APOD: Force from Empty Space: Casimir Effect (2010 Jan 03)
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APOD: Force from Empty Space: Casimir Effect (2010 Jan 03)
A Force from Empty Space: The Casimir Effect
Explanation: This tiny ball provides evidence that the universe will expand forever. Measuring slightly over one tenth of a millimeter, the ball moves toward a smooth plate in response to energy fluctuations in the vacuum of empty space. The attraction is known as the Casimir Effect, named for its discoverer, who, 50 years ago, was trying to understand why fluids like mayonnaise move so slowly. Today, evidence is accumulating that most of the energy density in the universe is in an unknown form dubbed dark energy. The form and genesis of dark energy is almost completely unknown, but postulated as related to vacuum fluctuations similar to the Casimir Effect but generated somehow by space itself. This vast and mysterious dark energy appears to gravitationally repel all matter and hence will likely cause the universe to expand forever. Understanding vacuum fluctuations is on the forefront of research not only to better understand our universe but also for stopping micro-mechanical machine parts from sticking together.
Explanation: This tiny ball provides evidence that the universe will expand forever. Measuring slightly over one tenth of a millimeter, the ball moves toward a smooth plate in response to energy fluctuations in the vacuum of empty space. The attraction is known as the Casimir Effect, named for its discoverer, who, 50 years ago, was trying to understand why fluids like mayonnaise move so slowly. Today, evidence is accumulating that most of the energy density in the universe is in an unknown form dubbed dark energy. The form and genesis of dark energy is almost completely unknown, but postulated as related to vacuum fluctuations similar to the Casimir Effect but generated somehow by space itself. This vast and mysterious dark energy appears to gravitationally repel all matter and hence will likely cause the universe to expand forever. Understanding vacuum fluctuations is on the forefront of research not only to better understand our universe but also for stopping micro-mechanical machine parts from sticking together.
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Alright, give me a Hamm on 5, hold the Mayo.
APOD Robot wrote: A Force from Empty Space: The Casimir Effect
Explanation: This tiny ball provides evidence that the universe will expand forever. Measuring slightly over one tenth of a millimeter, the ball moves toward a smooth plate in response to energy fluctuations in the vacuum of empty space. The attraction is known as the Casimir Effect, named for its discoverer, who, 50 years ago, was trying to understand why fluids like mayonnaise move so slowly.
- Airplane! (1980)
Operator: [Captain Oveur is on the phone with the Mayo Clinic]
Excuse me, Captain Oveur, but I have an emergency call on line 5 from a Mr. Hamm.
Captain Oveur: Alright, give me a Hamm on 5, hold the Mayo.
http://www.colbertnation.com/the-colber ... s-ad-space
Art Neuendorffer
Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
In my opinion Astronomy and religion have been too closely associated and, for too long. They started out by naming planets afters gods (or maybe it was naming gods after planets) and now the 'science? of Astronomy' is creating two whole new gods (Dark Matter and Dark Energy) to explain what they don't understand (much as long ago, Thor was created to explain lightning). Astronomers look at a far-off galaxy and surmise that it would require more gravity than they can 'discern' to hold the galaxy together at that rotation speed so they 'create' Dark Matter to explain it. Then they 'calculate' that the visible universe is expanding faster than they think it should be (according to their understanding of gravitational laws so they 'create' Dark Energy to explain it.
Have they never heard of Occam's Razor? "Occam's razor states that the explanation of any phenomenon should make as few assumptions as possible, eliminating those that make no difference in the observable predictions of the explanatory hypothesis or theory."
Rather than add two new unexplainable gods, isn't it much more likely that we simply do not understand the laws of gravity as they apply under different conditions and in different and distant parts of our universe?
Have they never heard of Occam's Razor? "Occam's razor states that the explanation of any phenomenon should make as few assumptions as possible, eliminating those that make no difference in the observable predictions of the explanatory hypothesis or theory."
