Penulis : Bapak Rois Fathoni
(PhD candidate dari Department of Chemical EngineeringUniversity of Waterloo, Kanada dan dosen di Teknik Kimia, Univ Muhammadiyah Surakarta)
Al ‘ilmu Nuurun. Ilmu itu bagaikan cahaya. Manfaat Ilmu pengetahuan bagi manusia dalam mengarungi samudra kehidupan adalah bagaikan cahaya yang membebaskan manusia dari kegelapan. Sedemikian besar kedudukan ilmu ini bagi keselamatan dan kesejahteraan manusia, hingga Allah swt mendahulukan perintah menuntut ilmu ini sebelum perintah perintah yang lainnya (Al ’Alaq (96) : 1-5).
Alqur’an menggunakan dua kata yang berbeda untuk melukiskan cahaya matahari dan rembulan: dhiyaa’un untuk matahari, dan nuurun untuk rembulan (Yunus (10) : 5). Hal ini sesuai dengan perbedaan karakter alami dari keduanya: matahari bersinar karena ia menghasilkan sinarnya sendiri, sedangkan rembulan bercahaya karena ia hanya memantulkan sinar yang sampai kepadanya.
Maka “al’ilmu nuurun” sesungguhnya akan lebih tepat jika diartikan “ilmu itu bagaikan cahaya rembulan.” Dan jika merujuk pada karakter cahaya rembulan yang berbeda dengan cahaya matahari, akan kita dapati paling tidak ada dua hal yang bisa dijadikan nasehat bagi orang yang berilmu.
Pertama, orang berilmu harus menyebarkan ilmunya kepada orang lain. Manfaat cahaya rembulan tidak akan pernah bisa dirasakan oleh penduduk bumi jika rembulan tidak mau memantulkan sinar matahari yang sampai kepadanya. Ilmu pengatahuan tidak akan bisa dirasakan oleh umat manusia jika orang yang memilikinya tidak mau menyampaikannya kepada orang lain. Keharusan penyampaian ilmu ini bukan hanya untuk kepentingan manusia yang lain, tetapi justru yang lebih utama adalah untuk kepentingan pribadi orang berilmu tersebut. Jika rembulan tidak memantulkan sinar matahari yang sampai kepadanya, maka energy sinar itu akan terakumulasi di dalam dirinya, dan kelak suatu saat ia akan hancur luluh karena tidak kuat menahan akumulasi energy itu. Maka, demi kemaslahatan diri dan orang lain, orang berilmu harus menyebarkan ilmunya kepada orang lain.
Kedua, orang berilmu yang telah menunaikan kewajibannya, menyampaikan ilmunya kepada orang lain, tidak boleh berlaku sombong. Seterang - terangnya cahaya rembulan di bulan purnama, sesungguhnya cahaya yang tampaknya berasal dari rembulan itu hanyalah pantulan dari sinar matahari. Rembulan tidak pernah menghasilkan cahayanya sendiri. Ia “hanya” beredar mengelilingi bumi dan pada saat yang bersamaan, bersama bumi, mengelilingi matahari. Sepandai pandainya orang yang tampak berilmu di mata manusia, sesungguhnya ia hanya sekedar memantulkan ilmu yang datang kepadanya. Ia tidaklah memproduksi sendiri ilmu itu. Benar, bahwa manusia harus berikhtiar menuntut ilmu dan menyebarkan ilmunya, sebagaimana bulan beredar mengelilingi bumi dan matahari. Tetapi ikhtiar manusia tidak serta merta linier dengan ilmu yang ia dapatkan. Dua orang siswa yang memiliki tingkat kecerdasan yang sama, dengan tingkat ketekunan belajar yang sama, tidak akan menjamin bahwa keduanya akan memiliki tingkat pemahaman yang sama. Tingkat kefahaman itu di luar kendali manusia. Ia adalah anugerah dari Allah swt. Orang berilmu faham betul hal ini, dan sungguh tidak pantas bagi dirinya untuk menyombongkan diri atas ilmu yang ia peroleh dan ia sampaikan kepada orang lain karena sesungguhnya, seperti rembulan, ia hanya memantulkan kefahaman yang diberikan oleh Allah kepadanya.
Benar, bahwa Allah menyuruh manusia menghormati orang berilmu, sebagaimana Beliau sendiri juga memuji dan menghormati orang berilmu (Al Mujaadalah (58): 11). Tetapi perintah ini berlaku bagi orang orang yang mendapatkan manfaat dari orang orang berilmu. Sanjungan dari Allah ini tidak boleh dijadikan dalil untuk merasa lebih tinggi dari manusia lain karena ilmu yang diberikan Allah kepada kita. Lagipula, bukankah semua orang pasti memiliki ilmu yang tidak dimiliki oleh orang lain? Petani, nelayan, penjahit, masinis, tukang batu, dokter, dosen, guru, pengelola sampah, dst., semua memiliki ilmunya masing - masing. Dengan ilmu dan keahlian merekalah hidup kita menjadi jauh lebih mudah.
Mudah mudahan Allah senantiasa melimpahkan semangat menuntut ilmu kepada kita, menambah ilmu dan kefahaman kepada kita, menganugerahi kita dengan kemampuan untuk menyampaikan kefahaman itu kepada orang lain, dan membersihkan hati kita dari sifat sombong karenanya. Mudah mudahan juga Allah memberikan kemampuan kepada kita untuk senantiasa melihat orang lain, siapapun dia, sebagai orang yang berilmu, mengambil manfaat dengan ilmunya, dan selalu bisa berterima kasih dan menghormatinya, Amiin.
Rabu, 24 Juni 2009
Selasa, 16 Juni 2009
mengenal lebih jauh antimateri (sorry dont have time for translating)
sumber : http://public.web.cern.ch/Public/en/Spotlight/SpotlightAandD-en.html
Does CERN exist?
