APOD: A Force from Empty Space: The Effect... (2015 Dec 06)

[APOD Robot]

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, 55 years ago, was trying to understand why fluids like mayonnaise move so slowly. Today, evidence indicates 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 energy 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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[daddyo]

Very interesting but possibly a bit too controversial to extrapolate to the expansion of the universe

[ygmarchi]

Very interesting and also an awesome wallpaper

[heehaw]

When Einstein worked toward General Relativity in 1914, he started by postulating that “spacetime curvature” = “stress-energy”. For spacetime curvature, he had, from the mathematicians Riemann and Ricci, the Ricci tensor Rij, while from ordinary physics he had the stress-tensor Tij : so, he guessed that Rij=Tij ; but that doesn’t work, because Tij is conserved (that is, "conservation of energy") - which means that its derivative is 0; but the derivative of Rij ain’t 0! Well, the derivative of (Rij - R) (where R is the Gaussian CURVATURE of spacetime) is 0! Now, notice that everything has derivative zero!! So the Field Equations of General Relativity were: Rij - R = Tij. But what if there’s an additional CONSTANT, call it Λ? Any constant has derivative 0! So what if it's really Rij - R + Λ = Tij ? That constant, if not 0, would gravitationally repel all matter! Those are today’s famous Field Equations of General Relativity, and it was discovered some years ago that Λ ≠ 0 because the Universe is, by observation, exploding, and has been for some billions of years. The Casimir effect is laboratory detection of dark energy.

[Ann]

This picture is very interesting, but a bit too math-heavy for me. So in the hopes of getting some explanations, I'll try to explain what I see and ask for some clarifications.

At left there is what looks to me like a sort of "table-top" which has been cut through so you see the material it is made of. On top of the "table top" is a perfectly flat "panel" of some sort, with a cut-off corner. (Now that I look a bit closer, I can see that there is some extra material below this panel.)

A few slats are attached to the panel. They stick out over the edge of the panel and the table top below it. A ball is resting on these slats.

Below the table top and the panel is a blurry, uneven surface of some sort. This blurry surface, which is out of focus, is clearly located below the table top and the panel, the slats and the ball, although it is hard to say how far below them it is.

Parts of the blurry surface is relatively - make that relatively - even. But there are some large "craters" in the blurry surface. One such crater is directly below the ball. Another, larger crater can be seen to the upper right of the ball, while a third crater is directly below the table top at top center in the picture. The crater below the ball appears to be the deepest one.

So can anyone explain any of these things to me:

1) What is the cut-through "table top"?

2) What is the "panel" resting on top of it?

3) What are the "slats" sticking out from the "panel"?

4) Why is the surface below the table top and the panel blurry?

5) How far below the table top and the panel is the blurry surface?

6) What are the "craters"?

7) Is there a reason why the crater below the ball appears to be extra deep?

Thanks for any help in clarifying this.

Ann

[Chris Peterson]

So can anyone explain any of these things to me...

What I think we're seeing here is an atomic force microscope probe with a sphere sitting on the end. The structure on the left consists of a plate with a floating cantilever above it, which extends off the edge of the plate via the web structure. We don't see the test plate at all (that's the thing that would be held close to the sphere to measure the Casimir effect). The blurry stuff in the background isn't part of the experiment- just material around the actual test structure. In operation, a flat surface would be brought near the sphere (probably at the top of this image), resulting in the sphere being attracted, lifting the cantilever, the deflection of which could be measured optically or by a change in capacitance between it and its support plate.

[RedFishBlueFish]

Alexander Pope wrote as an epitaph on Isaac Newton:

Nature and Nature's laws lay hid in night:
God said, "Let Newton be! and all was light."

This did seem true for about a century and a half - until Einstein came along.

Now all seems Dark Matter, Dark Energy with which one struggles to come to terms.

This APOD leaves one feeling the world is a bit grey - as an alexiteric, this fine and bright Winter's morn, an image of The City of Light...

[prsachar@Yahoo.com]

Dark energy is more than the expansion of space. It's the ever accelerating expansion of space. Big difference.

