The Age of Entanglement: When Quantum Physics Was Reborn - Louisa Gilder
Miss Gilder's forthcoming book stars Einstein, Schrödinger, Bell, Bohr, Heisenberg, de Broglie, and other giants. From the 26th Annual Meeting of Doctors for Disaster Preparedness, held July 12, 2008, in Mesa, AZ.
2010/09/05
Introduction of my dissertation (I)
The ability to convert an intiution into a formulation is what I obtain most during my PhD career. It was a long and lonely journey. I can’t stop thinking what causes the gap between complex mechanics and nowadays physics society. A simple question leads me to ponder over my research topic for dissertation. My intuition helps me a lot during dealing with this issue. Before I can discuss it, I did a survey to see how other classical approaches to quantum mechanics could or could not dismiss this gap.
Among all classical approaches, the quantum Hamilton-Jacobi formalism is the oldest one, which is discussed even as the same time quantum mechanics is established. Indeed, if we compare complex mechanics to the quantum H-J formalism, we will find out that at least, both theories have the same mathematical route-they all insert the wave function into the Schrodinger equation. The only difference is that the complex space structure is an assumption of the former, and a consqauece of the later. This difference did causes the gap because of the acceptance of complex space is not avariable in conventional physics field. I think it might not be the best choice to over emphasize the importance of considering complex space instead of real space that we could observe. There will be a lot of criticisms and demands for the evidence of proving the existence of complex space. This is the position where a pike meets a shield.
We shall define our issue in a physical interpretation or a mathematical interpretation at beginning. It becomes reasonable and might be an easier way to emphasize complex space if viewed mathematically. But in such a way, it totally disobeys the original thought provided by Prof. Yang that is our living world is complex. It becomes more difficult if we adopt a physical manner as to challenge the dimension of the space structure. I found out that maybe I can have both ways in the discussion of this issue in my dissertation, and leave the definition to the reader. I imply the necessary of consider a complex-valued wave function instead a regular one, and indicate the advantage of doing so. I try to avoid bringing the critical part into discussion, and try to show readers the complex space is naturally arose mathematically and physically.
My intuition tells me that the additional irregular velocity appeared in Bohm’s modified guidance law is originated from the imaginary subspace. Even Prof. Yang did mention this conjecture in his text book, however, only a simple relation is presented. We need a better understanding, or a derivation in detail, to confirm this conjecture. I found out that the form of the wave functions adopted in H-J formalism, or complex mechanics, and in Bohmian mechanics have an intense relationship. The wave function used in H-J formalism focuses on the action function; while the other form considers the magnitude and the phase most in Bohmian mechanics. In fact, the relationship between the quantum action function and the characteristic of the wave function is so important, which has been ignored by everyone. This is how I can verify the conjecture that the irregular motion is originated from the imaginary of the wave function.
A classical wave picture is mentioned in quantum H-J formalism and Bohmian mechanics, but not in complex mechanics. I am not sure the reason why there is no such a discussion in Prof. Yang’s text book, but I believe that it is an important issue and needed to be discussed within complex mechanics. In quantum H-J formalism, the Hamilton’s original wave picture is proposed in terms of the reconstruction of the wave function from the quantum action function. However, they did not interpret this process in detail. In Bohmian mechanics, Bohm proposed an assumption that the initial condition of the fluid must be taken otherwise the continuity equation cannot be satisfied. I do believe that a suitable interpretation in terms of trajectories can be given by complex mechanics. However, an important product came out in the middle way. The Born’s postulate of the quantum probability density can be derived from the energy conservation of the imaginary subspace. It quite makes sense since the continuity equation of probability density is from the imaginary part of the Schrodinger equation (after inserting the wave function).
Among all classical approaches, the quantum Hamilton-Jacobi formalism is the oldest one, which is discussed even as the same time quantum mechanics is established. Indeed, if we compare complex mechanics to the quantum H-J formalism, we will find out that at least, both theories have the same mathematical route-they all insert the wave function into the Schrodinger equation. The only difference is that the complex space structure is an assumption of the former, and a consqauece of the later. This difference did causes the gap because of the acceptance of complex space is not avariable in conventional physics field. I think it might not be the best choice to over emphasize the importance of considering complex space instead of real space that we could observe. There will be a lot of criticisms and demands for the evidence of proving the existence of complex space. This is the position where a pike meets a shield.
We shall define our issue in a physical interpretation or a mathematical interpretation at beginning. It becomes reasonable and might be an easier way to emphasize complex space if viewed mathematically. But in such a way, it totally disobeys the original thought provided by Prof. Yang that is our living world is complex. It becomes more difficult if we adopt a physical manner as to challenge the dimension of the space structure. I found out that maybe I can have both ways in the discussion of this issue in my dissertation, and leave the definition to the reader. I imply the necessary of consider a complex-valued wave function instead a regular one, and indicate the advantage of doing so. I try to avoid bringing the critical part into discussion, and try to show readers the complex space is naturally arose mathematically and physically.
My intuition tells me that the additional irregular velocity appeared in Bohm’s modified guidance law is originated from the imaginary subspace. Even Prof. Yang did mention this conjecture in his text book, however, only a simple relation is presented. We need a better understanding, or a derivation in detail, to confirm this conjecture. I found out that the form of the wave functions adopted in H-J formalism, or complex mechanics, and in Bohmian mechanics have an intense relationship. The wave function used in H-J formalism focuses on the action function; while the other form considers the magnitude and the phase most in Bohmian mechanics. In fact, the relationship between the quantum action function and the characteristic of the wave function is so important, which has been ignored by everyone. This is how I can verify the conjecture that the irregular motion is originated from the imaginary of the wave function.
