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Gravity's Engines
We’ve long understood black holes to be the points at which the universe as we know it comes to an end. Often billions of times more massive than the Sun, they...
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A vacuum might seem like empty space, but scientists have discovered a new way to seemingly get something from that nothingness, such as light. And the finding could ultimately help scientists build incredibly powerful quantum computers or shed light on the earliest moments in the universe's history.
Quantum physics explains that there are limits to how precisely one can know the properties of the most basic units of matter—for instance, one can never absolutely know a particle's position and momentum at the same time. One bizarre consequence of this uncertainty is that a vacuum is never completely empty, but instead buzzes with so-called “virtual particles” that constantly wink into and out of existence.
These virtual particles often appear in pairs that near-instantaneously cancel themselves out. Still, before they vanish, they can have very real effects on their surroundings. For instance, photons—packets of light—can pop in and out of a vacuum. When two mirrors are placed facing each other in a vacuum, more virtual photons can exist around the outside of the mirrors than between them, generating a seemingly mysterious force that pushes the mirrors together.
This phenomenon, predicted in 1948 by the Dutch physicist Hendrick Casimir and known as the Casimir effect, was first seen with mirrors held still . Researchers also predicted a dynamical Casimir effect that can result when mirrors are moved, or objects otherwise undergo change. Now quantum physicist Pasi Lähteenmäki at Aalto University in Finland and his colleagues reveal that by varying the speed at which light can travel, they can make light appear from nothing.
The speed of light in a vacuum is constant, according to Einstein's theory of relativity, but its speed passing through any given material depends on a property of that substance known as its index of refraction. By varying a material's index of refraction, researchers can influence the speed at which both real and virtual photons travel within it. Lähteenmäki says one can think of this system as being much like a mirror, and if its thickness changes fast enough, virtual photons reflecting off it can receive enough energy from the bounce to turn into real photons. "Imagine you stay in a very dark room and suddenly the index of refraction of light [of the room] changes," Lähteenmäki says. "The room will start to glow."
The researchers began with an array of 250 superconducting quantum-interference devices, or SQUIDs—circuits that are extraordinarily sensitive to magnetic fields. They inserted the array inside a refrigerator. By carefully exerting magnetic fields on this array, they could vary the speed at which microwave photons traveled through it by a few percent. The researchers then cooled this array to 50 thousandths of a degree Celsius above absolute zero. Because this environment is supercold, it should not emit any radiation, essentially behaving as a vacuum. "We were simply studying these circuits for the purpose of developing an amplifier, which we did," says researcher Sorin Paraoanu, a theoretical physicist at Aalto University. "But then we asked ourselves—what if there is no signal to amplify? What happens if the vacuum is the signal?"
The researchers detected photons that matched predictions from the dynamical Casimir effect. For instance, such photons should display the strange property of quantum entanglement—that is, by measuring the details of one, scientists could in principle know exactly what its counterpart is like, no matter where it is in the universe, a phenomenon Einstein referred to as "spooky action at a distance." The scientists detailed their findings online February 11 in Proceedings of the National Academy of Sciences.
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Add CommentAll very interesting; but I do not understand the notion that light would travel more slowly through a non-vacuum. Perhaps someone could explain or critique my conept: My conception is that the speed of light is "c", at all times and places. As a photon moves through a substance it takes a longer path to get from, say a point just outside a pool of water, to a point some distance away having emerged from the pool of water, thus clocking something less than "c" for the transit. That is, the photon may take more time to traverse this, say linear, distance than it would in a nominal vacuum but as the photon moves about in the medium, say from the vicinity of one H2O molecule to another, it is still making those tiny tiny paths at the speed of light, "c". I am positing that its velocity at the atomic or quantum level is still "c", and its longer traverse time is because it is going farther, i.e. the sum of all the zig zags, if you like. Is this a misconception? Indeed, if atoms and molecules in any given phase, including solid, is mostly space, then one would expect some light to traverse unimpeded. A photon at energies of x-rays, for example, do penetrate solids as we well know and make us of in medicine. Well, I am open to your insights on the question...
Reply | Report Abuse | Link to thisDo virtual photons contribute to dark matter?
Reply | Report Abuse | Link to thisSorry for all the typos in my post above, but I think the question is discernible. Thanks.
Reply | Report Abuse | Link to this"My conception is that the speed of light is "c", at all times and places."
Reply | Report Abuse | Link to thisThen that's where your problem lies. c is the speed of light in a (total) vacuum. Like all physical constants it is an idealisation. The actual speed of light in the actual Universe varies wildly.
http://en.wikipedia.org/wiki/Slow_light
Reply | Report Abuse | Link to thismight help. We have slowed light down so your theory doesn't really make sense.
Oneness of pairness, equator of self-contradiction, is Nature's absolute logic.-Aiya-Oba (Philosopher).
