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Physics, Astronomy & Cosmology / Re: does light 'bend' to a magnetic field?

« on: 11/09/2014 18:23:54 »

Not to mention that "direction-dependent phase" is well known in optics (anisotropy of the index of refraction).  The press release is poorly written and misleading. 

What they appear to be doing is using the fact that matter can interact with a magnetic field, and that light waves passing through that matter will depend on the matter's properties.  Therefore, by changing the magnetic field, you can indirectly influence light (by acting on whatever matter its passing through).  It seems a bit overblown to say this is demonstration of the Aharanov-Bohm effect for light, but its cool that the same mathematics describes the light waves in this experiment and it may be useful in designing photonic circuits.

The original paper that did this experiment, which is much clearer on what's going on, is here:
http://www.nature.com/ncomms/2014/140130/ncomms4225/pdf/ncomms4225.pdf

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Physics, Astronomy & Cosmology / Re: Are a Magnetic Force and Gravitional Force one and the same?

« on: 09/09/2014 22:26:23 »

In other words, if you have a strong magnetic field, it could be a source of gravity, but there would be two forces present: gravity and magnetism.

Can you elaborate please?

Energy is a source of gravity.  The magnetic field has energy.  Therefore magnetic fields should be able to produce gravitational effects.  As far as I know this is true, but we haven't seen big enough magnetic fields to observe this effect.

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Physics, Astronomy & Cosmology / Re: Are a Magnetic Force and Gravitional Force one and the same?

« on: 09/09/2014 15:46:49 »

No.  Gravitational force is due to mass (or mass, energy and momentum, depending on how you describe it), but not due directly to charges.  The magnetic force is due to charges in motion, and does not depend directly on their masses. 

On a subatomic scale, the magnetic force is transmitted by the electromagnetic field which is made up of photons, which we have observed and understand well.  The gravitational force is transmitted by a gravitational field which we theorize is transmitted by particles called "gravitons."  But gravity is so weak compared to magnetism that we haven't been able to experimentally detect gravitons yet, so exactly how they work (and if they really exist) is an open question.

Related question: time and space can be affected by intense magnetic fields, but that is because time and space are affected by distributions of energy and the magnetic field carries energy with it.  In other words, if you have a strong magnetic field, it could be a source of gravity, but there would be two forces present: gravity and magnetism.

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New Theories / Re: Bohr model of the atom:

« on: 08/09/2014 18:32:53 »

Your ideas have 2 major obstacles.

The first is that they aren't rigorous.  You can draw pictures all day that seem plausible, but the devil is in the details.  If you can show some math making predictions for measurements resulting from your theory, that'd be a huge step forward in getting anyone to take it seriously.

The second is that it has to be in agreement with models that we know are accurate.  This means it has to describe the same experimental results as both quantum electrodynamics and Maxwell's equations.  It's all well and good to say that your solenoidal fields will reulst in the exact same predictions as classical/quantum field theories.  I don't see how that's possible since we know little solenoids will respond to external fields and charges in a way that fields alone will not.  If you disagree, its up to you to prove it with some rigor, not just pictures and words.

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New Theories / Re: Bohr model of the atom:

« on: 08/09/2014 15:21:23 »

I've moved this since it's veered off the track of a legitimate question of how the Bohr model is used/what it is to a debate on the validity of mainstream quantum theory.

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New Theories / Re: Please tell me what is wrong

« on: 07/09/2014 23:11:56 »

Since this is turning into discussion/promotion of non-standard physics, I'm moving it to the New Theories section.

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Physics, Astronomy & Cosmology / Re: Do electrons capture nucleons?

« on: 06/09/2014 19:33:19 »

I suppose you could view it that way, but it's not usually used in practice.  The nucleus is so much more massive than the electron that it is pretty much just sitting there while the electron gets pulled in. 

It's a bit like how we generally assume the earth is orbiting the sun, although in reality, you could say the sun is orbiting the earth (or more correctly, that both are in orbit about a common center of mass).  But in practice, we can almost always neglect the sun's motion in response to the earth since it's just so much more massive.

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Physics, Astronomy & Cosmology / Re: Do insulators inhibit magnetism?

« on: 06/09/2014 19:30:08 »

You're right--I missed the "insulator" point in the OP's question.