[bystander]

APOD: 2002 Sep 17
APOD: 2004 Aug 01
APOD: 2006 Dec 17

APOD: 2010 Jan 03
http://asterisk.apod.com/viewtopic.php?t=17919

[chiralpaul@yahoo.com]

This is clearly an ordinary scanning electron microscope (SEM) image. Note experimental constants used, such as accelerating voltage, type of detector used (secondary electron), and working distance. As to what the various objects are, I haven't a clue. The stuff with the holes appears to be filter paper.

Paul Robinson
Senior Scientist Emeritus (ran a SEM lab for many years)

[Ron-Astro Pharmacist]

Figuratively speaking how fantastically wonderful is it that the “aether” in the physics world and the “ether” in the world of medicine are both so full of mysterious and baffling enigmas. They each have intrigued scientists since they were conceptualized with many theories put forward about how they work mechanistically in their distinct physical realms. Though very unlikely I would find it fitting if they turned out to be related in some twist of nature which would obviously have to be called “The Spatial Theory of Ethereal Relativity."

Of course that would mean there is “space” where my “mind” should be.

[Chris Peterson]

The stuff with the holes appears to be filter paper.

Yeah, I knew I'd seen that before. Makes sense, since the test spheres are probably prepared in a liquid or vapor phase, and harvested from something like filter paper- a process that is probably performed inside the SEM chamber.

[Ron-Astro Pharmacist]

This picture is very interesting, but a bit too math-heavy for me. So in the hopes of getting some explanations, I'll try to explain what I see and ask for some clarifications.

At left there is what looks to me like a sort of "table-top" which has been cut through so you see the material it is made of. On top of the "table top" is a perfectly flat "panel" of some sort, with a cut-off corner. (Now that I look a bit closer, I can see that there is some extra material below this panel.)

A few slats are attached to the panel. They stick out over the edge of the panel and the table top below it. A ball is resting on these slats.

Below the table top and the panel is a blurry, uneven surface of some sort. This blurry surface, which is out of focus, is clearly located below the table top and the panel, the slats and the ball, although it is hard to say how far below them it is.

Parts of the blurry surface is relatively - make that relatively - even. But there are some large "craters" in the blurry surface. One such crater is directly below the ball. Another, larger crater can be seen to the upper right of the ball, while a third crater is directly below the table top at top center in the picture. The crater below the ball appears to be the deepest one.

So can anyone explain any of these things to me:

1) What is the cut-through "table top"?

2) What is the "panel" resting on top of it?

3) What are the "slats" sticking out from the "panel"?

4) Why is the surface below the table top and the panel blurry?

5) How far below the table top and the panel is the blurry surface?

6) What are the "craters"?

7) Is there a reason why the crater below the ball appears to be extra deep?

Thanks for any help in clarifying this.

Ann

Buried somewhere in his research or his references I’ll bet your questions are answered though I would rather speculate on the universe than delve into journals this fine Sunday. Happy hunting!

[neufer]

<<A 2005 paper by Robert Jaffe of MIT states that "Casimir effects can be formulated and Casimir forces can be computed without reference to zero-point energies. They are relativistic, quantum forces between charges and currents." and that "The Casimir force is simply the (relativistic, retarded) van der Waals force between the metal plates.">>

• The Casimir effect is what holds a retarded relativistic Gecko on glass Waals:

[b][color=#0000FF]Retarded relativistic Gecko on a glass Waal[/color][/b]

---

<<In physical chemistry, the van der Waals forces (or van der Waals' interaction), named after Dutch scientist Johannes Diderik van der Waals, are the residual attractive or repulsive forces between molecules or atomic groups that do not arise from a covalent bond, or electrostatic interaction. The ability of geckos – which can hang on a glass surface using only one toe – to climb on sheer surfaces has been attributed to the van der Waals forces between these surfaces and the spatulae, or microscopic projections, which cover the hair-like setae found on their footpads. A later study suggested that capillary adhesion might play a role, but that hypothesis has been rejected by more recent studies.>>

[Ann]

So can anyone explain any of these things to me:

1) What is the cut-through "table top"?

2) What is the "panel" resting on top of it?

3) What are the "slats" sticking out from the "panel"?

4) Why is the surface below the table top and the panel blurry?

5) How far below the table top and the panel is the blurry surface?

6) What are the "craters"?

7) Is there a reason why the crater below the ball appears to be extra deep?

Thanks for any help in clarifying this.