Rather than add two new unexplainable gods, isn't it much more likely that we simply do not understand the laws of gravity as they apply under different conditions and in different and distant parts of our universe?
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Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
onucb,
Occam has been blunted - physics IS complicated, and has been complicated and de-complicated several times.
An example from history - William Thompson, Lord Kelvin, Professor of Natural Philosophy at Glasgow, was instrumental in destroying the complication that was the caloric theory of heat, yet proposed and promoted the complicated theory of an 'aether' that transmitted light.
Today, the so-called Standard Model for sub-atomic particles has been a successful method of explaining their interactions. It reduced a vastly complicated structure to, mostly, simple rational thinking. Classic use of Occam, you might say. But not quite. More complication is required to, for instance, reconcile that theory with gravity, hence strings, supersymmetry, hidden dimensions, etc. etc. We are still waiting for the Kelvin of our time, who will de-complicate it, no doubt introducing further complexities.
The only truly simple structure for the Univers is "turtles, all the way down"!
John
Occam has been blunted - physics IS complicated, and has been complicated and de-complicated several times.
An example from history - William Thompson, Lord Kelvin, Professor of Natural Philosophy at Glasgow, was instrumental in destroying the complication that was the caloric theory of heat, yet proposed and promoted the complicated theory of an 'aether' that transmitted light.
Today, the so-called Standard Model for sub-atomic particles has been a successful method of explaining their interactions. It reduced a vastly complicated structure to, mostly, simple rational thinking. Classic use of Occam, you might say. But not quite. More complication is required to, for instance, reconcile that theory with gravity, hence strings, supersymmetry, hidden dimensions, etc. etc. We are still waiting for the Kelvin of our time, who will de-complicate it, no doubt introducing further complexities.
The only truly simple structure for the Univers is "turtles, all the way down"!
John
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What JohnD tortoise
JohnD wrote:The only truly simple structure for the Universe is "turtles, all the way down"!
http://en.wikipedia.org/wiki/Turtles_all_the_way_down
<<In Stephen Hawking's 1988 book A Brief History of Time, which starts:
A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: "What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise." The scientist gave a superior smile before replying, "What is the tortoise standing on?" "You're very clever, young man, very clever", said the old lady. "But it's turtles all the way down!"
The suggested connection to Russell may be due to his 1927 lecture Why I Am Not a Christian. In it, while discounting the First Cause argument intended to be a proof of God's existence, Russell comments (with an argument not relevant to modern Hindu beliefs):
If everything must have a cause, then God must have a cause. If there can be anything without a cause, it may just as well be the world as God, so that there cannot be any validity in that argument. It is exactly of the same nature as the Hindu's view, that the world rested upon an elephant and the elephant rested upon a tortoise; and when they said, "How about the tortoise?" the Indian said, "Suppose we change the subject."
The origins of the turtle story are uncertain. In J. R. (Haj) Ross's 1967 linguistics dissertation, Constraints on Variables in Syntax, the scientist is identified as the Harvard psychologist and philosopher William James. Of the story's provenance, Ross writes:
I have been unable to find any published reference to it, so it may be that I have attributed it to the wrong man, or that it is apocryphal. Be that as it may, because of its bull's-eye relevance to the study of syntax, I have retold it here.
Additionally, Stephen Fry, in an episode of the BBC's comedy-quiz show QI (Series 1, episode 2), attributes the turtles anecdote to an exchange between an elderly lady and William James. Also, David Sloan Wilson does the same in his book Evolution for Everyone (Delacorte, 2007): 133.
Philosophical allusion to the story goes back at least as far as John Locke. In his 1690 tract An Essay Concerning Human Understanding, Locke compares one who would say that properties inhere in "substance" to the Indian who said the world was on an elephant which was on a tortoise "but being again pressed to know what gave support to the broad-backed tortoise, replied — something, he knew not what."
