speed of light, is it really constant?

[RichardT]

If it were, it would cause a huge problem for YEC. I was wondering if I can learn from what you guys have learned about this.

[arunma]

If it were, it would cause a huge problem for YEC. I was wondering if I can learn from what you guys have learned about this.

Yes Richard, the speed of light is constant. Here is the proof I wrote up yesterday from the other thread, in case you missed it:

http://www1.christianforums.com/attachment.php?attachmentid=90476&d=1164087057


I realize that vector calculus isn't exactly a standard component of high school curricula, but the derivation of the speed of light (light being an electromagnetic phenomenon) is a rather in-depth topic. The reason that the speed of light does not change throughout the universe is because it can be derived by manipulating Maxwell's Equations into the wave equation, and it can be shown that the speed of light does not depend on any properties of any spatial coordinates.

I am making the assumption that our understanding of electricity is correct. Seeing as how both of our computers seem to work properly, I think we can agree that this assumption is justified.

[yeshuaslavejeff]

simple

[MatthewDiscipleofGod]

I'm sorry but I have to disagree with Arunma on this one because he is leaving out factors that play a part in the answer to Richard's question. Arunma might find the articles I link to below interesting. There is evidence that a vacuum can speed up light and it's been proven that light slows down in matter.

Speed of light slowing down after all? Famous physicist makes headlines. (http://www.answersingenesis.org/docs2002/0809_cdk_davies.asp)

The Uncertain Speed of Light (http://www.icr.org/article/498/)

[Matthan]

Now, why can't our detractors from other forums stumble across this thread and see just how smart some of us are? Sure would make them think twice about their silly traditions of men, wouldn't it?

And I thought GordonSlokum's Greek was pretty neat. Heck, it can't even hold a candle to this speed of light thing, regardless of whether that light is going steady or slowing down....

Matthan

[arunma]

I'm sorry but I have to disagree with Arunma on this one because he is leaving out factors that play a part in the answer to Richard's question. Arunma might find the articles I link to below interesting. There is evidence that a vacuum can speed up light and it's been proven that light slows down in matter.

Speed of light slowing down after all? Famous physicist makes headlines. (http://www.answersingenesis.org/docs2002/0809_cdk_davies.asp)

The Uncertain Speed of Light (http://www.icr.org/article/498/)

May I ask what factors you believe I have left out?

In any case, this is an entirely different problem. I proved above that the speed of light does not change at different places in the universe (but if someone can provide a scientifically accurate argument against my proof, then you are free to do so, and I would be happy to entertain it). I did not address the issue of the speed of light changing in time.

If you believe that the speed of light has changed in time because of changes in the fine structure constant, then you may be interested in seeing this creationist web page:

http://www.godandscience.org/youngearth/speedlight.html

This person explains that the change in the fine structure constant does not agree with young earth creationist models.

While I believe in literal, Biblical creation, I find that most creation science literature is not very scientific at all (and this is my professional opinion, to whatever extent I am qualified to give one). The truth of the matter is that almost no science journal would entertain creationist research of any kind. And while I don't mean to step on any toes, the bluntly honest truth is that they are right to do so. As Christians we must respect truth over personal opinions, because the view that personal opinions define truth is a patently postmodern concept. While the Bible is incontrovertable truth, creationist dogma is not. As such, those who ardently hold to creationist models must be willing to give these beliefs up if scientific evidence shows otherwise. In defining our essential beliefs, we must be careful to adhere to precisely what the Bible says, and not take anything beyond the text as absolute truth. What I am trying to say, here, is that I would rather discuss peer-reviewed, accepted scientific literature as opposed to creationist models.

[PETE_]

Now, why can't our detractors from other forums stumble across this thread and see just how smart some of us are? Sure would make them think twice about their silly traditions of men, wouldn't it?

And I thought GordonSlokum's Greek was pretty neat. Heck, it can't even hold a candle to this speed of light thing, regardless of whether that light is going steady or slowing down....

