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> Silly question to ponder, This might spark a little
Good Elf
Posted: Mar 14 2006, 01:17 AM


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Hi atfpcop,

It is right to question everything, as long as we do not become unable to "proceed". Science is the only discipline where you can proceed without having "faith in authorities" other than a faith that the Universe does not "lie". wink.gif
QUOTE
How would one isolate the time the element (which ever kind it is ) from the measure of the light?
Interesting question. Light is really the most "special case" since it is the carrier of force in our universe. We say velocity is distance divided by time yet distance depends on the speed of light. What I mean by this if the speed of light was twice what we "externally" (as an observer) think it to be, we would see the "space" reduced in dimensional extent to a half because light would take half the time to traverse it. This is what we see when we peer into a rectangular prism of glass (from the outside) with a refractive index of 2.
user posted image
and
user posted image
where v is the phase velocity in the medium...
Wikipedia: Refractive index
So time and space are not "separate" entities. Einsteins Theories of "conventional" space-time suggest that space and time are not separate and prefers to refer to this "entity" as space-time... a sort of unity rather than the disparate parts that Newtonian Mechanics suggested. The maths of space-time also suggests you cannot deal with it in this piecemeal fashion. Time is certainly not the same kind of dimension that the other three are. Space-time is three spatial and one dimension of time. I think of time as a half a dimension since (at present) we can only go forward in it, never backwards. With Relativity we can go forward as fast as we want though. However individual particles can go backwards in time.

Not that it means anything here but this is why I believe in String Theories that "complete" the dimension of time as a complete dimension in 10 plus dimensions. Light is the special case and therefore it is not strictly a "velocity" but a "property" of space-time. IMHO You cannot then speak of the temporal and the spatial aspects of light as separate. Light "propagates" and "connects" it is not just "traveling" like a particle does. I guess that will not stop the discussions on this forum that deals with light as if it was just a "sound barrier" to be broken. There is another issue altogether that is velocity that does not exceed the speed of light but "connects" different places faster than light takes to travel there. A form of higher dimensional travel not forbidden by relativity. All you need are extra dimensions.

Cheers


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atfpcop
Posted: Mar 14 2006, 02:29 AM


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OK, i am a little confused but i think if i clarify my question i might help to figure this out what i meant was for example in an incandescent light the element must heat up from the electricity to create the light which would make my question in this case how do you separate that or is it like you said above that you cant, cause really if you used a spectrum type looking device at various levels of heat in the element you would see forms of light right? so OK i guess you answered it. light and time cannot be split. and since electricity does not have a set speed due to its nature that means that there can be no other conclusion the speed of light is as tested. Right?


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Good Elf
Posted: Mar 14 2006, 03:02 AM


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Hi atfpcop,

We are never sure of what is done in any particular case but I an sure your question "as stated" never crops up because it is an "ill conditioned" experiment. The timing is critical in any experiment regarding velocity. What they would do in a particular instance would be to remove any "switch on" period from the measuring system and deal only with light propagating. The remaining errors are literally calculated to give the maximum and minimum values of the result. The error analysis is critical to any "modern" experiment and must always be done to give confidence limits.

Cheers


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Why Not?
Posted: Mar 14 2006, 10:56 PM


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Hey atfpcop,

First of all, I would like to apologize for my flame regarding your head and your arse. I get frustrated when individuals ask questions that are honestly answered and then, generally out of ignorance and/or laziness, flame the individual that answered. I am far from a scientist and greatly appreciate those on this site that take the time to honestly respond to my questions. My fear is that with too many responses like your second in this post, those individuals will stop answering all of us. Regardless, I am happy that you took the time to look up Einstein's level of education and glad you had the guts to say so.

Now, if I can take a stab at your revised question...

QUOTE
i think if i clarify my question i might help to figure this out what i meant was for example in an incandescent light the element must heat up from the electricity to create the light which would make my question in this case how do you separate that


First of all, I would like to re-phrase your question to make sure that I am understanding what you are asking. If my re-phrasing is incorrect, please skip the rest and try again.

"How do we know that the speed of light (in vacuum), measured as +/-300,000Km/s is really the time it take for light to transverse a given distances and not simply the amount of time it take for the “filament” in the source to heat up to the point that light is radiated?"

The simplest way is to devise an experiment to remove the “filament” from the experiment. Ole Romer did just that in 1676 and came up with a pretty respectable answer, all things considered, and the precision in the experiments have only gotten better since then. Please look at the “Measuring the Speed of Light section” in this link, http://en.wikipedia.org/wiki/Speed_of_light .





