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How Light Regains its Velocity After Passing Through a Denser Medium?

05/09/2011 9:01 AM

Assume a beam of light is passing through a glass plate and emerges out to the air again.

Here the velocity of light before hitting the glass surface is same as that of once it has come out of the glass. But while it passes through the glass the velocity is less.

Now the question is how does the light beam gets acceleration to achieve its original speed once it gets out of the glass surface?

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#1

Re: How light regains its velosity after passing through a denser medium?

05/09/2011 9:24 AM

I was taught the speed of light was a Constant.

Are all the Constants becoming Variables these days?

I read where Alpha is in Jeopardy.

I am pretty sure Avagadro's Number is still intact

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#3
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Re: How light regains its velosity after passing through a denser medium?

05/09/2011 9:46 AM

It doesn't slow down when passing through glass, but this is something really weird that I hadn't read about before.

BTW, to anyone checking it out, don't get spooked by the religious reference in the beginning of the article, it's not a religious piece.

http://www.wnd.com/news/article.asp?ARTICLE_ID=39733

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#5
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Re: How light regains its velosity after passing through a denser medium?

05/09/2011 10:07 AM

In fact speed of light varies when it passes through different medium and which is the actual cause for refraction.

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#8
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Re: How light regains its velosity after passing through a denser medium?

05/09/2011 12:21 PM

Here is a rebuttal of Setterfield's theory of the speed of light, http://www.fsteiger.com/light.html

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#10
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Re: How light regains its velosity after passing through a denser medium?

05/09/2011 1:03 PM

This is a very interesting question.

Apparently, according to Dr Tom"s referrenced article this is a religous issue after all.

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#11
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Re: How light regains its velosity after passing through a denser medium?

05/09/2011 1:41 PM

I guess so. I just did a quick google on slowing the speed of light and it popped up.

I read through it pretty quickly, but it looked like there was some actual data to back it up. I have no idea.................I'll have to reread it and the rebuttal.

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#200
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Re: How light regains its velosity after passing through a denser medium?

06/08/2011 9:29 AM

think of a light wave not as a pond with ripples on it, but the ripples themselves. Light is limited to C, but C includes the movement up and down in the sine wave, which because of the laws of relativity slow down the forward progress. In some very dense materials, the path taken by the distorted sine wave is so complex that the forward movement of the light can slow down to 40 miles per hour. Your Fiat could beat the speed of light in a race downhill with the wind behind it. That's why Fiat keeps returning to the US market every couple of decades--it is going back in time. Sadly, the speed of rust is not affected by the speed of light, so the Fiat disintegrates at the same rate regardless of when it is permanently parked behind the apartment building where you live when you go to college. The Fiat-faster-than-light-returning-to-the-US-market theory is what I call a "desperation explanation." There is no other explanation for the return of the Fiat (Renault and Opel follow a similar pattern) and therefore it must be true--as Sherlock Holmes says, once you have exhausted all likely causes for a phenomenon, the cause is what remains, regardless of how unlikely. Remember that Holmes was a fictional character.

When the photons escape the dense material, they return to their sinus rhythm and forward speed.

Here's an odd one--light has been detected exiting the dense material at a rate higher than it would travel through the surrounding aether. That would require a speed greater than C. This has been explained by pretending there are two portals to a wormhole inside the material, with the photon in question popping into the wormhole shortly after entering the material and popping out shortly before exiting. How likely is that? Seems like another desperation explanation. Why not say, "We have no fracking idea why it happens. But we're pretty sure it happens." Just like "Ponzi Scheme" is part of the language familiar to anyone with money and its symptoms are obvious to anyone, no Bernie Madoff has yet starved to death depending on the ability of greed to overwhelm the influence of common sense. Our broker implied we were nuts twice in the past 20 years when we shifted our investments from an overheated stock market to bonds just before an historic crash. It's true. We're nuts. We have no idea why the market behaves the way it does and fools people like our broker into dumping cash into it. Maybe it has something to do with the speed of light and worm holes, too. All we know is that when you pull the trigger, six times out of seven, a bullet comes out of the gun. That's all that seems necessary to know. Some explanations that involve actions in a quantum, string, or alternative universe are inconceivable given the concepts we have learned in this human-scale relativistic universe.

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#4
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Re: How light regains its velosity after passing through a denser medium?

05/09/2011 10:05 AM

Speed of light is constant only in vacuum.

For denser medium speed is less than that in vacuum.

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#6
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Re: How light regains its velosity after passing through a denser medium?

05/09/2011 10:11 AM

Thanks Artist,

My education was a Variable as well

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#29
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Re: How light regains its velosity after passing through a denser medium?

05/10/2011 11:46 AM

Light speed in a vacuum not influeced by gravity is a constant.

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#32
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Re: How light regains its velosity after passing through a denser medium?

05/10/2011 10:30 PM

the energy is constant.

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#2

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/09/2011 9:44 AM

Interesting question!

Using one analogy from Wikipedia, the one of a marching band marching from a good surface into a muddy field at an angle (so some marchers get into the muddy field first), the angle of the marching band changes because the first marchers to enter the field slow down before others (in the same line).

It seems a good analogy with light, because, as the marchers emerge from the field, presumably still marching / trying to march at the same rate (steps per minute and length of step), the band would return to the original angle.

But, I don't know what, at the microscopic level, slows the light down in that different medium. Is it collisions with other particles? Is it interaction with the electric or nuclear forces in the material? Does anybody know? (I don't.)

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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/09/2011 10:49 AM

The mathematics gets very dense (and I haven't done it in a long while ) but it only seems to be a paradox when you think that light acts under the Newtonian rules of momentum. I'll give a synopsis then without most of the mathematics.

Momentum of photons (light particles) are still conserved however the momentum is not the Newtonian p=mv. Even though light in a vacuum has the fastest velocity possible, it has no mass. m=0. The momentum of a photon is p=h/λ, with h being Planck's constant and λ being the wavelength. (It is because momentum and energy must be conserved that the multi spectum quality of white light gets diffracted into the spectral frequencies in leaving a prism in the correct orientation.) So when a photo emerges from a media with a slower light velocity it now becomes the higher velocity. There is no energy transfer related acceleration here.

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#14
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/09/2011 11:37 PM

The point I was trying to get across with this explanation is that in Classical Newtonian Physics when a particle with mass changes its velocity, its energy and momentum gets partially transferred to or from something else. When massless particles like light changes its velocity to anything but a zero velocity (annihilation) the energy and momentum of the light remains the same. No energy or momentum gets transferred to the media that the light must pass through. So the particle immediately travels at the velocity that it has to in order to exist in that media, or it doesn't exist at all.

