[anasawad]

Its a ratio between speed and velocity or if you want it in easier terms, ratio between speed of movement and average speed of displacement or propagation. I answered that multiple times and i showed the background of the answer and why they're not the same thing.
Your refusal to accept basics definitions and ignoring the information posted is not my problem, its yours.
Anyone who bothers reading basic definition would know directly that this doesn't mean that the speed of light changes, but rather that the average displacement rate (i.e velocity) is lowered by interaction with the medium.

Since light is made of photons, energy. And photons interact with atoms. Generally absorbed by them.

So you can stop using circular logic as if i hadn't answered it, i answered it a dozen times and even went into the very details of it. You simply keep ignoring the answer and repeating the question as if it proves it self.

[Potemkin]

Yes, because velocity is not speed.

This is correct. Velocity is speed in a particular direction. If the direction changes but the speed does not, the velocity has changed but the speed has remained constant.

When you measure velocity in a medium its different than velocity in vacuum because it does not interact with anything in vacuum while it does interact with the medium if one exists.

This is also correct, but why not just call it "speed" rather than "velocity"? The important point is that the magnitude of its velocity changes when light passes from one medium into another. The magnitude of a velocity is just the speed.

Velocity is the distance divided by time in a given direction in a specific reference frame.

This is also correct.

Velocity of light changes, speed of light does not.

This is false. The only way that the velocity could change but not the speed would be if the direction of travel changed but the magnitude of its velocity did not. This is not what happens. The photons are absorbed and re-emitted by the atoms of the medium through which they are travelling. The "speed" of light through that medium is calculated as a macroscopic property of the medium (the refractive index is, after all, a macroscopic concept). The photons are, of course, travelling at c, the speed of light through a vacuum, when they are travelling at all, but the billions of absorption and re-emission events have the effect of making it seem, macroscopically speaking, as though the light has slowed down as it moves through the medium. After all, as Besoeker says, the refractive index is a dimensionless ratio. The units of the numerator and the denominator are exactly the same, and the physical property those units measure is exactly the same in both cases. You're dividing a speed by a speed.

[anasawad]

@Potemkin

This is false. The only way that the velocity could change but not the speed would be if the direction of travel changed but the magnitude of its velocity did not. This is not what happens. The photons are absorbed and re-emitted by the atoms of the medium through which they are travelling. The "speed" of light through that medium is calculated as a macroscopic property of the medium (the refractive index is, after all, a macroscopic concept). The photons are, of course, travelling at c, the speed of light through a vacuum, when they are travelling at all, but the billions of absorption and re-emission events have the effect of making it seem, macroscopically speaking, as though the light has slowed down as it moves through the medium. After all, as Besoeker says, the refractive index is a dimensionless ratio. The units of the numerator and the denominator are exactly the same, and the physical property those units measure are exactly the same in both cases. You're dividing a speed by a speed.

I already said that, just check former posts when i told what happens and why velocity changes.
Velocity does change if you consider it in reference of distance between 2 points.
Due to inability to measure all the absorption and re-emittions that happens, we measure the speed between 2 points, thus we measure time over distance. Basically using the very basic formula. Which is why we have "slower" velocity in results, because there is a delay.

When we measure velocity per displacement then yes it wont change, but due to inability we will have to measure it in a reference.

[Potemkin]

When we measure velocity per displacement then yes it wont change, but due to inability we will have to measure it in a reference.

Not sure what you mean by this, but I think the source of your confusion is that you are failing to grasp the idea that the whole concept of a "refractive index" is a macroscopic concept. We simply ignore the fact that the light is actually travelling at c, the speed of light in a vacuum, when it's travelling at all, and we ignore the fact that the light is undergoing countless absorption and re-emission events as it propagates through the medium. We're only interested in the macroscopic effects of the medium on any light that passes through it. All we are interested in is the macroscopic speed of the light through that medium, which is of course lower than the speed of light through a vacuum.

[anasawad]

@Potemkin

Not sure what you mean by this, but I think the source of your confusion is that you are failing to grasp the idea that the whole concept of a "refractive index" is a macroscopic concept.

Not really no, 'm not being confused about it, simply 'm not arguing about the refractive index rather about the speed of light. Specially since i build hand made custom cars and part of that job is to make specific types of glass depending on the order which includes all these measurments, so if we were to discuss these variables then i do know all about them.

We simply ignore the fact that the light is actually travelling at c, the speed of light in a vacuum, when it's travelling at all, and we ignore the fact that the light is undergoing countless absorption and re-emission events as it propagates through the medium.

