-4 and TNT, expand more rapidly, generating much greater pressure. Explosives experts refer to rapid explosive reactions as detonation and slower explosive reactions as deflagration.
What is C-4?
C-4, or composition 4, is one variety of plastic explosive. The basic idea of plastic explosives, also called plastic bonded explosives (PBX), is to combine explosive chemicals with a plastic binder material. The binder has two important jobs:
It coats the explosive material, so it's less sensitive to shock and heat. This makes it relatively safe to handle the explosive.
It makes the explosive material highly malleable. You can mold it into different shapes to change the direction of the explosion.
C-4 Ingredients
RDX - 91 percent
Di(2-ethylhexyl) sebacate - 5.3 percent
Polyisobutylene - 2.1 percent
Motor oil - 1.6 percent
The explosive material in C-4 is cyclotrimethylene-trinitramine (C3H6N6O6), commonly called RDX (which stands for "royal demolition explosive" or "research development explosive"). The additive material is made up of polyisobutylene, the binder, and di(2-ethylhexyl) sebacate, the plasticizer (the element that makes the material malleable). It also contains a small amount of motor oil and some 2, 3-dimethyl-2, 3-dinitrobutane (DMDNB), which functions as a chemical marker for security forces.
To make C-4 blocks, explosives manufacturers take RDX in powder form and mix it with water to form a slurry. They then add the binder material, dissolved in a solvent, and mix the materials with an agitator. They remove the solvent through distillation, and remove the water through drying and filtering. The result is a relatively stable, solid explosive with a consistency similar to modelling clay.
Just as with other explosives, you need to apply some energy to C-4 to kick off the chemical reaction. Because of the stabilizer elements, it takes a considerable shock to set off this reaction; lighting the C-4 with a match will just make it burn slowly, like a piece of wood (in Vietnam, soldiers actually burned C-4 as an improvised cooking fire). Even shooting the explosive with a rifle won't trigger the reaction. Only a detonator, or blasting cap will do the job properly.
Photo courtesy U.S. Department of DefenseA U.S. Army unit detonated C-4 explosives inside this Serbian battle tank during Operation Joint Guard.
A detonator is just a smaller explosive that's relatively easy to set off. An electrical detonator, for example, uses a brief charge to set off a small amount of explosive material. When somebody triggers the detonator (by transmitting the charge through detonator cord to a blasting cap, for example), the explosion applies a powerful shock that triggers the C-4 explosive material.
When the chemical reaction begins, the C-4 decomposes to release a variety of gases (notably, nitrogen and carbon oxides). The gases initially expand at about 26,400 feet per second (8,050 meters per second), applying a huge amount of force to everything in the surrounding area. At this expansion rate, it is totally impossible to outrun the explosion like they do in dozens of action movies. To the observer, the explosion is nearly instantaneous -- one second, everything's normal, and the next it's totally destroyed.
The explosion actually has two phases. The initial expansion inflicts most of the damage. It also creates a very low-pressure area around the explosion's origin -- the gases are moving outward so rapidly that they suck most of the gas out from the "middle" of the explosion. After the outward blast, gases rush back in to the partial vacuum, creating a second, less-destructive inward energy wave.
A small amount of C-4 packs a pretty big punch. Less than a pound of C-4 could potentially kill several people, and several military issue M112 blocks of C-4, weighing about 1.25 pounds (half a kilogram) each, could potentially demolish a truck. Demolition experts typically use a good amount of C-4 in order to do a job properly. To take out one 8-inch (20.3-centimeter) square steel beam, for example, they would probably use 8 to 10 pounds (3.6 to 4.5 kilograms) of C-4.
People apply C-4's explosive power toward all kinds of destruction. One common application is military demolition -- soldiers pack it into cracks and crevices to blow up heavy walls. It has also been widely used as an anti-personnel weapon, in battle and in terrorist attacks. In Vietnam, for example, soldiers used a number of C-4-based bombs and grenades. One notable weapon, the claymore mine, consisted of a C-4 block with several embedded ball bearings. When the C-4 was detonated, the ball bearings became deadly flying shrapnel (this sort of weapon was also featured in the movie Swordfish).