Reply | Report Abuse | Link to thisAre we sure we can produce an absolutely perfect vacuum? Probably not, and remember those bulbs where a sinning wheel made of mica squares forming a cross and oriented parallel to its rotation axis start moving when exposed to light or any radiation that may heat the darkened side of blade more than the brighter one, thus the dark part heats, and rejects the gas molecules inside the not true vacuum, starting to spin as a consequence of the principle of conservation of momentum. Material for the blades must be Mica, a very good isolating material, as others are better conductors of heat, and after a while both sides of the blade have the same temperature and the ejection of gas is the same in both sides of blade, thus no movemente at all. If you apply any strong force to a non perfect vacuum, the remaining matter inside it may split into many kinds of particles.
Reply | Report Abuse | Link to thisI meant spinning wheel, sorry
Reply | Report Abuse | Link to thisAs your 'Slow Light' reference states:
Reply | Report Abuse | Link to this"Slow light is the propagation of an optical pulse or other modulation of an optical carrier at a very low group velocity. Slow light occurs when a propagating pulse is substantially slowed down by the interaction with the medium in which the propagation takes place."
The key is that, when not propagating in a vacuum, light is propagating in a medium. To some extent photons are being absorbed by atoms and eventually reemitted. Between particles, light continues to propagate at c.
When light is transmitted through through a supercooled medium, the interactions that are involved in electrons' absorption of photons and eventual reemission are slowed, thus reducing the effective speed of light transmitted through that medium.
Please see:
http://en.wikipedia.org/wiki/Speed_of_light#In_a_medium
"The refractive index of air is approximately 1.0003. Denser media, such as water, glass, and diamond, have refractive indexes of around 1.3, 1.5 and 2.4, respectively, for visible light. In exotic materials like Bose–Einstein condensates near absolute zero, the effective speed of light may be only a few meters per second. However, this represents absorption and re-radiation delay between atoms, as do all slower-than-c speeds in material substances. As an extreme example of this, light "slowing" in matter, two independent teams of physicists claimed to bring light to a "complete standstill" by passing it through a Bose–Einstein Condensate of the element rubidium..."
"Instead, such research could help scientists learn more about the mysteries of quantum entanglement, which lies at the heart of quantum computers—advanced machines that could in principle run more calculations in an instant than there are atoms in the universe."
Reply | Report Abuse | Link to thisI want to buy some futures in those "'continuous variable' quantum information processing" products. Are we there yet? Wake me up when we get there...
"there are predictions that during cosmic inflation in the early universe, the boundaries of the universe were expanding nearly at light-speed or faster than the speed of light"
Reply | Report Abuse | Link to thisThis is not merely a prediction. It's actually observable even today. The universe is expanding faster than light speed. That's why the recessional velocity of most distant galaxies are greater than c and they are 46 billion light-yrs away when the universe is only 13.7 billion yrs old.
In classical thermodynamics, the Casimir device is a perpetual mobile machine as it creates energy out of nothing. But it does not violate the 1st law of thermodynamics if you include vacuum energy in the thermodynamic system.
Yes It depends upon the local density of the overall EMF that is Space Time.
Reply | Report Abuse | Link to thisIf I was a betting man I would bet that the best possible spot to look for information with regard to gaining insight into the true nature of a Photon of Light and how it actually travels and why its speed is what it is in different mediums, would be at the Quantum level of the interface between Mediums. What happens to a Photon at the instant it senses that its Medium has changed? Is the change abrupt or is it a graduated change and if it is a graduate what is happening to the Photon during the course of the graduated change at the Quantum level of the Medium interface? How does the Photon know that the Medium has changed or is gradually changing? Is there a pressure gradient between Mediums at the Quantum Level which is contributing to the speed differentials and if so is there a way to measure such a gradient directly or could it be indirectly expressed, as most things are which are inferred to exist at that level? Would there be any benefit to identifying such a pressure gradient, if it did exist, and would it lead to a better understanding of the Quantum world that permeates our Universe? After all everything that we can Sense and Measure is just our interpretation of the Macro-expression of what is actually happening at the Quantum Level.
Reply | Report Abuse | Link to thisAs far as I know, the distribution of virtual photon manifestations (and other virtual particles, including massive top quarks) in a vacuum is generally thought to be isotropic. Please see
Reply | Report Abuse | Link to thishttp://en.wikipedia.org/wiki/Virtual_particle#Manifestations
The galaxy rotation problem (used to infer the existence of galactic dark matter) requires specific configurations of dark matter densities to fit the observed flat rotation curves of spiral galaxies into the improperly applied Keplerian model - based on observations of sparse planets in the Solar system. An isotropic distribution of virtual particles could not achieve the gravitational effects thought to be required of galactic dark matter.