Well, yes, it does. You can see us to the left and slightly up from the centre of the city of Meyrin.
Is it located in Switzerland?
Part is in Switzerland, part in France across the border. CERN is not a Swiss institute, but an international organization. We are very close to Geneva's international airport.
What does the acronym CERN mean?
That is a long story, but the name CERN is derived from the French ‘Conseil Européen pour la Recherche Nucléaire’.
Does it consist of red brick buildings with white-frocked scientists running around carrying files?
No, that is rather far from reality; we have mostly white buildings made of concrete and the scientists wear everyday clothes and they mostly do not carry files.
Was the Web really invented at CERN as the book states?
Yes, indeed, the Web came from CERN, invented here by Tim Berners-Lee in 1989.
Does antimatter exist?
Yes, it does, and we produce it routinely at CERN. Antimatter was predicted by P.A.M. Dirac in 1928 and the first antiparticles were discovered soon after by Carl Anderson. CERN is not the only research institute to produce and study antimatter.
How is antimatter contained?
It is very difficult to contain antimatter, because any contact between a particle and its anti-particle leads to their immediate annihilation.
For electrically charged antimatter particles we know how to contain them by using ‘electromagnetic traps’. These traps make it possible to contain up to about 1012 (anti-) particles of the same charge. However, like charges repel each other. So it is not possible to store a much larger quantity of e.g. antiprotons because the repulsive forces between them would become too strong for the electromagnetic fields to hold them away from the walls.
For electrically neutral anti-particles or anti-atoms, the situation is even more difficult. It is impossible to use constant electric or magnetic fields to contain neutral antimatter, because these fields have no grip on the particles at all. Scientists work on ideas to use ‘magnetic bottles’ (with inhomogeneous magnetic fields acting on the magnetic moment), or ‘optical traps’ (using lasers) but this is still under development.
What is the future use of antimatter?
Anti-electrons (positrons) are already used in PET scanners in medicine (Positron-Emission Tomography = PET). One day it might be even possible to use antiprotons for tumour irradiation.
But antimatter at CERN is mainly used to study the laws of nature. We focus on the question of the symmetry between matter and antimatter. The LHCb experiment will compare precisely the decay of b-quarks and anti-b-quarks. Eventually we also hope to be able to use anti-hydrogen atoms as high-precision tools.
Do antimatter atoms exist?
The team of the PS210 experiment at the Low Energy Antiproton Ring (LEAR) at CERN made the first anti-hydrogen atoms in 1995. Then, in 2002 two experiments (ATHENA and ATRAP) managed to produce tens of thousands of antihydrogen atoms, later even millions. However, although "tens of thousands" may sound a lot, it's really a very, very small amount. You would need 10,000,000,000,000,000 times that amount to have enough anti-hydrogen gas to fill a toy balloon! If we could somehow store our daily production, it would take us several billion years to fill the balloon. But the universe has been around for only 13.7 billion years...So the Angels and Demons scenario is pure fiction.
Can we hope to use antimatter as a source of energy? Do you feel antimatter could power vehicles in the future, or would it just be used for major power sources?
There is no possibility to use antimatter as energy ‘source’. Unlike solar energy, coal or oil, antimatter does not occur in nature; we first have to make every single antiparticle, and we have to invest (much) more energy than we get back during annihilation.
You can imagine antimatter as a storage medium for energy, much like you store electricity in rechargeable batteries. The process of charging the battery is reversible with relatively small loss. Still, it takes more energy to charge the battery than you get back.
The inefficiency of antimatter production is enormous: you get only a tenth of a billion (10-10) of the invested energy back. If we could assemble all the antimatter we've ever made at CERN and annihilate it with matter, we would have enough energy to light a single electric light bulb for a few minutes.
I was hoping antimatter would be the future answer to our energy needs. It seems more research is needed for this to happen.
No, even more research will not change this situation fundamentally; antimatter is certainly not able to solve our energy problems. First of all, you need energy to make antimatter (E=mc2) and unfortunately you do not get the same amount of energy back out of it. (See above, the loss factors are enormous.)
Furthermore, the conversion from energy to matter and antimatter particles follows certain laws of nature, which also allow the production of many other, but very short-lived particles and antiparticles (e.g. muons, pions, neutrinos). These particles decay rapidly during the production process, and their energy is lost.
Antimatter could only become a source of energy if you happened to find a large amount of antimatter lying around somewhere (e.g. in a distant galaxy), in the same way we find oil and oxygen lying around on Earth. But as far as we can see (billions of light years), the universe is entirely made of normal matter, and antimatter has to be painstakingly created.
By the way, this shows that the symmetry between matter and antimatter as stated above does not seem to hold at very high energies, such as shortly after the Big Bang, as otherwise there should be as much matter as antimatter in the Universe. Future research might tell us is how this asymmetry came about.
Can we make antimatter bombs?
No. It would take billions of years to produce enough antimatter for a bomb having the same destructiveness as ‘typical’ hydrogen bombs, of which there exist more than ten thousand already.
Sociological note: scientists realized that the atom bomb was a real possibility many years before one was actually built and exploded, and then the public was totally surprised and amazed. On the other hand, the public somehow anticipates the antimatter bomb, but we have known for a long time that it cannot be realized in practice.
Why has antimatter received no media attention?
It has received a lot of media attention, but usually in the scientific press. Also, antimatter is not ‘new’. Antiparticles have been known and studied for 75 years. What is new is the possibility to produce anti-hydrogen atoms, but this is also mainly a matter of scientific interest.
Is antimatter truly 100% efficient?
It depends on what you mean by efficient. If you start from two equal quantities m/2 of matter and m/2 of antimatter, then the energy output is, of course, exactly E=mc2. Mass is converted into energy with 100% efficiency.