Unfortunately, C-4 will keep making headlines for years to come. Because of its stability and sheer destructive power, C-4 has attracted the attention of terrorists and guerilla fighters all over the world. A small amount of C-4 can do a lot of damage, and it's fairly easy to smuggle the explosive past light security forces. The U.S. military is the primary manufacturer of C-4, and it tightly guards its supply, but there are a number of other sources for similar explosive material (including Iran, which has a history of conflict with the United States). As long as it is readily accessible, C-4 will continue to be a primary weapon in the terrorist arsenal.
Source:
www.howstuffworks.com
Monday, June 25, 2007
Dear readers,
Hope would have enjoyed the last information on NASA.Here is some new information on mobile viruses:
The first known cell-phone virus appeared in 2004 and didn't get very far. Cabir.A infected only a small number of Bluetooth-enabled phones and carried out no malicious action -- a group of malware developers created Cabir to prove it could be done. Their next step was to send it to anti-virus researchers, who began the process of developing a solution to a problem that promises to get a lot worse.
Cell-phone viruses are at the threshold of their effectiveness. At present, they can't spread very far and they don't do much damage, but the future might see cell-phone bugs that are as debilitating as computer viruses. In this article, we'll talk about how cell-phone viruses spread, what they can do and how you can protect your phone from current and future threats.
Basics of mobile virus
A cell-phone virus is basically the same thing as a computer virus -- an unwanted executable file that "infects" a device and then copies itself to other devices. But whereas a computer virus or worm spreads through e-mail attachments and Internet downloads, a cell-phone virus or worm spreads via Internet downloads, MMS (multimedia messaging service) attachments and Bluetooth transfers. The most common type of cell-phone infection right now occurs when a cell phone downloads an infected file from a PC or the Internet, but phone-to-phone viruses are on the rise. Current phone-to-ph
one viruses almost exclusively infect phones running the Symbian operating system. The large number of proprietary operating systems in the cell-phone world is one of the obstacles to mass infection. Cell-phone-virus writers have no Windows-level marketshare to target, so any virus will only affect a small percentage of phones.
Infected files usually show up disguised as applications like games, security patches, add-on functionalities and, of course, pornography and free stuff. Infected text messages sometimes steal the subject line from a message you've received from a friend, which of course increases the likelihood of your opening it -- but opening the message isn't enough to get infected. You have to choose to open the message attachment and agree to install the program, which is another obstacle to mass infection: To date, no reported phone-to-phone virus auto-installs. The installation obstacles and the methods of spreading limit the amount of damage the current generation of cell-phone virus can do.
How they spread?
Phones that can only make and receive calls are not at risk. Only smartphones with a Bluetooth connection and data capabilities can receive a cell-phone virus. These viruses spread primarily in three ways:
Internet downloads - The virus spreads the same way a traditional computer virus does. The user downloads an infected file to the phone by way of a PC or the phone's own Internet connection. This may include file-sharing downloads, applications available from add-on sites (such as ringtones or games) and false security patches posted on the Symbian Web site.
Bluetooth wireless connection - The virus spreads between phones by way of their Bluetooth connection. The user receives a virus via Bluetooth when the phone is in discoverable mode, meaning it can be seen by other Bluetooth-enabled phones. In this case, the virus spreads like an airborne illness. According to TechnologyReview.com, cell-phone-virus researchers at F-Secure's U.S. lab now conduct their studies in a bomb shelter so their research topics don't end up spreading to every Bluetooth-enabled phone in the vicinity.
Multimedia Messaging Service - The virus is an attachment to an MMS text message. As with computer viruses that arrive as e-mail attachments, the user must choose to open the attachment and then install it in order for the virus to infect the phone. Typically, a virus that spreads via MMS gets into the phone's contact list and sends itself to every phone number stored there.
In all of these transfer methods, the user has to agree at least once (and usually twice) to run the infected file. But cell-phone-virus writers get you to open and install their product the same way computer-virus writers do: The virus is typically disguised as a game, security patch or other desirable application.