A classical wave picture is mentioned in quantum H-J formalism and Bohmian mechanics, but not in complex mechanics. I am not sure the reason why there is no such a discussion in Prof. Yang’s text book, but I believe that it is an important issue and needed to be discussed within complex mechanics. In quantum H-J formalism, the Hamilton’s original wave picture is proposed in terms of the reconstruction of the wave function from the quantum action function. However, they did not interpret this process in detail. In Bohmian mechanics, Bohm proposed an assumption that the initial condition of the fluid must be taken otherwise the continuity equation cannot be satisfied. I do believe that a suitable interpretation in terms of trajectories can be given by complex mechanics. However, an important product came out in the middle way. The Born’s postulate of the quantum probability density can be derived from the energy conservation of the imaginary subspace. It quite makes sense since the continuity equation of probability density is from the imaginary part of the Schrodinger equation (after inserting the wave function).
2010/08/06
Speculating about the Universe as a quantum fluid
Speculating about the Universe as a quantum fluid
By Chris Lee | Last updated January 25, 2010 9:35 PM
NASA
The first thing that struck me about Hitoshi Murayama was that he certainly did not fit the stereotype of a Japanese presenter—he's relaxed, eloquent, and clearly very, very excited about his work. He is the head of a new research center in Japan called the Institute for the Physics and Mathematics of the Universe—a purview that allows him to study just about anything. But he's chosen to study everything; Murayama wants to know why there is, in fact, a universe.
Because the Physics@FOM audience comes from a range of backgrounds, Murayama's talk was light on details and strong on providing a flavor of the problem and inspiring the audience. And inspired I was, as he took us on a whirlwind tour of the known Universe, including dark matter and inflation. He wrapped up by going completely off the map with some of the ideas that he has had floating around for some time now.
Murayama proposes that the Universe is, in fact, a quantum fluid, somewhat like a superconductor.
Starting with the energy budget of the Universe, he reminded us that less than five percent of the matter and energy in the Universe is understood, with the remainder being dark energy and dark matter. But, even if we could account for dark matter with a bunch of particles and dark energy was understood, we still wouldn't understand much. For instance, none of this knowledge would help us understand why the various forces behave the way they do.
Along the way, he provided a taste of the evidence for why we believe the things that we do. We know dark matter exists because galaxies don't fly apart, because we find gravity where there is no matter, and, most tellingly, our universe would be smooth and featureless in the absence of dark matter. He showed that, although dark matter allows structures to form, inflation provided the initial changes in density that allowed them to condense.
But, of course, we don't know what dark matter is. Murayama justified the idea that dark matter is almost certainly some sort of weakly interacting massive particle by showing how we account for the dimmest objects in the Universe and simply don't find enough of them. In short, we think that dark matter exists because it is just about impossible to account for all the evidence with any other proposals.
Now, with the LHC online, we should start finding particles that may well be dark matter, and we will soon know if cosmologists were on the right track. And that is kind of exciting: years of speculation and careful modeling about to be properly tested. But, even more exciting, if the LHC does find dark matter candidate particles, cosmologists will be able to claim that we pretty much understand the Universe from 10-10s after the big bang to the present day—a mind-boggling thought.
What really seems to turns Murayama on is the problem of explaining why some forces are long-range and some are short-range. Basically, gravity reaches out over huge distances. Electromagnetism would reach just as far, but because there are both negative and positive charges, forces due to one set of charges tend get screened out by opposite signed charges. This effectively limits the reach of electromagnetic forces. Nevertheless, the fundamental distance scaling for the two forces is the same. The strong and weak nuclear forces are very short range, extending no further than the width of a nucleus.
There is no fundamental reason for why these forces scale differently from gravity and electromagnetism. He proposes that the Universe is, in fact, a quantum fluid, somewhat like a superconductor. How does this work? The analogy with superconductivity is apt because superconductors reject magnetic fields. That is, the charges in a superconductor arrange themselves such that the field lines of a magnetic field get bent around the super-current. Now, imagine sitting in the superconductor, trying to make a magnetic field.
What you would see is that the field was incredibly short-ranged because of the way the field would interact with the surrounding charges. Therein lies the idea. Imagine that the Universe is a quantum fluid that interacts very strongly with the strong force and weak forces, but ignores gravity and electromagnetism. Our knowledge of the four forces allows us to calculate some of the properties that this fluid must have, and, from there, to figure out how much energy is tied up in this fluid.
If you are going to go into debt, you might as well do it properly. If Murayama is right, the current energy of the Universe is short by some 1062 percent of that required to create the fluid during the big bang—that is one hell of a mortgage. As he jokingly pointed out, we are constantly told that deficits are a bad thing, so if his dark field proposal is to become more than an idea, some creative accounting is required.
All in all, a great opening to Physics@FOM.
From:http://arstechnica.com/science/news/2010/01/quantum-universe.ars
By Chris Lee | Last updated January 25, 2010 9:35 PM
NASA
The first thing that struck me about Hitoshi Murayama was that he certainly did not fit the stereotype of a Japanese presenter—he's relaxed, eloquent, and clearly very, very excited about his work. He is the head of a new research center in Japan called the Institute for the Physics and Mathematics of the Universe—a purview that allows him to study just about anything. But he's chosen to study everything; Murayama wants to know why there is, in fact, a universe.
Because the Physics@FOM audience comes from a range of backgrounds, Murayama's talk was light on details and strong on providing a flavor of the problem and inspiring the audience. And inspired I was, as he took us on a whirlwind tour of the known Universe, including dark matter and inflation. He wrapped up by going completely off the map with some of the ideas that he has had floating around for some time now.
Murayama proposes that the Universe is, in fact, a quantum fluid, somewhat like a superconductor.
Starting with the energy budget of the Universe, he reminded us that less than five percent of the matter and energy in the Universe is understood, with the remainder being dark energy and dark matter. But, even if we could account for dark matter with a bunch of particles and dark energy was understood, we still wouldn't understand much. For instance, none of this knowledge would help us understand why the various forces behave the way they do.