Ann

Buried somewhere in his research or his references I’ll bet your questions are answered though I would rather speculate on the universe than delve into journals this fine Sunday. Happy hunting!

Eh... I think I'd rather live in ignorance.

Ann

[geckzilla]

The Casimir effect is what holds a retarded relativistic Gecko on glass Waals:

Is this to get back at me for saying your opinion doesn't matter the other day? Leave my kin out of this!

[tomatoherd]

Neufer: I don't think van der Waals and Casimir effects are the same. One is atomic/molecular, the other due to virtual photons. Maybe you were not claiming they were.
I think we have many of us experienced Casimir effects macroscopically/grossly: we have had 2 slick/smooth metal plates adhere to each other, and could only be separated by sliding them tangentially in opposite directions. Am I wrong?
And I thought van der Waals were demonstrated every time a painted door and door jamb came in contact and developed a very subtle stickiness. Or when a sheet of thin paper would momentarily stick to a vertical wall after being pressed there.

Anyway, HOW does a force causing nanoscopic attraction contribute to cosmological expansion???

[Chris Peterson]

Anyway, HOW does a force causing nanoscopic attraction contribute to cosmological expansion???

It doesn't. The Casmir effect can be understood in terms of virtual particles and quantum fluctuations of the vacuum, which is how dark energy is also treated. But they are different things. The Casmir effect simply validates this type of model, and demonstrates that vacuum fluctuations are real.

[neufer]

Click to play embedded YouTube video.

Neufer: I don't think van der Waals and Casimir effects are the same. One is atomic/molecular, the other due to virtual photons. Maybe you were not claiming they were.
I think we have many of us experienced Casimir effects macroscopically/grossly: we have had 2 slick/smooth metal plates adhere to each other, and could only be separated by sliding them tangentially in opposite directions. Am I wrong?
And I thought van der Waals were demonstrated every time a painted door and door jamb came in contact and developed a very subtle stickiness. Or when a sheet of thin paper would momentarily stick to a vertical wall after being pressed there.

One must always be careful in talking about the attraction of 2 smooth materials surrounded by outside air pressure.
-----------------------------------------------------------------------------------------------------------
Van der Waals attraction mostly has to do with dielectrics such as glass & the tiny hairs on the feet of geckos.

With a little (electric) prodding a neutral dielectric can be turned into an electric dipole of higher energy. However, two adjacent dielectrics can automatically be turned into oppositely directed electric dipoles of lower total energy as the electric field of each dielectric induces an electric dipole in the other dielectric.

The closer a dielectric is to another dielectric the lower the total energy state thus resulting in an attractive force.

Also: a dielectric adjacent to a conducting metal will interact with its mirror image to create a lower total energy state as the electric field of the dielectric induces an electric dipole in its opposite mirror image.

However, the Casimir attraction between two metals requires, I believe, the vacuum itself (with its temporary electron/positron pairs) to act as the Van der Waals dielectric. Or, perhaps, it is the retarded relativistic electromagnetic responses that cause the metals themselves to have effective dielectric characteristics.

[heehaw]

Anyway, HOW does a force causing nanoscopic attraction contribute to cosmological expansion???

It doesn't. The Casmir effect can be understood in terms of virtual particles and quantum fluctuations of the vacuum, which is how dark energy is also treated. But they are different things. The Casmir effect simply validates this type of model, and demonstrates that vacuum fluctuations are real.

I agree completely.

[Alohascope]

http://www.universetoday.com/107316/wha ... e-big-rip/

http://www.adrianberry.net/art54.htm

It appears the universe may expand itself to death, like stretching a rubber band until it snaps.

[neufer]

http://www.universetoday.com/107316/wha ... e-big-rip/
http://www.adrianberry.net/art54.htm

It appears the universe may expand itself to death, like stretching a rubber band until it snaps.

The accurately measured constancy of the sidereal year = 31,558,149.504 seconds
& the balanced tidal transference of energy & angular momentum from the Earth to the Moon
is perfectly consistent with:

• 1) a constant gravitational constant with
  2) no noticeable mechanical work being performed by dark energy.

Such measurements put limits on the ability of dark energy to tear apart bound systems
such as the Sun & Earth or the Earth & Moon anytime soon.

