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Author Topic: Why is c 299,792,458m/s and not some other value?  (Read 16508 times)

Offline JMLCarter

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Sure the equivalence principal implies a universal speed limit; but why is it not higher or lower than it is.

c^2= 1/sqrt( permittivity * permeability )

doesn't immediately provide the answer. Understanding why free space resists motion might explain why it has permittivity and permeability at all. This could help understand why are they not higher or lower? Perhaps it is something to do with the density of virtual particles in a vacuum? What would determine this density?

Another possible explanation, if it were higher or lower would we notice? If not why not?




 

Offline Heikki Rinnemaa

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Why is c 299,792,458m/s and not some other value?
« Reply #1 on: 24/03/2011 04:58:51 »
Hi.

My thought is that space can have speed more that that under 300000km/s,,, made image and i think that light speed is mayby not constant,,i mean long travell distance. I dont know if light speed has measured nowadays,,example through lightcabel,,or etc,,what is the speed change (m/s)/m,,if there is speed change?

 

Offline JP

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Why is c 299,792,458m/s and not some other value?
« Reply #2 on: 24/03/2011 05:45:26 »
If your question about why light speed is constant and the fastest thing in the universe, or why it has that particular numerical value?  Regarding the latter question, the meter was actually redefined so that it is now based on the speed of light.  That means that light speed has exactly that value simply because we've chosen a definition of meter to give it that value.
 

Offline JMLCarter

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Why is c 299,792,458m/s and not some other value?
« Reply #3 on: 24/03/2011 11:00:35 »
Thanks to respondants...

Heikki, not sure I follow you, but lightspeed has certainly been measured to death, I don't think there is much evidence to support its variation through space. You seem to be questioning the equivalence principal (which I think is reasonable to do, but its a different question froim the one I am trying to ask.).

JP: my question is not either of those things. I understand why c is a universal speed limit and I understand that the the meter was re-calibrated infinitesimally against it so light travels an integer number of meters each second.

What am I asking then? Why did c turn out to be 299792458 m/s and not 154675322m/s. Why is the universal speed limit set at the level it is? Why does light take 8ish minutes to get here from the sun, not 15ish minutes, or 4ish minutes? It doesn't matter to this question what units c is measured in.

 

Offline Soul Surfer

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Why is c 299,792,458m/s and not some other value?
« Reply #4 on: 24/03/2011 17:45:40 »
As you pointed out in your first question the speed of light as would be the speed of any wave motion comes directly from the properties of the medium (vacuum) in which the light travels.  So your question is really why does a vacuum have these elastic properties.  The easy get out is to say that's the way it is but a question as good as this is worthy of a bit of thought.

The quantum mechanical vacuum is considered to contain a whole array of particles appearing and disappearing according to the limits set by the uncertainty principle.  this can include photons  (which are their own anti particles as well as things like electrons and positrons etc) the net result is that there is nothing there in the long term but this does result in it having a certain sort of elasticity that allows electromagnetic waves to be generated and propagate.

The question then arises, if like a gas we could "compress" the vacuum in some way we might be able to change the velocity of light.

Now all calculations of the energy density in this vacuum suggest that it is absolutely enormous, maybe around 10^120 times the sort of energy densities we find in normal matter so it seems very unlikely that anything that we could do could affect the speed of light in any significant way.
 

Offline yor_on

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Why is c 299,792,458m/s and not some other value?
« Reply #5 on: 24/03/2011 17:48:39 »
I'm sorry JM but that question is impossible to answer. Light is a constant, it makes no sense to ask it why it is so, it just 'is', as proven repeatedly in experiments. It's us calling it 'speed', and it's us deciding how to measure that 'speed'. We are the ones defining things giving them 'values', the universe just 'is' and make it perfectly well without our measurements.