The Commwarrior virus arrived on the scene in January 2005 and is the first cell-phone virus to effectively spread through an entire company via Bluetooth (see ComputerWorld.com: Phone virus spreads through Scandinavian company). It replicates by way of both Bluetooth and MMS. Once you receive and install the virus, it immediately starts looking for other Bluetooth phones in the vicinity to infect. At the same time, the virus sends infected MMS messages to every phone number in your address list. Commwarrior is probably one of the more effective viruses to date because it uses two methods to replicate itself.
So what does a virus like this do once it infects your phone?
Damage that may occur:
The first known cell-phone virus, Cabir, is entirely innocuous. All it does is sit in the phone and try to spread itself. Other cell-phone viruses, however, are not as harmless.
A virus might access and/or delete all of the contact information and calendar entries in your phone. It might send an infected MMS message to every number in your phone book -- and MMS messages typically cost money to send, so you're actually paying to send a virus to all of your friends, family members and business associates. On the worst-case-scenario end, it might delete or lock up certain phone applications or crash your phone completely so it's useless. Some reported viruses and their vital statistics are listed below.
Cell-phone Viruses
Cabir.AFirst reported: June 2004Attacks: Symbian Series 60 phonesSpreads via: BluetoothHarm: noneMore information (including disinfection): http://www.f-secure.com/v-descs/cabir.shtml
Skulls.AFirst reported: November 2004Attacks: various Symbian phonesSpreads via: Internet downloadHarm: disables all phone functions except sending/receiving callsMore information (including disinfection): http://www.f-secure.com/v-descs/skulls.shtml
Commwarrior.AFirst reported: January 2005Attacks: Symbian Series 60 phonesSpreads via: Bluetooth and MMSHarm: sends out expensive MMS messages to everyone in phonebook (in course of MMS replication)More information (including disinfection): http://www.f-secure.com/v-descs/commwarrior.shtml
Locknut.BFirst reported: March 2005Attacks: Symbian Series 60 phonesSpreads via: Internet download (disguised as patch for Symbian Series 60 phones)Harm: crashes system ROM; disables all phone functions; inserts other (inactive) malware into phoneMore information (including disinfection): http://www.f-secure.com/v-descs/locknut_b.shtml
Fontal.AFirst reported: April 2005Attacks: Symbian Series 60 phonesSpreads via: Internet downloadHarm: locks up phone in startup mode; disables phone entirelyMore information (including disinfection): http://www.f-secure.com/v-descs/fontal_a.shtml
As you can see from the above descriptions, cell-phone viruses have gotten a lot more harmful since the Cabir worm landed in the hands of researchers in 2004. But on the bright side, there are some steps you can take to protect your phone.
Protecting your phone:
The best way to protect yourself from cell-phone viruses is the same way you protect yourself from computer viruses: Never open anything if you don't know what it is, haven't requested it or have any suspicions whatsoever that it's not what it claims to be. That said, even the most cautious person can still end up with an infected phone. Here are some steps you can take to decrease your chances of installing a virus:
Turn off Bluetooth discoverable mode. Set your phone to "hidden" so other phones can't detect it and send it the virus. You can do this on the Bluetooth options screen.
Check security updates to learn about filenames you should keep an eye out for. It's not fool-proof -- the Commwarrior program generates random names for the infected files it sends out, so users can't be warned not to open specific filenames -- but many viruses can be easily identified by the filenames they carry. Security sites with detailed virus information include:
F-Secure
McAfee
Symantec
Some of these sites will send you e-mail updates with new virus information as it gets posted.
Install some type of security software on your phone. Numerous companies are developing security software for cell phones, some for free download, some for user purchase and some intended for cell-phone service providers. The software may simply detect and then remove the virus once it's received and installed, or it may protect your phone from getting certain viruses in the first place. Symbian has developed an anti-virus version of its operating system that only allows the phone's Bluetooth connection to accept secure files.