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#28
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/10/2011 10:46 AM

GA. Another way to look at this is to consider that while the forward speed (distance per second) of the light is reduced while passing through a denser medium, the frequency of the light (oscillations per second) remains constant. So in the denser medium the wavelength of the light is increased inversely proportional to the loss of speed. The energy of the photon/wave is a function of frequency, not speed. In a sense you could say that the energy needed 'accelerate' the photon/wave is 'stored' in the shortened wavelength (shorter wavelengths have higher energy) while passing through denser media (and also of course in a vacuum with high gravity (wtf?)), and then 'released' when the wavelength increases upon entering a less dense medium, resulting in a higher speed.

From our low speed viewpoint the light appears to slow down and increase in wavelength in a denser medium, and then speed up and decrease in wavelength in a less dense medium. The photon doesn't 'care' about speed or wavelength, only frequency. From the photon's high speed 'point of view' it's as if nothing happened at all. I hope somebody can explain this better, and maybe let us know why matter and gravity both affect light is similar ways. Good question.

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#36
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/11/2011 8:01 AM

While I think what you have is a helpful answer, I'm confused because usually wavelength and frequency are inversely proportional to each other (aren't they?)--so if the wavelength increases, the frequency has to decrease? (and vice versa)

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#37
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/11/2011 10:09 AM

Wave length and frequency are inversely proportional but there is also the multiplicative term of velocity included in that relationship. So when the velocity is not a constant then both must also vary.

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#42
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/11/2011 11:17 AM

Thanks! I believe you (and it makes sense), but at some point I'd like to see the formula you refer to (that includes velocity, wavelength, and frequency). Maybe I'll come across it.

Hmm, maybe it the formula for what is apparently called the group velocity?

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#44
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/11/2011 11:24 AM

Sure,

This formula comes from Wikipedia. This works for acoustics in any media and electromagnetic signals, too.

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#47
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/11/2011 11:42 AM

Thanks! (Wow, sometimes I feel like I'm losing my brain--I should have remembered that!)

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#188
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

06/06/2011 11:03 PM

What a terrible thing to have lost one's mind. Or not to have a mind at all. How true that is. --J. Danforth Quayle (now a part of Bartlett's Famous Quotations)

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#45
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/11/2011 11:28 AM

Wavelength and frequency are only inversely proportional if the speed is constant. Since in this case the speed does change, the wavelength must also change for the frequency to remain constant. Remember that the photon's 'identity' is it's frequency. Except in the astronomical phenomenon of red or blue shift from fast moving stars, the color of a photon doesn't change from the time it is released until the time it is absorbed.[p]

You might think for example that the 'color' of a photon would change when viewed in different media: a 'red' photon with a wavelength of 600 nm would look 'blue' underwater because the wavelength would be reduced by 600 nm/1.333 = 450 nm. Clearly this doesn't happen. A red bathing suit seen underwater is still red on the pool deck. I think that this is due to the fact that no matter what medium the light has been traveling through when it reaches our eyes, it is traveling through water (actually vitreous humor) when it reaches the retina. So while we conventionally define color in terms of wavelength, it fact it is the frequency (or more specifically the energy) of a photon that defines color.

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#48
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/11/2011 11:44 AM

GA (but I'm out of them)--thanks!

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#181
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

06/06/2011 5:36 PM

The wavelength of radio waves changes from free space to an atmosphere. As I recall, radio antennas are 5% shorter in space. As for light, I remember this from HS physics but it was long ago. The change in velocity is what permits the use of optics and why we can't see clearly when under water. I wonder how well our eyes could see if you were able to take off your helmet in space?

One further note, the velocity of light was tied to the frequency of Krypton 86, it has changed. The velocity of light is now "constant" but they adjust the length of a meter. Therefore a meter is the distance a beam of light travels in 1/299,999,998 seconds

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#202
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

06/08/2011 9:42 AM

There is only a fairly small difference between the speed of light in air and in vacuum, but I suppose there might have to be a refractive correction if one were capable of being in a vacuum and observing an optical target. By the way, I will keep my helmet on, why don't "you" take "yours" off?

In the original question, the term "regains" is used, when in fact the light lost nothing to begin with. Since the frequency (and energy) of the light wave-particle was constant, no energy transfer is needed is a true statement.

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#189
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

06/07/2011 1:23 AM

I think your's is the most plausible answer. The frequency being remaining constant, the wavelength must decrease within the denser medium in order to cope up with the decreasing velocity. This one can imagine as a compressed spring which stores the energy. The kick to accelerate out of the denser medium comes from the release of the spring, that is the wavelength increases again thereby increasing the velocity. Makes sense?

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#196
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

06/07/2011 12:53 PM

This is the only good answer I have heard that is independent of either my theory (UT) or the Standard Model. Frequency change is the key, energy, per se, can be ignored in this case.

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#187
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

06/06/2011 10:59 PM

can light anihilate? Is there an antiphoton? since a photon is merely a packet of energy, isn't it immortal?

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#246
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

06/15/2011 5:45 PM

Being energy doesn't make it immortal in a singular form of energy. The energy can be translated to another form of energy. Light can translate to kinetic or heat energy for instance. The energy in general terms always exist, though it may be dissipated or aprtitioned into different forms and locations.

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#201
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

06/08/2011 9:36 AM

Red: Light has no rest mass. It does have mass while it remains light, traveling at the speed of light. And by the way, dispersion is the difference in the speed of light for various frequencies in a given medium, and thus since refraction begins at the phase boundary, the separation of light rays into a spectrum occurs during the entire transit through the medium.

It is much simpler to explain the slowing down and speeding back up by way of the electromagnetic wave progagation, and the electric permeability (and/or magnetic permeability) of the medium. Done.

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#243
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

06/15/2011 3:38 PM

I would like to help you understand light a little better. You said: "light has no mass at rest" I would assert that light ceases to be light if it is NOT moving. If it is 'at rest' then it has been absorbed by something, and has interacted with that 'thing' and has raised its' temperature, or imparted all its energy to that thing if it has ceased to 'move'.

It is my opinion that light does NOT have 'MASS', but it only 'ACTS' like it does when it interacts with something, which does have 'MASS'. Light is PURE energy. Anything with 'MASS' is merely another form of energy in a tightly compacted multidimensional form. Since you can only observe the 'MASS LIKE' properties of light when it interacts with an 'OBJECT', which has 'MASS', then I can't help but think that it is the 'interaction' itself, which causes people to erroneously assume that light actually has 'MASS', but it does not, never did, and never will! The 'proof' is in the 'pudding' and the 'pudding' is in the 'interaction' not in the light. There is a magnetic component to a light wave, and there are magnetic components to an object that has mass, and when these magnetic components 'interact', then you have an observable finding, which 'LOOKS' like the light possessed mass when it really doesn't.