What you seem to wondering is if the specific speed has a connection to the rest of the universe though? And absolutely, it has. A lot of things would be different with different 'speed' as measured by us. Red shift, blue shift, 'potential energy' etc.  Einstein called it SpaceTime, not Space alone, and he was right.
==

If you trust in that a Lorentz contraction is a real experience, actually shrinking SpaceTime from the travelers frame of reference, then you can look at muons and ask yourself if they see light coming at them as being of some other 'speed', as they themselves are at a very high speed relative us. But they don't, as far as I know they only see a blue shift, well, if they could see :)
« Last Edit: 24/03/2011 18:54:24 by yor_on »
 

Offline Heikki Rinnemaa

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Why is c 299,792,458m/s and not some other value?
« Reply #6 on: 24/03/2011 18:28:35 »

My thought is so that every motion thing has own speed-curve,,of cource example photon-particle start to go very fast ant accelerate speed to it's maximum speed,,but of cource it has also decceleration and when this traveller has going so long that there is no pushing power it stop,,speed is 0.

There is no different if motion thing is matter wave-vibration or matter-particle motion.

Car can go constant speed if cars engine has fuel and it work.

Do light-particle or wave has engine inside it?



 

Offline Heikki Rinnemaa

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Why is c 299,792,458m/s and not some other value?
« Reply #7 on: 24/03/2011 18:33:00 »

Why is the universal speed limit set at the level it is?


Hmm,,perhaps,,because universal,,space is not empty,,it is full of invisible (see through) space-matter,,and when some matter-particles or wave-vibration travel in this space-matter this matter cause brake-friction.

 

Offline Ron Hughes

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Why is c 299,792,458m/s and not some other value?
« Reply #8 on: 24/03/2011 19:16:45 »
If the density or energy of space sets the speed limit of C one would surmise that C may have been very much faster at the BB and is slowing down as the Universe becomes less dense as opposed to a hypothetical inflationary period?
« Last Edit: 24/03/2011 19:19:15 by Ron Hughes »
 

Offline lightarrow

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Why is c 299,792,458m/s and not some other value?
« Reply #9 on: 24/03/2011 19:47:39 »
Why is c 299,792,458m/s and not some other value?
For two essential reasons:
1. light speed is finite.
2. because a speed has dimensions, so its value depends on the units; with other units it would have another value.
That's all.
(I know, difficult answer...)
 

Offline Phractality

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Why is c 299,792,458m/s and not some other value?
« Reply #10 on: 25/03/2011 06:59:06 »
We came up with that odd number because we originally defined the meter and second in terms of Earth's size and rotation speed. Having measured the speed of light in meters per second, we changed the definition in terms of wavelengths of a particular atomic emission line.

In the standard model, c may be calculated in terms of permeability and permittivity of free space; c = √(1/ε₀μ₀). I suspect that is a truism. I think permeability and permittivity are defined in terms of light, so the defintions are circular. (I could be wrong about that, though.)

I don't like the standard model. I prefer to explain the speed of light as acoustic shear (transverse) waves in the solid medium of the ether. The formula from acoustics is c = √(G/ρ), where G is the shear modulus and ρ is the density. I like density and shear modulus because, unlike permeability and permittivity, I have an intuitive grasp of what they are.

Note the similarity of the two equations; c = √(1/ε₀μ₀) = √(G/ρ). This suggests to me that permeability and permittivity are closely related to density and shear modulus of the ether.

If we knew the inertial density (I don't believe the ether has any gravitational density) and shear modulus of the ether, then we could calulate the speed of light from those. Conversely, if we know density or modulus, we could calculate the other from the speed of light. I suspect both are incredibly high values. The density might be a googol times that of a white dwarf.
 

Offline syhprum

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Why is c 299,792,458m/s and not some other value?
« Reply #11 on: 25/03/2011 09:44:02 »
Phractality

Like me you hanker for a simpler universe, pre Lorenz, pre Einstein but it ain't like that we must live with facts that have been discovered no Šther, no fairies or ghosts or spirits.
 

Offline JMLCarter

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Why is c 299,792,458m/s and not some other value?
« Reply #12 on: 25/03/2011 10:22:51 »
Zero point energy, or vacuum potential, which are driven by the spontaneous appearance and annihilation of particles in quantum field theory seems to provide a kind of "aether like" property to free space?

...presumably one that would not be detectable by Michelson-Morley or its clones (not sure why, perhaps their even momentum distribution would make them relativistically identical regardless of the speed of the experiment [what is the momentum distribution of the particles in a vacuum potential?]).

