Plasma Physics and Applications

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MIT Open Course Ware

Posted: August 1, 2014 in Uncategorized

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The basic laws of physics don’t obviously prohibit it, but the criteria for a genuine “memory” do.

Since the laws of physics could allow time to run forward or backward, it’s not obvious why time as we perceive it must move in the same direction as that required by thermodynamics (entropy always increases). But theorists propose that a proper definition of “memory” shows why we can’t “remember the future.”

Why can we remember the past but not the future? It might seem like a bizarre question, but it’s not obvious why our psychological “arrow of time” should move in the same direction as that dictated by the second law of thermodynamics, which implies that events unfold in the direction that increases net entropy. A report in Physical Review E suggests that these two arrows of time are forced to coincide by the constraints on what it actually means to remember something.

The fundamental laws of physics are symmetrical in time: in Newtonian classical mechanics time is in principle reversible, and in general relativity it is just a coordinate much like those of space. Given the positions and velocities of a classical system of interacting particles, the past and future can in principle each be completely calculated from the laws of physics. So predictions of the future are just as accurate as descriptions of the past—they are equally “knowable” based on the present.

The existence of an arrow of time is usually explained in terms of the thermodynamic concept of entropy. In systems of many components, it is overwhelmingly more probable that changes will occur in the direction that increases the total entropy of the universe.

How we actually perceive the flow of time is another matter. Theorists have argued that recording information always involves erasing—for example, initializing a computer memory at the start . Since erasure always increases entropy, the psychological arrow of time aligns with the thermodynamic one.

But Leonard Mlodinow of the California Institute of Technology in Pasadena and Todd Brun of the University of Southern California in Los Angeles say that this argument is not quite complete. You can, in principle, get rid of any need for erasure and initialization just by remembering everything—which means that recording information in the memory is then fully reversible in time. But even in that case the arrows of time must align because, says Brun, “there is a broader principle at work.”

The researchers argue that this extra ingredient is something they call generality. They illustrate the argument with a rotating turnstile that records the passage of gas molecules from one chamber to another. The system starts with most of the molecules in the left-hand chamber, and at any instant the rotor reveals the net number that have passed from left to right since some earlier reference time. But since the system follows predictable and reversible Newtonian laws, the readout could also be interpreted as showing the number of molecules that will pass between the time of the reading and some future reference time. One can show that this would be a correct anticipation, since that number can, in principle, be calculated. “Why can’t we call that a memory of the future?” asks Brun.

The reason we cannot is that for the rotor to work as a memory of the past, the system’s state at an earlier reference time need not be precisely specified; any slight changes in the molecules’ positions at that time will not affect the readout at a later time. But equivalent small changes in the state at a future reference time—say, due to some unforeseen influence intervening—lead to inconsistencies.

To see this, recall that the molecules started mostly in the left-hand chamber and are gradually equalizing their numbers on both sides of the rotor. Imagine “running the movie backward” (according to Newtonian equations) from the future reference time to the readout time and seeing the molecules collectively move back toward the left-hand chamber. That extremely improbable event can only occur from one very specific arrangement of the molecules at the future time. If, before running time backward, you made any small changes, say, in the molecules’ positions, new collisions would occur during the time reversal that would rapidly set the system on a completely different course. The molecules would take the much more probable path of equalizing the populations and would not get close to the original state of the system at the readout time.

As Mlodinow and Brun put it, this kind of “future memory” lacks generality—a requirement that the memory accurately reflects the future state of the system regardless of unexpected events. The readout indicates a future state, but only one specific future state. They compare it to a camera that needs a different type of memory card to accommodate each photo. A real memory, they say, cannot be contingent on the system behaving a certain way.

“They have emphasized a very important problem in the meaning-of-time debate and provided an interesting solution,” says Lorenzo Maccone of the University of Pavia in Italy, who has previously considered the origin of the thermodynamic arrow of time in quantum physics.

But he isn’t yet persuaded by the answer, because the researchers allow the memory to track the system only in the “forward” time direction. “It seems to me that they are somehow introducing surreptitiously an arrow of time when they say that the memory tracks the system only in one direction.” But Maccone adds that “in such a difficult field, even highlighting what are the relevant questions to ask is already big progress.”

From the Quantum Diaries

Posted: April 27, 2014 in Uncategorized

If there are two particles that everyone has read about in the news lately, it’s the Higgs boson and the neutrino. Why do we continue to be fascinated by these two particles?

As just about everyone now knows, the Higgs boson is integrally connected to the field that gives particles their mass. But the excitement of this discovery isn’t over; now we need to figure out how this actually works and whether it explains everything about how particles get their mass. With time, this knowledge is likely to affect daily life.

One way it could possibly bridge the gap between fundamental research and the commercial market, I believe, is in batteries. The ultimate battery in nature is mass. The expression E=mc^2 is a statement of that fact. During the early moments of the universe, all particles were massless and traveling at the speed of light. Once the Higgs mechanism turned on, particles suddenly began interacting with the field and, in this process, converted their energy into what we now refer to as mass. In a recent address to the Canadian Nuclear Society, I suggested that if engineers of the future could learn how to manipulate the Higgs field (to “turn it on and off”), then we would have developed the ultimate energy source and the best battery nature has created. This idea definitely belongs in the science-fiction category, but remember that progress in science is driven by thinking “outside the box!”