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#9

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/09/2011 1:00 PM

Begin with this question instead: What causes the beam of light to slow down when it enters the glass?

The answer to both questions is that the photon(s) interact with the electrons in the material. The easiest way to imagine what is happening is to think of the electrons as absorbing the photons, then re-emitting the photons in a manner that preserves conservation of energy and momentum, so a photon enters on one side of the glass and is absorbed and re-radiated within the glass until it gets to the other side where the last layer of electrons emits the photon into the air, at which point the photon has its original speed again.

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#12
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/09/2011 11:14 PM

All of the above attempt to answer some of the aspects.

Basic: c/n is the speed speed of light in any media.

Expansion #1: n, where Snellius's law applies is frequency dependent in any media. Hence, an n determined in the optics does not applies at all in microwaves, etc.

Expansion #2: According to particle physics (learning from Feynman, etc.), the light does NOT slows down from the light of speed, merely ADJUST TO to the light of speed of the particular matter.

Nobody said, that particle physics is rational in the common sense, just that it is working phenomenally well.

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#199
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

06/07/2011 11:25 PM

Can you please quote any experimental evidence to support the statement that "causes the beam of light to slow down" ? I don't think that there is any conclusive experiment so far. The observation of a change in trajectory, or a change of colour does not imply that light slows down: no real time measurement has been taken. Even in a black hole the speed of light may well be the same, but the conditions for it's propagation may differ from that in open cosmos; light may be trapped in a black hole, going around in circles. For all we know, we cannot even assume that light exists in a black hole and from what I can understand, light can be reflected, scattered, refracted and polarized: but not slowed down, or accelerated past its constant. Below is a Wiki quote, however as you can see it is incomplete and needs clarification. A Bose-Einstein condensate (BEC) was used in these experiments, but there is still ample room before observations are translated into proof. the Wiki comment is not acceptable as "evidence of light slowing down", only that it appeared to have done so relative to the parameters used in the experiments. If light can be slowed down, and therefore sped up, we need to go back to the drawing board on a number of other assumptions. Even by stating that "The speed of light in a vacuum is defined to be exactly 299,792,458 m/s (approximately 186,282 miles per second)" as in Wiki, makes us assume that the speed will be different in denser media; but as I said before, the speed in any media does not change, the DISTANCE does. Although the following simile is crude, it makes my point clear: if a car covers 10KM of straight road in 10 minutes the speed is the same if the car covers 10KM of corners in 10 minutes. But if the accounted distance is as the crow flies, the corners of the road are going to make the actual distance covered a somewhat longer in the second instance. On observation, without considering the corners, we could "prove" that the car going from A to B around corners arrived later than the car going in a straight line. The fact which we cannot ignore is the increased path travelled: something which some of this experiment may not have included when talking about light in denser media than vacuum like glass, or Bose-Einstein condensate, or black holes.

Quote:"Working with Chien Liu, a postdoctoral fellow at Rowland, and Harvard graduate students Zachary Dutton and Cyrus Behroozi, Hau kept tweaking the atoms until they completely stopped laser light. This happens when a second laser beam directed at right angles to the cloud of atoms is cut off. When that laser is switched on again, it abruptly frees the light from the trap and it goes on its way".

The above quote is journalism, but even so the light is TRAPPED, this does not imply that it has slowed down.

Quote: In 1999, Danish physicist Lene Vestergaard Hau led a team from Harvard University which succeeded in slowing a beam of light to about 17 metres per second[clarification needed]

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#13

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/09/2011 11:37 PM

Very interesting Q.

I am surprised, how I never had this Q !!

Will have to search for the theories. Hope, some expert will come up and explain

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#15

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/09/2011 11:39 PM

Fundamentally - light is energy. There is no matter. Hence energy is not lost by travelling by way of friction etc. Light density or intensity may fall with distance, but light is energy. Going a bit towards spiritualism- Soul is known to be energy- which can pass through any medium and faster than light. In contrast visible spectrum of light can be obstructed by solid opaque objects

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#16

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 1:09 AM

Yeah, as the light reenters the ether, it gets an ethereal (spiritual) boost to its former velocity.

Just as when a Jeep hits mud, it slows down, but speeds up again when returning to pavement.

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#17

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 1:50 AM

So in theory, light could be 'stopped'?!

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#18
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 1:55 AM

Doesn't it stop every time it is reflected? First, it's going one way, then it hits the mirror/water/leaf/cloud and goes the other way.

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#19
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 2:11 AM

What happens when light hits an opaque surface?

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#20

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 5:56 AM

Don't ever question light

scientists failed

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#21

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 6:41 AM

Similar but a bit off topic (sorry) but it intrigues me.

I see all these as the same question (as it seems to me) but they may be separate.

e.g. The sun is unbelievably bright (light) as seen on earth, however space is
portrayed as being black? (or at least "dark") The sun's light is seen as "sky blue" on earth,
which is (supposedly) caused by... the atmosphere?
So we could assume the light is definitely "reaching" us - and for a considerable surrounding distance,
so what creates the dark / black space? i.e. the whole area "should" be decisively bright?

Perhaps it's the space between my ears?

jt

Some days I can see forever.

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#25
In reply to #21

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 8:56 AM

I'm trying to think of a way you could actually demonstrate this to yourself, but, if you shine a light (e.g., a laser) through a vacuum, you will not see the beam of light.

If you see a beam of light in air, it is because of light reflecting off particles in the air (dust, or the particles of air themselves).

Try using a laser pointer. Point it at a wall. You see the bright spot on the wall. How much of the beam do you see? Want to see more of the beam--maybe take some flour or some other dust and throw it into the laser beam. You now see (more of) the beam.

)A stickler for language might say you think you see the beam, you actually only see the particles in the beam that are reflecting light. In a vacuum, there are no particles to reflect off of.)

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#57
In reply to #21

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/13/2011 10:20 AM

"Black space" is the absence of light. One also needs a detector, or receptor of the light in order to be "seen". If the light strikes the receptor directly, it will be perceived at the appropriate wavelengths. If the light is intercepted, as in the case of a planet's atmosphere, then proceeds to the receptor the light is perceived in a shifted variation of wavelengths dependent on absorption and scattering.