Henry David Thoreau, in his journal entry of 4 May 1852, writes:
Men are making speeches… all over the country, but each expresses only the thought, or the want of thought, of the multitude. No man stands on truth. They are merely banded together as usual, one leaning on another and all together on nothing; as the Hindoos made the world rest on an elephant, and the elephant on a tortoise, and had nothing to put under the tortoise.
This quote also appears in Robert Anton Wilson's Prometheus Rising; he attributes the story to William James:
William James, father of American psychology, tells of meeting an old lady who told him the Earth rested on the back of a huge turtle. "But, my dear lady", Professor James asked, as politely as possible, "what holds up the turtle?" "Ah", she said, "that's easy. He is standing on the back of another turtle." "Oh, I see", said Professor James, still being polite. "But would you be so good as to tell me what holds up the second turtle?" "It's no use, Professor", said the old lady, realizing he was trying to lead her into a logical trap. "It's turtles-turtles-turtles, all the way!"
The story can also be found in Bernard Nietschmann's "When the Turtle Collapses, the World Ends", Natural History, 83(6):34 (June-July 1974). A version of the story also appears in Clifford Geertz's, "Thick Description: Towards an Interpretive Theory of Culture", in his 1973 book The Interpretation of Culture, with the scientist and old woman replaced by an Englishman and an Indian respectively.
Carl Sagan recited a version of the story as an apocryphal anecdote in his 1979 book Broca's Brain: Reflections on the Romance of Science, as an exchange between a "Western traveler" and an "Oriental philosopher".
Justice Antonin Scalia of the U.S. Supreme Court discussed his "favored version" of the tale in a footnote to his plurality opinion in Rapanos v. United States (decided June 19, 2006):
In our favored version, an Eastern guru affirms that the earth is supported on the back of a tiger. When asked what supports the tiger, he says it stands upon an elephant; and when asked what supports the elephant he says it is a giant turtle. When asked, finally, what supports the giant turtle, he is briefly taken aback, but quickly replies "Ah, after that it is turtles all the way down."
The anecdote has achieved the status of an urban legend on the Internet, as there are numerous versions in which the name of the scientist varies (e.g., Arthur Stanley Eddington, Thomas Huxley, Linus Pauling, or Carl Sagan) although the rest is the same.>>
Art Neuendorffer
Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
ROTFLMAO !
"provides evidence that the universe will expand forever"
"in response to energy fluctuations in the vacuum of empty space"
"evidence is accumulating that most of the energy density in the universe is in an unknown form dubbed dark energy"
"but generated somehow by space itself"
"This vast and mysterious dark energy appears to gravitationally repel all matter and hence will likely cause the universe to expand forever"
Here's a good sentence tho.
"Understanding vacuum fluctuations is on the forefront of research not only to better understand our universe but also for stopping micro-mechanical machine parts from sticking together."
Yes, the Casimir Effect is a real clue about the true nature of the universe and reality, but unfortunately the 'religulousness of science' is preventing any real investigation into what's really happening due to peer pressure cronyism and a lack of a 'real scientific investigation protocol'.
- - -
In response to the "turtles all the way down", of course it can't be turtles all the way down !
I heard it thusly: "The world is supported on the back of an elephant, who's standing on the back of a turtle, who is swimming in the Sea of Forever."
"provides evidence that the universe will expand forever"
"in response to energy fluctuations in the vacuum of empty space"
"evidence is accumulating that most of the energy density in the universe is in an unknown form dubbed dark energy"
"but generated somehow by space itself"
"This vast and mysterious dark energy appears to gravitationally repel all matter and hence will likely cause the universe to expand forever"
Here's a good sentence tho.
"Understanding vacuum fluctuations is on the forefront of research not only to better understand our universe but also for stopping micro-mechanical machine parts from sticking together."
Yes, the Casimir Effect is a real clue about the true nature of the universe and reality, but unfortunately the 'religulousness of science' is preventing any real investigation into what's really happening due to peer pressure cronyism and a lack of a 'real scientific investigation protocol'.