But that is not the point: how much effort do you have to put in to get m/2 grams of antimatter? Well, theoretically E=mc2 because half of the energy will become normal matter. So you gain nothing. But the process of creating antimatter is highly inefficient; when you dissipate energy into particles with mass, many different - also short-lived - particles and antiparticles are produced. A major part of the energy gets lost, and a lot of the stable antimatter-particles (e.g. positrons and antiprotons) go astray before you can catch them. Everything happens at nearly the speed of light, and the particles created zoom off in all directions. Somewhat like cooking food over a campfire: most of the heat is lost and does not go into the cooking of the food, it disappears as radiation into the dark night sky. Very inefficient.
Do you make antimatter as described in the book?
No. The production and storage of antimatter at CERN is not at all as described in the book: you cannot stand next to the Large Hadron Collider (LHC) and see it come out, especially since the LHC accelerator is not yet in operation.
To make antiprotons, we collide protons at nearly the speed of light (to be precise, with a kinetic energy of about 25 GeV) with a block of metal, e.g. copper or tungsten. These collisions produce a large number of particles, some of which are antiprotons. Only the antiprotons are useful, and only those that fly out in the right direction. So that's where your energy loss goes: it is like trying to water a pot of flowers but with a sprinkler that sprays over the whole garden. Of course, we constantly apply new tricks to become more efficient at collecting antiparticles, but at the level of elementary particles this is extremely difficult.
Why then do you build the LHC?
The reason for building the LHC accelerator is not to make antimatter but to produce an energy concentration high enough to study effects that will help us to understand some of the remaining questions in physics. We say concentrations, because we are not talking about huge amounts but an enormous concentration of energy. Each particle accelerated in the LHC carries an amount of energy equivalent to that of a flying mosquito. Not much at all in absolute terms, but it will be concentrated in a very minute volume, and there things will resemble the state of the universe very shortly (about a trillionth of a second) after the Big Bang.
You should compare the concentration effect to what you can learn about the quality of a wooden floor by walking over it. If a large man wearing normal shoes and a petite woman wearing sharp stiletto heels walk over the same floor, the man will not make dents, but the woman, despite her lower weight, may leave marks; the pressure created by the stiletto heels is far higher. So that is like the job of the LHC: concentrate a little energy into a very minute space to produce a huge energy concentration and learn something about the Big Bang.
Does CERN have a particle accelerator 27 kilometres long?
The LHC accelerator is a ring 27 kilometres in circumference. It is installed in a tunnel about 100 m underground. You can see the round outline of it marked on a map of the area.
In fact, why do you make antimatter at CERN?
The principal reason is to study the laws of nature. The current theories of physics predict a number of subtle effects concerning antimatter. If experiments do not observe these predictions, then the theory is not accurate and needs to be amended or reworked. This is how science progresses.
Another reason is to get extremely high energy densities in collisions of matter and antimatter particles, since they annihilate completely when they meet. From this annihilation energy other interesting particles may be created. This was mainly how the Large Electron Positron (LEP) collider functioned at CERN until 2000, or the Tevatron currently operates at Fermilab near Chicago.
How is energy extracted from antimatter?
When a normal matter particle hits an antimatter particle, they mutually annihilate into a very concentrated burst of pure energy, from which in turn new particles (and antiparticles) are created. The number and mass of the annihilation products depends on the available energy.
The annihilation of electrons and positrons at low energies produces only two (or three) highly energetic photons. But with annihilation at very high energy, hundreds of new particle-antiparticle pairs can be made. The decay of these particles produces, among others, many neutrinos, which do not interact with the environment at all. This is not very useful for energy extraction.
How safe is antimatter?
Perfectly safe, given the minute quantities we can make. It would be very dangerous if we could make a few grams of it, but this would take us billions of years.
If so, does CERN have protocols to keep the public safe?
There is no danger from antimatter. There are of course other dangers on the CERN site, as in any laboratory: high voltage in certain areas, deep pits to fall in, etc. but for these dangers the usual industrial safety measures are in place. There is no danger of radioactive leaks as you might find near nuclear power stations.
Does one gram of antimatter contain the energy of a 20 kilotonne nuclear bomb?
Twenty kilotonnes of TNT is the equivalent of the atom bomb that destroyed Hiroshima. The explosion of a kilotonne (=1000 tonnes) of TNT corresponds to a energy release of 4.2x1012 joules (1012 is a 1 followed by 12 zeros, i.e. a million million). For comparison, a 60 watt light bulb consumes 60 J per second.
You are probably asking for the explosive release of energy by the sudden annihilation of one gram of antimatter with one gram of matter. Let's calculate it.
To calculate the energy released in the annihilation of 1 g of antimatter with 1 g of matter (which makes 2 g = 0.002 kg), we have to use the formula E=mc2, where c is the speed of light (300,000,000 m/s):
E= 0.002 x (300,000,000)2 kg m2/s2 = 1.8 x 1014 J = 180 x 1012 J. Since 4.2x1012 J corresponds to a kilotonne of TNT, then 2 g of matter-antimatter annihilation correspond to 180/4.2 = 42.8 kilotonnes, about double the 20 kt of TNT.
This means that you ‘only’ need half a gram of antimatter to be equally destructive as the Hiroshima bomb, since the other half gram of (normal) matter is easy enough to find.
At CERN we make quantities of the order of 107 antiprotons per second and there are 6x1023 of them in a single gram of antihydrogen. You can easily calculate how long it would take to get one gram: we would need 6x1023/107=6x1016 seconds. There are only 365 (days) x 24 (h) x 60 (min) x 60 (sec) = around 3x107 seconds in a year, so it would take roughly 6x1016 / 3x107 = 2x109 = two billion years! It is quite unlikely that anyone wants to wait that long.