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#204
In reply to #21

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

06/08/2011 10:18 AM

space is black because you are looking into the dark period--a period shortly after the formation of the universe when hydrogen was the only element, when it was distributed relatively evenly through space, and no stars or quasars had yet formed. OR the existing universe is inside a black hole and you are looking outward into a place where the gravity of the hole causes light to stop and fall back on itself.

The sun is yellow because this is the color that is generated when the electrons in an hydrogen atom fall back into the shells of a helium atom, releasing a photon. Every atom whose electrons are moved from shell to shell and then drop back releases a photon of unique color. Copper is green, cadmium is red. You don't have to go to a lab to see this in action, though it's used in most labs to detect traces of elements in blood, hair, starlight, and so forth. On Chinese New Year or the Fourth of July in the US, you can see these atoms releasing their photons in pyrotechnic displays (fireworks). People assemble spheres containing black powder and shards of magnesium and other metals so that when the ball explodes, it explodes in a shower of colored light.

The sky is blue because our atmosphere is about 80% nitrogen. Nitrogen releases a faint blue light when it is excited by the rays of sunlight. It would be bluer if 20% wasn't oxygen (green) and .5% wasn't carbon dioxide (white). But you would have a hard time standing around admiring an atmosphere of 100% nitrogen. Eventually, you would pass out and die. The last I heard, the atmosphere of Neptune is blue because it has much more nitrogen in it than earth's.

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#22

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 7:14 AM

Is this glass in a vacuum or at atmospheric conditions?

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#23
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 7:26 AM

In atmospheric conditions. Does that really make a difference in this context?

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#24
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 7:31 AM

It makes a speed difference, yes.

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#26

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 9:27 AM

You may want to look up the 'Bose-Einstein Condensate'. It causes the speed of light to drop by lowering the temperature (energy level) to within a few billionths degrees Celsius of absolute zero. Very interesting experiments being conducted on this 'fifth state of matter'.

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#27
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 10:42 AM

It is interesting to see how "dark matter" was postulated to explain the change in velocity of light returning from Pioneer 10/11.

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#30

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/10/2011 1:07 PM

This is so far outside anything I know and I apologize ahead of time.

My imagination shows me an old game I've seen at carnivals called "Plinko" or some variation of any game where you drop a ball in the top and it works it's way down through the pins on a board.

If the ball were just dropped it maintains it's "light speed".

When dropped into the game board, it interacts with the pins on the way through. In the balls journey it doesn't really slow down but is bounced around inside the board and delayed.

In this very simple view, comparing the number of pins on the board and the opacity of the material light will pass through are similar.

Please don't hurt me. I'm not even sure why I had to post that.

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#31
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/10/2011 1:18 PM

A reasonable analogy. Like many analogies though there are inaccuracies. This would not be my first choice for a teaching example but it does incorporate a random process that can then be used to explain some of the quantum mechanics phenomena. I like it.

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#221
In reply to #30

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

06/11/2011 12:52 PM

Good job in laymen terms, is what happens to the light in a medium such as a prism. Therefore refraction redirects the light path not slowing but slight changes in its direction. OK, lets get a tougher question.

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#33

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/11/2011 6:43 AM

Good one....................I was wrong again.

I tend to think of things in simplistic terms though. So, when I turn on my flashlight, the light slows down when it passes through the glass bulb............and again when it passes through the glass lens on the front. I never would have known.

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#34
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/11/2011 7:18 AM

Yes, this is a simple way to put it. Light slows down when it passes through the glass of flash light. Once emerges out it regains the original speed which was there before hitting the glass. For anything to get acceleration including photons, there must be an energy supply. So what happens here and from where the light gets energy to bring its speed to a higher value? This was the point of my question.

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#35
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/11/2011 7:51 AM

the energy never changed. From the photons point of view, it didnt know that it's speed changed. it still thought it was moving at light speed. (what, you didn't know photons had brains?)

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#38
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/11/2011 10:32 AM

But what is the energy and momentum of a photon? K=1/2mv2 p=mv But a photon has no mass, so m=0. Photons do not conform to these classical physics equations for they obviously do have energy. (If they didn't this would be a very cold planet.)

Photons do not go through acceleration, they only exist while traveling at the speed of light for the media they are in. Change the media and the photon travels at a different speed.

Now if you think about this a little, you'll realize that there is another apparent paradox to the "Nothing travels faster than the speed of light" misquotation mantra. Light not in a vacuum has a slower velocity than c. So this implies that a particle with mass can travel faster than the speed of light in that media. When this happens we see the effect known as Cherenkov radiation.

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#39

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/11/2011 10:36 AM

I'm surprised this thread got so much attention. I'll steal a quote from someone else's work that explains this pretty clearly.

"In vacuum and in air, to a greater extent, light is not really interacting with the medium it is in. It's oscillating very fast like a very high frequency radio wave and travelling at its standard speed - the speed of light as we know it. When it enters the glass, the glass contains lots and lots of atoms. Around the atoms are electron clouds. Now, the light when it's in a transparent medium can't excite the electrons, it isn't absorbed, but the electrons do like to try and follow the oscillations of the field. As the electrons are trying to follow the oscillations of the field it means that some of the energy of the light is stored in those electrons. And that whole process, in effect, slows the whole light field down. So the light in the glass is a combination of the electromagnetic wave and the polarisation, as it's called, of the electrons which are travelling together through the glass. This oscillation of the electrons actually gives a rise to this dielectric constant and refractive index. Of course the refractive index is the ratio by which the light is slowed as it travels through the solid material. When the light reaches the end of the solid material, it goes back into air or vacuum and there are no more electrons so the energy that's been stored in the electrons is transferred back into the light field and it speeds up again."

Answered by Professor John Rarity.

So to answer the question....the energy that was stored in the electrons while passing through the glass.

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#40
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/11/2011 10:59 AM

I like this - 'the hitch hiking electrons did it'. Do you have a citation for Prof Rarity's article (I couldn't find it)? This might also explain why gravity has the same effect on photons but to a lesser degree, since gravitation is so much weaker than electromagnetism. Thanks for your answer.

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#41
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/11/2011 11:03 AM
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#50
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/11/2011 11:51 AM

thanks

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#43
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/11/2011 11:22 AM

I'd give you a GA, except I (or somebody on my network) used them up for today, already.

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#46
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/11/2011 11:30 AM

Thanks It's nice if someone likes an answer. I'm never trying to rack up points here. If I can assist someone that's all the thanks I require.

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#49
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/11/2011 11:45 AM

You're welcome!

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#185
In reply to #39

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

06/06/2011 9:09 PM

Good one Fredsky! I'd like to put it in even simpler language.