Matthan
where has gordon been? anybody know?

[MatthewDiscipleofGod]

May I ask what factors you believe I have left out?

In any case, this is an entirely different problem. I proved above that the speed of light does not change at different places in the universe (but if someone can provide a scientifically accurate argument against my proof, then you are free to do so, and I would be happy to entertain it). I did not address the issue of the speed of light changing in time.

If you believe that the speed of light has changed in time because of changes in the fine structure constant, then you may be interested in seeing this creationist web page:

http://www.godandscience.org/youngearth/speedlight.html

This person explains that the change in the fine structure constant does not agree with young earth creationist models.

While I believe in literal, Biblical creation, I find that most creation science literature is not very scientific at all (and this is my professional opinion, to whatever extent I am qualified to give one). The truth of the matter is that almost no science journal would entertain creationist research of any kind. And while I don't mean to step on any toes, the bluntly honest truth is that they are right to do so. As Christians we must respect truth over personal opinions, because the view that personal opinions define truth is a patently postmodern concept. While the Bible is incontrovertable truth, creationist dogma is not. As such, those who ardently hold to creationist models must be willing to give these beliefs up if scientific evidence shows otherwise. In defining our essential beliefs, we must be careful to adhere to precisely what the Bible says, and not take anything beyond the text as absolute truth. What I am trying to say, here, is that I would rather discuss peer-reviewed, accepted scientific literature as opposed to creationist models.

Reading your reply I'm not sure if you even read the articles I linked too. Secular science is appealed too. I think it is an interesting conversation and that people shouldn't be so dogmatic about the speed of light in the universe. We know for a fact that light can be slowed down. Why then should we be so certain it couldn't have been sped up? I can't make you look into these ideas if you don't want to but taking the classes that you are at the U of M I thought you would at least find some of this information interesting even if you didn't agree with it. If you didn't agree with it I was hoping for some specific insight you had to offer on the information offered.

Speaking of peer reviewed stuff you could consider this next link peer reviewed even though it is from a creationist source. There are many scientists that contribute papers, several with Ph.D's.

A new cosmology: solution to the starlight travel time problem (http://www.answersingenesis.org/home/area/magazines/tj/docs/v17n2_cosmology.pdf)

[MrJim]

arunma strikes again--you could tell me that's the formula for why chocolate is good and I would believe you ;)

[RajunCajun86]

with my limited knowledge and understand of the topic i must agree with arunma that the speed of light doesn't change
I believe in Christianity as I believe that the sun has risen: not only because I see it, but because by it I see everything else.
- C.S. Lewis
i would encourage us to use this approach when studying
let the Bible interpret what we find
as opposed to letting what we find interpret the Bible
don't forget where our faith lies

[arunma]

Reading your reply I'm not sure if you even read the articles I linked too. Secular science is appealed too. I think it is an interesting conversation and that people shouldn't be so dogmatic about the speed of light in the universe. We know for a fact that light can be slowed down. Why then should we be so certain it couldn't have been sped up? I can't make you look into these ideas if you don't want to but taking the classes that you are at the U of M I thought you would at least find some of this information interesting even if you didn't agree with it. If you didn't agree with it I was hoping for some specific insight you had to offer on the information offered.

Speaking of peer reviewed stuff you could consider this next link peer reviewed even though it is from a creationist source. There are many scientists that contribute papers, several with Ph.D's.

A new cosmology: solution to the starlight travel time problem (http://www.answersingenesis.org/home/area/magazines/tj/docs/v17n2_cosmology.pdf)

Sorry if I didn't mention anything about the second link you posted. I did read both of them, but the first seemed much more pertinent, because it mentioned more specific details.

Regarding the slowing of the speed of light, this phenomenon is often misunderstood. The vacuum speed of light is not actually changed in this case. In fact the process by which a material can slow the speed of light is very well understood. But the speed of light in a vacuum is an intrinsic property of the universe, and it is based on the nature of electric and magnetic fields. For it to change, the way electromagnetism works would have to change.