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Physics, Astronomy & Cosmology / Re: Do insulators inhibit magnetism?

« on: 05/09/2014 15:07:23 »

I agree with the above posts, but would like to add on minor point.  In electrodynamics, the electric field and magnetic field are linked, so if you block the electric field, you also block the magnetic field that is linked to it.  In this case, an insulator can block the magnetic field indirectly.

In detail, an electric field that is changing in time induces a magnetic field.  So if you block the electric field, it is zero for all time (not changing) and the induced magnetic field also vanishes. 

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Physics, Astronomy & Cosmology / Re: Does Einstein create the real General relativity ??

« on: 29/08/2014 16:32:27 »

But in truth there are many time that Einstein said that gravity is the curvature of space time.

No there isn't. If you beg to differ, give a few reference where he did say that.

He certainly realized that the mathematics of his theory describing gravitation also describe curvature in space-time
(http://www.nobelprize.org/nobel_prizes/physics/laureates/1921/einstein-lecture.pdf). 

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Physics, Astronomy & Cosmology / Re: Would gravitons experience time dilation?

« on: 28/08/2014 00:10:36 »

I don't know the answer to this, and it seems as if no one on the forum can do more than speculate (myself included), but it's worth pointing out that gravitational time dilation is a consequence of the general theory of relativity, which is a classical field theory.  Particles such as the graviton come from quantizing the classical field theory and so they should be able to explain how to build the classical theory from more fundamental, quantum building blocks.

For example, the properties of the electromagnetic field arise from photons.

So since time dilation as its currently understood is a consequence of general relativity and gravitons should explain how to build general relativity from particles, a graviton theory should probably explain how time dilation comes to be as a result of fundamental particles. 

And although we know some properties that a graviton theory has to satisfy, there is no accepted theory of a graviton yet...

There have been proposals that the graviton should exceed c. I doubt that. However there may be more to that point of view than meets the eye. At the moment I am grappling with the Maxwell equations very badly. Better people than me have attempted such things. I'll keep going simply because I love a mystery and you learn an awful lot on the way. Mathematics never ceases to amaze me.

While I can't help you much with Einstein's field equations and gravitons, I am an expert in Maxwell's equations should you have any questions.

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Physics, Astronomy & Cosmology / Re: Can you explain inflationary theory?

« on: 27/08/2014 17:17:47 »

God does not play marbles with the universe...?

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Physics, Astronomy & Cosmology / Re: Can you explain inflationary theory?

« on: 27/08/2014 15:46:34 »

There's no need for a "marble."  The universe could be infinite in size all the way back in time, at least as far as our current theories can describe...  It's not intuitive, but when we're talking about the birth of the universe, why should we be able to picture it in terms of marbles? 

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Physics, Astronomy & Cosmology / Re: Would gravitons experience time dilation?

« on: 27/08/2014 14:51:34 »

I don't know the answer to this, and it seems as if no one on the forum can do more than speculate (myself included), but it's worth pointing out that gravitational time dilation is a consequence of the general theory of relativity, which is a classical field theory.  Particles such as the graviton come from quantizing the classical field theory and so they should be able to explain how to build the classical theory from more fundamental, quantum building blocks.

For example, the properties of the electromagnetic field arise from photons.

So since time dilation as its currently understood is a consequence of general relativity and gravitons should explain how to build general relativity from particles, a graviton theory should probably explain how time dilation comes to be as a result of fundamental particles. 

And although we know some properties that a graviton theory has to satisfy, there is no accepted theory of a graviton yet...

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Physics, Astronomy & Cosmology / Re: Do photons (as waves) have fixed amplitude?

« on: 17/08/2014 13:42:18 »

By this logic, the amplitude of a single photon would be proportional to its frequency.

When you produce many photons of a single frequency, such as in a laser beam or a radio transmitter, the amplitude is proportional to the number of photons.

Yes, exactly!  The classical wave that David Cooper mentioned is not a single photon.  It is a collection of photons whose amplitude is proportional to the expected number of photons, which in turn is proportional to energy deposited on a detector if you were to take a measurement. 

If you were to write out a quantum wavefunction for a single photon, the amplitude would tell you the probability of finding a photon over a region of space.  This is not the same as energy, since you can obviously have a range of anywhere from 0 to 1 probability of finding a photon independently of the photon frequency.  (Though strictly speaking, you can't write out a quantum wavefunction for a single, pure photon, you can do so approximately in many cases).