Did CERN scientists actually invent the Internet?
No. The Internet was originally based on work done by Louis Pouzin in France, taken up by Vint Cerf and Bob Kahn in the US in the 1970s. However, the Web was invented and developed entirely by Tim Berners-Lee and a small team at CERN during 1989-1994. The story of the Internet and the Web can be read in ‘How the Web was born’. Perhaps not as sexy as Angels and Demons, but everything in ‘How the Web was born’ was first-hand testimony and research.
Does CERN own an X-33 spaceplane?
Unfortunately not.
Does CERN exist?
Well, yes, it does. You can see us to the left and slightly up from the centre of the city of Meyrin.
Is it located in Switzerland?
Part is in Switzerland, part in France across the border. CERN is not a Swiss institute, but an international organization. We are very close to Geneva's international airport.
What does the acronym CERN mean?
That is a long story, but the name CERN is derived from the French ‘Conseil Européen pour la Recherche Nucléaire’.
Does it consist of red brick buildings with white-frocked scientists running around carrying files?
No, that is rather far from reality; we have mostly white buildings made of concrete and the scientists wear everyday clothes and they mostly do not carry files.
Was the Web really invented at CERN as the book states?
Yes, indeed, the Web came from CERN, invented here by Tim Berners-Lee in 1989.
Does antimatter exist?
Yes, it does, and we produce it routinely at CERN. Antimatter was predicted by P.A.M. Dirac in 1928 and the first antiparticles were discovered soon after by Carl Anderson. CERN is not the only research institute to produce and study antimatter.
How is antimatter contained?
It is very difficult to contain antimatter, because any contact between a particle and its anti-particle leads to their immediate annihilation.
For electrically charged antimatter particles we know how to contain them by using ‘electromagnetic traps’. These traps make it possible to contain up to about 1012 (anti-) particles of the same charge. However, like charges repel each other. So it is not possible to store a much larger quantity of e.g. antiprotons because the repulsive forces between them would become too strong for the electromagnetic fields to hold them away from the walls.
For electrically neutral anti-particles or anti-atoms, the situation is even more difficult. It is impossible to use constant electric or magnetic fields to contain neutral antimatter, because these fields have no grip on the particles at all. Scientists work on ideas to use ‘magnetic bottles’ (with inhomogeneous magnetic fields acting on the magnetic moment), or ‘optical traps’ (using lasers) but this is still under development.
What is the future use of antimatter?
Anti-electrons (positrons) are already used in PET scanners in medicine (Positron-Emission Tomography = PET). One day it might be even possible to use antiprotons for tumour irradiation.
But antimatter at CERN is mainly used to study the laws of nature. We focus on the question of the symmetry between matter and antimatter. The LHCb experiment will compare precisely the decay of b-quarks and anti-b-quarks. Eventually we also hope to be able to use anti-hydrogen atoms as high-precision tools.
Do antimatter atoms exist?
The team of the PS210 experiment at the Low Energy Antiproton Ring (LEAR) at CERN made the first anti-hydrogen atoms in 1995. Then, in 2002 two experiments (ATHENA and ATRAP) managed to produce tens of thousands of antihydrogen atoms, later even millions. However, although "tens of thousands" may sound a lot, it's really a very, very small amount. You would need 10,000,000,000,000,000 times that amount to have enough anti-hydrogen gas to fill a toy balloon! If we could somehow store our daily production, it would take us several billion years to fill the balloon. But the universe has been around for only 13.7 billion years...So the Angels and Demons scenario is pure fiction.
Can we hope to use antimatter as a source of energy? Do you feel antimatter could power vehicles in the future, or would it just be used for major power sources?
There is no possibility to use antimatter as energy ‘source’. Unlike solar energy, coal or oil, antimatter does not occur in nature; we first have to make every single antiparticle, and we have to invest (much) more energy than we get back during annihilation.
You can imagine antimatter as a storage medium for energy, much like you store electricity in rechargeable batteries. The process of charging the battery is reversible with relatively small loss. Still, it takes more energy to charge the battery than you get back.
The inefficiency of antimatter production is enormous: you get only a tenth of a billion (10-10) of the invested energy back. If we could assemble all the antimatter we've ever made at CERN and annihilate it with matter, we would have enough energy to light a single electric light bulb for a few minutes.
I was hoping antimatter would be the future answer to our energy needs. It seems more research is needed for this to happen.
No, even more research will not change this situation fundamentally; antimatter is certainly not able to solve our energy problems. First of all, you need energy to make antimatter (E=mc2) and unfortunately you do not get the same amount of energy back out of it. (See above, the loss factors are enormous.)
Furthermore, the conversion from energy to matter and antimatter particles follows certain laws of nature, which also allow the production of many other, but very short-lived particles and antiparticles (e.g. muons, pions, neutrinos). These particles decay rapidly during the production process, and their energy is lost.
Antimatter could only become a source of energy if you happened to find a large amount of antimatter lying around somewhere (e.g. in a distant galaxy), in the same way we find oil and oxygen lying around on Earth. But as far as we can see (billions of light years), the universe is entirely made of normal matter, and antimatter has to be painstakingly created.
By the way, this shows that the symmetry between matter and antimatter as stated above does not seem to hold at very high energies, such as shortly after the Big Bang, as otherwise there should be as much matter as antimatter in the Universe. Future research might tell us is how this asymmetry came about.
Can we make antimatter bombs?
No. It would take billions of years to produce enough antimatter for a bomb having the same destructiveness as ‘typical’ hydrogen bombs, of which there exist more than ten thousand already.
Sociological note: scientists realized that the atom bomb was a real possibility many years before one was actually built and exploded, and then the public was totally surprised and amazed. On the other hand, the public somehow anticipates the antimatter bomb, but we have known for a long time that it cannot be realized in practice.