This sort of thinking comes from looking at the Higgs from another angle. According to the Standard Model, many particles come in left-handed and right-handed versions (in the former, the particle’s direction of spin matches its direction of motion, while in the latter, they are opposite).

Keeping this fact in mind, let’s look at the mass of the familiar electron as an example. When we say that the mass of the electron is created by interactions with the Higgs field, we can think of this as the Higgs field rapidly changing a left-handed electron into a right-handed electron, and vice versa. This switching back and forth is energy and, through E=mc^2, energy is mass. A heavier particle like the top quark would experience this flipping at a much higher frequency than a lighter particle like the electron. As we learn more about how this process works, I encourage physicists to also seek applications of that knowledge.

And what about neutrinos? Do they get their mass from the Higgs field or in a completely different way? Once thought to be massless, neutrinos are now known to have a tiny mass. If the Higgs mechanism is responsible for that mass, there must exist both a left-handed and a right-handed neutrino. A good number of physicists think that both are out there, but we do not yet know. That knowledge may help us understand why the neutrino mass is tiny, as well as why there is more matter than antimatter in the universe—one of the most important questions facing our field of particle physics.

But since the neutrino is a neutral particle, the story gets more interesting. It may instead be possible that there is another type of mass. Referred to as a Majorana mass, it is not a mass described by the flipping of left- and right-handed neutrinos back and forth, but it is “intrinsic,” not derived from any kind of “motional energy.” I expect that the efforts by our field of particle physics, in the collective sense, will pursue the questions associated with both the Higgs boson and the neutrino with enthusiasm, and that the results will lead to advancements we can’t even imagine today.

Identical twins will be separated when one heads to space, as NASA conducts tests to see the impact of space travel on the human body, in an experiment reminscient of Einstein’s “twin paradox” theory


NASA is to send an identical twin to space, whilst leaving their twin on earth, to see the effects of long-term space flight on the human body. The experiment harkens back to Einstein’s “twin theory” paradox thought experiment – where one twin goes to space high speed, while their twin remains on earth. Einstein’s theory of relativity means that the twin will return from space younger than his brother. However, as it is impossible to study the flow of time, in this experiment, NASA will instead be testing 10 research proposals to study the twins’ genetics, biochemistry, vision, cognition. NASA astronaut Scott Kelly will go on a one-year mission to the International Space Station, while his twin, Mark – who is a retired astronaut – remains on earth. Craig Kundrot of NASA’s Human Research Program at the Johnson Space Center, said: “We will be taking samples and making measurements of the twins before, during, and after the one-year mission. “For the first time, we’ll be able two individuals who are genetically identical. “Each proposal is fascinating and could be a feature-length story of its own. “We already know that the human immune system changes in space. It’s not as strong as it is on the ground. “In one of the experiments, Mark and Scott will be given identical flu vaccines, and we will study how their immune systems react.” Other tests will examine DNA ageing, the effects of space travel on vision, and the stomach’s inner bacteria. The experiment will be conducted in March 2015.

My Physics Lab :)

Quantum Wave Interference Simulator!!

Image  —  Posted: April 16, 2014 in Uncategorized
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Posted: April 13, 2014 in Uncategorized
  • Quantum physics proves that there Is an afterlife, claims scientist
  • Robert Lanza claims the theory of biocentrism says death is an illusion
  • He said life creates the universe, and not the other way round
  • This means space and time don’t exist in the linear fashion we think it does
  • He uses the famous double-split experiment to illustrate his point
  • And if space and time aren’t linear, then death can’t exist in ‘any real sense’ either

Most scientists would probably say that the concept of an afterlife is either nonsense, or at the very least unprovable. Yet one expert claims he has evidence to confirm an existence beyond the grave – and it lies in quantum physics. Professor Robert Lanza claims the theory of biocentrism teaches that death as we know it is an illusion created by our consciousness. Professor Robert Lanza claims the theory of biocentrism, also known as the theory of everything, teaches death as we know it is an illusion. 
Professor Robert Lanza claims the theory of biocentrism teaches death as we know it is an illusion. He believes our consciousness creates the universe, and not the other way round, and once we accept that space and time are ‘tools of our minds’, death can’t exist in ‘any real sense’ either
‘We think life is just the activity of carbon and an admixture of molecules – we live a while and then rot into the ground,’ said the scientist on his website.Lanza, from Wake Forest University School of Medicine in North Carolina, continued that as humans we believe in death because ‘we’ve been taught we die’, or more specifically, our consciousness associates life with bodies and we know that bodies die. His theory of biocentrism, however, explains that death may not be as terminal as we think it is. Biocentrism is classed as the theory of everything and comes from the Greek for ‘life centre’. It is the believe that life and biology are central to reality and that life creates the universe, not the other way round.  This suggests a person’s consciousness determines the shape and size of objects in the universe.Lanza uses the example of the way we perceive the world around us. A person sees a blue sky, and is told that the colour they are seeing is blue, but the cells in a person’s brain could be changed to make the sky look green or red.