Along the way, he provided a taste of the evidence for why we believe the things that we do. We know dark matter exists because galaxies don't fly apart, because we find gravity where there is no matter, and, most tellingly, our universe would be smooth and featureless in the absence of dark matter. He showed that, although dark matter allows structures to form, inflation provided the initial changes in density that allowed them to condense.
But, of course, we don't know what dark matter is. Murayama justified the idea that dark matter is almost certainly some sort of weakly interacting massive particle by showing how we account for the dimmest objects in the Universe and simply don't find enough of them. In short, we think that dark matter exists because it is just about impossible to account for all the evidence with any other proposals.
Now, with the LHC online, we should start finding particles that may well be dark matter, and we will soon know if cosmologists were on the right track. And that is kind of exciting: years of speculation and careful modeling about to be properly tested. But, even more exciting, if the LHC does find dark matter candidate particles, cosmologists will be able to claim that we pretty much understand the Universe from 10-10s after the big bang to the present day—a mind-boggling thought.
What really seems to turns Murayama on is the problem of explaining why some forces are long-range and some are short-range. Basically, gravity reaches out over huge distances. Electromagnetism would reach just as far, but because there are both negative and positive charges, forces due to one set of charges tend get screened out by opposite signed charges. This effectively limits the reach of electromagnetic forces. Nevertheless, the fundamental distance scaling for the two forces is the same. The strong and weak nuclear forces are very short range, extending no further than the width of a nucleus.
There is no fundamental reason for why these forces scale differently from gravity and electromagnetism. He proposes that the Universe is, in fact, a quantum fluid, somewhat like a superconductor. How does this work? The analogy with superconductivity is apt because superconductors reject magnetic fields. That is, the charges in a superconductor arrange themselves such that the field lines of a magnetic field get bent around the super-current. Now, imagine sitting in the superconductor, trying to make a magnetic field.
What you would see is that the field was incredibly short-ranged because of the way the field would interact with the surrounding charges. Therein lies the idea. Imagine that the Universe is a quantum fluid that interacts very strongly with the strong force and weak forces, but ignores gravity and electromagnetism. Our knowledge of the four forces allows us to calculate some of the properties that this fluid must have, and, from there, to figure out how much energy is tied up in this fluid.
If you are going to go into debt, you might as well do it properly. If Murayama is right, the current energy of the Universe is short by some 1062 percent of that required to create the fluid during the big bang—that is one hell of a mortgage. As he jokingly pointed out, we are constantly told that deficits are a bad thing, so if his dark field proposal is to become more than an idea, some creative accounting is required.
All in all, a great opening to Physics@FOM.
From:http://arstechnica.com/science/news/2010/01/quantum-universe.ars
2010/07/09
The proton shrinks in size
The proton shrinks in size
Tiny change in radius has huge implications.
Geoff Brumfiel
Measurements with lasers have revealed that the proton may be a touch smaller than predicted by current theories.PSI / F. Reiser
The proton seems to be 0.00000000000003 millimetres smaller than researchers previously thought, according to work published in today's issue of Nature1.
The difference is so infinitesimal that it might defy belief that anyone, even physicists, would care. But the new measurements could mean that there is a gap in existing theories of quantum mechanics. "It's a very serious discrepancy," says Ingo Sick, a physicist at the University of Basel in Switzerland, who has tried to reconcile the finding with four decades of previous measurements. "There is really something seriously wrong someplace."
Protons are among the most common particles out there. Together with their neutral counterparts, neutrons, they form the nuclei of every atom in the Universe. But despite its everday appearance, the proton remains something of a mystery to nuclear physicists, says Randolf Pohl, a researcher at the Max Planck Institute of Quantum Optics in Garching, Germany, and an author on the Nature paper. "We don't understand a lot of its internal structure," he says.
From afar, the proton looks like a small point of positive charge, but on much closer inspection, the particle is more complex. Each proton is made of smaller fundamental particles called quarks, and that means its charge is roughly spread throughout a spherical area.
Physicists can measure the size of the proton by watching as an electron interacts with a proton. A single electron orbiting a proton can occupy only certain, discrete energy levels, which are described by the laws of quantum mechanics. Some of these energy levels depend in part on the size of the proton, and since the 1960s physicists have made hundreds of measurements of the proton's size with staggering accuracy. The most recent estimates, made by Sick using previous data, put the radius of the proton at around 0.8768 femtometres (1 femtometre = 10-15 metres).
Small wonder
Pohl and his team have a come up with a smaller number by using a cousin of the electron, known as the muon. Muons are about 200 times heavier than electrons, making them more sensitive to the proton's size. To measure the proton radius using the muon, Pohl and his colleagues fired muons from a particle accelerator at a cloud of hydrogen. Hydrogen nuclei each consist of a single proton, orbited by an electron. Sometimes a muon replaces an electron and orbits around a proton. Using lasers, the team measured relevant muonic energy levels with extremely high accuracy and found that the proton was around 4% smaller than previously thought.
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That might not sound like much, but the difference is so far from previous measurements that the researchers actually missed it the first two times they ran the experiment in 2003 and 2007. "We thought that our laser system was not good enough," Pohl says. In 2009, they looked beyond the narrow range in which they expected to see the proton radius and saw an unmistakable signal.
"What gives? I don't know," says Sick. He says he believes the new result, but that there is no obvious way to make it compatible with years of earlier measurements.
"Something is missing, this is very clear," agrees Carl Carlson, a theoretical physicist at the College of William & Mary in Williamsburg, Virginia. The most intriguing possibility is that previously undetected particles are changing the interaction of the muon and the proton. Such particles could be the 'superpartners' of existing particles, as predicted by a theory known as supersymmetry, which seeks to unite all of the fundamental forces of physics, except gravity.