Which is exactly what i said multiple times so far. For god's sake, i clearly stated that differenciation should be made and the details should be considered when arguing about the speed of light becuase using the casual terms is simply misleading.
When we say the speed of light in a medium, for someone not familiar it would be understood as if the speed of light which is a constant is changing, which is not. I literally said these exact same words in a previous post. Its called the speed of light but in reality, what we're measuring is the time needed for light to travel between 2 points in a medium. Thats why 'm putting emphasis on the term velocity and just a little ago i pointed out that we're talking about propagation, since its measurment without consideration of whats happening to the light it self. Thats why these terms are also emphasised in explanatory pieces. Because not knowing them would lead to misconceptions and would be generally misleading.

We're only interested in the macroscopic effects of the medium on any light that passes through it. All we are interested in is the macroscopic speed of the light through that medium, which is of course lower than the speed of light through a vacuum.

And the reason its lower is because of the delay it gets.
The photons them selves don't change speed, they constantly move at the speed of light "c". But when they're absorbed, they cease to exist for a period of time.

Again, 've been saying this all over the past posts, and its simply ignored as if it doesn't matter.
The speed of light, i.e the speed of which photons move at, is constant, and not a variable. Which is what the entire thread is about.

[Potemkin]

And the reason its lower is because of the delay it gets.

True, but so what? The whole concept of a refractive index is a macroscopic one, which means that we are not interested in what it actually happening on a microscopic level, at the level of individual photons and individual atoms and their actual interactions. The whole concept of a 'refractive index' is, as Einstein called scientific concepts in general, "a free creation of the human mind". It exists only inside our heads rather than 'out there' in reality. This is how science works - it's not some divinely revealed truth about the world, but is a particular way of approaching the world in order to make qualitative and quantitative predictions about the way the physical, observable world behaves. Nothing more.

The photons them selves don't change speed, they constantly move at the speed of light "c". But when they're absorbed, they cease to exist for a period of time.

Again, this is true but irrelevant.

Again, 've been saying this all over the past posts, and its simply ignored as if it doesn't matter.

It's been ignored because it really doesn't matter for the purposes of this discussion, which is about the definition of the refractive index and the fact that light macroscopically is perceived to propagate through various physical media at different speeds.

The speed of light, i.e the speed of which photons move at, is constant, and not a variable.

This is true, but the very definition of the refractive index of a medium is based on the simplifying assumption that the various microscopic interactions between photons and atoms don't matter and we can speak of the speed of light being slower when propagating through a medium than when propagating through a vacuum. It's a fiction, but it's a useful fiction, as every scientific theory is.

Which is what the entire thread is about.

You're the one who insisted on redefining the concepts of 'speed' and 'velocity' and throwing doubt on the whole idea of a 'refractive index'. Claiming that light has a different velocity but the same speed through a medium as it has through a vacuum is just plain wrong. We define the refractive index of a medium by dividing the speed of light through a vacuum by the speed of light through that medium. And that's that. Besoeker is right about this one.

[anasawad]

@Potemkin

BTW, Just to be clear.
I will continue to point out how stupid and perhaps even retarded the "argument" presented using the index of refraction to try to prove that the speed of light is not a constant but a variable, because its entirely irrelevant, and it is infact a fallacy to do so. And then to use it to reach a conclusion that is even irrelevant to the context in which its used is also a fallacy in it self.

So it should be kept in mind, that with all the fallacies used, and the circular reasoning in an irrelevant context that is being used.it is still nevertheless not presenting an argument about the speed of light being absolute or variable.

True, but so what? The whole concept of a refractive index is a macroscopic one, which means that we are not interested in what it actually happening on a microscopic level, at the level of individual photons and individual atoms and their actual interactions. The whole concept of a 'refractive index' is, as Einstein called scientific concepts in general, "a free creation of the human mind". It exists only inside our heads rather than 'out there' in reality. This is how science works - it's not some divinely revealed truth about the world, but is a particular way of approaching the world in order to make qualitative and quantitative predictions about the way the physical, observable world behaves. Nothing more.

Because it the entire thing of the refractive index is brought up to "prove" that the speed of light is not constant but rather variable.
This act in itself is a fallacy and an attempt of decieving any reader.

It's been ignored because it really doesn't matter for the purposes of this discussion, which is about the definition of the refractive index and the fact that light macroscopically is perceived to propagate through various physical media at different speeds.

No its not, the discussion is not about the refractive index, the discussion is about the speed of light.
The refractive index is brought up as a stupid attempt to show that the speed of light is not constant which is false.

You're the one who insisted on redefining the concepts of 'speed' and 'velocity' and throwing doubt on the whole idea of a 'refractive index'. Claiming that light has a different velocity but the same speed through a medium as it has through a vacuum is just plain wrong. We define the refractive index of a medium by dividing the speed of light through a vacuum by the speed of light through that medium. And that's that. Besoeker is right about this one.