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atfpcop
Posted: Mar 15 2006, 10:58 PM


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Why Not,

I see your point but I am a little skeptical about using the Moon of another planet as judgment of light speed. OK i admit it i am alot skeptical. I am more inclined to accept the fact that some one chose to actually measure the time it took to light the filament and subtracted that from the time it took for light to traverse a set distance. So much is unknown about our solar system that it is likely to me that the moon Rommer saw has an irregular orbit. My opinion. But if you are aware of a light source that has no medium to excite then that might clarify the test results a little more precise. Rommer is responsible for getting us on this road and i commend him for that. now we are in need of answers related to that. Like can we travel at that speed eventually, or is it even relevant? Would it not be Easier to search for a way to make Good Elf's suggestion possible. Or as far out and science fiction as it sounds what about using gravity in our favor to create gateways? The speed of light is what it is i will not question that, reasons be that you and Elf and others have satisfied my skeptic mind in that area. I am greatful for the insight and help. So i move forward now to other avenues because in truth all of my questions have a hidden agenda, That be Me getting into space to explore cause i am not patient enough to wait for NASA to do so. Sorry if my lack of respect offends But i feel NASA is capable of so much more and does so little. My reason for this Belief is the X-Prize competition. I could explain further but i suppose i have rattled enough.


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Y.T.
Posted: Mar 21 2006, 08:35 AM


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... and during all this blah blah none of you folks thought of googling it. It's really pretty trivial:

The speed of light is 299 792 458 meter per second exactly. With absolute precision. Because the speed of light in a vacuum is NOT a measured quantity. It is defined to be this number.

The SI unit "meter" is defined as the distance that light travels in 1/299792458 second.

And the second is defined as the time taken by some specified (large) number of oscillations of a certain cesium isotope.

All of which you'd know had you made the token effort of looking it up in Wikipedia.

I find it perfectly acceptable to rebuke the willfully ignorant.
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Good Elf
Posted: Mar 21 2006, 09:17 AM


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Hi Y.T.,

QUOTE (Y.T. Posted on Mar 21 2006 @ 08:35 AM)
The speed of light is 299 792 458 meter per second exactly. With absolute precision. Because the speed of light in a vacuum is NOT a measured quantity. It is defined to be this number... I find it perfectly acceptable to rebuke the willfully ignorant.

Are you telling me that you can "derive" the speed of light EXACTLY from fundamental constants of the Universe other than anything that intrinsically involves the speed of light itself? like those bogus "Planck Units"?

Yep... I am waiting ... reference please.
Here is the Wikipedia reference if you need it....
Wikipedia: Speed of light
Alternatively explain how you were able to derive this number... 1/299792458 second or put another way... 3.335640951981520495755576714474919 e -9 second (according to my trusty calculator) I am pretty sure that this is transcendental... exactly. Obviously the next question is how you measure this with your "stopwatch" exactly.
Go for it!

Cheers


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atfpcop
Posted: Mar 21 2006, 04:49 PM


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All praise wikpedia as they have never been questioned right? was there something in the news about them screwing up a simple definition? At any rate Get your head out of the dictionary and try looking in all possible places, The truth shall search you out if you look.


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Good Elf
Posted: Mar 22 2006, 03:22 AM


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Hi atfpcop,

Wikipedia is not the problem. It is a great resource but an even better resource is your own minds. I was referred to an extract from the Encyclopedia Britannica the other day on the forum and it too was "lacking in in-depth analysis". ohmy.gif wink.gif It is not who said it or how much you paid for it that matters it must also "add up". You must always be continually thinking about what is being said and if what is quoted is fair and appropriate. There are no no-brainers in Physics.

Cheers


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Y.T.
Posted: Mar 22 2006, 04:21 AM


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QUOTE (Good Elf @ Mar 21 2006, 01:17 AM)
Hi Y.T.,

QUOTE (Y.T.  Posted on Mar 21 2006 @  08:35 AM)
The speed of light is 299 792 458 meter per second exactly. With absolute precision. Because the speed of light in a vacuum is NOT a measured quantity. It is defined to be this number... I find it perfectly acceptable to rebuke the willfully ignorant.

Are you telling me that you can "derive" the speed of light EXACTLY from fundamental constants of the Universe other than anything that intrinsically involves the speed of light itself?


No, I am rubbing your nose in the fact that the speed of light is DEFINED. Not "derived", not "measured" nor any other such nonsense. DEFINED.

Has been for decades.

Your reading comprehension needs work.

QUOTE

like those bogus "Planck Units"?


There's absolutely nothing "bogus" about Planck units. Let me advise you not to deride that what you do not understand.

QUOTE

Here is the Wikipedia reference if you need it....
Wikipedia: Speed of light


I pointed you to that resource. Here you're pointing me back to it WITHOUT EVER HAVING READ IT. Or otherwise you would have noticed this sentence in the very first paragraph: "Note that this speed is a definition, not a measurement, in that the fundamental SI unit of distance, the metre, is defined in terms of the speed of light: one metre is the distance light travels in a vacuum in 1/299,792,458 of a second."