But, Carlson says, "the first thing is to go through the existing calculations with a fine tooth comb". It could be that an error was made, or that approximations made in existing quantum calculation simply aren't good enough. "Right now, I'd put my money on some other correction," he says. "It's also where my research time will be going over the next month."
From:http://www.nature.com/news/2010/100707/full/news.2010.337.html
Tiny change in radius has huge implications.
Geoff Brumfiel
Measurements with lasers have revealed that the proton may be a touch smaller than predicted by current theories.PSI / F. Reiser
The proton seems to be 0.00000000000003 millimetres smaller than researchers previously thought, according to work published in today's issue of Nature1.
The difference is so infinitesimal that it might defy belief that anyone, even physicists, would care. But the new measurements could mean that there is a gap in existing theories of quantum mechanics. "It's a very serious discrepancy," says Ingo Sick, a physicist at the University of Basel in Switzerland, who has tried to reconcile the finding with four decades of previous measurements. "There is really something seriously wrong someplace."
Protons are among the most common particles out there. Together with their neutral counterparts, neutrons, they form the nuclei of every atom in the Universe. But despite its everday appearance, the proton remains something of a mystery to nuclear physicists, says Randolf Pohl, a researcher at the Max Planck Institute of Quantum Optics in Garching, Germany, and an author on the Nature paper. "We don't understand a lot of its internal structure," he says.
From afar, the proton looks like a small point of positive charge, but on much closer inspection, the particle is more complex. Each proton is made of smaller fundamental particles called quarks, and that means its charge is roughly spread throughout a spherical area.
Physicists can measure the size of the proton by watching as an electron interacts with a proton. A single electron orbiting a proton can occupy only certain, discrete energy levels, which are described by the laws of quantum mechanics. Some of these energy levels depend in part on the size of the proton, and since the 1960s physicists have made hundreds of measurements of the proton's size with staggering accuracy. The most recent estimates, made by Sick using previous data, put the radius of the proton at around 0.8768 femtometres (1 femtometre = 10-15 metres).
Small wonder
Pohl and his team have a come up with a smaller number by using a cousin of the electron, known as the muon. Muons are about 200 times heavier than electrons, making them more sensitive to the proton's size. To measure the proton radius using the muon, Pohl and his colleagues fired muons from a particle accelerator at a cloud of hydrogen. Hydrogen nuclei each consist of a single proton, orbited by an electron. Sometimes a muon replaces an electron and orbits around a proton. Using lasers, the team measured relevant muonic energy levels with extremely high accuracy and found that the proton was around 4% smaller than previously thought.
ADVERTISEMENT
That might not sound like much, but the difference is so far from previous measurements that the researchers actually missed it the first two times they ran the experiment in 2003 and 2007. "We thought that our laser system was not good enough," Pohl says. In 2009, they looked beyond the narrow range in which they expected to see the proton radius and saw an unmistakable signal.
"What gives? I don't know," says Sick. He says he believes the new result, but that there is no obvious way to make it compatible with years of earlier measurements.
"Something is missing, this is very clear," agrees Carl Carlson, a theoretical physicist at the College of William & Mary in Williamsburg, Virginia. The most intriguing possibility is that previously undetected particles are changing the interaction of the muon and the proton. Such particles could be the 'superpartners' of existing particles, as predicted by a theory known as supersymmetry, which seeks to unite all of the fundamental forces of physics, except gravity.
But, Carlson says, "the first thing is to go through the existing calculations with a fine tooth comb". It could be that an error was made, or that approximations made in existing quantum calculation simply aren't good enough. "Right now, I'd put my money on some other correction," he says. "It's also where my research time will be going over the next month."
From:http://www.nature.com/news/2010/100707/full/news.2010.337.html
2010/06/18
confinement and chanllenge
Have seen a movie, named "Einstein and Eddington". It was a period of confining people's mind, ruled by their religion. Or we could say that this confinement exists all the time no matter what period it is. Those two scientists try to break the confinement, try to free their mind from the cage. Eddington said, there is nothing can stop the conservation of science, there should not exist any boundary between nations, people, and races. Imagination is the only thing really free from the mind, even if so many stumbling stones located in front of us. They choiced what they want to do and dealed with the coming challenge. I am wondering that they also understand how much new confinement try to stuck young people's mind on their way to persue their knowledge. Imagination, that is what I have which is truly free from all those cages. We still strugle to looking for freedom on the way to find the truth. If there is any oppertunity that we can really approach to the truth of the universe, it must be "free mind" and "imagination". Nothing impossible! That's waht I want to say to Einstein, and tell him that there are always young people keeping this belief to start their research career.
2010/05/13
Largest scientific instrument ever built to prove Einstein's theory of general relativity
Three spacecraft flying three million miles apart are to fire laser beams at each other across the emptiness of space in a bid to finally prove whether a theory proposed by Albert Einstein is correct.
By Richard Gray, Science Correspondent
Published: 8:30AM BST 09 May 2010
Albert Einstein was awarded the Nobel Prize for Physics in 1921 Photo: AFP/GETTY
Physicists hope the ambitious mission will allow them to prove the existence of gravitational waves – a phenomenon predicted in Einstein's famous theory of general relativity and the last piece of his theory still to be proved correct.
The mission, a collaboration between Nasa and the European Space Agency, will use three spacecraft flying in formation while orbiting the sun, with each housing floating cubes of gold platinum.
Laser beams fired between the spacecraft will then be used to measure minute changes in the distance between each of the cubes, caused by the weak waves of gravity that ripple out from catastrophic events in deep space.
Einstein's theory of general relativity predicted that when large objects such as black holes collide, ripples in space and time flow outwards. These ripples are called gravitational waves.