I don't think that galactic dark matter is necessary to explain galactic rotation - please see:
http://fqxi.org/data/essay-contest-files/Dwyer_FQXi_2012__Questionin_1.pdf
I do think that general relativity very accurately describes the effects of gravitation using geometrical distortions in the abstract dimensional coordinates of spacetime. However, I do not think that unphysical abstractions can actually cause the physical effects of gravitation; that the described geometric topology of spacetime must accurately represent some undescribed physical aspect of spacetime.
I suggest that the geometric topology of spacetime describes physical gradient fields of vacuum energy density; that vacuum energy also produces the manifestations of virtual particles and that gradient densities of vacuum energy should produce varying rates of virtual particle manifestations, to some extent proportional to gravitational effects.
The device I spoke about is named "Radiometer", as you know, it's useful just for fun. Salut +
Reply | Report Abuse | Link to thisI always thought that 3D computer images in mid-air shown in many sci-fi movies/shows someday maybe realized by using a device that can modify properties of vacuum so that virtual photons would be generated with different colors at different points.
Reply | Report Abuse | Link to thisJapanese scientists invented a different device which intersects infrared lasers so that in the intersection point air breakdowns and glows in white.
I know this article states that it takes energy to create these pairs but I still have to wonder if that is true. In normal nature (read vacuum) there is nothing to interfere with them recombining/canceling each other.
Reply | Report Abuse | Link to thisWould it be possible to create a series of "mirrors" where they cannot recombine and thus yield energy?
dang..forgot to click the follow;-)
Reply | Report Abuse | Link to thisLight travels at different speeds in different mediums because of its wave property and refraction. This is known since 1600s. Nothing mysterious.
Reply | Report Abuse | Link to thistaking cue from ancient sanskrit and properties of everything a radical paradigm is possible - guNA - which also is string! there are three types - rajas - the inciter, the static and dull and satvika - the harmonious blender or equalizer. Everything observed including our selves are knots having different admixture of properties.
Reply | Report Abuse | Link to thisTaking cue from ancient sanskrit and virews on properties of everything a radical paradigm is posible - guNA - This also means strings! three types of guNA are 1) tamas dull and lazy heavy 2) rajas - energetic inciting 3) sattvik a harmonious leveler. What we observe around are knots having different admixtures of (the guNA and we ourselves are knots) the photon guy is an admixture - a wave along the sting that has been stopped (sensed)and is a tiny knot - heat and light are as much functions of the sender it is a function of the receiver. The green leaf - chlorophyll is an excellent example of the use of the mostly rajas in sunlight photons to split up the knotted water molecule into hydrogen - the ultimate fuel into a knotted but sweet molecule sugar. guys getting the nobel for this better share sattvikally - regards
Reply | Report Abuse | Link to thisEvery mathematical description of “anything” is simply one conventionally accepted “Estimate” of actuality. Sounds pretty stupid until you think about it, but think about this; any real or imaginary number is simply the end product of a definition that we are willing to accept and employ to allow us to describe events within a mathematical framework. So yes, in the case of light as the wave-front transitions from one medium to another we are able to describe “mathematically” the changes it undergoes, be they changes in velocity or changes in direction or a combination of both, as witnessed when light strikes a prism. And yes as you so rightly point this has been know and mathematically describable for hundreds of years, but this is “not” what I am talking about. I put it to you that there is probably a vast divide of knowledge separating our ability to “mathematically” describe an event and our ability to “understand” and event or sequence of events. Now as a scientist you will probably say you are not interested in some “Metaphysical nonsensical” interpretation of what happens when light moves from one medium to another since it is non-testable and hence cannot serve any useful scientific purpose. I choose not to close my mind to any avenue of thought when it comes to trying to understand my surroundings. Therefore I try to visualize a Quantum world where “Absolutes” are forbidden and Time is perhaps irrelevant. So it is down in this murky world where Mathematical Statistics is the only descriptive tool available to the Scientist “Certainty” is never certain and therefore absolute certainty is just a lie we allow ourselves to believe to facilitate mathematically acceptable progress. Saying I know what will “likely” happen is a far cry from actually understanding “what” is happening and why it “has to happen” at that given instant. A pleasure to talk to you, as always.
Reply | Report Abuse | Link to thisOkay here's how it works (warning this is a simplification.) When you have light, say an individual photon traveling from say a vacuum on one side of a glass of water, to the vacuum on the other side. You have the photon traveling through the vacuum at c, which approximately 300,000,000 meters per second. Then it reaches the glass of water. First as it travels through the container it may "collide" with an atom in the container. It is "absorbed" by the atom, which which gains the energy of the photon, eventually it "settles down" at near it's original energy level. The difference in energy, between the "excited" state" and the "unexcited" state is emitted as another photon, one with slightly less energy than the original. Now when the photon is traveling in the vacuum between each atom, it travels with a velocity of "c" however, when it collides with an atom, there is a short, delay between the absorption of the original photon, and the emission of the new, and slightly less energetic photon. The delay will vary based on different factors. Thus while light always travels at the same speed in a vacuum, including the vacuum between individual atoms and molecules, over an entire substance, the glass of water, it slows down. Of course in the vast majority of instances it is still much to fast to notice the difference, but the difference does exist.