Except i didn't redifine the definitions of concepts of speed and velocity.
I literally copy pasted the definitions at first so it is clear what they are and in what way they're used in this measurements, inorder to counter the usage of the refractive index to show variability of the speed of light.
And no, the velocity in this sense when measured in reference frame of 2 points differs when measured in vacuum and in a medium because velocity is measured without consideration of other factors.
Thats why in any source you'll find that they all make that point very clear and note that the speed of light is not changing.

[Potemkin]

Because it the entire thing of the refractive index is brought up to "prove" that the speed of light is not constant but rather variable.
This act in itself is a fallacy and an attempt of decieving any reader.

I agree with you. Anyone who tries to argue that the fact that light macroscopically travels at different speeds through various media 'proves' that the speed of light is a variable rather than a constant clearly doesn't understand the physical processes involved in the refraction of light. When a photon travels at all, it travels at c, the speed of light in a vacuum.

And no, the velocity in this sense when measured in reference frame of 2 points differs when measured in vacuum and in a medium because velocity is measured without consideration of other factors.

I'm sorry, anasawad, but this is just plain wrong. Speed is simply the magnitude of a velocity. And the speed of light through a medium is macroscopically less than the speed of light through a vacuum. Microscopically, of course, at the level of individual photons and individual atoms and their interactions, of course it isn't. But that doesn't enter into the definition of the refractive index. The refractive index is not a ratio between a speed and a velocity, but a ratio between a speed and another speed. Your distinction between speed and velocity makes no sense to me.

[anasawad]

@Potemkin

I'm sorry, anasawad, but this is just plain wrong. Speed is simply the magnitude of a velocity. And the speed of light through a medium is macroscopically less than the speed of light through a vacuum. Microscopically, of course, at the level of individual photons and individual atoms and their interactions, of course it isn't. But that doesn't enter into the definition of the refractive index. The refractive index is not a ratio between a speed and a velocity, but a ratio between a speed and another speed. Your distinction between speed and velocity makes no sense to me.

Actually 'm putting the distinction as a response particularly because the refractive index is a ratio between a velocity and anther velocity.
Its the velocity of light in a vacuum divided on the its velocity in the medium.
Most people including my self are used to simply put c as the first velocity, so i admit it did slip pass me that its pure speed but rather should have cleared its velocity of light in vacuum.
The argument got to my nerve so i missed this false terminology when describing the law it self but regardless, i apologize for not putting full attention.
Nevertheless this doesn't contradict or dis-validate my point.
Because when you're measuring velocity, you're not measuring speed, you're measuring speed in relation to a reference frame.
In this case, its usually between 2 points. So you're not measuring microscopically on atomic level , but rather macroscopically. Thats why i said in an earlier post, i believe previous page, that the speed of light is constant, but the velocity of light changes.
Its not the speed of light in a vacuum, its the velocity of light in a vacuum that is being used in Snell's laws. Because the speed of light is constant everywhere, while the velocity of light in vacuum since its the same as the abstract speed is used in the ratio.

Now why did i point that out. Because to debunk the given "argument" its needed to make the clear distinction that we're not talking about the speed of light in abstract but rather the speed of light in a specific reference frame , which is what velocity is . And then explain why is this difference, being that photons are absorbed and re-emitted multiple times microscopically in a medium while not being the case in vacuum.


The misconception, or better say, the incorrect terminology is rather spread which is why i saw the need to point it out when discussing this, as saying the speed differs would not only seem but also factually be contradictory to the point 'm making.




Side Note:
I do stand by my comment about the standards of education and skill being low in the UK and many other countries of Europe and north America. This is because these things lead to misconceptions and thus leads to falsehoods being spread which is why you see many idiots in the newer generations honestly. And this is evident by the fact that currently Europe and specially the UK need immigrants for high skill jobs, with immigrants being on average more educated than natives, and in some cases overqualified for the jobs. And the same for the US with most of its scientists being foreign migrants.
These small things are on the other hand have large emphasis on them in countries like Russia, like Iran, like India, etc in physics classes. And those countries happen major sources of science degrees graduates who takes the jobs in the west.
I know they put emphasis on these things because both my step sisters teach physics one in Russia general physics, and one in Iran nuclear physics and both tell they put huge focus in their classes on the small details because thats where the student could either understand the topic or flat out not understand it at all.

[B0ycey]

I have experience in the field of power electronics.
I have not claimed anything else. Please stick to the truth.

And gave me a 50 year career desiging power electronics.

And just to be clear to everyone, I have enjoyed your debates between one another and actually both sides are correct, but it appears your arguing on different aspects and issues. The refractive index uses 'c' as a constant to calculate the indexes ratio. The fact 'c' is a factor in the calculation means that unless the velocity has no value then of course the time taken to travel through the medium is going to be slower. But that's the whole point. The value of 'c' remains the same as light travels through the medium but the time the light travels through the medium is slower due to velocity. So it all depends on your definition of 'speed of light'. Do you consider the speed of light to be it's value in a vacuum ('c') or do you consider its speed on calculus, velocity, reflection, refraction and propagation between point 'a' to point 'b'.