Could there be a link between vacuum potential and c?
 

Offline Heikki Rinnemaa

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Why is c 299,792,458m/s and not some other value?
« Reply #13 on: 25/03/2011 11:06:21 »
 :)

---
Like me you hanker for a simpler universe, pre Lorenz, pre Einstein but it ain't like that we must live with facts that have been discovered no Šther, no fairies or ghosts or spirits.
---

Fairies or ghosts or spirits,,no comments,, :)

Ether,,one question.

If round of moon dont have any matter, only empty, how it can goes any direction?

I havent seen yet engine in the moon :)
 

Offline syhprum

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Why is c 299,792,458m/s and not some other value?
« Reply #14 on: 25/03/2011 13:12:35 »
The generally accepted theory for the creation of the Moon is that it was created as the result of a Mars sized body colliding with the Earth in the early days of the Solar system.
Basically the materiel blasted off the Earth would have acquired a certain momentum and would have continued away in a straight line but for the influence of the Earths gravitational field.
The best theory that we have how a gravitational field operates is covered by the theory of General relativity which states that massive bodies like the Earth make a well like depression in the fabric of space/time and the materiel from the collision would lie in this depression.
Now although this materiel that collased into the Moon would in empty space tend to move in a straight line it would now be moving in a region of space/time distorted by the Earth and can be visualised as moving around the periphery of the depression hence orbiting the Earth as though is was attracted to it.   
 

Offline Heikki Rinnemaa

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Why is c 299,792,458m/s and not some other value?
« Reply #15 on: 25/03/2011 13:26:41 »
:)

---
The generally accepted theory for the creation of the Moon is that it was created as the result of a Mars sized body colliding with the Earth in the early days of the Solar system.
---
Or it's start to growing small size,,or comes out of space,,or perhaps it's size is get smaller,,,do we accepted what,,how,,evidence,,do we have?

---
Basically the materiel blasted off the Earth would have acquired a certain momentum and would have continued away in a straight line but for the influence of the Earths gravitational field.
---

What exis-thing is that gravitational field,,ether?

---
The best theory that we have how a gravitational field operates is covered by the theory of General relativity which states that massive bodies like the Earth make a well like depression in the fabric of space/time and the materiel from the collision would lie in this depression.
---
Time is not existing matter-particle,,only measuring unit time=s.

So fabric of space,,


---
Now although this materiel that collased into the Moon would in empty space tend to move in a straight line it would now be moving in a region of space/time distorted by the Earth and can be visualised as moving around the periphery of the depression hence orbiting the Earth as though is was attracted to it.
---

If round of space-station dont have any matter, only empty, how it can goes any direction?

If it goes,,it goes in that fabric,,that is my thought,,when i look the space and observ.
   
 

Offline lightarrow

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Why is c 299,792,458m/s and not some other value?
« Reply #16 on: 25/03/2011 17:49:24 »
If round of space-station dont have any matter, only empty, how it can goes any direction?
If it goes,,it goes in that fabric,,that is my thought,,when i look the space and observ.
So you are one of those (many) people who don't believe in General Relativity? If you don't want to simply "believe", you have only one solution: to study physics. Then you will be able to say which theory is better. Before you know physics well, you can't say a lot...
« Last Edit: 25/03/2011 17:53:47 by lightarrow »
 

Offline yor_on

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Why is c 299,792,458m/s and not some other value?
« Reply #17 on: 25/03/2011 19:12:17 »
That the universe sort of still moves seems to indicate that there is no resistance in a vacuum. At some point there should have been a almost 'flat' SpaceTime, when we only had radiation, probably fluctuating with gravity depending on if radiation can/will bend the Space fabric. Before radiation we might have had an instant of 'pure energy', maybe? And energy, seems to be able to create gravity, doesn't it? That gravity should have been directed only one way though, shouldn't it? Inwards towards that point of energy, unless we imagine it to have been a 'white hole' that created the radiation. White holes are time reversed black holes, spewing out 'energy' and radiation. In a black hole the singularity is in its past, if I understood it right, but in a white hole the singularity still awaits it in the future. Weird stuff :)

But there should have been a state of 'energy' before the radiation at least? But then again, if we imagine that times arrow needs gravity to express itself? Then we had one state that definitely had gravity before radiation, that in its turn may or may not have been expressed in 'gravity'. Maybe?
==

Radiation :)
Ouch, there was no state of pure radiation at all, was there?
Well in the plasma maybe.