<<The motion of the Moon can be followed with an accuracy of a few centimeters by lunar laser ranging (LLR). Laser pulses are bounced off mirrors on the surface of the moon, emplaced during the Apollo missions of 1969 to 1972 and by Lunokhod 2 in 1973. Measuring the return time of the pulse yields a very accurate measure of the distance. These measurements are fitted to the equations of motion. This yields numerical values for the Moon's secular deceleration, i.e. negative acceleration, in longitude and the rate of change of the semimajor axis of the Earth–Moon ellipse. From the period 1970–2012, the results are:

−25.82±0.03 arcsecond/century2 in ecliptic longitude
+38.08±0.04 mm/yr in the mean Earth–Moon distance

This is consistent with results from satellite laser ranging (SLR), a similar technique applied to artificial satellites orbiting Earth, which yields a model for the gravitational field of Earth, including that of the tides. The model accurately predicts the changes in the motion of the Moon.

Finally, ancient observations of solar eclipses give fairly accurate positions for the Moon at those moments. Studies of these observations give results consistent with the value quoted above.

The other consequence of tidal acceleration is the deceleration of the rotation of Earth.

From the observed change in the Moon's orbit, the corresponding change in the length of the day can be computed:

+2.3 ms/century

However, from historical records over the past 2700 years the following average value is found:

+1.70 ± 0.05 ms/century

Opposing the tidal deceleration of Earth is a mechanism that is in fact accelerating the rotation. Earth is not a sphere, but rather an ellipsoid that is flattened at the poles. SLR has shown that this flattening is decreasing. The explanation is that during the ice age large masses of ice collected at the poles, and depressed the underlying rocks. The ice mass started disappearing over 10000 years ago, but Earth's crust is still not in hydrostatic equilibrium and is still rebounding (the relaxation time is estimated to be about 4000 years). As a consequence, the polar diameter of Earth increases, and because the mass and density remain the same, the volume remains the same; therefore the equatorial diameter is decreasing. As a consequence, mass moves closer to the rotation axis of Earth. This means that its moment of inertia is decreasing. Because its total angular momentum remains the same during this process, the rotation rate increases. This is the well-known phenomenon of a spinning figure skater who spins ever faster as she retracts her arms. From the observed change in the moment of inertia the acceleration of rotation can be computed: the average value over the historical period must have been about −0.6 ms/century. This largely explains the historical observations.>>

[Ron-Astro Pharmacist]

If you have:

http://www.scientificamerican.com/artic ... -of-light/

Can the opposite be true? That there be "Nothing from Something"?

I know speculation really has no place in this forum but it's fun to make an "educatedly "guess about phenomena that are utterly without any known reason for being present. I'll try to slip one in here just because we all are just trying to understand what could drive universe's smallest and largest objects into and, possibly, out of existence. Black holes are one off those objects and virtual particles are another. We know they both exist but we do not exactly know why. Since we can measure that the universe is expanding and a Casmir effect that can produce quantum fluctuations which results in virtual particles, has a theory ever put forward black holes are just the result of that expansion?
Hypothesis:
- On the small scale when things are so close together so that there will be more on the outside than on the inside that it generates a force creating matter - a Casmir effect

- On the large scale when things are so far removed that there will be less on the inside than on the outside that all force is removed destroying matter – an "anti-Casmir" effect.

Just a "sort of" thought experiment…

[neufer]

Hypothesis:

- On the small scale when things are so close together so that there will be more on the outside than on the inside that it generates a force creating matter - a Casmir effect

- On the large scale when things are so far removed that there will be less on the inside than on the outside [sic] that all force is removed destroying matter – an "anti-Casmir" effect.

• 1) No one is talking about creating or destroying matter.
  
  2) Do you mean "less on the outside than on the inside"
  
  (Yet if the universe is infinite how can there be "less on the outside than on the inside" )
  
  3) Is "anti-Casimir" anything like an "anti-macassar"

---

<<An antimacassar is a small cloth placed over the backs or arms of chairs, or the head or cushions of a sofa, to prevent soiling of the permanent fabric. The name also refers to the cloth flap 'collar' on a sailor's shirt/top, used to keep macassar oil off the uniform.

Macassar oil was an unguent for the hair commonly used in the early 19th century. The poet Byron called it "thine incomparable oil, Macassar." The fashion for oiled hair became so widespread in the Victorian and the Edwardian period that housewives began to cover the arms and backs of their chairs with washable cloths to preserve the fabric coverings from being soiled. Around 1850, these started to be known as antimacassars. They were also installed in theatres, from 1865.