[Besoeker]

Its a ratio between speed and velocity or if you want it in easier terms, ratio between speed of movement and average speed of displacement or propagation. I answered that multiple times and i showed the background of the answer and why they're not the same thing.
Your refusal to accept basics definitions and ignoring the information posted is not my problem, its yours.
Anyone who bothers reading basic definition would know directly that this doesn't mean that the speed of light changes, but rather that the average displacement rate (i.e velocity) is lowered by interaction with the medium.

Since light is made of photons, energy. And photons interact with atoms. Generally absorbed by them.

So you can stop using circular logic as if i hadn't answered it, i answered it a dozen times and even went into the very details of it. You simply keep ignoring the answer and repeating the question as if it proves it self.

And you have singularly failed to accept why c is defined as being in a vacuum.
What is c? Why is it specifict to a vacuum?
Why not water or glass if neither would result in a different value for c?
Think about that before you try to fudge it yet again.

[B0ycey]

And you have singularly failed to accept why c is defined as being in a vacuum.
What is c? Why is it specifict to a vacuum?
Why not water or glass if neither would result in a different value for c?

Oh dear Besoeker! This unfortunately is an epic FAIL. C is the value of the speed of light in a vacuum. C is Einstein's constant for light and its value has to be determined in a vacuum because of interference with matter in other formats. I actually mentally disagreed with anasawad about the standard of education in the UK. But comments like that strengthen his claim and weaken mine.

[B0ycey]

Ok, back to my idea, if anyone is interested in the maths, can you try out this equation for me.

(^ ly) + (h bd)
_____________ = n

(^ ly) - d


n ec = c

(n x ec = c)

^ is the time unit we use to determine the age of our universe 'The Milky Way'

ly is a light year

bd is distance from the blackhole in the centre of our galaxy to another blackhole at the centre of another galaxy

h is hubbles constant

d is distance between objects

n is B0yceys constant

ec is Einstein's constant of light in a vacuum on Earth

And c is the speed of light in spacetime.

[anasawad]

@Besoeker
Because of 2 things:
1- its actually velocity in a vacuum.
2- since its the same as the c constant then it is used as a reference point for establishing the ratio.

C on its own if you're talking about the constant does not define that its in a vacuum but rather as a fundamental constant.

I just explained this above i believe and multiple other times.

[anasawad]

@B0ycey
Ok, a couple of questions about the elements of the equation.

(d) is distance between which objects ? can it be defined randomly or there is a specific set ?

'm not sure why this part is "^ ly". Isn't this a time unit multiplied by a distance unit ?
And why is it summed with a distance between 2 black holes.

Basically what are the basic concepts behind those being like they are ?

[B0ycey]

Ok, still not perfect but nearly there. Think this is right though until I figure out I'm wrong again. But still capable of doing maths if interested. I have a life so not going to fuck about with sums today.

I think it's wrong @anasawad . Keep figuring out errors.

[anasawad]

Ok, latter on. Going to get food and tobacco.

[B0ycey]

(d) is distance between which objects ? can it be defined randomly or there is a specific set ?

Distance needs to be considered because time is different anywhere you are in my theory.

'

m not sure why this part is "^ ly". Isn't this a time unit multiplied by a distance unit ?

Correct and it has to be. Because time in my theory is expansion of the universe and this is distance.

And why is it summed with a distance between 2 black holes.

The speed of light is determined by them in my theory. Anywhere in our galaxy Einsteins c is correct for that reason. However it's not correct in other galaxies in my theory.

Basically what are the basic concepts behind those being like they are ?

I try and explain another day. I'm still trying to figure out the kinks in a theory that is more likely than not wrong.

[Besoeker]

@Potemkin


I already said that, just check former posts when i told what happens and why velocity changes.
Velocity does change if you consider it in reference of distance between 2 points.
Due to inability to measure all the absorption and re-emittions that happens, we measure the speed between 2 points, thus we measure time over distance. Basically using the very basic formula. Which is why we have "slower" velocity in results, because there is a delay.

When we measure velocity per displacement then yes it wont change, but due to inability we will have to measure it in a reference.

OK. Let's make this simple for you.

The thread title is about the speed of light.
The speed of light which is defined as 3 times 10^8 in a vacuum.
Is the speed different in other mediums?
That's just yes or no.

[anasawad]

No. Its not different between different mediums. Velocity differs.
Speed of light does not change. The velocity, being a macroscopic speed as Potemkin described, differs.


Though it does appear we need to make this much much simpler since many appear unable to comprehend the difference in terminology.