Light is light and to be so it always retains constant speed, because it is its nature, or it just would not be in the state we call "light"; a simile would be the difference between milk and cheese (lol), or helium and gold. When light travels through a theoretical vacuum it makes no adjustments to its trajectory (it does not take detours around the magnetic fields which bend its path). The denser the medium, the stronger and more tightly packed the fields, the more detours. The farther the distance through this mass of fields, the greater the energy is dissipated as heat. This is why lights bends within a lens (refraction). In conclusion: light does not slow down and then accelerates: it simply goes around more bends and it gets from A to B slower than if it had been travelling in a straight line. We just did not notice the path's complexity. The common description of "light slows down in a medium denser than vacuum" is deceiving and was probably originally coined as a metaphor.

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#191
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

06/07/2011 8:02 AM

Re: (it does not take detours around the magnetic fields which bend its path)

Did you mean to say it does take detours" Other statements in your response seem to contradict the "does not take detours" statement, like the following:

The denser the medium, the stronger and more tightly packed the fields, the more detours.

it simply goes around more bends and it gets from A to B slower than if it had been travelling in a straight line.

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#192
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

06/07/2011 8:48 AM

Yes, that's right. Sorry for the error. I meant to say "it does take detours". In astronomy this "detours" are called "lensing". Lensing observations can be used to deduce the existence of normally invisible celestial bodies.

Thanks for noticing this rhkramer.

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#193
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

06/07/2011 9:13 AM

You're welcome!

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#194
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

06/07/2011 11:13 AM

for lensing, I think you meant gravitational wells not magnetic fields

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#198
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

06/07/2011 9:55 PM

Of course

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#203
In reply to #39

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

06/08/2011 9:58 AM

I think some of these questions have been with us for a long time. Speaking only for myself, I've learned more about light in the past couple of days than in my entire high school career. I always gravitate to any article about light, but no one ever seems to take the issue from the ground up. Sound like a book or major article opportunity? I hope someone here will take the initiative.

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#223
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

06/11/2011 1:19 PM

Once again: (1) the speed of light in vacuum is a universal constant (unless near a very massive black hole), (2)when light enters a dielectric medium (gas, liquid, solid, or plasma), that medium interacts with the light, effectively slowing it down, but the frequency of oscillation of the electric/magnetic fields remains constant (for any given "color" of light). Once the dielectric medium is no longer coupled with the light waveform, the original speed is intrinsically restored. It has more to do with a "speed limit" analogy than milk, or cheese.

It actually has no so much to do with the "density" of the medium, rather it has more to do with stimulated absorption of radiation (Einstein equation). The refractive index for a given energy band of light actually goes through a critical point near the absorption band for the material in question.

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#222
In reply to #39

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

06/11/2011 1:12 PM

Thanks to the professor, he has defined what is refraction.

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#51

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/12/2011 1:43 PM

Basically to understand this you have to understand what light is. Light is a varying electric field with a corresponding varying magnetic field. See below:

Glass or any other solid is filled with bound electrons. As the light passes through the material (glass in this case), charged electrons move with the electromagnetic field of the light. If you look at the diagram above you'll see that the electric field reverses over and over again, so the effect is the electrons are basically shaken in place. Moving (shaking) a charge (like an electron) back and forth produces an electromagnetic wave. This wave is mostly of the same frequency of the light traveling through it, so it interactions with that light (interferes) leading to a shift in whats called the Phase (the sine peaks in the above diagram).

This phase velocity is the "lower speed" of light in the material, the actual speed of light through the material is the same (c).

Here is the explanation from wikipedia, which is more precise and correct than my explanation above:

At the microscale, an electromagnetic wave's phase speed is slowed in a material because the electric field creates a disturbance in the charges of each atom (primarily the electrons) proportional to the permittivity of the medium. The charges will, in general, oscillate slightly out of phase with respect to the driving electric field. The charges thus radiate their own electromagnetic wave that is at the same frequency but with a phase delay. The macroscopic sum of all such contributions in the material is a wave with the same frequency but shorter wavelength than the original, leading to a slowing of the wave's phase speed. Most of the radiation from oscillating material charges will modify the incoming wave, changing its velocity. However, some net energy will be radiated in other directions (see scattering).

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#53
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/13/2011 1:14 AM

Neat.

Does any of that account for the seeming anomaly, i.e, particle/wave appearance, of the two slit experiment?

j.

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#79
In reply to #51

Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/15/2011 2:44 AM

Thanks. This seems to be a reasonable explanation unless someone comes up with something different and better.

Thanks to all those actively participated in this discussion.

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#82
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Re: How Light Regains its Velosity After Passing Through a Denser Medium?

05/15/2011 7:21 PM

Fredski gave pretty much the same answer, before I did. Worth noting.

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#52

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/12/2011 7:06 PM

Not trying to muddy the water, but I'd just like to point out that the explanations given relate to "physics as we know it".

Theories (built on hypotheses) are being described which haven't (yet) been disproven by experimental observations - these are the best we can currently come up with.

(Note: I'm not saying they're wrong - but they might be!).

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#54
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 1:26 AM

John,

What is wrong with this..

"At the microscale, an electromagnetic wave's phase speed is slowed in a material because the electric field creates a disturbance in the charges of each atom (primarily the electrons) proportional to the permittivity of the medium."

Isn't that as obvious as the nose on your face?

j.

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#55
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 1:33 AM

"What is wrong with this..?" - absolutely nothing, using our currently-accepted models.

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#56
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 7:55 AM

Also considering that this 'interaction' happens immediately as wave penetrates the mediun 'surface' and then no speed change happens all the way through the medium, just some expected loss of intensity and 'scattering', we're obviously missing something. I'm with you as for these 'explanations'. S.M.

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#58
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 10:25 AM

Good point. Obviously everything anyone knows or has ever known is wrong - that is the nature of being human. But I appreciated that Roger and Fredski have taken the time to show us what is probably the least wrong explanation currently available. At the beginning of this thread there were opinions offered that seemed to question the very idea that the speed of light could be slowed down. If those folks are still following the discussion their views on the subject are more complete than they were. The more that people know where our current theory stands the sooner the flaws will become apparent.

(Maybe in addition to a sarcasm font we need a punctuation mark that indicates that the preceding sentence may be wrong. Oh yeah - we have one that looks like this: → . ← )

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#59
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 11:03 AM

Agreed.

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#60

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 11:09 AM

When relativity improved upon Newton's gravitation it didn't mean 100s of years of explanations regarding ballistics were "incorrect". What I described and what Fredski had described before me explains what's going on. It's not even that hard to understand when one gets familiar with the science.