The speed of light is exact. It is plus/minus zero. Because it is not something that is measured. It is defined to be a certain number and THEN the meter is defined as something that is dependent on the speed of light. And on the second.

It is valid to ask "how well do we know the length of a second" as this depends on our ability to count a godawful number of oscillations but it is invalid, ignorant gibberish to ask "how well do we know the speed of light" since the latter is defined to be a certain exact number.

QUOTE

You must always be continually thinking about what is being said and if what is quoted is fair and appropriate.


It does not matter one whit whether anything is "fair" or whether any moron on the planet finds anything "appropriate". If it is true, then it is true. And if it isn't, then it's wrong. It doesn't matter how beautiful your ideas are and it doesn't matter how smart you are: if it doesn't agree with experiment, it's wrong.



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George
Posted: Mar 22 2006, 05:22 AM


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I think you might be misinterpreting that statement. The meter is defined using the speed of light, that has no relation to whether we can calculate its speed. We could have just as easily said that light goes a meter a second and that would exactly true, a meter is whatever we say it is, but it just means our meters are a lot bigger. Defining a unit of measurement by a physical constant doesn't mean that we know the constant's precise value; it may not even exist. See the wikipedia article on the gram. Yeah, the SI reference bar is EXACTLY one gram, but that doesn't mean it we really know how much it weighs, it seems to have changed slightly!. That's the nice thing about defining things by the speed of light, it doesn't change (as far as we know). Still, the definitional speed of light isn't really different from the definitional demarkation of time, it's just based on something we think won't change on us and we can measure with high precision.
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Good Elf
Posted: Mar 22 2006, 05:50 AM


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Hi Y.T.,

George is right... I am still waiting for you to define the speed of light or the units of distance without recursive reference to the speed of light itself. Calculation of the number 1/299792458 second needs your attention since you are making the claim. Speed of light defined from constants of the Universe rather than the distance light travels in 1/299792458 second in Km/sec. Where did that number come from... explain please. Do not feign ignorance with me... it is your claim. It is not just the time they changed but the distance ... the distance of one meter is now defined as the distance light travels in 1/299792458 sec. The measuring rule has been modified to "fit" the speed of light.

Read my lips: The errors remain as always since they are the result of the measurements made in actual experiments. You cannot "derive" the speed of light.

Cheers


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yesitdid
Posted: Mar 22 2006, 06:16 AM


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Very elementary page on measuring the speed of light
http://www.colorado.edu/physics/2000/waves...d_evidence.html
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Good Elf
Posted: Mar 25 2006, 03:39 AM


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Y.T.,

Thank you for demonstrating to all concerned you are a total idiot. Have a nice day! biggrin.gif


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1shooter
Posted: Mar 25 2006, 06:43 AM


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QUOTE (atfpcop @ Mar 12 2006, 06:02 AM)
We set a specific number, a value to represent how fast the particles of light travel from source to destination. The value (299,792,458 meters per second) give or take, set by a test that (grab your seats folks) by all possibilities could be faulty. Depending on the light in question (the test subject) the speed would vary in my humble opinion. see if it were an incandescent light used for the Test or a tube in which was aimed at the sun with a high speed trap door to let the light in, either way how do we know we are not measuring a reaction time and not light itself. i mean what if the above mentioned number is the amount of time it takes for the element in a light bulb to heat up and produce light. Just chew on it for a while and really look into the tests preformed to prove the speed of light.

I am not a scientist i am not a great thinker and pretty bad speeller.

But all that doesnt matter much. As for the subject matter does the light travel at different speeds from different sources. I believe that was the nature of the question. From this bulb or that bulb.

I would have to suppose im my opinion if i where in some part of a great experiement. That inception of light comes in at different times. Ie The light get born at different times if per say you gave x number of electron to bulb a and x to bulb b. At relatively the same place.

But my assumption would be that after the light was (born) it would travel the speed of light.

The speed of light is constant allthough light itself is not constant.

i would also have to suppose that as it leave the fillement it would travel at a slower speed as it leaves the glass as glass tends to slow speed down by about 40 mph last time i read about that stuff.

So if one bulb is thicker or thinner than the other the intial speed may be slower or faster than the other but after said impedence is broken it would assume the speed of light once again.

Allthough these would be very small differences i think that was the point of the question.

Oh yeah sorry for the bad spelling bad english and a all around bad way of trying to explain myself.

If you any of you have a rock to throw let me jump in a bit further so you can hit me hard.

According Einstien geez can i say that on this site. E=m c2 and the whole of theory says that light is a constant.

Funny thing is light doesnt have to travel at the speed of light.

Bring on the rocks i got a hard head.
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