The Naked Scientists

The Naked Scientists Forum

Author Topic: How does light speed up when it exits a denser material?  (Read 27033 times)

Offline timey

  • Neilep Level Member
  • ******
  • Posts: 1297
  • Thanked: 7 times
    • View Profile
    • Patreon
Re: How does light speed up when it exits a denser material?
« Reply #50 on: 05/08/2015 11:39:32 »
JeffreyH :) You wouldn't be the first person to say I have trouble expressing myself.  Thank you very much for the positive comment!
 

Offline timey

  • Neilep Level Member
  • ******
  • Posts: 1297
  • Thanked: 7 times
    • View Profile
    • Patreon
Re: How does light speed up when it exits a denser material?
« Reply #51 on: 05/08/2015 14:29:30 »
A further point of interest might be found in the consideration of whether or not the changes in the rate of time themselves are delivered in quantum packages...

(Edit: Light traveling through changes in the gravity field being the main point of relevance here)
« Last Edit: 05/08/2015 16:21:03 by timey »
 

Offline timey

  • Neilep Level Member
  • ******
  • Posts: 1297
  • Thanked: 7 times
    • View Profile
    • Patreon
Re: How does light speed up when it exits a denser material?
« Reply #52 on: 05/08/2015 18:29:18 »
Anyway, since no one wishes to 'engage' in actual discussion about my speculations, I will make this my last post here on the subject.  I do monologues in my head all day long.  It's boring.

I just want to point out that although it may seem as though I am arguing in favour of classical physics in my questioning of the mathematical structure of Planck's h constant, whereas it is a logical consideration that 'perhaps' the quantum nature of his measurements "may" be ironed out by my suggestion - it is also just as logical to assume that any re-measuring of Planck's derivation of the h constant, under the remit of the quantum worlds own time structure and rate of time, could 'also' result in evidence of a quantum nature...but 'perhaps' a more 'readable' quantum nature than we have now.

IF it did become clear that the quantum world is subject to 'differently oriented' time structure/s, logical process denotes that this avenue of investigation through time dilation considerations could 'perhaps' either lead to quantum being united with classical physics or quantum being united with gravity.
 

Offline Bill S

  • Neilep Level Member
  • ******
  • Posts: 1806
  • Thanked: 11 times
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #53 on: 05/08/2015 22:59:16 »
Quote from: Timey
IF it did become clear that the quantum world is subject to 'differently oriented' time structure/s, logical process denotes that this avenue of investigation through time dilation considerations could 'perhaps' either lead to quantum being united with classical physics or quantum being united with gravity.

I think I see what you are suggesting here, but you may have to come up with a sound argument in favour of 'differently oriented' time structure/s in order to spark the interest of the experts, or even the general run of posters.
 

Offline timey

  • Neilep Level Member
  • ******
  • Posts: 1297
  • Thanked: 7 times
    • View Profile
    • Patreon
Re: How does light speed up when it exits a denser material?
« Reply #54 on: 05/08/2015 23:17:29 »
Well yes... The best I can do is re-iterate a passage from an earlier post...

"IF we can view gravity fields on a smaller scale, as in our own personal gravity field, ie: if we get fatter we feel heavier, if we go to the moon we feel lighter... on the basis that a black hole will change the rate of time fairly drastically, 'maybe' the gravity fields of the quantum world are 'differently oriented' in relation to to time dilation." 

And point to the suggestions of questioning Planck's h constant and looking at the changes in the rate of time being quantised as to being avenues of potential investigation.

NIST have been stringently testing time dilation.  Of course it is a matter of what tests they run and why, I have not heard of any further tests planned.

One is either inspired or not, I guess.  Thanks for the reply Bill.
« Last Edit: 05/08/2015 23:23:59 by timey »
 

Offline timey

  • Neilep Level Member
  • ******
  • Posts: 1297
  • Thanked: 7 times
    • View Profile
    • Patreon
Re: How does light speed up when it exits a denser material?
« Reply #55 on: 08/08/2015 22:35:07 »
Bill... I've been giving some thought to your comment on coming up with a sound argument in favour of the quantum world being subject to a different time structure or different time structures than our own, ie: a different rate or different rates in the occurrence of time.