A panel of international experts have now set out a detailed plan for the mission and how it can be used to reveal new insights about the universe around us.
Professor Jim Hough, an expert on gravitational waves at Glasgow University and a member of the committee that drew up the plans, said: "Gravitational waves are the last piece of Einstein's theory of general relativity that has still to be proved correct.
"They are produced when massive objects like black holes or collapsed stars accelerate through space, perhaps because they being pulled towards another object with greater gravitational pull like a massive black hole.
"Unfortunately we haven't been able to detect them yet because they are very weak. However, the new experiments we are working on have great potential to allow detection."
Ground based attempts to detect gravitational waves on Earth have so far been unsuccessful and can only look for gravitational waves with relatively high frequencies.
Scientists have already been able to prove a number of predictions made by Einstein's theory of general relativity, including that light is bent by gravity, gravity travels at a constant speed, that time can be warped by gravity and that space and time can bend.
Einstein's other theories including his most famous formula E=mc2 have also withstood scientific testing.
The Laser Interferometer Space Antenna, or LISA as the new space based mission is called, will be able to detect gravitational waves of very low frequencies due to the huge distance between the three spacecraft. It will be the largest detector ever built.
A smaller test mission called LISA Pathfinder, which is being built by British engineers at space company Astrium EADS and is due to be launched next year, is to pave the way for the more ambitious mission by demonstrating the technology to be used to detect the waves.
Scientists have already begun building the instruments that will be used in LISA itself, but it is not expected to be launched before 2020.
They hope that once detected, gravitational waves will be able to provide new information about the universe that cannot currently be seen using electromagnetic radiation such as light, radio waves and X-rays.
Professor Sheila Rowan, who also studies gravitational waves at Glasgow University, added: "Black holes are so dense that no light or radiation escapes from inside them.
"Gravitational waves from the warped spacetime around black holes could give us new ways of looking at them.
"We could also learn about the state of matter inside collapsed stars."
Dr Ralph Cordey, science and exploration business development manager at Astrium UK who are building LISA Pathfinder, said: "Trying to measure cosmic events such as collapsing star systems or the collision of massive black holes throughout our universe requires ultra-high precision technology.
"The ultimate goal is to prove that this technology works, before we attempt to put three spacecraft into orbits at a distance of 5 million kilometres from one another, connected only by a laser beam that will measure their positions accurate to 40 millionths of a millionth of a metre."
From:http://www.telegraph.co.uk/science/space/7695994/Largest-scientific-instrument-ever-built-to-prove-Einsteins-theory-of-general-relativity.html
By Richard Gray, Science Correspondent
Published: 8:30AM BST 09 May 2010
Albert Einstein was awarded the Nobel Prize for Physics in 1921 Photo: AFP/GETTY
Physicists hope the ambitious mission will allow them to prove the existence of gravitational waves – a phenomenon predicted in Einstein's famous theory of general relativity and the last piece of his theory still to be proved correct.
The mission, a collaboration between Nasa and the European Space Agency, will use three spacecraft flying in formation while orbiting the sun, with each housing floating cubes of gold platinum.
Laser beams fired between the spacecraft will then be used to measure minute changes in the distance between each of the cubes, caused by the weak waves of gravity that ripple out from catastrophic events in deep space.
Einstein's theory of general relativity predicted that when large objects such as black holes collide, ripples in space and time flow outwards. These ripples are called gravitational waves.
A panel of international experts have now set out a detailed plan for the mission and how it can be used to reveal new insights about the universe around us.
Professor Jim Hough, an expert on gravitational waves at Glasgow University and a member of the committee that drew up the plans, said: "Gravitational waves are the last piece of Einstein's theory of general relativity that has still to be proved correct.
"They are produced when massive objects like black holes or collapsed stars accelerate through space, perhaps because they being pulled towards another object with greater gravitational pull like a massive black hole.
"Unfortunately we haven't been able to detect them yet because they are very weak. However, the new experiments we are working on have great potential to allow detection."
Ground based attempts to detect gravitational waves on Earth have so far been unsuccessful and can only look for gravitational waves with relatively high frequencies.
Scientists have already been able to prove a number of predictions made by Einstein's theory of general relativity, including that light is bent by gravity, gravity travels at a constant speed, that time can be warped by gravity and that space and time can bend.
Einstein's other theories including his most famous formula E=mc2 have also withstood scientific testing.
The Laser Interferometer Space Antenna, or LISA as the new space based mission is called, will be able to detect gravitational waves of very low frequencies due to the huge distance between the three spacecraft. It will be the largest detector ever built.
A smaller test mission called LISA Pathfinder, which is being built by British engineers at space company Astrium EADS and is due to be launched next year, is to pave the way for the more ambitious mission by demonstrating the technology to be used to detect the waves.
Scientists have already begun building the instruments that will be used in LISA itself, but it is not expected to be launched before 2020.
They hope that once detected, gravitational waves will be able to provide new information about the universe that cannot currently be seen using electromagnetic radiation such as light, radio waves and X-rays.
Professor Sheila Rowan, who also studies gravitational waves at Glasgow University, added: "Black holes are so dense that no light or radiation escapes from inside them.
"Gravitational waves from the warped spacetime around black holes could give us new ways of looking at them.
"We could also learn about the state of matter inside collapsed stars."
Dr Ralph Cordey, science and exploration business development manager at Astrium UK who are building LISA Pathfinder, said: "Trying to measure cosmic events such as collapsing star systems or the collision of massive black holes throughout our universe requires ultra-high precision technology.
"The ultimate goal is to prove that this technology works, before we attempt to put three spacecraft into orbits at a distance of 5 million kilometres from one another, connected only by a laser beam that will measure their positions accurate to 40 millionths of a millionth of a metre."