Although some in the cell-phone industry think the potential problem is overstated, most experts agree that cell-phone viruses are on the brink of their destructive power. Installing a "security patch" that ends up turning your phone into a useless piece of plastic is definitely something to be concerned about, but it could still get worse. Future possibilities include viruses that bug phones -- so someone can see every number you call and listen to your conversations -- and viruses that steal financial information, which would be a serious issue if smartphones end up being used as payment devices (see Bankrate.com: Paying by cell phone on the way). Ultimately, more connectivity means more exposure to viruses and faster spreading of infection. As smartphones become more common and more complex, so will the viruses that target them.
Source:www.howstuffworks.com
Hope would have enjoyed the last information on NASA.Here is some new information on mobile viruses:
The first known cell-phone virus appeared in 2004 and didn't get very far. Cabir.A infected only a small number of Bluetooth-enabled phones and carried out no malicious action -- a group of malware developers created Cabir to prove it could be done. Their next step was to send it to anti-virus researchers, who began the process of developing a solution to a problem that promises to get a lot worse.
Cell-phone viruses are at the threshold of their effectiveness. At present, they can't spread very far and they don't do much damage, but the future might see cell-phone bugs that are as debilitating as computer viruses. In this article, we'll talk about how cell-phone viruses spread, what they can do and how you can protect your phone from current and future threats.
Basics of mobile virus
A cell-phone virus is basically the same thing as a computer virus -- an unwanted executable file that "infects" a device and then copies itself to other devices. But whereas a computer virus or worm spreads through e-mail attachments and Internet downloads, a cell-phone virus or worm spreads via Internet downloads, MMS (multimedia messaging service) attachments and Bluetooth transfers. The most common type of cell-phone infection right now occurs when a cell phone downloads an infected file from a PC or the Internet, but phone-to-phone viruses are on the rise. Current phone-to-ph
one viruses almost exclusively infect phones running the Symbian operating system. The large number of proprietary operating systems in the cell-phone world is one of the obstacles to mass infection. Cell-phone-virus writers have no Windows-level marketshare to target, so any virus will only affect a small percentage of phones.
Infected files usually show up disguised as applications like games, security patches, add-on functionalities and, of course, pornography and free stuff. Infected text messages sometimes steal the subject line from a message you've received from a friend, which of course increases the likelihood of your opening it -- but opening the message isn't enough to get infected. You have to choose to open the message attachment and agree to install the program, which is another obstacle to mass infection: To date, no reported phone-to-phone virus auto-installs. The installation obstacles and the methods of spreading limit the amount of damage the current generation of cell-phone virus can do.
How they spread?
Phones that can only make and receive calls are not at risk. Only smartphones with a Bluetooth connection and data capabilities can receive a cell-phone virus. These viruses spread primarily in three ways:
Internet downloads - The virus spreads the same way a traditional computer virus does. The user downloads an infected file to the phone by way of a PC or the phone's own Internet connection. This may include file-sharing downloads, applications available from add-on sites (such as ringtones or games) and false security patches posted on the Symbian Web site.
Bluetooth wireless connection - The virus spreads between phones by way of their Bluetooth connection. The user receives a virus via Bluetooth when the phone is in discoverable mode, meaning it can be seen by other Bluetooth-enabled phones. In this case, the virus spreads like an airborne illness. According to TechnologyReview.com, cell-phone-virus researchers at F-Secure's U.S. lab now conduct their studies in a bomb shelter so their research topics don't end up spreading to every Bluetooth-enabled phone in the vicinity.
Multimedia Messaging Service - The virus is an attachment to an MMS text message. As with computer viruses that arrive as e-mail attachments, the user must choose to open the attachment and then install it in order for the virus to infect the phone. Typically, a virus that spreads via MMS gets into the phone's contact list and sends itself to every phone number stored there.
In all of these transfer methods, the user has to agree at least once (and usually twice) to run the infected file. But cell-phone-virus writers get you to open and install their product the same way computer-virus writers do: The virus is typically disguised as a game, security patch or other desirable application.
The Commwarrior virus arrived on the scene in January 2005 and is the first cell-phone virus to effectively spread through an entire company via Bluetooth (see ComputerWorld.com: Phone virus spreads through Scandinavian company). It replicates by way of both Bluetooth and MMS. Once you receive and install the virus, it immediately starts looking for other Bluetooth phones in the vicinity to infect. At the same time, the virus sends infected MMS messages to every phone number in your address list. Commwarrior is probably one of the more effective viruses to date because it uses two methods to replicate itself.