There is conclusive evidence via NIST that even the slightest change in a gravity field will change the rate time occurs at.  When one is dealing with such minuscule fractions of a second such as Planck's h constant, the tiniest change in the length of a second will indeed affect the measurement of a length (edit: if that length measurement is in relation to momentum.)

We are inured, due to current thinking and experimentation as of date, to only consider the change in a gravity field due to 'elevation'.  Admittedly, it is very hard to make tests on a gravity field.  However... the phenomenon of time dilation 'could' prove to be an excellent window into the subtleties of the gravitational phenomena.

IF one were interested in reconciling the world of quantum with classical physics, in examining the gaps between the quantum leaps one 'might' try stretching or shrinking the length of a second until the quanta are delivered smoothly.  Taking the length of the second that this is achieved at and relating it to the NIST experiments, this 'may' unlock further secrets of the gravitational phenomenon.

On the other hand, IF one were interested in uniting quantum mechanics with gravity, then one 'might' examine the possibility of the changes in the rate of time being quantised, and look at the changes of the frequency in light being caused by the changes in the rate of time. (photon with no mass)

Whichever takes your fancy... Fact is that if you mathematicians can get your heads around using different lengths of a second when appropriate in your equations, then your mathematics will gain more depth and transform from being 2 dimensional to 3D. 

Mathematics gone IMAX, if you like...
This giving your maths much more 'reach'.
« Last Edit: 09/08/2015 00:30:21 by timey »
 

Offline evan_au

  • Neilep Level Member
  • ******
  • Posts: 4106
  • Thanked: 245 times
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #56 on: 10/08/2015 21:42:26 »
Quote from: lightarrow
have a look at: http://www.sheffield.ac.uk/polopoly_fs/1.14183!/file/photon.pdf
Thanks for that link. Over the past week, I have read these 6 essays on “What is a Photon?”. I learnt quite a lot about the quantum nature of light, and where the boundary is drawn between classical and quantum representations of light.

As I now understand it:
  • Maxwell’s  equations allow light to carry any energy at any frequency.
  • However, quantum theory tells us that there is a minimum energy for light, E=hf. This minimum quantum of energy is called a photon.
  • Maxwell’s equations work for high intensity light as it is propagating through space (or glass); in this case you can ignore the quantisation of energy.
  • Maxwell did not predict photons – but someone forgot to tell the photons. A photon still obeys Maxwell’s equations as it is propagating through space (or glass).
  • A photon is described by its energy, spin/polarization and momentum (where momentum is a vector, giving the photon’s direction).
  • There was an interesting discussion about why quantum descriptions of the photon don’t ascribe a definite position vs time to the photon (apparently, this is beyond the usual fuzziness described by Heisenberg?).
  • The characteristics of entangled photons or parametric down-conversion is not described by classical optics.
  • Nor are photons which can take multiple paths through an optical bench.
  • Clearly, quantum representation of light is a more complete description of light than classical optics. 
Quote
how can you deduce that the photon which exits a piece of glass is the same which entered?
This example does not involve entangled photons, mirror mazes, Lamb shifts or Bose-Einstein condensates, so I don't think we need the full power of a quantum representation to crack this particular nut (mainly Planck’s hypothesis which quantizes the energy of a light beam into a stream of photons).
 
From classical optics, we can measure the polarization of a beam of photons striking a detector. In addition, using classical particle physics, we can determine the energy and position vs time of bunches of photons or individual photons (subject to diffraction limits and Heisenberg’s limits), allowing us to determine the path of a beam of photons on either side of the glass block.

A photon exiting a sheet of glass has the same energy, spin and momentum as the one which entered*. In the quantum world, if these parameters are the same, it is the same photon.