The only viable evidence I've seen thus far for a change in the speed of light is the shifting of atomic spectra in distant quasars. And another creationist says that even this does not solve the problem that young earth creationists are approaching. But I don't know much about this research yet, so I can read a peer-reviewed paper (I've found one in Physical Review) and get back to you).

[arunma]

arunma strikes again--you could tell me that's the formula for why chocolate is good and I would believe you ;)

Well, there are the chemical pathways that make your taste buds work. But biology isn't really my field. They don't have any equations, and you know how much I love equations.

with my limited knowledge and understand of the topic i must agree with arunma that the speed of light doesn't change

i would encourage us to use this approach when studying
let the Bible interpret what we find
as opposed to letting what we find interpret the Bible
don't forget where our faith lies

Yes, I would agree completely.

[cubanito]

As I write this, I'm setting 140,000 volts to jump through about an inch of vacuum unto a rotating cathode. The resultant X-rays should help me decide if it's safe for me to introduce a hollow needle between some lady's bones.

OK, she survived.

I do believe in the constancy of lightspeed. It's one of the major reasons I gave up being a YEC and became an Old Universe Creationist (OEC, or old Earth creationist) long ago.

In addition, methinks there might be a simple solution to the shifted atomic spectra of distant quasars. Since the cosmological constant is back, and space spontaneously grows, this would slightly seem to prolong lightspeed as the sapce covered lengthens during travel. But, like Arumna, this is way over my head.

What I do wish to say is that we are all making a basic assumption: that all the constants remain stable throughout the universe. There's an inherent monotheism in the thought that the Universe is all places the same. While some of this can be supported by spectral analysis, it does not guarantee that all the constants together change in some complicated fashion "out there, somewhere."

Nowhere in any of this can it be presuposed that any such subtle changes can whittle down the age from billions to even tens of thousands. The whole argument, while interesting, is completely irrelevant as a support for YEC.

JR

[aReformedPatriot]

Arunma, I will pay you 4000 blessings a week to do my Chemistry homework. *nudge*

[HypoTypoSis]

Concerning the Early History of Planet Earth (http://www.ldolphin.org/Early.html)

by
Lambert Dolphin (http://www.ldolphin.org/)


The most popular current secular scientific explanation for the origin of the solar system and the planets suggests that everything formed by a cold accretionary process involving the coalescence, accretion and compression of the abundant gas and dust molecules that "fill" empty space most everywhere.

The Bible, on the other hand describes the formation of the earth's surface as being accomplished by the hand of God from surrounding waters on the Second Day of creation. The sun, moon, stars and other objects in space were specifically made on the Fourth Day. There was light (Heb., or) created on Day One (which may explain the present background radiation temperature of space), but the stars themselves (maor), the "light-holders," were not activated until Day Four.

Both the secular and the Biblical views would suggest that the earth should be a uniform sphere with all the elements mixed uniformly from crust to core. However this is not what we know to be true. Sometime in earth's early history most of the iron sank to the core while silicon, aluminum, calcium, potassium and sodium have been concentrated in the crust. How did this differentiation come about? The vertical arrangement found within the earth is not according to relative weights.

The answer may be that the elements in the earth occur in the form of compounds having various melting points, chemical activities, and densities. These properties determine the vertical distribution of elements-assuming that the interior of the earth was hot enough to melt everything at some time in the past.

Certain silicates of calcium, sodium, potassium and aluminum, known as feldspars, are easily melted (700-1000 degrees C) and when molten they are relatively light and tend to "float" upwards. Feldspars are common in the earth's crust.

The mantle of the earth, between the crust and the core became the reservoir presumably because magnesium-iron silicates melt less easily than the feldspars, so the principal minerals in the mantle seem to be olivine and pyroxene.