- - -
In response to the "turtles all the way down", of course it can't be turtles all the way down !
I heard it thusly: "The world is supported on the back of an elephant, who's standing on the back of a turtle, who is swimming in the Sea of Forever."
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Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
Occam's Razor still applies nicely here. Both dark matter and dark energy are supported by multiple lines of theory and observational evidence. Each represents the simplest explanation for the observed behaviors. No simpler explanations are available.onucb wrote:Have they never heard of Occam's Razor? "Occam's razor states that the explanation of any phenomenon should make as few assumptions as possible, eliminating those that make no difference in the observable predictions of the explanatory hypothesis or theory."
Note that "simplest" doesn't always mean "simple". Note also that while Occam's Razor is a useful reasoning tool, it isn't at all uncommon for the simplest interpretation of an observation to be completely wrong.
Chris
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Re: The Casimir Effect (2010 Jan 03)
http://en.wikipedia.org/wiki/Casimir_pressure wrote:
<<According to experiments, the Casimir force F between two closely spaced neutral parallel plate conductors is directly proportional to their surface area A. Therefore, dividing the magnitude of Casimir force by the area of each conductor, Casimir pressure can be found. Because Casimir force between conductors is attractive then the Casimir pressure in space between the conductors is negative.
Because virtual particles are physical representations of the zero point energy of physical vacuum, then the Casimir pressure can be associated with the density of the zero point energy of empty space. Some scientists believe that zero point energy is the dominant energy of the Universe and that the Casimir pressure of this energy is the main cause of the observed accelerated expansion of Universe. By other words, one may say that virtual particles drive the accelerated expansion of Universe.>>
http://en.wikipedia.org/wiki/Casimir_effect wrote:
<<In quantum field theory, the Casimir effect and the Casimir-Polder force are physical forces arising from a quantized field. The typical example is of two uncharged metallic plates in a vacuum, placed a few micrometers apart, without any external electromagnetic field. When this field is studied using quantum electrodynamics, it is seen that the plates affect the virtual photons which constitute the field, and generate a net force—either an attraction or a repulsion depending on the specific arrangement of the two plates.
"Casimir's original goal was to compute the van der Waals force between polarizable molecules" of the metallic plates. Thus it can be interpreted without any reference to the zero-point energy (vacuum energy) or virtual particles of quantum fields. The classic form of the experiment, described above, successfully demonstrated the force to within 15% of the value predicted by the theory. Because the strength of the force falls off rapidly with distance, it is only measurable when the distance between the objects is extremely small. On a submicrometre scale, this force becomes so strong that it becomes the dominant force between uncharged conductors. In fact, at separations of 10 nm—about 100 times the typical size of an atom—the Casimir effect produces the equivalent of 1 atmosphere of pressure.>>
Art Neuendorffer
Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
Sound the non-conformance alarm! Arm the blasphemy torpedoes! Activate the la-la-la noise cover-over! We have posters who are skeptical of accepted and settled science!
Of course the universe started as an entity the size of an atom and exploded in a creational big bang and has been expanding ever since. And that happened precisely fourteen and one-half billion years ago, give or take a year. What was before that, you ask? Why nothing, of course.
And the universe will keep expanding forever, until it is so disperse that you will have to travel forever to find a single spec of matter. Either that or it will fall back together in a big crunch and repeat the whole cycle, depends on how much non-existent dark energy there is.
And if we build a bigger telescope than the Hubble and put it farther out in space, what will we see? Why farther of course! But that won’t change our beliefs any, we’ll just recalculate the universe to be a bit bigger and older than previous calculations. And when the next telescope sees even farther? Nothing to be concerned about, the universe is just a tad bigger than we had originally calculated.