*The reverse is not necessarily true, because not all photons approaching a glass sheet will exit it towards the detector, due to classical effects like partial reflection, scattering and absorption.
 

Offline jeffreyH

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 3914
  • Thanked: 53 times
  • The graviton sucks
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #57 on: 10/08/2015 22:49:21 »
If we move away from photons for a second and consider particles with rest mass we can propose something interesting. I will state straight away that a particle with rest mass, if it could travel at c, cannot possibly have angular momentum. This is because the velocity of angular momentum would be summed to the straight line velocity giving an overall value > c. This reduction of angular momentum should relate directly to time dilation and should also be present in a gravitational field.
« Last Edit: 10/08/2015 23:00:09 by jeffreyH »
 

Offline jeffreyH

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 3914
  • Thanked: 53 times
  • The graviton sucks
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #58 on: 10/08/2015 23:04:46 »
This brings up the possibility that in the total absence of gravitation the photon would have no angular momentum.
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #59 on: 11/08/2015 13:07:34 »
Quote from: lightarrow
have a look at: http://www.sheffield.ac.uk/polopoly_fs/1.14183!/file/photon.pdf
Thanks for that link. Over the past week, I have read these 6 essays on “What is a Photon?”. I learnt quite a lot about the quantum nature of light, and where the boundary is drawn between classical and quantum representations of light.
As I now understand it:
  • Maxwell’s  equations allow light to carry any energy at any frequency.
  • However, quantum theory tells us that there is a minimum energy for light, E=hf. This minimum quantum of energy is called a photon.
  • Maxwell’s equations work for high intensity light as it is propagating through space (or glass); in this case you can ignore the quantisation of energy.
Ok.
Quote
  • Maxwell did not predict photons – but someone forgot to tell the photons. A photon still obeys Maxwell’s equations as it is propagating through space (or glass).
The problem is you cannot describe a photon as an electromagnetic wave, so, maybe what you say is true but I don't know how we apply Maxwell’s equations to a single photon.
Quote
[/li]
[li]A photon is described by its energy, spin/polarization and momentum (where momentum is a vector, giving the photon’s direction).
Quite. A photon never has an exact momentum and an exact energy, it's always in a superposition of states with different momentums and energies. A photon of a very collimated and monochromatic laser beam will have more precise momentum and energy, but a photon emitted from an excited atom will have less definite momentum and energy.
Quote
[/li]
[li]There was an interesting discussion about why quantum descriptions of the photon don’t ascribe a definite position vs time to the photon (apparently, this is beyond the usual fuzziness described by Heisenberg?).
I only know that it's very difficult to define a position operator for a photon, because of the fact it's impossible to find a frame of reference in which the photon is stationary.
Quote
[/li]
[li]The characteristics of entangled photons or parametric down-conversion is not described by classical optics.
[/li]
[li]Nor are photons which can take multiple paths through an optical bench.
[/li]
[li]Clearly, quantum representation of light is a more complete description of light than classical optics.  [/li]
[/list]
Quote
how can you deduce that the photon which exits a piece of glass is the same which entered?
This example does not involve entangled photons, mirror mazes, Lamb shifts or Bose-Einstein condensates, so I don't think we need the full power of a quantum representation to crack this particular nut (mainly Planck’s hypothesis which quantizes the energy of a light beam into a stream of photons).
 
From classical optics, we can measure the polarization of a beam of photons striking a detector. In addition, using classical particle physics, we can determine the energy and position vs time of bunches of photons or individual photons (subject to diffraction limits and Heisenberg’s limits), allowing us to determine the path of a beam of photons on either side of the glass block.

A photon exiting a sheet of glass has the same energy, spin and momentum as the one which entered*. In the quantum world, if these parameters are the same, it is the same photon.
In this sense, yes, but what I intended is: if an object enters a "black box" and it exits as (seemingly) the same, can we be sure that it wasn't destroyed somewhere inside the box and then re-created? In my opinion it's exactly what happens but I don't know QED enough to have a definite answer.
Nontheless you can be the one who is right.