Presumably most of the earth's gold and platinum---inert as far as oxygen is concerned-sank to the core, while other heavier elements such as uranium and thorium formed lighter oxides which rose to accumulate in the crust.

How did the early earth become hot enough for the core to melt? Genesis One suggests the early earth was no colder than ice and no hotter than steam, otherwise the description of the original main continent being brought forth out of the waters (on Day Two as stated in Gen. 1:6) would not be correct. For discussion purposes, if God had "compacted" the sphere of the earth together allowing gravity to do most of the work, the resulting interior temperature would have been less than 1000 degrees C. Iron does not melt, nor could liquid iron sink to the core of the earth where most of it resides today, without the temperature being at least 3700 degrees C. (Heat flow measurements and calculations place an upper limit of about 4300 degrees C as the probable maximum temperature at the center of the earth).

Note Added: Laboratory measurements of the melting point of iron at the pressures found at the depth of the earth's core suggest the temperature in the core could be as high as 6200 degrees C which is hotter than the surface of the sun.

One important feature of the zoning of minerals in the earth is that the radioactive elements are now almost all located in the crust. Careful measurements of heat flowing up from the interior of the earth under the continents, ocean floors, in deep mines and drill holes tells us that most of the interior heat comes from radioactive decay of elements (isotopes of uranium, thorium, potassium) concentrated in the crust in a few parts per million. This heat flow (averaging about 1.5 microcalories per square centimeter per second) adds up to about 250,000 megatons of energy released to the surface per year, a thousand times the energy released by all the earthquakes per year, but 5000 times less than the energy received from the sun.

Radioactive heating of the earth's interior could have provided enough energy to heat the early earth on the interior from 1000 to perhaps 3000 degrees or higher resulting in "core meltdown." When the melting point of iron was reached, it is suggested that iron sank to the core and liberated immediately an additional 1022 megatons of gravitational energy! As this meltdown process took place the radioactive elements floated to the top and became concentrated in the top 10-20 kilometers of crust where they are found today.

Not all astronomers agree with the above model. Those who favor a proto-sun with planetesimals propose a spinning nebula cloud with a plasma disk that cooled from perhaps 5000 degrees at the sun's surface to about 300 degrees at the distance of earth from the sun to 0 degrees at Jupiter's position. In this view, differentiation of the planetary interiors occurred as they were being formed. Depending on the temperature and size of the planet helium and hydrogen were retained or lost.

How can this contemporary secular scientific view of earth's early history be fitted to the Genesis record? It is impossible to be dogmatic but this author believes that radioactive processes may have been "switched on" at the time of the fall of man or the angels. The curse on the earth described in Genesis 3 suggests that God decreased the power flow from the spiritual realm into the physical realm at that time. The whole creation then became subject to "the bondage of decay". In physics we see this principal operating today---it is the familiar Second Law of Thermodynamics---the tendency of things to rot, rust, decay, run down and fall apart with the passage of time-as well as the increasing unavailability of energy to do useful work and nature's inexorable tendency towards chaos and disorder.

Thus the creation as it existed at the end of Creation Week operated very differently from the observed behavior of the present universe. The laws of physics have been disrupted and we can not project present data back to t = 0. There have been one or more discontinuities in the laws of nature in the past associated with the fall and with God's miraculous interventions in history. That is, the commonly-held principle of uniformitarianism is invalid---as the Apostle Peter speaks so clearly about in the third chapter of his second epistle.