Might some theory come that supplants Electromagnetism (EM)? It already has, 60 years ago. It's called Quantum Electrodynamics (QED). It's discovery improved our understanding, however the earlier explanations provided were more than sufficient for the question being asked.

The very nature of induction, by which most scientific theories are formed, precludes the possibility of exactly knowing anything. Still, knowing 99.9% of the details involved instead of 100% of the details involved (and I'm being generous here at how much QED modifies EM) doesn't invalidate the EM explanation.

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#61
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 2:00 PM

Roger,

Nothing at all wrong with what you say about the evolution of our understanding.

My question above drawn from the diagram of wave and magnetic field at right angles and the comments that talk about electromagnetic dragging and jostling of nearby particles was the result of my long held view that there is something conceptually wrong with how we speak of the two slit experiment asserting that light is both a particle and a wave.

I was trying to draw comment without showing where I was headed so as not to prejudice the response.

My thought is that the kind of electromagnetic interference that occurs around a beam of light, as suggested by the diagram might easily account for the classical interference patterns seen in the two slit rather than the conceptually messy both particle and wave.

Mind! I would not be disturbed if the rhetoric read that light, e.g., photons/particles, travel in packets which in motion and because of electromagnetic or particle polarity issues moves in wave formations.

Quantum theory I know presents many apparent contradictions and counter intuitive theses, but I think, as someone interested in physics, but devoid of the math, that is so simply because much is just theory advanced to cover gaps where we simply lack sufficient empirical data.

My view philosophically is that nature when we have the data is obvious. Up until the holes that Heisenberg covered with his uncertainty math I think that is so. There are folks that say our "model" of the atom is only a conception, that it ain't necessarily so, but nowadays we can photograph the little buggers refuting that argument.

When we lack adequate data human minds, for whatever reason (Fritjoff Capra, The Tao of Physics) without a firm attachment to a materialist conceptual foundation, and therefore material concrete evidence, wanders into the kind of garbage that Capra wrote about the relationship between physics and mysticism.

I don't say, getting back to light, that our observations of light are wrong. I just suspect that our assertion as to the interference patterns is a misapprehension of what is actually the cause of the appearing wave formation.

Like the issue about the alteration of time at light speeds in space I think there is a conceptual error. In the case of time I suspect most of you all that have the math understand that when speaking about alteration of time you are speaking about the alteration of speed and motion of sub atomic particles caused by earths gravity. That of course is not what the public, sometimes even well educated public, thinks it means.

They think that somehow subjective apprehension of time changes, an entirely different issue easily discarded by the synchronized mutual operations on the space lab and the base stations here on Earth, or for that matter Earth to Mars Rover operations.

Anyway the diagram of magnetic field turned ninety degrees to the photon wave, and the related disturbance, is what set this up.

j.

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#62
In reply to #61

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 2:23 PM

I think there is something backwards in your interpretation of scientific method. theories aren't provided based on empirical data, the data isfrom experiements is gathered to to attempt to disprove theories. Thus you do not develop theories to cover gaps in empirical data, youd evelop theories to explain the mechanics where some generally applicable theories are not supported by experimental data. In otherwords, the theory that exist works well in every application except this one narrow local discrepancy occurs in the data under some specific situation. If the data diverges from the theory in multiple situations then the theory is likely not valid. If data diverges at the extreme limits then the theory may be bounded. If it divergence only when some specific condition occurs, then there is something in the mechanical understanding that is missing and the theory needs to be amended with another theory to explain the mechanics (not the divergence of data). Now this is why engineering differs, engineering theories are satisfactory just fitting the theory to the empirical data that has been collected. A best fit is good enough in engineering (it gets the job done with soe factor of safety), until we can understand the mechanics.

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#63
In reply to #61

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 5:21 PM

I'll say this. I think most scientists would agree that there is something disconcerting regarding some aspects of quantum mechanics. However experiment has shown that quantum mechanics is correct.

I suspect, and I am far from alone in this belief, that a common sense explanation as to the origin of the uncertainty principle, which itself is the source of the "weirdness" of quantum mechanics, will eventually be found. However, when it is, it will not invalidate the results of quantum mechanics or make it go away. It will just make the theory more rational.

I find that people get confused with the idea that we can know a theory is correct even though we don't precisely understand why a theory is correct. This is the case with quantum mechanics. It is correct, that is certain. We've tested it a ton of different ways. But why is nature like this? That is the question scientists now struggle to understand.

Science in general is self consistent. That means any new theory must explain the old theories that came before it and were proven by experiment to be correct. So when Einstein introduced relativity, he showed that his equations became Newton's equations at slower speeds. When Quantum Mechanics was introduced, it was shown that when you get to a larger scale, the equations become the equations of classical mechanics.

Any new theories that come will build upon these current theories, not replace them. I understand your unease with the weirdness of quantum mechanics. That is an excellent instinct that you should trust that tells you that we don't have the whole picture. But you must also respect experiment, which tells us that if we don't have the whole picture, we've certainly got a lot of it. As Feynman once said "Anyone who says that they understand Quantum Mechanics does not understand Quantum Mechanics".

Someday some smart kid will have an epiphany and will provide an explanation that makes sense, but then that will simply introduce new questions. And thank god for that. Woe to us the day we run out of questions to ask.

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#65
In reply to #63

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 6:16 PM

Actually experiments never show a scientific theory is correct, only that it has not been disproven. So the idea that a theory is proven correct by an experiment is absolutely incorrect, it is only accepted because a substantial body of experimental testing of the theory has not disproved it. You can not prove a theory is correct through experimental testing.

Also, i am not sure that it is a valid position to take that theories don't get replaced. while I can not think of any immediately, I am sure there are at least a few accepted scientific theories that have been replaced at some time in our history. Hmm, maybe the whole conservation of momentum versus conservation of energy issue, where for a time momentum was the more accepted until disproven through experimental testing.

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#66
In reply to #65

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 6:49 PM

You are correct that experiments cannot "Prove" a theory. However you are incorrect that scientific theory cannot be correct. I believe because you have a misconception of what "correct" means. The websters dictionary definition of correct is:

conforming to an approved or conventional standard or conforming to or agreeing with fact, logic, or known truth

Notice nowhere in the definition does it says "correct" means proven. When I say that a scientific theory is correct, I'm saying that it has achieved a level of probability of being true or that it conforms with experiment to a significant extent, so much so that that it would be an illusion of extraordinary proportions if it were found to be wrong.

If in my above posts I used the word "proven", you are quite right to correct me. If I did use that term, which I could have easily done, I'm not going to go back and check if I did, then I was being sloppy.