--
lightarrow
« Last Edit: 11/08/2015 13:16:04 by lightarrow »
 

Offline timey

  • Neilep Level Member
  • ******
  • Posts: 1297
  • Thanked: 7 times
    • View Profile
    • Patreon
Re: How does light speed up when it exits a denser material?
« Reply #60 on: 11/08/2015 13:38:53 »
This brings up the possibility that in the total absence of gravitation the photon would have no angular momentum.


Ok, I've left you to think about that one for a bit, but for me it becomes clear that the 'reasoning' is a catch 22.  Because if light has no angular momentum in a 0 gravity field, the implications of this are that the speed of light is only constant to the strength of a gravity field.  We experience the speed of light as we do in our gravity field and we appreciate that light 'can' move slower.  What happens in a gravity field that is greater than our own?

For me this leads to questioning the fact of the speed of light being the uppermost speed limit of the universe, but if you 'do' consider this, then it requires a complete re-assessment of the current view of the mechanics of the universe... But that's just my humble take and I'd be interested to know what 'takes' others may have...
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #61 on: 11/08/2015 16:10:28 »
If we move away from photons for a second and consider particles with rest mass we can propose something interesting. I will state straight away that a particle with rest mass, if it could travel at c,
But it can't, so every consequence of an incorrect assumption have to be incorrect.
Quote
cannot possibly have angular momentum. This is because the velocity of angular momentum would be summed to the straight line velocity giving an overall value > c.
This is not true, velocities composition is not a mere sum, relativistically.

--
lightarrow
 

Offline timey

  • Neilep Level Member
  • ******
  • Posts: 1297
  • Thanked: 7 times
    • View Profile
    • Patreon
Re: How does light speed up when it exits a denser material?
« Reply #62 on: 11/08/2015 16:44:35 »
But lightarrow, what if they could?

What IF relativity has its place in describing motions relative to each other in relation to the observer but is inadequate when describing the universe. (There is evidence of this)

IF a particle 'can' travel faster than the speed of light, then I suspect that we have just arrived back on the doorstep of the importance of using the appropriate length of a second to calculate momentum, and we can go on to see that the 'distance travelled' then becomes quite 'interesting'.
« Last Edit: 11/08/2015 16:46:26 by timey »
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #63 on: 12/08/2015 12:43:15 »
But lightarrow, what if they could?
What IF relativity has its place in describing motions relative to each other in relation to the observer but is inadequate when describing the universe. (There is evidence of this)
Do you mean if you can accelerate a massive object to light speed without having to use infinite energy? And what if we all were blue angels with green wings and bright eyes? :) If physics doesn't count, everything is allowed, isnt'it?
Of course physics is not "static", it evolves and maybe what you say could even be true in a remote future, but in this forum we should talk of what we know and of what is possible, not of any idea which we can have in our mind, in my opinion.
Quote
IF a particle 'can' travel faster than the speed of light,
Not if its mass is different from zero (and real).

--
lightarrow
« Last Edit: 12/08/2015 12:47:23 by lightarrow »
 

Offline timey

  • Neilep Level Member
  • ******
  • Posts: 1297
  • Thanked: 7 times
    • View Profile
    • Patreon
Re: How does light speed up when it exits a denser material?
« Reply #64 on: 12/08/2015 15:49:25 »
Erm, no lightarrow... what I was thinking about (in relation to Jeff's 'experimental speculation') with regards to particles with rest mass - was a situation where a very massive body (black hole) jets very small bodies of mass (particles) into space - potentially at a rate faster than the light speed we experience on earth. This being on the basis - (again in relation to Jeff's 'experimental speculation' on light experiencing no angular momentum in a 0 gravity field) - that the speed of light, in relation to a more massive body of mass than earths, 'may' (speculative) be going faster. This being 'a' logical progression of such speculations...and that these particles in that situation would have no trouble reaching 'our' speed of light, but would not be able to reach the faster speed of light of their own reference frame (this being the black hole), for the same reason that the same particles could not reach the speed of 'our' light in our reference frame of earth.