Radioactive isotopes are unstable (several nuclear processes are involved) because there is insufficient nuclear binding energy in the potential well of the nucleus to contain all the particles of the nucleus. As a result these isotopes spontaneously decay with characteristic half-lives. They emit alpha, beta and gamma particles as they decay and these energies ultimately end up as heat inside the earth. As a side note, the various rates of radioactive decay are mathematically proportional to the velocity of light, and according to the work of Barry Setterfield and Trevor Norman the rate of radioactive heating of the early earth could have been much faster than it is now. Also, the run rate of the atomic clock is proportional to c-Setterfield and Norman believe the initial value of c at the time of creation was nine to eleven million times greater than the present value. A higher initial velocity of light in the past would indicate a very recent creation of the universe because the atomic clock would slow down with respect to dynamical time if c were higher in the past. The statistical evidence that c has decreased in the past 300 years is very strong.

This author suspects (but can not prove) that all atomic elements and isotopes were stable before the fall. Not only is man fallen and subject to death, but the evil resulting from the rebellion led by Lucifer has damaged the physical universe as well. Colossians 1:17 states that "all things hold together" in Christ. The Greek word usually translated "consist" can be translated "cohere" or "are compacted together" which suggests that all the forces of nature---especially those which hold the atoms together in stable configurations-are forces that originate in Christ's sustaining power over the creation. As the old spiritual suggests, "He's got the whole world in His hands..." (quite literally). Peter the Apostle vividly alludes to these atomic forces being under God's direct control as well. Any decrease in the spiritual power which holds the universe "compacted together" would produce a more unstable situation, and a tendency towards chaos and disorder. I believe this instability could have included certain previously stable atomic nuclei becoming radioactive after the fall. Before the fall the universe was probably self-restoring and self-healing, and that state of the affairs will probably be re-established when Christ brings about the new heavens and new earth, making all things new.

There is another great mystery in science that would be partially explained by the assumption that radioactive decay was switched on subsequent to the completion of creation week. Thin slices of many crustal rocks (granites for example, but also certain sedimentary rocks such as coalified wood) contain tiny spherical radiation burn rings known as "pleochroic halos." The study of these halos has occupied much of the professional career of a distinguished scientific researcher by the name of Robert Gentry. If the rocks on the interior of the earth were once molten and formed over millions of years many radioactive elements would have totally decayed long before the rocks crystallized and there would be no halos. It is as if the rocks and their included radioactive isotopes were all created in an instant of time so that the halos began to form immediately in rock that was already differentiated, and cool.

The most puzzling pleochroic halos are those due to Polonium 210. Although the decay of Uranium 238 to Lead 206 involves Polonium as an intermediate daughter isotope, and although the half-life of U238 is 4.5 billion years, some halos are found that clearly had no Uranium parent isotopes. The half life of Po218 is only minutes, yet perfectly clear pleochroic halos from polonium decay are found in the heart of solid rock!

Either the radioactive polonium atoms were frozen nearly instantly into the parent rocks at the "moment" of creation by divine fiat, or the Polonium was not originally radioactive when the rocks crystallized. In either case there is no way to reconcile these Polonium halos with an old universe and the supposedly slow processes (millions of years) of rock formation and slow geologic processes.

In light of Gentry's work it is quite possible that radioactive heating of the earth was not the cause of core meltdown of the early earth after all-the observed differentiation of the elements could have some other cause. If isotopes which were originally stable later became radioactive after they were concentrated by some other mechanism into the crust, the heat released in the crust might help to explain rapid fracturing of the earth's crust at the time of the Flood of Noah, and rapid continental drift perhaps a hundred years later.

Speaking of the Flood of Noah, various calculations of the amount of water that might have been contained in a vapor canopy above the earth show that most of the water for the flood apparently came not from rainfall, but from the opening of the so-called "fountains of the deep" mentioned in Genesis 7:11. The evidence from many passages of scripture is that very large quantities of water were once trapped within the earth. Most of this water now resides in earth's oceans having been violently released by run-away heating and cracking of the crust at the time of the Flood.

Perhaps the mechanism of the Flood, and its very timing 1656 years after Adam left the garden was all set into motion by Adam's fall. This would be but one example suggested in the Bible that man's sin affects nature, and that the forces of nature are delicately balanced and very much related to the design of the universe with man placed on center stage in the design of things.