But how the ** did 'energy' turn into a plasma?
And why?

Someone that remembers?
« Last Edit: 25/03/2011 21:42:03 by yor_on »
 

Offline Phractality

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Why is c 299,792,458m/s and not some other value?
« Reply #18 on: 25/03/2011 23:38:12 »
Phractality

Like me you hanker for a simpler universe, pre Lorenz, pre Einstein but it ain't like that we must live with facts that have been discovered no Šther, no fairies or ghosts or spirits.

Einstein reluctantly went along with the crowd for lack of evidence that the ether has the property which he called "immovability". Without that property, there is no way to distinguish between the reference frame of the ether and any other inertial reference frame. If recent successes with so called "quantum teleportation" are verified, they will prove that the ether does have immovability.

Instantaneous communication means that sending and receiving are simultaneous events at different locations. Events which are simultaneous in the reference frame of the ether are not sumultaneous in reference frames with motion relative to the ether. So "quantum teleportation", if proven, will provide a direct measure of our velocity relative to the ether. For faster than light phenomena, there has to be a preferred reference frame, and that has to be the ether.

It's a good guess that the ether is stationary relative to the CMB. The CMB is blueshifted in the direction of Virgo, suggesting velocity of the Solar system toward Virgo of about 627 km/s, which translates to a relativistic gamma of 1.0000022. So clocks closer to Virgo in Earth's reference frame should indicate earlier times at a rate of about 9 ns/km.

The Chinese team, last May, claimed that their quantum data was receive before it was sent in the reference frame of Earth. If they sent it 16 km directly toward Virgo, and it was instantaneous in the reference frame of the ether, then we should expect it to arrive about 9 x 16 = 151 144 ns before it was sent, according to Earth clocks. [The math corner of my brain had gone to sleep. How come nobody corrected me?]

This in no way violates causality, and there is no paradox, because a signal sent in the opposite direction would be delayed by the same amount according to Earth clocks. A 2-way communication which is instantaneous in the ether frame is instantaneous in all reference frames. In other words, A may send a question to B, receive B's answer and acknowledge the answer, all in the time it takes to respond locally. A and B may record the exchange at different times, but neither will perceive any propagation delay.
« Last Edit: 26/03/2011 19:55:41 by Phractality »
 

Offline Ron Hughes

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Why is c 299,792,458m/s and not some other value?
« Reply #19 on: 26/03/2011 04:57:53 »
Ah but your are wrong yor-on, the vacuum does have resistance it's called inertia.
 

Offline Heikki Rinnemaa

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Why is c 299,792,458m/s and not some other value?
« Reply #20 on: 26/03/2011 05:05:20 »
:)

---
So you are one of those (many) people who don't believe in General Relativity? If you don't want to simply "believe", you have only one solution: to study physics. Then you will be able to say which theory is better. Before you know physics well, you can't say a lot...
---

I'm sorry,,but i dont have read 18-19centuryes physics,,do i have?,,i can tell my thoughts what i have observe this world,,without knowing some mathematical formulaes,hmm,,i make image what i meant, hope that it help this conversation.

 

Offline yor_on

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Why is c 299,792,458m/s and not some other value?
« Reply #21 on: 26/03/2011 14:40:48 »
Yes Ron, good point. Inertia is weird :)
And it's a form of resistance.

I see it as a proof of 'gravity' myself though, and as 'gravity' is no force then it's not what we mean by 'resistance' as some form of 'particles' retarding your system.
 

Offline yor_on

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Why is c 299,792,458m/s and not some other value?
« Reply #22 on: 26/03/2011 14:51:04 »
Phractality, I'm not sure what you are talking about there?
'Instantaneous transmission' of what? And using the name ether might make people think that it is a accepted description. It's not, and for the same reason that we don't find any 'resistance' to lights propagation, as tested uncountable times. A 'entanglement' is about something being 'identical' and somehow connected outside the boundaries light puts on the rest of us. And one of the really big premises it still follows is that there is no way to use it for sending usable information. If that one would be shown to be wrong though? But I don't think it has, as far as I know?