These 'speculations' are born of the 'very real' possibility that the mathematics of quantum are operating minus an important factor - this being time dilation.  IF this is true, (speculative) then logically speaking the implications of this 'may be' that the changes in the rate of time are 'responsible' for the changes in the frequency of light - rather than current view which is that  the changes in the gravity field itself are responsible for redshift/blueshift. This current view actually being based upon the 'speculative' basis of a photon having 'relativistic' mass.

Of course to think in 'these alternative terms' does require one to consider the phenomenon of time as a 'force', (a phenomenon that does something).  And to conduct a rethink as to the current view of time dilation and how it works.

I take on board your comment about 'real physics', and point you in the direction of Lee Smolin's book, "The Trouble With Physics".  Physics is very far from being in possession of the whole picture.

Perhaps it might be better if I took my speculations back to my own thread... I'm open to suggestion... however I myself would find this to be a shame... There is some good 'form' written above and so long as everybody is 'aware' that these consideration are but 'speculations', I think we are ok...personally.

I think it also worth mentioning that 'most' people are not aware that a lot of the concepts that are being discussed as "proper physics" are in fact hardly based on anything but speculation and supposition themselves.
 

Offline evan_au

  • Neilep Level Member
  • ******
  • Posts: 4106
  • Thanked: 245 times
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #65 on: 12/08/2015 22:33:34 »
Quote from: timey
a very massive body (black hole) jets very small bodies of mass (particles) into space - potentially at a rate faster than the light speed we experience on earth
Superluminal jets have been known since the 1970s. They are believed to be associated with black holes, but it is thought that they are explainable within relativity.

Quote
possibility that the mathematics of quantum are operating minus an important factor - this being time dilation
Einstein's relativity was well-known by 1920. From the late 1920s, efforts were made to integrate relativity (including time dilation) into the new field of quantum mechanics.

With particle accelerators like the LHC operating so close to the speed of light, and the collision debris also travelling near c, particle physicists have to consider relativistic effects on a day-by-day basis (and their computers need to deal with it many times per microsecond).
 

Offline timey

  • Neilep Level Member
  • ******
  • Posts: 1297
  • Thanked: 7 times
    • View Profile
    • Patreon
Re: How does light speed up when it exits a denser material?
« Reply #66 on: 12/08/2015 23:19:11 »
True enough... However the stark, in your face facts remain that quantum, all these years later is not reconciled with gravity, relativity, all these years later does not 'fully' describe the universe, and Planck's h constant was derived before it was possible to 'measure' time and time dilation with such great accuracy... And LHC, despite its multitude of funding, hasn't really brought the situation much further along at-all considering...

So...where do you go from there?

Can you explain what the efforts made to integrate time dilation into quantum mechanics consisted of?  Were they successful?  And why is it that time dilation is thought to be relativistic?  It's an actual phenomenon of the universe and does not need relativity to explain it...
 

Offline chiralSPO

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 1872
  • Thanked: 143 times
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #67 on: 13/08/2015 00:52:39 »
True enough... However the stark, in your face facts remain that quantum, all these years later is not reconciled with gravity, relativity, all these years later does not 'fully' describe the universe, and Planck's h constant was derived before it was possible to 'measure' time and time dilation with such great accuracy... And LHC, despite its multitude of funding, hasn't really brought the situation much further along at-all considering...

So...where do you go from there?

Can you explain what the efforts made to integrate time dilation into quantum mechanics consisted of?  Were they successful?  And why is it that time dilation is thought to be relativistic?  It's an actual phenomenon of the universe and does not need relativity to explain it...

Can you give some concrete examples of where quantum falls short? I don't mean "it's not elegant" or "it doesn't make sense" or "disagrees with gravity or relativity." In which situations do they disagree? How much different are their predictions, and which one is right? (if "neither" you have to explain how the correct answer was determined).