Nevertheless, to say a scientific theory is correct is perfectly acceptable based on the definition of correct.

You Wrote:" Also, i am not sure that it is a valid position to take that theories don't get replaced. while I can not think of any immediately, I am sure there are at least a few accepted scientific theories that have been replaced at some time in our history."

Some theories are replaced, but not all theories are equal. Quantum mechanics and relativity are the most precisely experimentally tested theories ever. It is literally more likely that F=ma is wrong than Quantum Mechanics is wrong. What I'm saying is, there is a level of precision of experimental evidence where we know that "ok, even if there is another theory, it will somehow reduce to this theory under certain conditions". We have long reached that point with Quantum Mechanics (and Relativity for that matter).

Now string theory on the other hand hasn't be experimentally proven, and though it is a widely supported theory, it easily could be replaced in the future. Thus the book "Not Even Wrong". The steady state model of the universe was replaced by the big bang model. The steady state model had even had some experimental support, but only a little. Eventually experiments caught up with the theory and showed expansion. Good science.

So please be careful. There are theories and there are theories. Just as there is a chance I'll wake up tomorrow in my bed and a chance I'll wake on the top floor of the Trump tower. Obviously those two chances aren't even remotely equivalent.

Unfortunately, if you are unfamiliar with the math and history of theories, you don't know which is "pretty much determined" and which is "snowball's chance in hell". That is a major source of disconnect between scientists and the general public.

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#67
In reply to #65

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 6:57 PM

Scientific theories have been replaced many times. You may remember the ancient Greek (Ptolemy or was it Archimedes) scientific theory that the four elements that made up everything are air, earth, water and fire. Then there was that idea that electromagnetism was an effect from the aether.

While you are correct that you cannot prove a theory through experimentation, you certainly can disprove a theory with experimentation. There is one significant positive thing that experimentation does to a theory that many laymen don't quite grasp and that I wished Science would give these theories a new title to show their significance.

Sometimes a Scientific theory predicts something that nobody has noticed before. Sometimes this is because technology is not yet capable of permitting this observation or just that nobody has bothered to look under that particular rock before the theory was presented. In either case if the predicted phenomena is not found then scientists look for a better theory, question the experiment, reinterpret the theory and/or do all the normal things that scientists do when a mystery appears. What bothers me is that when the prediction correctly identifies the previously unnoticed phenomena we now call this.... a theory. Scientists don't even grant this the honor of calling it a confirmed theory. Confirming a theory does not prove a theory. But a confirmed theory is clearly more credible that we understand the underlying mechanism than the mechanism implied of an unconfirmed theory.

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#68
In reply to #67

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 7:11 PM

The reason scientists don't use a term like "confirmed theory" is because the line at which a theory would be considered "confirmed" would be arbitrary. The use of the term theory is a reminder of what RCE was saying, when using induction, nothing is ever truly proven.

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#69
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 7:25 PM

I think that you're evading my point. Then again most scientists I found dismiss a point they don't understand. Evolution and Creationism are both theories. The aether and QED are both theories. Jimmy Hoffa had JFK killed on J. Edgar Hoover's order, now that's a theory.

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#70
In reply to #69

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/13/2011 7:27 PM

If I am, it's not intentional. Please restate your point and I'll try to address it.

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#80
In reply to #70

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/15/2011 6:30 PM

I took a little extra time to formulate a better approach for my proposal, I hope this works.

I think that Science needs to start using a clarifying adjective to identify the accepted quality of a theory. I earlier proposed the poor adjective of "confirmed" to accompany the term, theory. You correctly identified that this adjective implies added layers of assurance that should not be granted to a theory. Confirmed is too close in meaning to the term, proven, that it will just apply a bias much farther than I intended. I'll hold off on my proposed new adjective for now just so I can focus on the concept and not the verbiage.

Actually you yourself inadvertently touched on the point I was trying to make. In your reply that just preceded my proposal you stated that Newton's law of motion, F=ma, is more likely wrong than Quantum Mechanics. This is because QM has more of the quality I'm talking about than Newton's earlier theory. And yet both theories have accurately predicted things that were not observed prior to their use. It's not that QM has predicted more events than Classical Mechanics. CM has been around for a lot longer than QM, so CM has a big head start. The difference is that QM just as accurately predicts phenomena that CM accurately predicts but QM also accurately predicts many of the things that CM fails to accurately predict. If the mathematics of QM wasn't so complicated, I'm sure that CM would have been relegated to the archives long ago. This is not to say that QM is perfect and that it explains all known Physics phenomena. But the anomalies of QM are a much smaller set than the anomalies of CM.

Getting back to my word choice, as I said earlier "confirmed theories" implies more than it should. How about these two mechanics theories being both realized theories, but QM has more realizations than CM. In contrast there are two different contrasts for theories. String theory would be considered an unrealized theory for while it is still consistent with earlier theories, it has yet to realize any new predictions. Then there's the refuted theory, like the steady state universe theory or the flat Earth theory, where many predictions prove to be grossly wrong.

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#81
In reply to #80

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/15/2011 7:20 PM

Certainly you make a valid point that there is no way for the layman to know what theories are more accepted among scientists (based on experiment) than others.

There is something called Bayesian Hypothesis Testing that does something of the sort. But I am now wandering into territory where I am not well informed.

http://en.wikipedia.org/wiki/Statistical_hypothesis_testing

I think this will make an interesting post in my blog. I'm currently writing a series of blogs on the history of the scientific method. After that series I wanted to then write a blog called "modern misconceptions of the Scientific method". Perhaps a good one after that would be "possible improvements to the scientific method" where this idea could be investigated and discussed more fully.

I do want to hedge a bit and warn that any sort of "clarify adjective" or "Bayesian Hypothesis Testing Score" runs the risk of being a little arbitrary. It's sort of like giving a numerical value for beauty. We all know when we see something beautiful, but how do we quantify or score that beauty impartially? Certainly one could use symmetry measurements and tricks like that, but it doesn't quite capture the whole concept of beautiful. In the same way, the "correctness" of a scientific theory based on experimental evidence might be hard to capture in a quantifiable way.

Still, it is a problem within science worth discussing.

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#83
In reply to #69

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/16/2011 11:10 AM

Actually neither evolution or creationism would rise to the standard of scientific theory. Evolution would be something more along the lines of a scientific observation or concept, as it still lacks a rational proof in a logical language. Creationism, doesn't meet any criteria at all for a scientific theory, it is fairly irrational and contradictory to observed evidence. The standard to mee for a true scientific theory is quite rigorous for the hard sciences, this is why there is an issue with the soft "science" like biology and sociology (the dual standard in terminology).