So what does a virus like this do once it infects your phone?
Damage that may occur:
The first known cell-phone virus, Cabir, is entirely innocuous. All it does is sit in the phone and try to spread itself. Other cell-phone viruses, however, are not as harmless.
A virus might access and/or delete all of the contact information and calendar entries in your phone. It might send an infected MMS message to every number in your phone book -- and MMS messages typically cost money to send, so you're actually paying to send a virus to all of your friends, family members and business associates. On the worst-case-scenario end, it might delete or lock up certain phone applications or crash your phone completely so it's useless. Some reported viruses and their vital statistics are listed below.
Cell-phone Viruses
Cabir.AFirst reported: June 2004Attacks: Symbian Series 60 phonesSpreads via: BluetoothHarm: noneMore information (including disinfection): http://www.f-secure.com/v-descs/cabir.shtml
Skulls.AFirst reported: November 2004Attacks: various Symbian phonesSpreads via: Internet downloadHarm: disables all phone functions except sending/receiving callsMore information (including disinfection): http://www.f-secure.com/v-descs/skulls.shtml
Commwarrior.AFirst reported: January 2005Attacks: Symbian Series 60 phonesSpreads via: Bluetooth and MMSHarm: sends out expensive MMS messages to everyone in phonebook (in course of MMS replication)More information (including disinfection): http://www.f-secure.com/v-descs/commwarrior.shtml
Locknut.BFirst reported: March 2005Attacks: Symbian Series 60 phonesSpreads via: Internet download (disguised as patch for Symbian Series 60 phones)Harm: crashes system ROM; disables all phone functions; inserts other (inactive) malware into phoneMore information (including disinfection): http://www.f-secure.com/v-descs/locknut_b.shtml
Fontal.AFirst reported: April 2005Attacks: Symbian Series 60 phonesSpreads via: Internet downloadHarm: locks up phone in startup mode; disables phone entirelyMore information (including disinfection): http://www.f-secure.com/v-descs/fontal_a.shtml
As you can see from the above descriptions, cell-phone viruses have gotten a lot more harmful since the Cabir worm landed in the hands of researchers in 2004. But on the bright side, there are some steps you can take to protect your phone.
Protecting your phone:
The best way to protect yourself from cell-phone viruses is the same way you protect yourself from computer viruses: Never open anything if you don't know what it is, haven't requested it or have any suspicions whatsoever that it's not what it claims to be. That said, even the most cautious person can still end up with an infected phone. Here are some steps you can take to decrease your chances of installing a virus:
Turn off Bluetooth discoverable mode. Set your phone to "hidden" so other phones can't detect it and send it the virus. You can do this on the Bluetooth options screen.
Check security updates to learn about filenames you should keep an eye out for. It's not fool-proof -- the Commwarrior program generates random names for the infected files it sends out, so users can't be warned not to open specific filenames -- but many viruses can be easily identified by the filenames they carry. Security sites with detailed virus information include:
F-Secure
McAfee
Symantec
Some of these sites will send you e-mail updates with new virus information as it gets posted.
Install some type of security software on your phone. Numerous companies are developing security software for cell phones, some for free download, some for user purchase and some intended for cell-phone service providers. The software may simply detect and then remove the virus once it's received and installed, or it may protect your phone from getting certain viruses in the first place. Symbian has developed an anti-virus version of its operating system that only allows the phone's Bluetooth connection to accept secure files.
Although some in the cell-phone industry think the potential problem is overstated, most experts agree that cell-phone viruses are on the brink of their destructive power. Installing a "security patch" that ends up turning your phone into a useless piece of plastic is definitely something to be concerned about, but it could still get worse. Future possibilities include viruses that bug phones -- so someone can see every number you call and listen to your conversations -- and viruses that steal financial information, which would be a serious issue if smartphones end up being used as payment devices (see Bankrate.com: Paying by cell phone on the way). Ultimately, more connectivity means more exposure to viruses and faster spreading of infection. As smartphones become more common and more complex, so will the viruses that target them.