From:http://www.telegraph.co.uk/science/space/7695994/Largest-scientific-instrument-ever-built-to-prove-Einsteins-theory-of-general-relativity.html
The 10 weirdest physics facts, from relativity to quantum physics
People who think science is dull are wrong. Here are 10 reasons why.
By Tom Chivers
Published: 7:00AM GMT 12 Nov 2009
Physics is weird. There is no denying that. Particles that don’t exist except as probabilities; time that changes according to how fast you’re moving; cats that are both alive and dead until you open a box.
We’ve put together a collection of 10 of the strangest facts we can find, with the kind help of cosmologist and writer Marcus Chown, author of We Need To Talk About Kelvin, and an assortment of Twitter users.
The humanities-graduate writer of this piece would like to stress that this is his work, so any glaring factual errors he has included are his own as well. If you spot any, feel free to point them out in the comment box below.
Equally, if you feel we’ve missed any of your favourite physics weirdnesses off the list, do tell us that as well.
If the Sun were made of bananas, it would be just as hot
The Sun is hot, as the more astute of you will have noticed. It is hot because its enormous weight – about a billion billion billion tons – creates vast gravity, putting its core under colossal pressure. Just as a bicycle pump gets warm when you pump it, the pressure increases the temperature. Enormous pressure leads to enormous temperature.
If, instead of hydrogen, you got a billion billion billion tons of bananas and hung it in space, it would create just as much pressure, and therefore just as high a temperature. So it would make very little difference to the heat whether you made the Sun out of hydrogen, or bananas, or patio furniture.
Edit: this might be a little confusing. The heat caused by the internal pressure would be similar to that of our Sun. However, if it's not made of hydrogen, the fusion reaction that keeps it going wouldn't get under way: so a banana Sun would rapidly cool down from its initial heat rather than burning for billions of years. Thanks to people who pointed this out.
All the matter that makes up the human race could fit in a sugar cube
Atoms are 99.9999999999999 per cent empty space. As Tom Stoppard put it: "Make a fist, and if your fist is as big as the nucleus of an atom, then the atom is as big as St Paul's, and if it happens to be a hydrogen atom, then it has a single electron flitting about like a moth in an empty cathedral, now by the dome, now by the altar."
If you forced all the atoms together, removing the space between them, crushing them down so the all those vast empty cathedrals were compressed into the first-sized nuclei, a single teaspoon or sugar cube of the resulting mass would weigh five billion tons; about ten times the weight of all the humans who are currently alive.
Incidentally, that is exactly what has happened in a neutron star, the super-dense mass left over after a certain kind of supernova.
The weirdness of the quantum world is well documented. The double slit experiment, showing that light behaves as both a wave and a particle, is odd enough – particularly when it is shown that observing it makes it one or the other.
But it gets stranger. According to an experiment proposed by the physicist John Wheeler in 1978 and carried out by researchers in 2007, observing a particle now can change what happened to another one – in the past.
According to the double slit experiment, if you observe which of two slits light passes through, you force it to behave like a particle. If you don’t, and observe where it lands on a screen behind the slits, it behaves like a wave.
But if you wait for it to pass through the slit, and then observe which way it came through, it will retroactively force it to have passed through one or the other. In other words, causality is working backwards: the present is affecting the past.
Of course in the lab this only has an effect over indescribably tiny fractions of a second. But Wheeler suggested that light from distant stars that has bent around a gravitational well in between could be observed in the same way: which could mean that observing something now and changing what happened thousands, or even millions, of years in the past.
Almost all of the Universe is missing
There are probably more than 100 billion galaxies in the cosmos. Each of those galaxies has between 10 million and a trillion stars in it. Our sun, a rather small and feeble star (a “yellow dwarf”, indeed), weighs around a billion billion billion tons, and most are much bigger. There is an awful lot of visible matter in the Universe.
But it only accounts for about two per cent of its mass.
We know there is more, because it has gravity. Despite the huge amount of visible matter, it is nowhere near enough to account for the gravitational pull we can see exerted on other galaxies. The other stuff is called “dark matter”, and there seems to be around six times as much as ordinary matter.
To make matters even more confusing, the rest is something else called “dark energy”, which is needed to explain the apparent expansion of the Universe. Nobody knows what dark matter or dark energy is.
Things can travel faster than light; and light doesn’t always travel very fast
The speed of light in a vacuum is a constant: 300,000km a second. However, light does not always travel through a vacuum. In water, for example, photons travel at around three-quarters that speed.
In nuclear reactors, some particles are forced up to very high speeds, often within a fraction of the speed of light. If they are passing through an insulating medium that slows light down, they can actually travel faster than the light around them.
When this happens, they cause a blue glow, known as “Cherenkov radiation ”, which is (sort of) comparable to a sonic boom but with light. This is why nuclear reactors glow in the dark.
Incidentally, the slowest light has ever been recorded travelling was 17 meters per second – about 38 miles an hour – through rubidium cooled to almost absolute zero, when it forms a strange state of matter called a Bose-Einstein condensate.
Light has also been brought to a complete stop in the same fashion, but since that wasn't moving at all, we didn't feel we could describe that as "the slowest it has been recorded travelling".
There are an infinite number of mes writing this, and an infinite number of yous reading it
According to the current standard model of cosmology, the observable universe – containing all the billions of galaxies and trillions upon trillions of stars mentioned above – is just one of an infinite number of universes existing side-by-side, like soap bubbles in a foam.
Because they are infinite, every possible history must have played out. But more than that, the number of possible histories is finite, because there have been a finite number of events with a finite number of outcomes. The number is huge, but it is finite. So this exact event, where this author writes these words and you read them, must have happened an infinite number of times.
Even more amazingly, we can work out how far away our nearest doppelganger is. It is, to put it mildly, a large distance: 10 to the power of 10 to the power of 28 meters. That number, in case you were wondering, is one followed by 10 billion billion billion zeroes
Black holes aren’t black
hey’re very dark, sure, but they aren’t black. They glow, slightly, giving off light across the whole spectrum, including visible light.