Why has antimatter received no media attention?
It has received a lot of media attention, but usually in the scientific press. Also, antimatter is not ‘new’. Antiparticles have been known and studied for 75 years. What is new is the possibility to produce anti-hydrogen atoms, but this is also mainly a matter of scientific interest.
Is antimatter truly 100% efficient?
It depends on what you mean by efficient. If you start from two equal quantities m/2 of matter and m/2 of antimatter, then the energy output is, of course, exactly E=mc2. Mass is converted into energy with 100% efficiency.
But that is not the point: how much effort do you have to put in to get m/2 grams of antimatter? Well, theoretically E=mc2 because half of the energy will become normal matter. So you gain nothing. But the process of creating antimatter is highly inefficient; when you dissipate energy into particles with mass, many different - also short-lived - particles and antiparticles are produced. A major part of the energy gets lost, and a lot of the stable antimatter-particles (e.g. positrons and antiprotons) go astray before you can catch them. Everything happens at nearly the speed of light, and the particles created zoom off in all directions. Somewhat like cooking food over a campfire: most of the heat is lost and does not go into the cooking of the food, it disappears as radiation into the dark night sky. Very inefficient.
Do you make antimatter as described in the book?
No. The production and storage of antimatter at CERN is not at all as described in the book: you cannot stand next to the Large Hadron Collider (LHC) and see it come out, especially since the LHC accelerator is not yet in operation.
To make antiprotons, we collide protons at nearly the speed of light (to be precise, with a kinetic energy of about 25 GeV) with a block of metal, e.g. copper or tungsten. These collisions produce a large number of particles, some of which are antiprotons. Only the antiprotons are useful, and only those that fly out in the right direction. So that's where your energy loss goes: it is like trying to water a pot of flowers but with a sprinkler that sprays over the whole garden. Of course, we constantly apply new tricks to become more efficient at collecting antiparticles, but at the level of elementary particles this is extremely difficult.
Why then do you build the LHC?
The reason for building the LHC accelerator is not to make antimatter but to produce an energy concentration high enough to study effects that will help us to understand some of the remaining questions in physics. We say concentrations, because we are not talking about huge amounts but an enormous concentration of energy. Each particle accelerated in the LHC carries an amount of energy equivalent to that of a flying mosquito. Not much at all in absolute terms, but it will be concentrated in a very minute volume, and there things will resemble the state of the universe very shortly (about a trillionth of a second) after the Big Bang.
You should compare the concentration effect to what you can learn about the quality of a wooden floor by walking over it. If a large man wearing normal shoes and a petite woman wearing sharp stiletto heels walk over the same floor, the man will not make dents, but the woman, despite her lower weight, may leave marks; the pressure created by the stiletto heels is far higher. So that is like the job of the LHC: concentrate a little energy into a very minute space to produce a huge energy concentration and learn something about the Big Bang.
Does CERN have a particle accelerator 27 kilometres long?
The LHC accelerator is a ring 27 kilometres in circumference. It is installed in a tunnel about 100 m underground. You can see the round outline of it marked on a map of the area.
In fact, why do you make antimatter at CERN?
The principal reason is to study the laws of nature. The current theories of physics predict a number of subtle effects concerning antimatter. If experiments do not observe these predictions, then the theory is not accurate and needs to be amended or reworked. This is how science progresses.
Another reason is to get extremely high energy densities in collisions of matter and antimatter particles, since they annihilate completely when they meet. From this annihilation energy other interesting particles may be created. This was mainly how the Large Electron Positron (LEP) collider functioned at CERN until 2000, or the Tevatron currently operates at Fermilab near Chicago.
How is energy extracted from antimatter?
When a normal matter particle hits an antimatter particle, they mutually annihilate into a very concentrated burst of pure energy, from which in turn new particles (and antiparticles) are created. The number and mass of the annihilation products depends on the available energy.
The annihilation of electrons and positrons at low energies produces only two (or three) highly energetic photons. But with annihilation at very high energy, hundreds of new particle-antiparticle pairs can be made. The decay of these particles produces, among others, many neutrinos, which do not interact with the environment at all. This is not very useful for energy extraction.
How safe is antimatter?
Perfectly safe, given the minute quantities we can make. It would be very dangerous if we could make a few grams of it, but this would take us billions of years.
If so, does CERN have protocols to keep the public safe?
There is no danger from antimatter. There are of course other dangers on the CERN site, as in any laboratory: high voltage in certain areas, deep pits to fall in, etc. but for these dangers the usual industrial safety measures are in place. There is no danger of radioactive leaks as you might find near nuclear power stations.
Does one gram of antimatter contain the energy of a 20 kilotonne nuclear bomb?
Twenty kilotonnes of TNT is the equivalent of the atom bomb that destroyed Hiroshima. The explosion of a kilotonne (=1000 tonnes) of TNT corresponds to a energy release of 4.2x1012 joules (1012 is a 1 followed by 12 zeros, i.e. a million million). For comparison, a 60 watt light bulb consumes 60 J per second.
You are probably asking for the explosive release of energy by the sudden annihilation of one gram of antimatter with one gram of matter. Let's calculate it.
To calculate the energy released in the annihilation of 1 g of antimatter with 1 g of matter (which makes 2 g = 0.002 kg), we have to use the formula E=mc2, where c is the speed of light (300,000,000 m/s):
E= 0.002 x (300,000,000)2 kg m2/s2 = 1.8 x 1014 J = 180 x 1012 J. Since 4.2x1012 J corresponds to a kilotonne of TNT, then 2 g of matter-antimatter annihilation correspond to 180/4.2 = 42.8 kilotonnes, about double the 20 kt of TNT.
