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Physics, Astronomy & Cosmology / Re: Are all photons mediated in the same way through the quantum vacuum

« on: 18/07/2019 08:51:32 »

I sorry, but we don’t have the time to run a detailed course on QED/QFT but I’ll try to answer as much as time allows and then suggest that you spend time trying to understand the theory via a course in Quantum Systems.

Feynmans virtual photons are just mathematical simplifications of field interactions, for peasants, which I think I realized already.

you obviously have a very poor opinion of students of quantum theory 
Feynman originally developed the diagrams as a calculation aid for students on his course on quantum theory. Just as Einstein had a ‘thing’ about quantum theory, Feynman had a ‘thing’ about field theory and wanted to express the interactions as particles - there are indications that he later regretted this terminology. The virtual particles are internal processes and are only metaphors for multivariate integrals. The term is often used between researchers as jargon/shorthand rather than meaning particles as we think of them eg electron. The real problem is that in physics a lot of prior understanding is taken for granted, so a QED/QFT text book doesn’t expect you to leap in without studying a few years of physics and quantum theory and so doesn’t bother to explain the background.

I am correct in concluding that Feynmans virtual particles do not exist in reality,

Correct.
The virtual particles are metaphors for multivariate integrals, there are no 'time processes of virtual particles. Nobody ever has written down an equation for the time evolution of virtual particles. While a case can be made that virtual particles exist at least as lines on paper, no such case can be made for their time evolution.

and are not the same virtual particles as those predicted to exist in space by Casimir via calculations based on the uncertainty principle, supported experimentally. Giving rise to various quantum foam/gravity theories.

They are the very same, but their ‘existence’ is not predicted or supported experimentally. Experiments can confirm that results of the calculations represented by the shorthand/diagrams are correct (real).

Further more virtual particle pairs borrowing there energy from the quantum vacuum of space momentarily, are nothing to do with QFT, other than they both use the term virtual particles.

They are the same.

You keep mentioning space when referring to vacuum.
3D space (which can have a vacuum) is not the same as quantum vacuum. A quantum vacuum is the lowest energy state of a quantum system, any quantum system eg molecular bonds, it is not the same as spacial vacuum. If we take a simple Newtonian system eg a weight hanging from a string it has zero energy as it hangs there (disregarding the energy in the mass of the weight and the potential energy which would be released if you cut the string); if you set this system oscillating it will have its maximum ke at the bottom and its minimum at the top of the arc - where it spends most of its time.
The quantum version of this oscillator has its minimum energy at the bottom - where it spends most of its time - but this energy is not zero. This none zero minimum energy is a feature of all quantum systems and is due to the fact that there is uncertainty in the position and momentum of the particles. It’s not that they are flitting about, it’s a way of handling the uncertainty of a probabilistic system.
You don’t really borrow energy from the quantum vacuum, the correct way to look at this is with time/energy uncertainty ie Δt ≥ h/2ΔE . What this is telling you is that if you want to detect the presence or absence of a particle whose rest mass energy (E = mc²) is equal to ΔE, you need to look for at least a time Δt. You can look for longer if you like, but this is the minimum observation time needed to ensure that the uncertainty in your measurement is less than the energy of the particle. If you look for less time, your energy uncertainty will be bigger than the mass energy, and you can't be sure whether the particle was really there or not and in QM the probability is nonzero, but if you look for a longer time they aren’t there - you didn’t see them. Again this is a way of handling uncertainty in the equations.

Adding further to my confusion I googled for a link on evidence for the Casimir effect experiment which I know exists, and stumbled across this link https://www.scientificamerican.com/article/are-virtual-particles-rea/ Which leads me to think perhaps the terminology used by different Quantum theories leads to further confusion

.
He was criticised by a number of physicists for this article as being misleading. Remember also the difference between physics and the maths we use to describe it - "existence" for physics means "measurable", for mathematics "possible to be included in a self consistent theory”, quite often there is confusion in the use of these terms.
I’ve already given you links on the problems of virtual particles being considered real (in the physics sense) and the problem of considering them as cause of Hawking radiation, but here is another link explaining, try to read and understand beyond where it says “this visualization is not for real particles, but virtual ones. They are calculational tools only, not physically observable entities”. https://medium.com/starts-with-a-bang/ask-ethan-how-do-hawking-radiation-and-relativistic-jets-escape-from-a-black-hole-b7a4ef7d9bdf

Just to recap on virtual particles and vacuum fluctuation, important to read and understand before diving into your QED book:
https://www.physicsforums.com/insights/misconceptions-virtual-particles/
https://www.physicsforums.com/insights/physics-virtual-particles/
https://www.physicsforums.com/insights/vacuum-fluctuation-myth/
Also some comments by Prof Baez http://physicsfaq.co.uk/Relativity/BlackHoles/hawking.html

No. They are real photons.