It would be interesting if you could inject 'energy' in a entanglement though by 'observing' its state. Then we would have to discuss if you could see that as information. And to me it would be :) as you might find a way to utilize that 'new energy'. As well as it would make some problems for the conservation laws I think, as we then actually would have 'doubled' the 'energy' by our way of observing.
« Last Edit: 26/03/2011 14:58:55 by yor_on »
 

Offline Phractality

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Why is c 299,792,458m/s and not some other value?
« Reply #23 on: 26/03/2011 18:05:49 »
Phractality, I'm not sure what you are talking about there?
'Instantaneous transmission' of what?

As far as I can tell, the Chinese experiment is only supposed to have transmitted an effect across 16 km. A pair of entangled photons went in opposite directions from a point approximately midway between the sender and the receiver (but slightly closer to the sender). When the quantum states of photons were detected at the slightly nearer end, the quantum state of their twins at the other end were determined instantaneously, before being measured. The act of detection at one end instantaneously affected the measurement at the other end.

I appreciate the problems with using that to communicate information, but to prove the existence of ether, you only need to prove afterward (at sub-light speed) that the effect was transmitted instantaneously in one reference frame. Special relativity proves that simultaneous events (sending and receiving) in one reference frame cannot be simultaneous in other reference frames (with relative motion not perpendicular to the line between the two events). There can be only one reference frame in which quantum entanglement transmits effects instantaneously regardless of direction.

And using the name ether might make people think that it is a accepted description.
The Chinese experimenters refered to it as "the quantum ether". I believe they distinguished it from the "luminiferous ether" in order to shield themselves from disbelief due to pervasive prejudice against the existence of any form of ether.

It's not, and for the same reason that we don't find any 'resistance' to lights propagation, as tested uncountable times.

I assume you are referring to experiments like Michelson-Morley. Their null result is perfectly explained by special relativity, and it has nothing to do with resistance. Where the speed of light is the limit, you can't detect any difference among reference frames (except in the Doppler shift of the CMB). That is because of the length contraction and time dilation of the measuring aparatus; it has nothing to do with resistance or ether dragging. Einstein explained that perfectly, soon after the original experiment, but the message still hasn't sunk in with those who think Michelson-Morley disproved the existence of ether. Whether ether exists or not, the result is the same. You need a faster-than-light phenomenon to detect any difference in reference frames. If any such phenomenon had been discovered in Einstein's day, he would have said, "Told you so! There is an ether."


A 'entanglement' is about something being 'identical' and somehow connected outside the boundaries light puts on the rest of us. And one of the really big premises it still follows is that there is no way to use it for sending usable information. If that one would be shown to be wrong though? But I don't think it has, as far as I know?
There's more to the method than what I know. I think it has something to do with interference patters. When a measurement is made at one end, the interference pattern instantaneously disappears at both ends. Or something like that.

It would be interesting if you could inject 'energy' in a entanglement though by 'observing' its state. Then we would have to discuss if you could see that as information. And to me it would be :) as you might find a way to utilize that 'new energy'. As well as it would make some problems for the conservation laws I think, as we then actually would have 'doubled' the 'energy' by our way of observing.

I don't expect that energy will ever be transmitted faster than light. Information is not energy. As long as only information is transmitted, I don't see any violation of the conservation laws.
 

Offline lightarrow

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Why is c 299,792,458m/s and not some other value?
« Reply #24 on: 26/03/2011 21:55:54 »
:)

---
So you are one of those (many) people who don't believe in General Relativity? If you don't want to simply "believe", you have only one solution: to study physics. Then you will be able to say which theory is better. Before you know physics well, you can't say a lot...
---

I'm sorry,,but i dont have read 18-19centuryes physics,,do i have?,,i can tell my thoughts what i have observe this world,,without knowing some mathematical formulaes,hmm,,i make image what i meant, hope that it help this conversation.


And what that picture should mean?
 

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Why is c 299,792,458m/s and not some other value?
« Reply #24 on: 26/03/2011 21:55:54 »

 

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