This means that you ‘only’ need half a gram of antimatter to be equally destructive as the Hiroshima bomb, since the other half gram of (normal) matter is easy enough to find.
At CERN we make quantities of the order of 107 antiprotons per second and there are 6x1023 of them in a single gram of antihydrogen. You can easily calculate how long it would take to get one gram: we would need 6x1023/107=6x1016 seconds. There are only 365 (days) x 24 (h) x 60 (min) x 60 (sec) = around 3x107 seconds in a year, so it would take roughly 6x1016 / 3x107 = 2x109 = two billion years! It is quite unlikely that anyone wants to wait that long.
Did CERN scientists actually invent the Internet?
No. The Internet was originally based on work done by Louis Pouzin in France, taken up by Vint Cerf and Bob Kahn in the US in the 1970s. However, the Web was invented and developed entirely by Tim Berners-Lee and a small team at CERN during 1989-1994. The story of the Internet and the Web can be read in ‘How the Web was born’. Perhaps not as sexy as Angels and Demons, but everything in ‘How the Web was born’ was first-hand testimony and research.
Does CERN own an X-33 spaceplane?
Unfortunately not.
Lampu dioda dari hibridisasi benang nano ZnO dengan polimer organik
Lampu dioda dari hibridisasi benang nano ZnO dengan polimer organik
oleh Iwan
Perkembangan teknologi lampu diode (LED) menggunakan bahan inorganic yang fleksibel dan lentur telah mampu direalisasikan dengan menggunakan ZnO yang berbentuk benang nano. Benang nano dari ZnO bertindak sebagai komponen optis.
Diawali oleh emisi sinar ultra violet(uv) dengan panjang gelombang 393 nm dari benang nano ZnO (ZnO Nanowire LEDs Have UV Output,” Photonics Spectra, January 2006, page 135), para peneliti kini telah menemukan spectrum yang berada pada rentang cahaya tampak hingga mendekati sinar infra merah (500-1100 nm) mampu dihasilkan oleh LED yang berbasiskan benang nano dari ZnO.
Gambar 1. Diagram dari struktur LED berbasis benang nano pada substrate plastik
Penemuan ini di pelopori oleh Prof. Rolf Könenkamp dari Portland State University in Oregon. Hasil penemuannya melaporkan bahwa LED dari bahan inorganic diprediksikan menjadi alternative masa depan untuk menggantikan semua perangkat elektronik dan photonic dari bahan organic.
Struktur dari divais LED berbasiskan benang nano yang lentur dapat di lihat pada gambar 1. Dari gambar tersebut benang nano ZnO ditumbuhkan diatas substrate polyethylene terephtalate (bahan plastic) yang telah dilapisi oleh indium tin okside (ITO). Kristal tunggal benang nano tersebut ditumbuhkan dengan metode elektrodeposisi dengan temperature 80oC di atas ITO. Proses penumbuhan kira-kira memakan waktu satu jam dengan arah tumbuh vertical dan homogeny. Dari hasil karakterisasi, panjang benang nano rata-rata 2 mm dan diameter 70-120 nm. Lalu benang-benang nano tersebut di lapisi dengan lapisan tipis polysterene sebagai isolator yang mengisi tiap celah diantara benang-benang nano. Lapisan tipis polysterene melapisi benang nano dengan ketebalan kira-kira 10 nm. Proses pengisian celah atau pelapisan benang-benang nano tersebut menggunakan metode spin coating. Lalu bagian atas dilapisi pula menggunakan poly(3,4-ethylene-dioxythiophene) poly(styrenesulfonate), PEDOT/PSS, selanjutnya dilapisi emas (sebagai kontak Ohmic) yang berperan sebagai anoda (elektroda positif). Gambar 2. Benang-benang nano ZnO yang berada dilapisi oleh lapisan tipis polystyrene
Dari penelitian lebih lanjut, ternyata benang-benang nano ZnO tersebut melekat sangat kuat diatas substrate meskipun dibengkokan dengan jari-jari kelengkungan <10 μm.Dari sisi intensitas cahaya yang diemisikan, LED benang nano yang berada diatas substrate plastic memancarkan cahaya dengan intensitas lebih rendah dibandingkan diatas substrate gelas. Namun demikian distribusi spectrum cahaya yang teramati dari elektroluminisensi memiliki kemiripan yaitu berada di rentang cahaya tampak.
Penemuan ini mengindikasikan bahwa hibridisasi teknologi nano dengan polimer organic memiliki potensi untuk dikembangkan dalam ranah aplikasi optoelektronika di masa depan.
Referensi :
Photonics Spectra, January 2006, page 135
Nano Letters, February 2008, pp. 534-537.
oleh Iwan
Perkembangan teknologi lampu diode (LED) menggunakan bahan inorganic yang fleksibel dan lentur telah mampu direalisasikan dengan menggunakan ZnO yang berbentuk benang nano. Benang nano dari ZnO bertindak sebagai komponen optis.
Diawali oleh emisi sinar ultra violet(uv) dengan panjang gelombang 393 nm dari benang nano ZnO (ZnO Nanowire LEDs Have UV Output,” Photonics Spectra, January 2006, page 135), para peneliti kini telah menemukan spectrum yang berada pada rentang cahaya tampak hingga mendekati sinar infra merah (500-1100 nm) mampu dihasilkan oleh LED yang berbasiskan benang nano dari ZnO.
Gambar 1. Diagram dari struktur LED berbasis benang nano pada substrate plastik
Penemuan ini di pelopori oleh Prof. Rolf Könenkamp dari Portland State University in Oregon. Hasil penemuannya melaporkan bahwa LED dari bahan inorganic diprediksikan menjadi alternative masa depan untuk menggantikan semua perangkat elektronik dan photonic dari bahan organic.