Reply | Report Abuse | Link to this"I put it to you that there is probably a vast divide of knowledge separating our ability to “mathematically” describe an event and our ability to “understand” and event or sequence of events."
Reply | Report Abuse | Link to thisIMO this is an oxymoron. Mathematics is a description of the world when used in mathematical physics. "Understanding" is not separate from "mathematics." Only philosophers are interested in non-mathematical description of the world. Physicists use mathematics to understand the world. Equations tell a story far more complex and accurate than logic and reason used by philosophers.
The light photons are not absorbed and emitted by the medium. When light passes through a medium, the electrons in the medium emits electromagnetic waves than interfere with the light waves. The result of that superposition of electromagnetic waves is a lower velocity light wave. Refraction is best understood using the wave property of light rather than its particle property.
Reply | Report Abuse | Link to thisI would caution you to not be so quick to dismiss the contribution that the Logic and Reason of the Philosopher may make to our understanding our World; especially since the discipline of Mathematics itself owes its own very existence to both of these. This would seem to me to be somewhat like a Machinist saying his tools are better suited to repair a machine than are those Mathematical principles used by the Mechanical Engineer who designed them.
Reply | Report Abuse | Link to thisHypothesis based on '66 B.S. Physics. Refraction, caused by the interaction of the "wave" nature of light with a medium other than vacuum slows light because vibration at right-angles, and otherwise independant of medium. Sound, with compression waves in direction of motion speeds up up in a denser medium, but may also be attenuated. Final statement, speed is based on d/t, where d i d1-d2, regardles of intermeditate curves. think of it as your avg. speed LA to SF on interstate, vs. pure two lane former roads that take you past every B&B ad vineyard. So yes, maybe C is constant between collisions but these are so frequent, what is the pracitcal value?
Reply | Report Abuse | Link to this"However, this represents absorption and re-radiation delay between atoms, as do all slower-than-c speeds in material substances."
Reply | Report Abuse | Link to thisDon't believe everything you read in Wikipedia. Particularly not when it's based on a simplified model of matter which has been known to be insufficient since the development of quantum physics.
Say instead that the slowdown is caused by the interaction between the (non-localized) quantum field of the photon(s) with the (non-localized) quantum fields of all the particles making up the substance the photon(s) are passing through. In a dense medium such as glass, there is not much vacuum between the atoms for the light to move at light speed in - the wavelength of the light is much larger than the distance between atoms. The simplified model described in Wikipedia can perhaps be used for some simplified calculations, but it's important to be aware of the shortcomings of the model - for one thing the Wikipedia model would render refractive lenses impossible, light would be scattered evenly in all directions as soon as any refraction took effect.
"This would seem to me to be somewhat like a Machinist saying his tools are better suited to repair a machine than are those Mathematical principles used by the Mechanical Engineer who designed them."
Reply | Report Abuse | Link to thisYour attempt at irony is flawed because the statement is true. Tools are indeed better suited to repair a machine. Mathematical principles cannot repair a machine because they exist only in the mind of the Mechanical Engineer.
There I go again sacrificing clarity on the Alter of expediency. I guess I will never learn. If you were not as I suspect, just “jerking my chain” I would attempt to clarify my point.
Reply | Report Abuse | Link to thisThat's okay. "Sinning wheel" is even more interesting.
Reply | Report Abuse | Link to thisThere is something radically wrong (but can't say it is not convenient for human mind) to assume " speed of light is "c", at all times and places. " speed is distance/time. distance is reality BUT "time" is an agreed with neighbours and standardized arbitrary measure. "Time" is no more or less that "litre". meter" "gram" etc. "litre" is in the calculating mind - water is the observable reality. Time is a measure of what? The difference of a marked shadow of a stick here and the shadow there? If the world wants to make a big deal of nothing, viz. time the measure, why not the litre or gram? And if it is nothing but a figment of collective human imagination c = distance / 0(zero) which is infinity - and nether here nor there. regards
Reply | Report Abuse | Link to this"Spinning top", "Spinning Wheel", "Cocaine", many things can run around many others, just feeling pressed to finish something because you have more things to engage in, makes you loss care. Keep the quality up!
Reply | Report Abuse | Link to thisProduction of light from vacuum is not a new thing.
Reply | Report Abuse | Link to thisIn November, 2011, research was published in the journal "Nature" showing the development of "real photons" from vacuum.
Read the article here http://saypeople.com/2011/11/17/production-of-light-from-vacuum/