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#84
In reply to #83

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/16/2011 12:00 PM

No, Biology is a real Science. Evolution is a realized theory that has revealed many observations that were not known prior to the application of this theory. It can and has been said that it is only once Physics accepted the random processes and uncertainty of Quantum Mechanics that it reached the level of the real Science of Biology instead of just the fundamentals of Engineering mechanics. (I wish I could remember who said this. Well at the very least, I say it.)

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#87
In reply to #84

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/16/2011 2:01 PM

That doesn't even approach the definition of scientific method, Just espousing some crazy rhetoric to be accepted doesn't mean you strictly meet the criteria set forth by the method. Accomplishing a few elements of the method while totally avoiding all others, doesn't classify something as a science. Otherwise pretty much anything can be classified as a science if they so desire. What differentiates Biology from Sociology, Religion or Cosmetology even? If you observe something and comment on that observation that doesn't make your comments a scientific theory. Lawyers in practice make "rational arguments" all the time and they can be conflicting arguments solely because of the ambiguity of the langauge used to express the arguments. I don't believe lawyers arguments in court cases are classified as scientific theories, or meet the standard though many are more rationally established based on observations than many ecological biology theories regarding habitats and species preservation (As a matter of fact many biological theories regarding species preservation and maintaining habitats be contradictory to the theory of evolution).

Randomness is expressed in quantum mechanics in a rational theory expressing the mechanics of a system utilizing a logical language, mathematics, from which accurate and precise prediction may be developed. It was peer reviewed by numerous physicists, including dissenters like Albert Einstein, all of whom found no fault with the argument based on the current observations of how the system behaved (though einstein did not like the argument because of its inherent lack of lets say elegance). It has subsequently be tested numerous times through experiments explicitly meant to test the validity of the theory and disprove it if possible (this is the only way to test a scientific theory, so it is the first sign that someone is not practicing science when they conduct experiments designed to prove a theory). Quantum mechanics while not the best symbol of a scientific theory, unlike relativity. It is accepted as the best we can approach at this time to representing the mechanics of the system because of what we do not know about the systems history. There are attempts ongoing, since Einstien to develop a more precise theory that more properly represents the mechanics of the system. There is absolutely nothing in common to the approach to the development of a biological "theory" and the scientific method taken to develop of quantum mechanics.

Soemthign else to consider, statistical analysis in engineering is an extremely old practice, that is incorporated regularly to account for variability due to unknown factors. in Quantum mechanics expression of randomness it is much more consistent with engineering in the approach to unknown factors for evaluating the variability in engineered quantities, reliability analysis, or other engineering anaylsis that all consider the factor we can not quantify that contribute to variability in the system, and how much that variability may be constrained. Quantum mechanics constrains that variability to h bar over 2. However, a far better approach to the scientific method is that in developing relativity. You observe something, develop a concept of the mechanics, develop a rational argument from which precise and accurate prediction based on the argument can be developed, express that argument in a logical language, have the arguments peer reviewed for rational flaws, then conduct experiments specifically designed to disprove the theory by testing the precision and accuracy of prediction made from that theory, after some number of very extensive tests are conducted that do not disprove theory it becomes accepted. Essentially all biological theories repeated fail to complete this process in to meet the criteria of a scisentific theory, with possibly the exception of early genetics (which has different roots than other fields of biology).

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#89
In reply to #87

Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/16/2011 2:29 PM

There is literally tens of 1000s of experimental observations that support evolution. DNA base evidence. Fossil based evidence. Cell biology based evidence. Medical evidence.

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#92
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Re: How Light Regains its Velocity After Passing Through a Denser Medium?

05/16/2011 7:15 PM

A. You answered your own response by using the statement supported by experimental observations. That doesn't necessarily qualify or disqualify it as a scientific theory, it just forms the basis from which you would begin to postulate a theory. All you can ever do with regards to a scientific theory is test it in experiments designed to disprove it. There are theories about many things that do not qualify as scientific theories. Some guy observed that blood letting seemed to have some effect that for a time was positive in the past, and begin to use it in general, others followed, and it became a practice for everything. It took a long time for them to realize the negative effects, because it was observed in some cases to hav had a positive effect in the past and no one questioned its applicability, when under a scientific approach it would have been disproven quite rapidly by the dead bodies piling up (blood letting as a general solution to all ailments was a medical theory based on inital observations).

B. DNA evidence doesn't necessarily support evolution (or disprove it, except in specific cases), frequently it disproves certain aspects of evolution, like how fast evolution can occur and sometimes how things perceived as evolutionarily distinctive are actually genetically closer than those that biologist would classify as being more closely related. Cell biology is actually explained in a manner to make it fit to evolutionary theory at the time it is developed, not the reverse. Also, many of the estimates for things like mutation time and such are just rough estimators derived from a very limited number of observations for a few species that are applied broadly to draw conclusions about what DNA results meanings are in relations to evolution of species. We actually adapt the results of DNA testing and twist the findings to support whatever interpretation is commonly held by the biological establishment. Also, we create explanations to make sense in relation to evolutionary theories as to why cell biology is so distinctive. Just 20 years ago archaea were a type of bacteria, now they have been determined after molecular biology and biochemical analysis to be distinctive having some evolutionary traits in common with animals that bacteria haven't yet evolved. The only way to test evolution is to make a prediction based on it and test that prediction such that you see consistent repeatable results (repeatable is extremely important, ask the cold fusion guys). Say something like if all the wolves go extinct in an area the coyotes will evolve traits that make them much larger physically more adept to hunt down the prey animals wolves used to feed on, or maybe theat the elk devolve their horns with in 10 generations as they no longer suffer predation from wolves. You make that prediction and if it doesn't come true in the time schedule predicted then you just have disproven the theory and it is not a valid theory. You could have 10 million observed cases which fit the theory and never prove it (the proof is the rational argument of the theory in a unambiguous logical language), and only one observed case though is needed to disprove it. Just because something kind of sounds reasonable and it is constantly updated to stay current with the evidence gathered doesn't qualify that as a theory, as stated earlier, lawyers make rational arguments all the time based on observed evidence collected to that time, and there have been a number of people falsely imprisoned. It is much like DNA evidence can never proven absolutely a person committed a crime, it can only demonstrate that they did not commit a crime in certain types of cases. Observations can never prove a scientific theory, only disprove it or form the basis from developing a theory.

Engineering on the other hand can take observations, fit a equation and maybe a variance to some observed data, then assume that is a engineering theory.

This is actually really simple and fundamental to scientific method.

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