If you're interested in pursuing the details of how to build a classical wave from individual photons, you want to look up "quantum coherent state."  The math can get ugly, but it describes how to build a classical wave from individual photons.

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Physics, Astronomy & Cosmology / Re: Can magnets affect water viscosity?

« on: 15/08/2014 13:24:00 »

It sounds like a scam working off peoples' desire to conserve water.  The effects discussed above will be tiny compared to mechanical effects such as hose/sprinkler design and water temperature.  There's also the fact that unless you carefully measure the water flow pre- and post-magnet, your mind can fudge things to make it seem as if the $10,000 device you got is actually working.  My guess is that they're just trying to conserve water more carefully now that they've installed it and that they could have gotten the same level of conservation pre-magnet.

Aside from this, magnets have a history of being applied to do all sorts of things to water.  Some are plausible, but many are fantasy.  We've had threads on magnetic water softeners (which don't seem to work reliably, but may do something in some cases) before.  You can find a lot more here: http://www.chem1.com/CQ/magscams.html

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Physics, Astronomy & Cosmology / Re: Understanding reaction in example

« on: 14/08/2014 01:46:12 »

If they're working on a frictionless surface and all they're doing is pushing, then yes.  They exert equal and opposite forces and given their unequal masses, the lower mass wrestler will lose.  But as Ethos points out, wrestling is not simply two people pushing on a frictionless surface!  Once you put in friction and the option to use leverage to tip your opponent over, this simple model goes out the window and the less massive wrestler can certainly win.

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Physics, Astronomy & Cosmology / Re: How significant is this?

« on: 09/08/2014 16:48:15 »

The uncertainty principle (and uncertainty) can be useful outside the context of physically taking many measurements.  For example, if I know a priori what my wavefunction is, I can characterize the standard deviation of the set of possible measurements.  This is the wave interpretation of uncertainty relationships--a single particle's wavefunction will satisfy an uncertainty relationship, even if defining the standard deviation of a measurement of a single particle is nonsensical.  In this sense, it is reasonable to talk about the uncertainty in an observable of a single particle insofar as this describes the possible outcomes of experiments.

As for what describes a measurement, there's no strict line between a measurement and an interaction.  Imagine putting a circular hole in an opaque screen and firing photons at it.  If we have a detector after the screen, and we get a "click" on the detector, we know a photon went through the hole and we can say we've "measured" its position.  But there's no sharp line that says "if the hole is below X size, this is a position measurement, otherwise it isn't."  We have just as much right to claim that a 500 nanometer hole made a measurement as we do that a 1 meter hole made a measurement.  We just have a very poor precision in our 1 meter measurement (which we should disclose) if we want to get the exact position.  You may say that we could come up with a thought experiment where the pinhole becomes infinitesimally small and we do have perfect measurement in position, but once you do that, you have to account for quantum effects in the pinhole itself and so you still don't get perfect localization of the particle.

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Physics, Astronomy & Cosmology / Re: What do you think of my physics magic tricks?

« on: 08/08/2014 22:45:14 »

I've deleted all stream of off topic posts about spelling.  If you want to discuss this further, please do so in the Just Chat forum rather than bringing this thread off-topic.  If you have a complaint about users using spelling" errors" as a method of trolling, please bring it up with the moderators.

Thanks,
The Mods

Edit: while I was deleting/posting this, I see the matter was resolved.  I've still deleted the posts, but I'm glad it was settled amicably and we can get back to the thread at hand. 

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Physics, Astronomy & Cosmology / Re: How significant is this?

« on: 08/08/2014 17:51:33 »

Sure you can, but you haven't localized it with the same precision as if you used a single pinhole.  Even if you don't like calling that a measurement, and I can understand why it might not be the best term for it, it's the standard terminology in the field.

A car leaves Boston MA at 8:00 am travels to and arrives in Haverhill MA 45 minute later. You're telling me that given this information you can state that you've measured the cars position? If so then I'd have to strongly disagree. Especially for a quantum particle which can't even be said to have a position until it's been measured. For all you know it tunneled through the entire space and skipped the region between Boston and Haverhill altogether.

Of course I'd say I'd measured it.  But the precision of my measurement would be low.