This statement disagrees with my text book, section on QED. I will re read the section very slowly, I do not think I have misunderstood what I read.

Are you possibly redefining what a photon is, and giving it EM characteristics?

I think you must be misreading, it would be unusual for a book on QED to mention antenna and radio waves specifically, all em fields are treated in the same way no matter what their energy. Are you sure your not looking at the evanescent field close to the antenna?
A photon does not need to be redefined to have em characteristics, they are embedded in its Maxwell equation source where a photon is just a quantisation of the em gauge field (in other words it is the field measured with a value of one quanta when detected). See first few paragraphs of: https://www.imperial.ac.uk/media/imperial-college/research-centres-and-groups/theoretical-physics/msc/current/qed/Photons.pdf

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Guest Book / Re: Hello Everyone

« on: 28/06/2019 08:13:02 »

Hi, everyone I'm new for this place. I'm here to share my views and opinion to all of you.
Well, by profession I'm CEO of spamcommerciallink.com.

Poor attempt to advertise your food delivery service.
If you serve up spam you must be ancient roadside caf quality.
Go fry

3

New Theories / Re: New Theories: Will all moving objects with mass generate gravitational waves?

« on: 26/06/2019 15:00:34 »

Since the threads in the Alternative Theories sub-forum are not consideration as “hard science” I will say that I have seen no objection to the comment that all space is filled with gravitational wave energy, coming and going in all directions.

No objection does not mean agreement. In New Theories any ideas other than conspiracy and religious theories are allowed. Generally most of us don’t have the time to follow them all.

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Technology / Re: Will this 2-probe oscilloscope produce an XY display?

« on: 24/06/2019 14:39:07 »

I'm an amateur musician when not being an artist, you simply cannot get decent visualisation software,

Takes me back to my early teenage when I made a sound to light unit. Different coloured lights for each frequency band.

Re. Pico, also a geek - so tinkering with stereo leads & probes appeals

As Alan says “Lissajous figures from raw stereo music are likely to be very messy”. You are basically creating vectorscope which is very useful in recording as you can see the phase relationship between the channels and monitor the effects of limiting.

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Physics, Astronomy & Cosmology / MOVED: New Theories: Will all moving objects with mass generate gravitational waves?

« on: 23/06/2019 23:11:36 »

This topic has been moved to New Theories.

https://www.thenakedscientists.com/forum/index.php?topic=77230.0

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Technology / Re: Will this 2-probe oscilloscope produce an XY display?

« on: 23/06/2019 23:02:45 »

I did wonder why you had rejected Pico as it seems ideal. Iknow some people dislike the quantisation of the levels, but the pico has enough resolution for what you need.
Like Alan I’ve used one of these - still have one in the spares box - and can agree with him that they are excellent tools.
Let us know how you get on.

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Technology / Re: Will this 2-probe oscilloscope produce an XY display?

« on: 23/06/2019 08:22:38 »

It would need an x input sometimes labeled external timebase. There would also be a switch to change from internal timebase to external - often on the timebase selector.

By the way, I have vague recollections of someone making a box to display lissajous figures on a tv. Might be worth investigating.

PS I’m moving this to technology because it isn’t really a physics question

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Physics, Astronomy & Cosmology / Re: Is it possible to connect a second analogue display to an oscilloscope?

« on: 23/06/2019 00:32:44 »

That would depend on whether the grid was software generated and what display options are available.
I have both Tektronix and Fluke ‘scopes and they have display options to have a border rather than grid or dot pattern; neither have a blank screen option, both are digital.

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Physics, Astronomy & Cosmology / Re: Is it possible to connect a second analogue display to an oscilloscope?

« on: 21/06/2019 23:46:22 »

Sounds like you would be better off with an old analogue scope. The glass grid acted as a protector for the crt and could be removed to clean dust off the crt face. Usually held by a bezel you could unscrew or prise out

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Physics, Astronomy & Cosmology / Re: Is "Space" distinct from "nothingness"? (and the Vacuum)

« on: 21/06/2019 23:26:28 »

Yes, I am afraid it is beyond me. But the 'virtual particle' is a theory, I don't see that it can be proved or disproved beyond laboratory conditions, with all due respects to Mr Arnold Neumaier.

Virtual particles are not a theory, they are representations of mathematical models of internal processes in QM. Prof Neumaier has done a lot of work on the maths of QM and is keen to dispel some of the misunderstandings that arise due to poor interpretation of the maths and concepts.
Examples abound. There is one poor soul in new theories who is completely confused by his misunderstanding of observation, measurement, wave/particle duality, matter waves etc; such that he is unable to understand some very simple concepts.