Then we focus our attention on those descrepancies.
 

Offline jeffreyH

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 3914
  • Thanked: 53 times
  • The graviton sucks
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #68 on: 13/08/2015 01:05:40 »
If we move away from photons for a second and consider particles with rest mass we can propose something interesting. I will state straight away that a particle with rest mass, if it could travel at c,
But it can't, so every consequence of an incorrect assumption have to be incorrect.
Quote
cannot possibly have angular momentum. This is because the velocity of angular momentum would be summed to the straight line velocity giving an overall value > c.
This is not true, velocities composition is not a mere sum, relativistically.

--
lightarrow

We use imaginary and complex numbers as a way to determine eigenvalues. Those numbers don't exist and yet they are used. We use the impossible to find the possible so why not use the impossible with respect to the speed of light? If you take a spiral, it moves along a straight line path as well as an angular path. If we project each infinitesimal point from the spiral path onto the straight line path we can see that the path of the spiral is moving faster than the straight line path is indicating. It travels a greater distance. We need to add the difference to get the correct result. This is very like the change in wavelength of light in a gravitational field. As the length in the direction of travel contracts then so the energy path through space increases as if light still has to travel a set distance in another way to compensate. This is an unproven speculation but it answers some questions about how real the wave function might actually might be.
 

Offline timey

  • Neilep Level Member
  • ******
  • Posts: 1297
  • Thanked: 7 times
    • View Profile
    • Patreon
Re: How does light speed up when it exits a denser material?
« Reply #69 on: 13/08/2015 04:07:28 »


Can you give some concrete examples of where quantum falls short? I don't mean "it's not elegant" or "it doesn't make sense" or "disagrees with gravity or relativity." In which situations do they disagree? How much different are their predictions, and which one is right? (if "neither" you have to explain how the correct answer was determined).

Then we focus our attention on those descrepancies.

Ok, quantum gives a description of everything except gravity and relativity is a theory of gravity.  Relativity 'needs' the so far unknown and unseen (there are perhaps hints in The Bullet Cluster, unproved) additions of dark matter to make it work outside the solar system... and dark energy to expand the universe.  It falls short at black holes, where the time vector has to be swapped with a distance vector in the space time matrix.
If relativity could be reconciled with quantum, apart from the other niggly matters, we'd be close to a fully operational and unified theory, except for the fact of what happens inside and before the Big Bang.

Unfortunately relativity cannot be reconciled with quantum.  If it could, I'm pretty certain that after the 100, give or take a few, years since the discovery and progression of quantum, that the means to do so would already have been discovered by now. (Hence, I imagine, the emergence of the hugely funded String Theory saga)

The suggestion that I made in post 49, bottom of page 2, IF relevant, 'could' give an insight into either reconciling quantum with gravity or reconciling quantum into the sphere of classical physics.

The 'proposed' discrepancy being: In the questioning of the mathematical structure of Planck's h constant in relation to there possibly being a time dilation factor within the quantum region and exploring how this 'could ' affect or change our perception of the phenomenon of light with regards to energy and frequency in relation to time dilation, and time dilations relationship with the gravitational field.

(Sorry, I'm not sure about the 'predictions' aspect of quantum, so I won't comment there)

(Edit: The predictions of relativity have been pretty right on so far, therefore I don't think that there is 'all' that much wrong with it... although clearly, considering the non-unification of both working hypothesis, quantum and relativity, there must be some aspect of it that 'is' slightly off.  Personally I feel that the time dilation aspect of relativity is misconceived, at fault, and in need of further investigation.)
« Last Edit: 13/08/2015 05:16:03 by timey »
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #70 on: 13/08/2015 08:13:47 »
Quote from: jeffreyH link=topic=50714.msg465295#msg465295