That’s right, we, the twenty-first century man, now have gotten the science right! No more embarrassing befuddlements like the sun orbiting the earth or time being a constant. We now know precisely how the universe was created and how it will end, you see, the science is settled. And if you do not believe me, then you just aren’t smart enough to understand the science! Don’t question a scientist, for crying out loud, they are always completely impartial, unprejudiced, and, well, scientific.
Of course the universe started as an entity the size of an atom and exploded in a creational big bang and has been expanding ever since. And that happened precisely fourteen and one-half billion years ago, give or take a year. What was before that, you ask? Why nothing, of course.
And the universe will keep expanding forever, until it is so disperse that you will have to travel forever to find a single spec of matter. Either that or it will fall back together in a big crunch and repeat the whole cycle, depends on how much non-existent dark energy there is.
And if we build a bigger telescope than the Hubble and put it farther out in space, what will we see? Why farther of course! But that won’t change our beliefs any, we’ll just recalculate the universe to be a bit bigger and older than previous calculations. And when the next telescope sees even farther? Nothing to be concerned about, the universe is just a tad bigger than we had originally calculated.
That’s right, we, the twenty-first century man, now have gotten the science right! No more embarrassing befuddlements like the sun orbiting the earth or time being a constant. We now know precisely how the universe was created and how it will end, you see, the science is settled. And if you do not believe me, then you just aren’t smart enough to understand the science! Don’t question a scientist, for crying out loud, they are always completely impartial, unprejudiced, and, well, scientific.
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Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
Is it already that time again?
Just call me "geck" because "zilla" is like a last name.
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Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
I'm afraid so. You have to wonder why it is that people who so fundamentally misunderstand science are so interested in hanging around science forums.geckzilla wrote:Is it already that time again?
Chris
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Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
geckzilla wrote:Is it already that time again?
http://en.wikipedia.org/wiki/Jean-Luc_Picard wrote:
<<Captain Jean-Luc Picard is deeply moral, highly logical and cerebral. Picard is a master of diplomacy and debate who resolves seemingly intractable issues between multiple parties. Though such resolutions are usually peaceful, Picard is also shown utilizing his remarkable tactical cunning in situations when it is required. Patrick Stewart was knighted in the 2010 New Year Honours for services to drama.
Picardy is a historical province in the north of France.
The historical capital and largest city is Amiens.
Most of Picardy is a vast plain with open fields, famed for the gruesome Battle of the Somme.>>
http://en.wikipedia.org/wiki/Amiens_Cathedral wrote:
<<Amiens Cathedral, is a Roman Catholic cathedral and seat of the
Bishop of Amiens, Jean-Luc Marie Maurice Louis Bouilleret. The cathedral is
the tallest complete cathedral in France, with the greatest interior volume.>>
The floor in the Amiens Cathedral features Swastikas:
http://en.wikipedia.org/wiki/Swastika wrote:
<<[In his book Comet, Carl Sagan] reproduces an ancient Chinese manuscript (the Book of Silk) that shows comet tail varieties: most are variations on simple comet tails, but the last shows the comet nucleus with four bent arms extending from it, recalling a swastika. Sagan suggests that in antiquity a comet could have approached so close to Earth that the jets of gas streaming from it, bent by the comet's rotation, became visible, leading to the adoption of the swastika as a symbol across the world.>>
A seal from the Indus Valley Civilization recovered at Dholavira in India.
Art Neuendorffer
Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
I'm so happy for you that you are secure in your knowledge of the answers to life, the universe, and everything. I'm not sure I even know all of the questions.Redbone wrote:Sound the non-conformance alarm! Arm the blasphemy torpedoes! Activate the la-la-la noise cover-over! We have posters who are skeptical of accepted and settled science!
...
That’s right, we, the twenty-first century man, now have gotten the science right! No more embarrassing befuddlements like the sun orbiting the earth or time being a constant. We now know precisely how the universe was created and how it will end, you see, the science is settled. And if you do not believe me, then you just aren’t smart enough to understand the science! Don’t question a scientist, for crying out loud, they are always completely impartial, unprejudiced, and, well, scientific.