They came to have elaborate patterns, often in matching sets for the various items of parlour furniture; they were either made at home using a variety of techniques such as crochet or tatting, or purchased. The original antimacassars were usually made of stiff white crochet-work, but in the third quarter of the 19th century they became simpler and softer, usually fabric embroidered with a simple pattern in wool or silk. Annie Chapman, the second canonical victim of Jack the Ripper, was said to have made antimacassars for a living shortly before she was murdered.>>

[Alohascope]

http://www.universetoday.com/107316/wha ... e-big-rip/
http://www.adrianberry.net/art54.htm

It appears the universe may expand itself to death, like stretching a rubber band until it snaps.

The accurately measured constancy of the sidereal year = 31,558,149.504 seconds
& the balanced tidal transference of energy & angular momentum from the Earth to the Moon
is perfectly consistent with:

• 1) a constant gravitational constant with
  2) no noticeable mechanical work being performed by dark energy.

Such measurements put limits on the ability of dark energy to tear apart bound systems
such as the Sun & Earth or the Earth & Moon anytime soon.

<<The motion of the Moon can be followed with an accuracy of a few centimeters by lunar laser ranging (LLR). Laser pulses are bounced off mirrors on the surface of the moon, emplaced during the Apollo missions of 1969 to 1972 and by Lunokhod 2 in 1973. Measuring the return time of the pulse yields a very accurate measure of the distance. These measurements are fitted to the equations of motion. This yields numerical values for the Moon's secular deceleration, i.e. negative acceleration, in longitude and the rate of change of the semimajor axis of the Earth–Moon ellipse. From the period 1970–2012, the results are:

−25.82±0.03 arcsecond/century2 in ecliptic longitude
+38.08±0.04 mm/yr in the mean Earth–Moon distance

This is consistent with results from satellite laser ranging (SLR), a similar technique applied to artificial satellites orbiting Earth, which yields a model for the gravitational field of Earth, including that of the tides. The model accurately predicts the changes in the motion of the Moon.

Finally, ancient observations of solar eclipses give fairly accurate positions for the Moon at those moments. Studies of these observations give results consistent with the value quoted above.

The other consequence of tidal acceleration is the deceleration of the rotation of Earth.

From the observed change in the Moon's orbit, the corresponding change in the length of the day can be computed:

+2.3 ms/century

However, from historical records over the past 2700 years the following average value is found:

+1.70 ± 0.05 ms/century

Opposing the tidal deceleration of Earth is a mechanism that is in fact accelerating the rotation. Earth is not a sphere, but rather an ellipsoid that is flattened at the poles. SLR has shown that this flattening is decreasing. The explanation is that during the ice age large masses of ice collected at the poles, and depressed the underlying rocks. The ice mass started disappearing over 10000 years ago, but Earth's crust is still not in hydrostatic equilibrium and is still rebounding (the relaxation time is estimated to be about 4000 years). As a consequence, the polar diameter of Earth increases, and because the mass and density remain the same, the volume remains the same; therefore the equatorial diameter is decreasing. As a consequence, mass moves closer to the rotation axis of Earth. This means that its moment of inertia is decreasing. Because its total angular momentum remains the same during this process, the rotation rate increases. This is the well-known phenomenon of a spinning figure skater who spins ever faster as she retracts her arms. From the observed change in the moment of inertia the acceleration of rotation can be computed: the average value over the historical period must have been about −0.6 ms/century. This largely explains the historical observations.>>

Well Art what do I know besides what 'they' (John Hopkins and NASA.)tell me? 'The Hubble Site.'
"With dark energy, the fate of the universe might go well beyond the Big Chill. In the strangest and most speculative scenario, as the universe expands ever faster, all of gravity's work will be undone. Clusters of galaxies will disband and separate. Then galaxies themselves will be torn apart. The solar system, stars, planets, and even molecules and atoms could be shredded by the ever-faster expansion. The universe that was born in a violent expansion could end with an even more violent expansion called the Big Rip."
This from a site called 'The Hubble Site'
http://hubblesite.org/hubble_discoverie ... iverse.php
"A free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA."
http://www.stsci.edu/institute/