Source:www.howstuffworks.com
Thursday, May 31, 2007
NASA
Dear readers,
I have collected some history of NASA that I thought you may like.Here it is:
President Dwight D. Eisenhower established the National Aeronautics and Space Administration in 1958, partially in response to the Soviet Union's launch of the first artificial satellite. NASA grew out of the National Advisory Committee on Aeronautics, which had been researching flight technology for more than 40 years. President John F. Kennedy focused NASA and the nation on sending astronauts to the moon by the end of the 1960s. Through the Mercury and Gemini projects, NASA developed the technology and skills it needed for the journey. On July 20, 1969, Neil Armstrong and Buzz Aldrin became the first of 12 men to walk on the moon, meeting Kennedy's challenge. In the meantime, NASA was continuing the aeronautics research pioneered by NACA. It also conducted purely scientific research and worked on developing applications for space technology, combining both pursuits in developing the first weather and communications satellites. After Apollo, NASA focused on developing America's ready access to space: the space shuttle. First launched in 1981, the Space Shuttle has had 112 successful flights, though two crews have been lost. In 2000, the United States and Russia established permanent human presence in space aboard the international space station, a multinational project representing the work of 16 nations. NASA has also continued its scientific research. In 1997, Mars Pathfinder became the first in a fleet of spacecraft that will explore Mars in the next decade, as we try to determine if life ever existed there. The Terra and Aqua satellites are flagships of a different fleet, this one in Earth orbit, which is designed to help us understand how our home world changes. NASA's aeronautics teams are focused on improved aircraft travel and making it safer and less polluting. Throughout its history, NASA has conducted or funded research that has led to numerous improvements to life here on Earth. Organization NASA Headquarters, in Washington, provides overall guidance and direction to the Agency, under the leadership of Administrator Michael Griffin. Ten field centers and a variety of installations conduct the day-to-day work, in laboratories, on air fields, in wind tunnels and in control rooms. NASA Today NASA conducts its work in four principle organizations, called mission directorates: Aeronautics: pioneering and proving new flight technologies that improve our ability to explore and which have practical applications on Earth. Exploration Systems: creating new capabilities for affordable, sustainable human and robotic exploration Science: exploring the Earth, moon, Mars and beyond; charting the best route of discovery; and reaping the benefits of Earth and space exploration for society. Space Operations: providing critical enabling technologies for much of the rest of NASA through the space shuttle, the international space station and flight support. In 2005, NASA's reach spans the universe. Spirit and Opportunity, the Mars Exploration Rovers, are still going on Mars after more than a year. Cassini is in orbit around Saturn. The Hubble Space Telescope continues to explore the deepest reaches of the cosmos. Closer to home, the latest crew of the international space station is extending the permanent human presence in space. Earth Science satellites are sending back unprecedented data on Earth's oceans, climate and other features. NASA's aeronautics team is working with other government organizations, universities, and industry to fundamentally improve the air transportation experience and retain our nation's leadership in global aviation. And, most importantly, NASA has begun returning the space shuttle to flight. Led by Commander Eileen Collins, the crew of Discovery tested new in-flight safety procedures and carried supplies to the international space station. The Vision for Space Exploration NASA's future is the Vision for Space Exploration, set forth by President George W. Bush in 2004. The key elements of the vision are: safely return the Space Shuttle to flight complete the International Space Station and retire the Space Shuttle by 2010 begin robotic missions to the moon by 2008 and return people there by 2020 continue robotic exploration of Mars and the Solar System develop a Crew Exploration Vehicle and other technologies required to send people beyond low Earth orbit. In September 2005, Administrator Michael Griffin unveiled NASA's initial plans for implementing the vision, returning to the moon by 2018. Included in the plan is the Crew Exploration Vehicle, NASA's next spaceship. Combining the best of Apollo and space shuttle technology, this new vehicle will replace the shuttle in flying to the international space station as well as take a crew of four to the surface of the moon. Though nearly 50 years old, NASA is only beginning the most exciting part of its existence.