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor
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Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
are we to read between the lines and assume that this ball is a sphere?Measuring slightly over one tenth of a millimeter
and if so, does the measurement mean that the ball is just a little over a tenth of a millimeter in diamter? or radius?
ah, so we have to read the entire explanation before we REALLY get to the point of the picture.but also for stopping micro-mechanical machine parts from sticking together.
I wonder how many yawns would have been counted if this statement was at the beginning of the explanation???
IOW,
lets see how it sounds wrote this way....
Understanding vacuum fluctuations is on the forefront of research for stopping micro-mechanical machine parts from sticking together. Measuring slightly over one tenth of a millimeter, the ball moves toward a smooth plate in response to energy fluctuations in the vacuum of empty space. The attraction is known as the Casimir Effect, named after its discoverer. Today, with mounting evidence, the fluctuations in the vacuum of empty space may be related to different densities of dark energy (although still unknown how or why) and has been postulated to be similar to the Casimir Effect.
ahh, that's better.
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Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
Hmph.
For Christmas I bought my son a set of "Bucky Balls", which are 216 spherical rare earth magnets. I put one of these on a level table, on which normally things don't roll, and it oriented itself and began to roll. I can only assume because of a slight magnetic field (the Earths?). Or maybe the table just isn't really, really level.
I find it hard to envision that the motion of a microscopic ball of material can be attributed to something as tenuous as Dark Energy when there are so many more immediate and well-known forces of physics all around.
The best theory of the Universe I've run across so far is that it's a grand simulation on an unbelievably powerful computer, with a bunch of arbitrary rules, and the granularity of the simulator ever so slightly apparent to us as quantum effects. Probably some grad student's project at Supreme Being U. Who knows if while I was typing this the system was taken down for backup for a couple of hours, then restarted where it left off.
-Noel
For Christmas I bought my son a set of "Bucky Balls", which are 216 spherical rare earth magnets. I put one of these on a level table, on which normally things don't roll, and it oriented itself and began to roll. I can only assume because of a slight magnetic field (the Earths?). Or maybe the table just isn't really, really level.
I find it hard to envision that the motion of a microscopic ball of material can be attributed to something as tenuous as Dark Energy when there are so many more immediate and well-known forces of physics all around.
The best theory of the Universe I've run across so far is that it's a grand simulation on an unbelievably powerful computer, with a bunch of arbitrary rules, and the granularity of the simulator ever so slightly apparent to us as quantum effects. Probably some grad student's project at Supreme Being U. Who knows if while I was typing this the system was taken down for backup for a couple of hours, then restarted where it left off.
-Noel
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Re: What JohnD tortoise
neufer,
YOU DON'T EXPLAIN OTHER PEOPLE'S JOKES.
(The turtle one)
If jokes work, we laugh.
If they don't, we move on, but you do not have to explain them.
It's one of the social skills that we all have to learn.
So, please don't explain my jokes?
Thank you.
John
YOU DON'T EXPLAIN OTHER PEOPLE'S JOKES.
(The turtle one)
If jokes work, we laugh.
If they don't, we move on, but you do not have to explain them.
It's one of the social skills that we all have to learn.
So, please don't explain my jokes?
Thank you.
John
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Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
I don't believe the suggestion is that dark energy is responsible for the force on the ball. The Casimir effect falls into the category of a "well-known force"; it is described by theory which is well supported by multiple observations. The purpose in bringing up the Casimir effect is that it is caused by fluctuations in the vacuum, which is one of the proposed mechanisms behind dark energy. That doesn't mean they are the same thing, only that the one can help us understand the other.NoelC wrote:I find it hard to envision that the motion of a microscopic ball of material can be attributed to something as tenuous as Dark Energy when there are so many more immediate and well-known forces of physics all around.