[HypoTypoSis]

Implications of a Non-Constant Velocity of Light (http://www.ldolphin.org/cdkconseq.html)

[cubanito]

Again: I am very ignorant of Geology.

However there's something I find peculiar in the above. Radioactive elements are very heavy and dense. How is it that they would float to the surface?

Well, maybe this is the wrong thread to ask.

However I do agree w this: all our physics is based on the presuposition that physical constants have not changed. There have been several supports put forth that this is the case (I remember something about a natural natural fission reactor). I personally think this is a very good assumption to make, so long as it is remembered it is an assumption.

JR

[JPPT1974]

HypoTypoSis, you act as though you
Are a professor of chemistry?
Are you because you speak like a
Very intelligent person!:thumbsup:

[HypoTypoSis]

Again: I am very ignorant of Geology.

However there's something I find peculiar in the above. Radioactive elements are very heavy and dense. How is it that they would float to the surface?

Well, maybe this is the wrong thread to ask.

However I do agree w this: all our physics is based on the presuposition that physical constants have not changed. There have been several supports put forth that this is the case (I remember something about a natural natural fission reactor). I personally think this is a very good assumption to make, so long as it is remembered it is an assumption.

JR

I don't that that is all the case as we typically see uranium oxide in as little as 100 to 300 feet. 600 is kinda deep. The first discovery was on the surface.

The 3 article brings back an interesting argument regarding the young earth creation theory. Since many of the stars are billions (and more) light years from earth that light has been traveling for billions of years before reaching earth.

On the other hand, if everything was created at once and proceeded outward then the light would be trailing the passage of the celestial bodies as they traveled at (presumably, instantaeous) "creation speed" to their (then) ultimate (and relative) positions.

[HypoTypoSis]

HypoTypoSis, you act as though you
Are a professor of chemistry?
Are you because you speak like a
Very intelligent person!:thumbsup:

Not likely. Check out the two links at the top of the article/post. The author, Lambert Dolphin, is a Christian physicist who has written extensively. His website is most unique.

[daveleau]

I don't know, and I don't know if any scientist can say for sure that the speed of light is constant over light years. But, Gerald Schroeder wrote a very interesting book called "The Science of God" that discusses Young Earth creation with a twist. He views it in light of Einstein's theory of relativity. Some of the book is tough to digest, but he warns people of it when he's about to get really into deeper physics, and tells the reader what to skip to avoid it (ie: start reading again in 10 pages...). It's an interesting view of Young Earth.

(I just realized this is the 3rd post of yours I've responded to today. Strange. We just have similar interests, I guess. :))

In Him,
Dave

[cubanito]

Hmmm... two different questions.

Is lightspeed constant throughout the Universe?

Has lightspeed remained constant through time?

The second one is especially tricky. Most cosmological models include a period of inflation from plank length (10-32 meter) to something like a volleyball in a fraction of a second, but some add a second inflationary period. Neither violates lightspeed.

You know what, forget it.

I've a grasp on biochemistry and the areas right around it. I am too old, tired, short of time and money to start wracking my head over this. I have 4 kids and a wife to provide for.

I'll remain an Old Earth Creationist, open to YEC, and totally convinced that irreducible complexity demolishes neodarwinism. That much I can understand.

Bye, I'm going to drink my prune juice now.

JR

[HypoTypoSis]

Is everything God does perfect first time every time?

If so, then, this would seem to be a good argument against radioactive half lifes being turned on at creation but, rather, at the fall of Satan.

The fall of Satan would appear to be what damaged creation while man's Fall damaged the natural order of things.

[cubanito]

Perfect does not necessarily mean "completed".

One of the most fascinating parts of Scripture to me is when He says of the pre-fall Adam: "It is not Good for man to be alone."