This radiation is called “Hawking radiation”, after the former Lucasian Professor of Mathematics at Cambridge University Stephen Hawking, who first proposed its existence. Because they are constantly giving this off, and therefore losing mass, black holes will eventually evaporate altogether if they don’t have another source of mass to sustain them; for example interstellar gas or light.
Smaller black holes are expected to emit radiation faster compared to their mass than larger ones, so if – as some theories predict – the Large Hadron Collider creates minuscule holes through particle collisions, they will evaporate almost immediately. Scientists would then be able to observe their decay through the radiation.
The fundamental description of the universe does not account for a past, present or future
According to the special theory of relativity, there is no such thing as a present, or a future, or a past. Time frames are relative: I have one, you have one, the third planet of Gliese 581 has one. Ours are similar because we are moving at similar speeds.
If we were moving at very different speeds, we would find that one of us aged quicker than the other. Similarly, if one of us was closer than the other to a major gravity well like the Earth, we would age slower than someone who wasn’t.
GPS satellites, of course, are both moving quickly and at significant distances from Earth. So their internal clocks show a different time to the receivers on the ground. A lot of computing power has to go into making your sat-nav work around the theory of special relativity.
A particle here can affect one on the other side of the universe, instantaneously
When an electron meets its antimatter twin, a positron, the two are annihilated in a tiny flash of energy. Two photons fly away from the blast.
Subatomic particles like photons and quarks have a quality known as “spin”. It’s not that they’re really spinning – it’s not clear that would even mean anything at that level – but they behave as if they do. When two are created simultaneously the direction of their spin has to cancel each other out: one doing the opposite of the other.
Due to the unpredictability of quantum behaviour, it is impossible to say in advance which will go “anticlockwise” and the other “clockwise”. More than that, until the spin of one is observed, they are both doing both.
It gets weirder, however. When you do observe one, it will suddenly be going clockwise or anticlockwise. And whichever way it is going, its twin will start spinning the other way, instantly, even if it is on the other side of the universe. This has actually been shown to happen in experiment (albeit on the other side of a laboratory, not a universe).
The faster you move, the heavier you get
If you run really fast, you gain weight. Not permanently, or it would make a mockery of diet and exercise plans, but momentarily, and only a tiny amount.
Light speed is the speed limit of the universe. So if something is travelling close to the speed of light, and you give it a push, it can’t go very much faster. But you’ve given it extra energy, and that energy has to go somewhere.
Where it goes is mass. According to relativity, mass and energy are equivalent. So the more energy you put in, the greater the mass becomes. This is negligible at human speeds – Usain Bolt is not noticeably heavier when running than when still – but once you reach an appreciable fraction of the speed of light, your mass starts to increase rapidly.
Originated from: http://www.telegraph.co.uk/science/6546462/The-10-weirdest-physics-facts-from-relativity-to-quantum-physics.html
By Tom Chivers
Published: 7:00AM GMT 12 Nov 2009
Physics is weird. There is no denying that. Particles that don’t exist except as probabilities; time that changes according to how fast you’re moving; cats that are both alive and dead until you open a box.
We’ve put together a collection of 10 of the strangest facts we can find, with the kind help of cosmologist and writer Marcus Chown, author of We Need To Talk About Kelvin, and an assortment of Twitter users.
The humanities-graduate writer of this piece would like to stress that this is his work, so any glaring factual errors he has included are his own as well. If you spot any, feel free to point them out in the comment box below.
Equally, if you feel we’ve missed any of your favourite physics weirdnesses off the list, do tell us that as well.
If the Sun were made of bananas, it would be just as hot
The Sun is hot, as the more astute of you will have noticed. It is hot because its enormous weight – about a billion billion billion tons – creates vast gravity, putting its core under colossal pressure. Just as a bicycle pump gets warm when you pump it, the pressure increases the temperature. Enormous pressure leads to enormous temperature.
If, instead of hydrogen, you got a billion billion billion tons of bananas and hung it in space, it would create just as much pressure, and therefore just as high a temperature. So it would make very little difference to the heat whether you made the Sun out of hydrogen, or bananas, or patio furniture.
Edit: this might be a little confusing. The heat caused by the internal pressure would be similar to that of our Sun. However, if it's not made of hydrogen, the fusion reaction that keeps it going wouldn't get under way: so a banana Sun would rapidly cool down from its initial heat rather than burning for billions of years. Thanks to people who pointed this out.
All the matter that makes up the human race could fit in a sugar cube
Atoms are 99.9999999999999 per cent empty space. As Tom Stoppard put it: "Make a fist, and if your fist is as big as the nucleus of an atom, then the atom is as big as St Paul's, and if it happens to be a hydrogen atom, then it has a single electron flitting about like a moth in an empty cathedral, now by the dome, now by the altar."
If you forced all the atoms together, removing the space between them, crushing them down so the all those vast empty cathedrals were compressed into the first-sized nuclei, a single teaspoon or sugar cube of the resulting mass would weigh five billion tons; about ten times the weight of all the humans who are currently alive.
Incidentally, that is exactly what has happened in a neutron star, the super-dense mass left over after a certain kind of supernova.
The weirdness of the quantum world is well documented. The double slit experiment, showing that light behaves as both a wave and a particle, is odd enough – particularly when it is shown that observing it makes it one or the other.
But it gets stranger. According to an experiment proposed by the physicist John Wheeler in 1978 and carried out by researchers in 2007, observing a particle now can change what happened to another one – in the past.
According to the double slit experiment, if you observe which of two slits light passes through, you force it to behave like a particle. If you don’t, and observe where it lands on a screen behind the slits, it behaves like a wave.