Chris
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Re: What JohnD tortoise
Oh...that was a joke.JohnD wrote: YOU DON'T EXPLAIN OTHER PEOPLE'S JOKES.
(The turtle one)
If jokes work, we laugh.
I thought you were serious.
Art Neuendorffer
Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
A nice story, but this goes a bit too far imho. First, how could we be so sure all the laws of nature will be absolutely same forever?provides evidence that the universe will expand forever.
(You can call me a barbarian and pirat, because I say it in plaintext while many others are making just funny allusions here.)
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Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
How big is a turtle?
- 1 billionth of a proton + 0 + 0 = A number so big, nobody knows what it is.
- 1 billionth of a proton + 0 + 0 = A number so big, nobody knows what it is.
Always trying to find the answers
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Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
Nobody makes that assumption. One area of interesting and valid research is studying just how constant physical constants and laws really are. But that research has placed constraints on the degree to which there might be variability, and those constraints are such that most people are comfortable with the idea that physical laws probably don't change with time (outside the first moments of the Big Bang). So there's nothing at all extreme with the comment you reference. It doesn't say that the Universe will expand forever, it says that the existence of repulsive gravitational-like forces provides evidence for that, which is absolutely true.mesinik wrote:A nice story, but this goes a bit too far imho. First, how could we be so sure all the laws of nature will be absolutely same forever?provides evidence that the universe will expand forever.
Chris
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Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
I may be thought to be picky in mentioning it but once again an explanation has been reused in an APOD without updating information. As soon as I saw the image to this APOD I knew it had been used several times before as an APOD (the oldest such use seems to be September 17th 2002). In the explanation to the current APOD it still states "the Casimir Effect, named for its discoverer, who, 50 years ago, was trying to understand why fluids like mayonnaise move so slowly". According to information from a link in the explanation the Casimir Effect was discovered in 1948, so the "50 years ago" should at least now state 59 or 60 years ago.
Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
In regards to what it is that the Casimir Effect is actually measuring, it is:
The Entropic Floor of the local area, or of the universe if you prefer to call it that way.
It is measuring the 'pressure' exerted on the outside of the plates, and the lack of pressure inbetween the plates, as it isn't present there, because the entropic pressure is arriving from outside the plates, so to speak.
[quote from an above poster]
"Because the strength of the force falls off rapidly with distance, it is only measurable when the distance between the objects is extremely small. On a submicrometre scale, this force becomes so strong that it becomes the dominant force between uncharged conductors. In fact, at separations of 10 nm—about 100 times the typical size of an atom—the Casimir effect produces the equivalent of 1 atmosphere of pressure."
The Entropic Floor of the local area, or of the universe if you prefer to call it that way.
It is measuring the 'pressure' exerted on the outside of the plates, and the lack of pressure inbetween the plates, as it isn't present there, because the entropic pressure is arriving from outside the plates, so to speak.
[quote from an above poster]
"Because the strength of the force falls off rapidly with distance, it is only measurable when the distance between the objects is extremely small. On a submicrometre scale, this force becomes so strong that it becomes the dominant force between uncharged conductors. In fact, at separations of 10 nm—about 100 times the typical size of an atom—the Casimir effect produces the equivalent of 1 atmosphere of pressure."
Re: A Force from Empty Space: The Casimir Effect (2010 Jan 0
The search for the graviton continues.
The Casimir Effect has no mediating particle. It is a fluctuation of quantum density.
Gravity is not a force.
It is a fluctuation of quantum density.
There is no graviton, only a single quantum field made up of the potential states of particles that cannot be isolated.
Look for the Quantum chromodynamics binding energy in empty space
The Casimir Effect has no mediating particle. It is a fluctuation of quantum density.
Gravity is not a force.
It is a fluctuation of quantum density.
There is no graviton, only a single quantum field made up of the potential states of particles that cannot be isolated.
Look for the Quantum chromodynamics binding energy in empty space