That aside, as an OEC I believe (though not firmly) that Gen 1:1 is a statement about the totality of Creation. That some unknown period of time elapsed between Gen 1:1 and Gen !:2, and that after some cataclysmal event on the earth what we read thereafter is a restitution of the Earth (as viewed from an Earthbound viewpoint), as well as some de novo creations, such as man.

This is an old idea, promulgated in the old "Scofield Bible" notes. It therefore allows for the fossil record, an old Earth and Universe, AND a literal 6 day "re-creation. It certainly has many problems, as frankly doe all the ideas I've read so far, but it's what I currently hold.

One thing I'm sure of from Biochem: there is indeed all manner of irreducible complexity that is unable to be fitted in with naturalistic evolution.

JR

[HypoTypoSis]

Perfect does not necessarily mean "completed".

One of the most fascinating parts of Scripture to me is when He says of the pre-fall Adam: "It is not Good for man to be alone."

That aside, as an OEC I believe (though not firmly) that Gen 1:1 is a statement about the totality of Creation. That some unknown period of time elapsed between Gen 1:1 and Gen !:2, and that after some cataclysmal event on the earth what we read thereafter is a restitution of the Earth (as viewed from an Earthbound viewpoint), as well as some de novo creations, such as man.

This is an old idea, promulgated in the old "Scofield Bible" notes. It therefore allows for the fossil record, an old Earth and Universe, AND a literal 6 day "re-creation. It certainly has many problems, as frankly doe all the ideas I've read so far, but it's what I currently hold.

One thing I'm sure of from Biochem: there is indeed all manner of irreducible complexity that is unable to be fitted in with naturalistic evolution.

JR

Yes, well, there is indeed a "seeming" contradiction with respect of the continuity of Gen 1:1 and 1:2. I tend to agree with you in this respect and that it is in this interim period is the source of all archeological discoveries with respect to dinosaurs, what could possible be Satan's earlier attempts at creation or even supplanting the coming of mankind (Adam), and other anomalies assigned generally to and ascribed to by the humanists, evolutionists, New Agers, etc. Yes, whatever God does He does perfect. It only takes the likes of pridefully sinful angels and men to screw it up. So, in this respect, the events that follow from 1:3 onward would appear to logically account for a subsequent recreation.

[arunma]

Arunma, I will pay you 4000 blessings a week to do my Chemistry homework. *nudge*

Oh...I'm not sure you want me to do that, since chemistry isn't really my thing. I can balance a few equations and construct a Lewis dot diagram, but I have a healthy fear of organic chemistry. I think that would be JR's department.

[Andyman_1970]

There is evidence that a vacuum can speed up light and it's been proven that light slows down in matter.


Where in the universe does a perfect vacuum exist??

[arunma]

There is evidence that a vacuum can speed up light and it's been proven that light slows down in matter.

I'm sorry, I missed this specific sentence until Andy quoted it. It is true that light is retarded by a medium. In fact this is one of the oldest results of electrodynamics. It is not that a vacuum speeds up light. On the contrary, the vacuum speed of light is regarded as the speed of light, and the tabulated value of the speed of light assumes a perfect vacuum. The reason the speed of light does not change spatially is because of the fact that the derivation of the speed of light does not make reference to any medium. Since a vacuum is the absence of matter rather than a thing in and of itself, this result actually attests to the unchanging nature of the speed of light.

[JPPT1974]

I'm sorry, I missed this specific sentence until Andy quoted it. It is true that light is retarded by a medium. In fact this is one of the oldest results of electrodynamics. It is not that a vacuum speeds up light. On the contrary, the vacuum speed of light is regarded as the speed of light, and the tabulated value of the speed of light assumes a perfect vacuum. The reason the speed of light does not change spatially is because of the fact that the derivation of the speed of light does not make reference to any medium. Since a vacuum is the absence of matter rather than a thing in and of itself, this result actually attests to the unchanging nature of the speed of light.


Man that is something about the value
Of speed of light doesn't change at all.
That they do stay the same.