Struktur dari divais LED berbasiskan benang nano yang lentur dapat di lihat pada gambar 1. Dari gambar tersebut benang nano ZnO ditumbuhkan diatas substrate polyethylene terephtalate (bahan plastic) yang telah dilapisi oleh indium tin okside (ITO). Kristal tunggal benang nano tersebut ditumbuhkan dengan metode elektrodeposisi dengan temperature 80oC di atas ITO. Proses penumbuhan kira-kira memakan waktu satu jam dengan arah tumbuh vertical dan homogeny. Dari hasil karakterisasi, panjang benang nano rata-rata 2 mm dan diameter 70-120 nm. Lalu benang-benang nano tersebut di lapisi dengan lapisan tipis polysterene sebagai isolator yang mengisi tiap celah diantara benang-benang nano. Lapisan tipis polysterene melapisi benang nano dengan ketebalan kira-kira 10 nm. Proses pengisian celah atau pelapisan benang-benang nano tersebut menggunakan metode spin coating. Lalu bagian atas dilapisi pula menggunakan poly(3,4-ethylene-dioxythiophene) poly(styrenesulfonate), PEDOT/PSS, selanjutnya dilapisi emas (sebagai kontak Ohmic) yang berperan sebagai anoda (elektroda positif). Gambar 2. Benang-benang nano ZnO yang berada dilapisi oleh lapisan tipis polystyrene
Dari penelitian lebih lanjut, ternyata benang-benang nano ZnO tersebut melekat sangat kuat diatas substrate meskipun dibengkokan dengan jari-jari kelengkungan <10 μm.Dari sisi intensitas cahaya yang diemisikan, LED benang nano yang berada diatas substrate plastic memancarkan cahaya dengan intensitas lebih rendah dibandingkan diatas substrate gelas. Namun demikian distribusi spectrum cahaya yang teramati dari elektroluminisensi memiliki kemiripan yaitu berada di rentang cahaya tampak.
Penemuan ini mengindikasikan bahwa hibridisasi teknologi nano dengan polimer organic memiliki potensi untuk dikembangkan dalam ranah aplikasi optoelektronika di masa depan.
Referensi :
Photonics Spectra, January 2006, page 135
Nano Letters, February 2008, pp. 534-537.
Anti materi, sebuah realitaskah?
Silahkan dibaca tulisan berikut..menarik lo..
Penulis : Robert Roy Britt (Senior Science Writer)
Antimatter sounds like the stuff of science fiction, and it is. But it's also very real. Antimatter is created and annihilated in stars every day. Here on Earth it's harnessed for medical brain scans.
"Antimatter is around us each day, although there isn't very much of it," says Gerald Share of the Naval Research Laboratory. "It is not something that can be found by itself in a jar on a table."
So Share went looking for evidence of some in the Sun, a veritable antimatter factory, leading to new results that provide limited fresh insight into these still-mysterious particles.
Simply put, antimatter is a fundamental particle of regular matter with its electrical charge reversed. The common proton has an antimatter counterpart called the antiproton. It has the same mass but an opposite charge. The electron's counterpart is called a positron.
Antimatter particles are created in ultra high-speed collisions.
One example is when a high-energy proton in a solar flare collides with carbon, Share explained in an e-mail interview. "It can form a type of nitrogen that has too many protons relative to its number of neutrons." This makes its nucleus unstable, and a positron is emitted to stabilize the situation.
But positrons don't last long. When they hit an electron, they annihilate and produce energy.
"So the cycle is complete, and for this reason there is so little antimatter around at a given time," Share said.
The antimatter wars
To better understand the elusive nature of antimatter, we must back up to the beginning of time.
In the first seconds after the Big Bang, there was no matter, scientists suspect. Just energy. As the universe expanded and cooled, particles of regular matter and antimatter were formed in almost equal amounts.
But, theory holds, a slightly higher percentage of regular matter developed -- perhaps just one part in a million -- for unknown reasons. That was all the edge needed for regular matter to win the longest running war in the cosmos.
"When the matter and antimatter came into contact they annihilated, and only the residual amount of matter was left to form our current universe," Share says.
Antimatter was first theorized based on work done in 1928 by the physicist Paul Dirac. The positron was discovered in 1932. Science fiction writers latched onto the concept and wrote of antiworlds and antiuniverses.
Potential power
Antimatter has tremendous energy potential, if it could ever be harnessed. A solar flare in July 2002 created about a pound of antimatter, or half a kilo, according to new NASA-led research. That's enough to power the United States for two days.
Laboratory particle accelerators can produce high-energy antimatter particles, too, but only in tiny quantities. Something on the order of a billionth of a gram or less is produced every year.
Nonetheless, sci-fi writers long ago devised schemes using antimatter to power space travelers beyond light-speed. Antimatter didnt get a bad name, but it sunk into the collective consciousness as a purely fictional concept. Given some remarkable physics breakthrough, antimatter could in theory power a spacecraft. But NASA researchers say it's nothing that will happen in the foreseeable future.
Meanwhile, antimatter has proved vitally useful for medical purposes. The fleeting particles of antimatter are also created by the decay of radioactive material, which can be injected into a patient in order to perform Positron Emission Tomography, or PET scan of the brain. Here's what happens:
A positron that's produced by decay almost immediately finds an electron and annihilates into two gamma rays, Share explains. These gamma rays move in opposite directions, and by recording several of their origin points an image is produced.
Looking at the Sun
In the Sun, flares of matter accelerate already fast-moving particles, which collide with slower particles in the Sun's atmosphere, producing antimatter. Scientists had expected these collisions to happen in relatively dense regions of the solar atmosphere. If that were the case, the density would cause the antimatter to annihilate almost immediately.
Share's team examined gamma rays emitted by antimatter annihilation, as observed by NASA's RHESSI spacecraft in work led by Robert Lin of the University of California, Berkeley.