We use imaginary and complex numbers as a way to determine eigenvalues. Those numbers don't exist
No, you are wrong. They exist as numbers, but not only! Quantum description of nature is impossible without them and this suggests they are more deeply "ingrained" with reality.
Quote
and yet they are used. We use the impossible to find the possible
You are making a big mistake. What is real is the result of a measure of an observable; since observables are associated with hermitian operators and these have (mathematically) real eigenvalues, the result is a real number (not a complex one).
Quote
so why not use the impossible with respect to the speed of light? If you take a spiral, it moves along a straight line path as well as an angular path. If we project each infinitesimal point from the spiral path onto the straight line path we can see that the path of the spiral is moving faster than the straight line path is indicating. It travels a greater distance. We need to add the difference to get the correct result.
But, be it a spiral or what you want, in relativity, and I've already wrote it, velocities don't sum up.

--
lightarrow
« Last Edit: 13/08/2015 08:16:20 by lightarrow »
 

Offline timey

  • Neilep Level Member
  • ******
  • Posts: 1297
  • Thanked: 7 times
    • View Profile
    • Patreon
Re: How does light speed up when it exits a denser material?
« Reply #71 on: 13/08/2015 10:58:19 »
Well lightarrow, to say so I'm going to reply to your post above even though it isn't directed at me, because that is something I can do, in the hope that Jeff is busy doing some mathematics, which I can't do.

Your reasoning is coming over as slightly cockeyed.  It is, as Jeff stated, perfectly normal to use imaginary numbers (and therefore imaginary concepts, which are actually also mathematical in practice) to equate and then renormalise, whether dealing with quantum or classical physics.  I believe it is actually the basis of Gauge theory. (although I do stand to be corrected, as I'm otherwise unfamiliar with Gauge theory.) The link below is quite interesting with regards to rest mass and the photon.

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html

If Jeff is considering rest mass then he 'is' operating within the region of quantum, and your reasoning does not hold.  If imaginary numbers can be used to determine the reality of the hidden quantum world, then logic derives that imaginary concepts may also be used in a similar fashion.

We can no more 'prove' that a particle of any kind can or cannot reach the speed of light in a reference frame of a greater gravity field than our own, than we can prove if a photon has mass or not.  Therefore, as with the photon, any concept can be 'experimented' with, so long as one keeps track and renormalises as appropriate.  It may even turn out that to do so 'could' reveal some other hidden reality of our universe as indeed you have stated using imaginary numbers reveals the reality of quantum!

You say that velocities do not sum up, I don't pretend to understand 'exactly' where you are coming from with this - I'm sure I might not be the only one, could you please explain?
« Last Edit: 13/08/2015 11:01:06 by timey »
 

Offline jeffreyH

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 3914
  • Thanked: 53 times
  • The graviton sucks
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #72 on: 13/08/2015 11:51:27 »
Yes you are correct that in relativity it is more complex.

https://en.wikipedia.org/wiki/Velocity-addition_formula

However I am attempting to gain a better understanding of some issues.
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: How does light speed up when it exits a denser material?
« Reply #73 on: 13/08/2015 12:59:08 »
Well lightarrow, to say so I'm going to reply to your post above even though it isn't directed at me, because that is something I can do, in the hope that Jeff is busy doing some mathematics, which I can't do.

Your reasoning is coming over as slightly cockeyed.  It is, as Jeff stated, perfectly normal to use imaginary numbers (and therefore imaginary concepts,
Imaginary numbers exist, as numbers; what do you mean with "imaginary concepts"?
Quote
which are actually also mathematical in practice) to equate and then renormalise, whether dealing with quantum or classical physics.  I believe it is actually the basis of Gauge theory. (although I do stand to be corrected, as I'm otherwise unfamiliar with Gauge theory.) The link below is quite interesting with regards to rest mass and the photon.