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New Theories / Re: New Theories: Will all moving objects with mass generate gravitational waves?

« on: 20/06/2019 09:45:54 »

The force of gravity is in the proximity of the surrounding massive objects, in accord with the equations that have been developed to quantify it. So isn’t it safe to say that the cause of gravity is in the relative mass of objects, their relative motion, and the potential for their masses to cause relative motion?

We know that any form of energy bends spacetime and causes the effect we can measure as a gravitational field.
Mass is a very, very concentrated form of energy - there is a lot of energy locked up in it - so it bends spacetime more than any other form of energy. But it is the absolute masses  not the relative masses that determines the field.
Yes, the gravitational field at any point is the sum of the effects of all the masses and will change with their motion.
Short version 

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Geology, Palaeontology & Archaeology / Re: Spam.com

« on: 15/06/2019 08:50:57 »

Well, let us assist you to travel away from this forum.

13

Physics, Astronomy & Cosmology / Re: Will all moving objects with mass generate gravitational waves?

« on: 14/06/2019 23:21:28 »

Since accelerated objects emit gravitational waves at the speed of light, and therefore gravity is said to have an ever expanding reach, it seems fair to postulate that all locations in space would contain fluctuating levels of gravitational wave energy that influence the relative motion of the surrounding celestial objects.”

I think there is a danger here of confusing 2 related but different things, the gravitational field and gravitational waves.
The gravitational field is due to a mass and gravitational waves are a propagating disturbance/oscillation of this field in much the same way that light is a disturbance/oscillation of the em field. The gravitational waves are not strong enough to influence the motion of celestial objects, but the gravitational field is.
Changes to a gravitational field (caused by a moving mass) propagate at the speed of light, but in a somewhat surprising way that means the force experienced by a test mass will always point to the current position of the moving mass rather than it’s position x light seconds ago. Below is a popsci article that explains what happens and below that I’ve compared it with a similar effect due to a moving charge.

https://medium.com/starts-with-a-bang/what-is-the-speed-of-gravity-8ada2eb08430

There are similarities between em radiation and gravity and comparisons can be made which help us to understand them better.
Let’s start with the field surrounding an electron. A test +ve charge will be attracted to the electrons position. We know that the electric field propagates at light speed, but if the electron is moving the test charge will move towards the current position of the electron, not where it was. In this way the field behaves in a similar way to gravity.
What is less well known is that if the electron changes velocity the test charge will move towards the position the electron would have been at had it not accelerated, until such time as the change in the field propagates to the test charge’s position. How does the test charge know where the electron will be? I can offer an analogy that shows that this behaviour of fields is not so mysterious.
Imagine a boat crossing a lake, the bow wave propagates away from the boat, but even at some distance from the boat the crests point to the boat’s current position (almost,  because waves in water don’t propagate exactly as do em waves). If the boat changes direction it will take time for the change to propagate to the observer, and until it does the bow wave will point to the predicted position of the boat had it not changed course.
In the case of the accelerating electron we know the speed at which the change propagates, because the change causes a discontinuity in the field which we detect as em radiation - light, radio etc (and if we have a quantum detector we can say we detected a photon).  We can describe the electron field at any point as being dependent on the history of both the position and derivative of position (velocity) of the electron.
A similar effect occurs with gravity. As @Halc pointed out, the force felt by the moon is directed to the current position of the earth rather than it’s historical position. This led early researcher to conclude that the speed of gravity was either instantaneous or extremely fast whereas it does not need to be for similar reasons as I have described for the electron.
It’s worth pointing out that the gravity situation is slightly more complex because there is a higher order effect which allows the masses to ‘point’ towards each other’s current positions despite both being in non-linear motion around a common centre of mass. This higher order effect is also why em waves are dipole and gravitational waves are quadrupole. It also means that gravitational waves cannot be produced by a simple acceleration of a single mass. However, the gravitational waves we have detected (which are analogous to the em radiation of the electron) show that the speed of propagation, and hence the speed at which gravity changes propagate, is as close to light speed as can be measured.

EDIT Whoops, @evan_au was posting as I was typing.

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Chemistry / Re: Why Choose Full Lace Remy Hair Bundles?

« on: 13/06/2019 08:37:59 »

Oh dear, trying to spam us eh?
Well, hair today, gone tomorrow 

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General Science / Re: Can you make a huge prism, and disperse light in different colors?

« on: 29/05/2019 22:35:22 »

If one has access to red and/or green laser pointers, one can easily see that a single laser point generates a whole diffraction pattern (multiple bright spots), and that the spacing of the diffraction pattern is different for red (typically 600-700 nm, depending on source) and green (typically 532 nm doubled Nd:YAG).