If you want to know more about NASA,log on to:
http://www.nasa.gov/
I have collected some history of NASA that I thought you may like.Here it is:
President Dwight D. Eisenhower established the National Aeronautics and Space Administration in 1958, partially in response to the Soviet Union's launch of the first artificial satellite. NASA grew out of the National Advisory Committee on Aeronautics, which had been researching flight technology for more than 40 years. President John F. Kennedy focused NASA and the nation on sending astronauts to the moon by the end of the 1960s. Through the Mercury and Gemini projects, NASA developed the technology and skills it needed for the journey. On July 20, 1969, Neil Armstrong and Buzz Aldrin became the first of 12 men to walk on the moon, meeting Kennedy's challenge. In the meantime, NASA was continuing the aeronautics research pioneered by NACA. It also conducted purely scientific research and worked on developing applications for space technology, combining both pursuits in developing the first weather and communications satellites. After Apollo, NASA focused on developing America's ready access to space: the space shuttle. First launched in 1981, the Space Shuttle has had 112 successful flights, though two crews have been lost. In 2000, the United States and Russia established permanent human presence in space aboard the international space station, a multinational project representing the work of 16 nations. NASA has also continued its scientific research. In 1997, Mars Pathfinder became the first in a fleet of spacecraft that will explore Mars in the next decade, as we try to determine if life ever existed there. The Terra and Aqua satellites are flagships of a different fleet, this one in Earth orbit, which is designed to help us understand how our home world changes. NASA's aeronautics teams are focused on improved aircraft travel and making it safer and less polluting. Throughout its history, NASA has conducted or funded research that has led to numerous improvements to life here on Earth. Organization NASA Headquarters, in Washington, provides overall guidance and direction to the Agency, under the leadership of Administrator Michael Griffin. Ten field centers and a variety of installations conduct the day-to-day work, in laboratories, on air fields, in wind tunnels and in control rooms. NASA Today NASA conducts its work in four principle organizations, called mission directorates: Aeronautics: pioneering and proving new flight technologies that improve our ability to explore and which have practical applications on Earth. Exploration Systems: creating new capabilities for affordable, sustainable human and robotic exploration Science: exploring the Earth, moon, Mars and beyond; charting the best route of discovery; and reaping the benefits of Earth and space exploration for society. Space Operations: providing critical enabling technologies for much of the rest of NASA through the space shuttle, the international space station and flight support. In 2005, NASA's reach spans the universe. Spirit and Opportunity, the Mars Exploration Rovers, are still going on Mars after more than a year. Cassini is in orbit around Saturn. The Hubble Space Telescope continues to explore the deepest reaches of the cosmos. Closer to home, the latest crew of the international space station is extending the permanent human presence in space. Earth Science satellites are sending back unprecedented data on Earth's oceans, climate and other features. NASA's aeronautics team is working with other government organizations, universities, and industry to fundamentally improve the air transportation experience and retain our nation's leadership in global aviation. And, most importantly, NASA has begun returning the space shuttle to flight. Led by Commander Eileen Collins, the crew of Discovery tested new in-flight safety procedures and carried supplies to the international space station. The Vision for Space Exploration NASA's future is the Vision for Space Exploration, set forth by President George W. Bush in 2004. The key elements of the vision are: safely return the Space Shuttle to flight complete the International Space Station and retire the Space Shuttle by 2010 begin robotic missions to the moon by 2008 and return people there by 2020 continue robotic exploration of Mars and the Solar System develop a Crew Exploration Vehicle and other technologies required to send people beyond low Earth orbit. In September 2005, Administrator Michael Griffin unveiled NASA's initial plans for implementing the vision, returning to the moon by 2018. Included in the plan is the Crew Exploration Vehicle, NASA's next spaceship. Combining the best of Apollo and space shuttle technology, this new vehicle will replace the shuttle in flying to the international space station as well as take a crew of four to the surface of the moon. Though nearly 50 years old, NASA is only beginning the most exciting part of its existence.
If you want to know more about NASA,log on to:
http://www.nasa.gov/
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