The research suggests the antimatter perhaps shuffles around, being created in one spot and destroyed in another, contrary to what scientists expect for the ephemeral particles. But the results are unclear. They could also mean antimatter is created in regions where extremely high temperatures make the particle density 1,000 times lower than what scientists expected was conducive to the process.
Details of the work will be published in Astrophysical Journal Letters on Oct. 1.
Unknowns remain
Though scientists like to see antimatter as a natural thing, much about it remains highly mysterious. Even some of the fictional portrayals of mirror-image objects have not been proven totally out of this world.
"We cannot rule out the possibility that some antimatter star or galaxy exists somewhere," Share says. "Generally it would look the same as a matter star or galaxy to most of our instruments."
Theory argues that antimatter would behave identical to regular matter gravitationally.
"However, there must be some boundary where antimatter atoms from the antimatter galaxies or stars will come into contact with normal atoms," Share notes. "When that happens a large amount of energy in the form of gamma rays would be produced. To date we have not detected these gamma rays even though there have been very sensitive instruments in space to observe them."
This article is part of SPACE.com's weekly Mystery Monday series
Penulis : Robert Roy Britt (Senior Science Writer)
Antimatter sounds like the stuff of science fiction, and it is. But it's also very real. Antimatter is created and annihilated in stars every day. Here on Earth it's harnessed for medical brain scans.
"Antimatter is around us each day, although there isn't very much of it," says Gerald Share of the Naval Research Laboratory. "It is not something that can be found by itself in a jar on a table."
So Share went looking for evidence of some in the Sun, a veritable antimatter factory, leading to new results that provide limited fresh insight into these still-mysterious particles.
Simply put, antimatter is a fundamental particle of regular matter with its electrical charge reversed. The common proton has an antimatter counterpart called the antiproton. It has the same mass but an opposite charge. The electron's counterpart is called a positron.
Antimatter particles are created in ultra high-speed collisions.
One example is when a high-energy proton in a solar flare collides with carbon, Share explained in an e-mail interview. "It can form a type of nitrogen that has too many protons relative to its number of neutrons." This makes its nucleus unstable, and a positron is emitted to stabilize the situation.
But positrons don't last long. When they hit an electron, they annihilate and produce energy.
"So the cycle is complete, and for this reason there is so little antimatter around at a given time," Share said.
The antimatter wars
To better understand the elusive nature of antimatter, we must back up to the beginning of time.
In the first seconds after the Big Bang, there was no matter, scientists suspect. Just energy. As the universe expanded and cooled, particles of regular matter and antimatter were formed in almost equal amounts.
But, theory holds, a slightly higher percentage of regular matter developed -- perhaps just one part in a million -- for unknown reasons. That was all the edge needed for regular matter to win the longest running war in the cosmos.
"When the matter and antimatter came into contact they annihilated, and only the residual amount of matter was left to form our current universe," Share says.
Antimatter was first theorized based on work done in 1928 by the physicist Paul Dirac. The positron was discovered in 1932. Science fiction writers latched onto the concept and wrote of antiworlds and antiuniverses.
Potential power
Antimatter has tremendous energy potential, if it could ever be harnessed. A solar flare in July 2002 created about a pound of antimatter, or half a kilo, according to new NASA-led research. That's enough to power the United States for two days.
Laboratory particle accelerators can produce high-energy antimatter particles, too, but only in tiny quantities. Something on the order of a billionth of a gram or less is produced every year.
Nonetheless, sci-fi writers long ago devised schemes using antimatter to power space travelers beyond light-speed. Antimatter didnt get a bad name, but it sunk into the collective consciousness as a purely fictional concept. Given some remarkable physics breakthrough, antimatter could in theory power a spacecraft. But NASA researchers say it's nothing that will happen in the foreseeable future.
Meanwhile, antimatter has proved vitally useful for medical purposes. The fleeting particles of antimatter are also created by the decay of radioactive material, which can be injected into a patient in order to perform Positron Emission Tomography, or PET scan of the brain. Here's what happens:
A positron that's produced by decay almost immediately finds an electron and annihilates into two gamma rays, Share explains. These gamma rays move in opposite directions, and by recording several of their origin points an image is produced.
Looking at the Sun
In the Sun, flares of matter accelerate already fast-moving particles, which collide with slower particles in the Sun's atmosphere, producing antimatter. Scientists had expected these collisions to happen in relatively dense regions of the solar atmosphere. If that were the case, the density would cause the antimatter to annihilate almost immediately.
Share's team examined gamma rays emitted by antimatter annihilation, as observed by NASA's RHESSI spacecraft in work led by Robert Lin of the University of California, Berkeley.
The research suggests the antimatter perhaps shuffles around, being created in one spot and destroyed in another, contrary to what scientists expect for the ephemeral particles. But the results are unclear. They could also mean antimatter is created in regions where extremely high temperatures make the particle density 1,000 times lower than what scientists expected was conducive to the process.
Details of the work will be published in Astrophysical Journal Letters on Oct. 1.
Unknowns remain
Though scientists like to see antimatter as a natural thing, much about it remains highly mysterious. Even some of the fictional portrayals of mirror-image objects have not been proven totally out of this world.
"We cannot rule out the possibility that some antimatter star or galaxy exists somewhere," Share says. "Generally it would look the same as a matter star or galaxy to most of our instruments."
Theory argues that antimatter would behave identical to regular matter gravitationally.
"However, there must be some boundary where antimatter atoms from the antimatter galaxies or stars will come into contact with normal atoms," Share notes. "When that happens a large amount of energy in the form of gamma rays would be produced. To date we have not detected these gamma rays even though there have been very sensitive instruments in space to observe them."
This article is part of SPACE.com's weekly Mystery Monday series
Langganan:
Postingan (Atom)