But if you wait for it to pass through the slit, and then observe which way it came through, it will retroactively force it to have passed through one or the other. In other words, causality is working backwards: the present is affecting the past.
Of course in the lab this only has an effect over indescribably tiny fractions of a second. But Wheeler suggested that light from distant stars that has bent around a gravitational well in between could be observed in the same way: which could mean that observing something now and changing what happened thousands, or even millions, of years in the past.
Almost all of the Universe is missing
There are probably more than 100 billion galaxies in the cosmos. Each of those galaxies has between 10 million and a trillion stars in it. Our sun, a rather small and feeble star (a “yellow dwarf”, indeed), weighs around a billion billion billion tons, and most are much bigger. There is an awful lot of visible matter in the Universe.
But it only accounts for about two per cent of its mass.
We know there is more, because it has gravity. Despite the huge amount of visible matter, it is nowhere near enough to account for the gravitational pull we can see exerted on other galaxies. The other stuff is called “dark matter”, and there seems to be around six times as much as ordinary matter.
To make matters even more confusing, the rest is something else called “dark energy”, which is needed to explain the apparent expansion of the Universe. Nobody knows what dark matter or dark energy is.
Things can travel faster than light; and light doesn’t always travel very fast
The speed of light in a vacuum is a constant: 300,000km a second. However, light does not always travel through a vacuum. In water, for example, photons travel at around three-quarters that speed.
In nuclear reactors, some particles are forced up to very high speeds, often within a fraction of the speed of light. If they are passing through an insulating medium that slows light down, they can actually travel faster than the light around them.
When this happens, they cause a blue glow, known as “Cherenkov radiation ”, which is (sort of) comparable to a sonic boom but with light. This is why nuclear reactors glow in the dark.
Incidentally, the slowest light has ever been recorded travelling was 17 meters per second – about 38 miles an hour – through rubidium cooled to almost absolute zero, when it forms a strange state of matter called a Bose-Einstein condensate.
Light has also been brought to a complete stop in the same fashion, but since that wasn't moving at all, we didn't feel we could describe that as "the slowest it has been recorded travelling".
There are an infinite number of mes writing this, and an infinite number of yous reading it
According to the current standard model of cosmology, the observable universe – containing all the billions of galaxies and trillions upon trillions of stars mentioned above – is just one of an infinite number of universes existing side-by-side, like soap bubbles in a foam.
Because they are infinite, every possible history must have played out. But more than that, the number of possible histories is finite, because there have been a finite number of events with a finite number of outcomes. The number is huge, but it is finite. So this exact event, where this author writes these words and you read them, must have happened an infinite number of times.
Even more amazingly, we can work out how far away our nearest doppelganger is. It is, to put it mildly, a large distance: 10 to the power of 10 to the power of 28 meters. That number, in case you were wondering, is one followed by 10 billion billion billion zeroes
Black holes aren’t black
hey’re very dark, sure, but they aren’t black. They glow, slightly, giving off light across the whole spectrum, including visible light.
This radiation is called “Hawking radiation”, after the former Lucasian Professor of Mathematics at Cambridge University Stephen Hawking, who first proposed its existence. Because they are constantly giving this off, and therefore losing mass, black holes will eventually evaporate altogether if they don’t have another source of mass to sustain them; for example interstellar gas or light.
Smaller black holes are expected to emit radiation faster compared to their mass than larger ones, so if – as some theories predict – the Large Hadron Collider creates minuscule holes through particle collisions, they will evaporate almost immediately. Scientists would then be able to observe their decay through the radiation.
The fundamental description of the universe does not account for a past, present or future
According to the special theory of relativity, there is no such thing as a present, or a future, or a past. Time frames are relative: I have one, you have one, the third planet of Gliese 581 has one. Ours are similar because we are moving at similar speeds.
If we were moving at very different speeds, we would find that one of us aged quicker than the other. Similarly, if one of us was closer than the other to a major gravity well like the Earth, we would age slower than someone who wasn’t.
GPS satellites, of course, are both moving quickly and at significant distances from Earth. So their internal clocks show a different time to the receivers on the ground. A lot of computing power has to go into making your sat-nav work around the theory of special relativity.
A particle here can affect one on the other side of the universe, instantaneously
When an electron meets its antimatter twin, a positron, the two are annihilated in a tiny flash of energy. Two photons fly away from the blast.
Subatomic particles like photons and quarks have a quality known as “spin”. It’s not that they’re really spinning – it’s not clear that would even mean anything at that level – but they behave as if they do. When two are created simultaneously the direction of their spin has to cancel each other out: one doing the opposite of the other.
Due to the unpredictability of quantum behaviour, it is impossible to say in advance which will go “anticlockwise” and the other “clockwise”. More than that, until the spin of one is observed, they are both doing both.
It gets weirder, however. When you do observe one, it will suddenly be going clockwise or anticlockwise. And whichever way it is going, its twin will start spinning the other way, instantly, even if it is on the other side of the universe. This has actually been shown to happen in experiment (albeit on the other side of a laboratory, not a universe).
The faster you move, the heavier you get
If you run really fast, you gain weight. Not permanently, or it would make a mockery of diet and exercise plans, but momentarily, and only a tiny amount.
Light speed is the speed limit of the universe. So if something is travelling close to the speed of light, and you give it a push, it can’t go very much faster. But you’ve given it extra energy, and that energy has to go somewhere.
Where it goes is mass. According to relativity, mass and energy are equivalent. So the more energy you put in, the greater the mass becomes. This is negligible at human speeds – Usain Bolt is not noticeably heavier when running than when still – but once you reach an appreciable fraction of the speed of light, your mass starts to increase rapidly.
Originated from: http://www.telegraph.co.uk/science/6546462/The-10-weirdest-physics-facts-from-relativity-to-quantum-physics.html
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