That’s really interesting, I had assumed thin plastic layer over reflective surface = interference, but the laser test sounds conclusive.
I’m tempted to get some grating and try the double diffraction back through mirror. As @Bored chemist says it won’t reassemble, but it might be an interesting effect especially if you cut shapes out of the grating so some single others double diffraction. Flexible mirror might be fun!

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General Science / Re: Can you make a huge prism, and disperse light in different colors?

« on: 29/05/2019 07:46:58 »

So, if the grating is attached to the mirror light passing through the grating to the mirror will be diffracted. What happens when the diffracted light passes back through the grating? What effect do you get? Has anyone tried it?

PS I thought the CD rainbow effect was similar to oil on water, a thin film interference pattern rather than a grating effect.

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General Science / Re: Is radon gas a health concern in Australia?

« on: 21/05/2019 17:56:02 »

Please update this Information. links not able open and read this facts.
Thanks

the links work fine for me

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Physics, Astronomy & Cosmology / Re: Does a photon self propagate due to the interactions of the electric and magnetic fields?

« on: 15/05/2019 14:59:12 »

I’ve split this off from the relativity thread as it’s now moving away from that topic.

Is the photon particle itself “light”,

If you fire a single photon at a photographic film then, as long as the film is sensitive to that frequency, it will register a spot. Same for any detector sensitive to that frequency including the eye. So, we assume the photon is light.

or does the photon, which is made up of multiple quanta of energy contained in the photon particle, emit electromagnetic wave energy, which is “light”?

The photon is a single quantum it does not contain multiple quanta.
It does not emit anything, it is an oscillating em field disturbance moving through space.

The photon displays wave properties eg diffraction/interference and particle properties eg transfer of momentum.

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Physics, Astronomy & Cosmology / Re: Can Special Relativity be derived from Newtonian Mechanics?

« on: 14/05/2019 09:14:08 »

There is no perfect vacuum, and in that context, there is never an “absence of anything”. So can we say that the refractive index is variable, relative to the medium?

You have copied a large section of Wiki but don’t seem to have answered the question or shown it’s relevance to the topic.
Although there is rarely a perfect vacuum, space is extremely close (even the speed of light in air is not far off vacuum) and CERN is able to produce pressure of the order of 10^-10 to 10^-11 mbar - a vacuum almost as rarefied as that found on the surface of the Moon. At these pressures there is little practical difference between the theoretical speed of light in vacuum and that measured in the accelerator.

So, within the limits we can measure SR hangs together and tests in particle accelerators confirm this.

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New Theories / Re: Can a photon be visualized ?

« on: 06/05/2019 18:12:56 »

Sorry, missed this

Can I just clarify this, are you saying there is no clear link between virtual particle pairs around the transmitter, acquiring energy, momentum. Followed by them becoming real photons due to either instability or coming back together and annihilating each, not unlike a positron electron collision, but at much lower energy levels.

If you look at the fields in the near field you see something akin to what sailors call a confused sea, many small (compared to a propagating photon) disturbances with no clear relationship. The E field is often greater than the H and then this will reverse, the phase relationship between E and H varies, and all polarisations are present. Although all these field disturbances will superpose there is not enough consistency to generate  a regular supply of photons - although some can be found in this zone - and the confused disturbances will be viewed as virtual photons. As the fields get further from the influence of the inductance and capacitance of the antenna the fields become more coherent with E and H becoming orthogonal and having a clear phase relationship, polarisation settles to that of the antenna and we begin to see what we would describe as coherent photons (as with a laser).
By the way, you might want to read this which puts what Strassler was saying in different words. https://www.livescience.com/55833-what-are-virtual-particles.html
One of my pet hates is the way people take physics shorthand and reinterpret it as a ‘thing’.

Are you viewing the photons in a quantized radio wave as individual photons, or something else?

They are individual photons. Not so obvious as the low energy means they are in the thermal noise and you need cooled detectors to find them.

Since the electromagnetic field of Maxwell's theory based on Faraday's induction effect is expanding, how do you depict the particle STRUCTURE of a Planck's EM photon, Einstein's EM photon, QM photon, QED photon, QFT photon or a string photon.

The em field is only expanding for a point source spherical wave. The photon is a plane wave group so propagates in one direction only.

For instance maxwells equations state an EM wave travels from A to B, and shows how it spreads out.

Maxwell’s equations do not show how an em wave spreads out. The inverse sq law spread is only valid for point source spherical waves. Maxwell’s equations are equally valid for plane waves, which do not spread out. Photon equations in qft use Maxwell’s equations.