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html

If Jeff is considering rest mass then he 'is' operating within the region of quantum, and your reasoning does not hold.  If imaginary numbers can be used to determine the reality of the hidden quantum world, then logic derives that imaginary concepts may also be used in a similar fashion.
[?]
Quote
We can no more 'prove' that a particle of any kind can or cannot reach the speed of light in a reference frame of a greater gravity field than our own, than we can prove if a photon has mass or not.
In physics we can talk of what we know, not of what we don't know. But physics evolves and if now we say that a photon is massless, it doesn't mean "it's established that it will be so forever"! Physics (differently from phylosophy or else) can only describe what is known at the moment; everything else is speculation and not physics.
Quote
Therefore, as with the photon, any concept can be 'experimented' with, so long as one keeps track and renormalises as appropriate.  It may even turn out that to do so 'could' reveal some other hidden reality of our universe as indeed you have stated using imaginary numbers reveals the reality of quantum!
It may turn out everything, so this reasoning is meaningless.
Quote
You say that velocities do not sum up, I don't pretend to understand 'exactly' where you are coming from with this - I'm sure I might not be the only one, could you please explain?
If an object moves with velocity v1 with respect to a frame of reference S and S moves at velocity v2 with respect to another frame S' (v1 and v2 be parallel) then the object moves with respect to S' at velocity:

V = (v1 + v2)/(1 + v1*v2/c2)

As you see it's not a mere sum.
Try with v1 = v2 = c (or one of them = c and the other non zero) and then tell me what is V (you don't need to put numbers, you can leave the letters, the computation is immediate).

--
lightarrow
« Last Edit: 13/08/2015 13:07:51 by lightarrow »
 

Offline timey

  • Neilep Level Member
  • ******
  • Posts: 1297
  • Thanked: 7 times
    • View Profile
    • Patreon
Re: How does light speed up when it exits a denser material?
« Reply #74 on: 13/08/2015 13:52:58 »
Ok, well dark matter (which may have been observed - as yet unproven) and dark energy are imaginary concepts based on mathematical necessity.  It is only 'when' we observe their reality that they will come out of the 'theoretical' region.  Anything unobserved is an imaginary concept.  Any imaginary concept can have a basis in mathematics whether is becomes necessary as a result of mathematical necessity or as a theoretical necessity.  For instance we observe redshift and we have theorised that the fact of redshift means that a light source is moving away from us.  Although this concept is widely accepted as fact, this being because it is 'the' most logical reasoning in relation to our current understanding, but it is still an imaginary concept non-the-less.  Other theories concerning redshift have been extrapolated...I really can't be bothered to relate them here :) , suffice to say there are other imaginary concepts attached to the observation of redshift.  I could go on...and on :).

Yes, I agree, we can talk about what we know. (Edit: or what we think we know). In fact its all people ever do, I'm literally bored to tears over it!
If there had been no speculation about black body radiation we wouldn't have a quantum theory.  Logically speaking speculation is an absolute 'must' if progress is to be made, and the reality is that we 'actually know' very little, although we have 'theorised' immensely.  And we have taken the concepts of this theorising, the real and the proven concepts along side the theorised, and the therefore imaginary concepts and attached mathematics to them.  Mathematica isn't fussy you know, it's quite capable of calculating all manner of wrongness as well as wonderfully illuminating the right and the real.

The maths you have included (I'm not good with maths) are related to a particle or wavelength in relation to the momentum of another particle or wave length.  I don't see how this relates to a path taken by light round a spiral as opposed to a path taken by light in a straight line.  I didn't read it that Jeff was measuring 2 situations in relation to each other, just that if light took one path that it would not be the same as if it took the other, but I'll state again that I'm not at-all that mathematically adept and I may have misconceived his intent.  I stand to be corrected.  In a situation where the speed of light 'may' be slowed, or speeded up, when adding the concept of time dilation, for me it is the distance travelled that becomes interesting.
« Last Edit: 13/08/2015 14:18:55 by timey »
 

The Naked Scientists Forum

Re: How does light speed up when it exits a denser material?
« Reply #74 on: 13/08/2015 13:52:58 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums