It is always interesting to speculate on the dispersion of the speed of light. The most accurate values to date are at the CH4 transition at 88.4 THz and the one reported here. Using formula

“Considering: that the present definition does not allow a sufficiently precise realization of the meter for all requirements,

Articles from Journal of Research of the National Bureau of Standards are provided here courtesy of National Institute of Standards and Technology

that a new definition of the meter has been envisaged in various forms all of which have the effect of giving the speed of light an exact value, equal to the recommended value, and that this introduces no appreciable discontinuity into the unit of length, taking into account the uncertainty of ±4×10−9 of the best realizations of the present definition of the meter,

About the Authors: D. A. Jennings, R. E. Drullinger, K. M. Evenson, and J. S. Wells are physicists with the NBS Time and Frequency Division. C. R. Pollock, an electrical engineer, is a former member of the division who is now with the School of Electrical Engineering, Cornell University, Ithaca, NY 14853.

by means of one of the radiations from the list below, whose stated wavelength in vacuum or whose stated frequency can be used with the uncertainty shown, provided that the given specifications and accepted good practice are followed;

It goes where you put it, can be moulded a little, and can be sanded or carved, but it is ‘brittle’ so can be chiseled off if unwanted. I filled a 5mm deep drilled hole & 2x3mm square in an afv club part. It did set all the way through.

with an estimatedc overall relative uncertainty of ±6×10−10 [which results from an estimated relative standard deviation of 2×10−10] apply to the radiation of a dye laser (or frequency-doubled He-Ne laser) stabilized with a cell of iodine, within or external to the laser, having a cold-finger temperature of 6 °C±2 °C.

“..that … the fundamental measurements of the international and national prototypes of the meter [has] been made with all the accuracy and reliability that the present state of science permits; that the international and national prototypes of the meter are made of an alloy of platinum with 10 percent iridium, to within 0.0001; the equality in length of the international Meter … with the length of the Meter kept in the Archives of France;

that progress made in the measurement of the frequency and wavelength of these radiations has resulted in concordant determinations of the speed of light whose accuracy is limited principally by the realization of the present definition of the meter,

I’ve tried the glue from Revell and a German none model company both with mixed results, mainly on wargame figures. If the UV light can’t get all the way through the resin then it will not cure and in one instance I couldn’t even get the resin to cure that the light was immediately above, so as stated above it does seem to have a limited shelf life. So not something you can put in the tool rack for when you need it, more of something you get just for that task you are doing now.

The Journal of Research of the National Bureau of Standards is a publication of the U.S. Government. The papers are in the public domain and are not subject to copyright in the United States. Articles from J Res may contain photographs or illustrations copyrighted by other commercial organizations or individuals that may not be used without obtaining prior approval from the holder of the copyright.

This value of c, the most accurate ever measured for visible light, is in good agreement with the defined value of c proposed by the CCDM within the recognized uncertainties in the use of the krypton length standard (±1.2 m/s, 3σ) [11], and was the final confirmation in the choice of the new definition for the standard of length.

with an estimated overall relative uncertainty of ±1.1×10−9 [which results from an estimated relative standard deviation of 3.7×10−10] apply to the radiation of a He-Ne laser stabilized with a cell of iodine, within or external to the laser, having a cold-finger temperature of −5 °C±2 °C.

by means of the length l of the path travelled in vacuum by a plane electromagnetic wave in a time t; this length is obtained from the measured time t, using the relation l =c · t and the value of the speed of light in vacuum c = 299 792 458 m/s;

with an estimated overall relative uncertainty of ±1.3×10−9 [which results from an estimated relative standard deviation of 4.3×10−10] apply to the radiation of an Ar+ laser stabilized with a cell of iodine, within or external to the laser, having a cold-finger temperature of −5 °C±2 °C.

considering the excellent agreement among the results of wavelength measurements on the radiations of lasers locked on a molecular absorption line in the visible or infrared region, with an uncertainty estimated at ±4×10−9 which corresponds to the uncertainty of the realization of the meter,

that progress made in the stabilization of lasers allows radiations to be obtained that are more reproducible and easier to use than the standard radiation emitted by a krypton 86 lamp,

Bondic is great for some applications. It is very good for attaching and repairing 3D UV Resin printed parts since it effectively the same compound and literally welds to UV resin. It’s good for similar use on wood. Metal needs to be roughen to give it some bite. It’s dubious for styrene since it doesn’t adhere well. It’s great for making lens and instrument glass since it cures in about firve seconds. Since I am a massive 3D printer modeler, I rely on Bondic a lot.

I’ve used UV glues as well, but so far the applications in modeling I have found are pretty limited. If you want to bond two pieces together, one of them has to be clear in order for the light to get in and cure the resin. Also, as Jon already mentioned, it can be brittle, which means that if you only use a thin layer to bond a small piece it doesn’t hold very well, especially with PE and such. It also seems to have a surprisingly short shelf life. Once it starts to yellow, it doesn’t seem to like to cure thoroughly. My experience is that it seems to work best for applications in which you can build up a pretty substantial blob of the stuff layer-by-layer.

that the CCDM is now in a position to give instructions for the practical realization of such a definition, instructions which could include the use of the orange radiation of krypton 86 used as standard up to now, and which may in due course be extended or revised,

I haven’t used it myself, but I have watched a number of videos of large-scale figure modelers using it with their 3D prints to assemble and fill gaps. In this use it does seem to fit their needs.

The unit of length is the meter, defined by the distance, at 0°, between the axes of the two central lines marked on the bar of platinum-iridium kept at the BIPM, and declared Prototype of the meter by the 1st CGPM, this bar being subject to standard atmospheric pressure and supported on two cylinders of at least one centimeter diameter, symmetrically placed in the same horizontal plane at a distance of 571 mm from each other.”

with an estimated overall relative uncertainty of ± 1×10−9 [which results from an estimated relative standard deviation of 3.4×10−10] apply to the radiation of a stabilized He-Ne laser containing an iodine cell, subject to the conditions:

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recommends the use of the resulting value for the speed of propagation of electromagnetic waves in vacuum c = 299 792 458 meters per second.

“Sanctions The Prototype of the meter chosen by the Comité International des Poids et Mesures (CIPM). This Prototype, at the temperature of melting ice, shall henceforth represent the metric unit of length.”

that these various forms, making reference either to the path travelled by light in a specified time interval or to the wavelength of a radiation of measured or specified frequency, have been the object of consultations and deep discussions, have been recognized as being equivalent and that a consensus has emerged in favor of the first form,

“The 17th CGPM invites the CIPM to draw up instructions for the practical realization of the new definition of the meter to choose radiations which can be recommended as standards of wavelength for the interferometric measurement of length and to draw up instructions for their use.”

If some manufacturer sold it in a pen-form with a built in UV light and somewhat flexible resin, I might be interested in trying it for gluing PE parts. Shock-resistance and slight flexibility might trump the added volume in the glue joint. However, the brittle nature of the cured resin doesn’t seem to offer any advantage over CA which can be cured as fast with an accelerator.

I have a Resin Chevvy & have a HobbyBoss windscreen that ‘almost’ fits. A bit of Fettling & a shot of UV resin should be good. IF I get round to finishing it, I’ll let you know.

If some manufacturer sold it in a pen-form with a built in UV light and somewhat flexible resin, I might be interested in trying it for gluing PE parts.

We are reporting a value of c using visible rather than infrared radiation. This has been made possible by the absolute frequency measurement of the visible He-Ne laser stabilized on the ith hyperfine component of the 11-5, R(127) transition of the molecule 127I2 [8]. The reported value for the frequency of this transition is 473 612 214.830 MHz with a fractional uncertainty of 1.6×10−10. The wavelength for this transition is obtained from four published values which are 632 991 399.0±0.8 fm [9], 632 991 399.8±0.9 fm [10], 632 991 400.0±1.2 fm [11], and 632 993 398.0±3 fm [12]. These four wavelengths are from direct wavelength measurements referred to the wavelength of krypton. The weighted average of these measurements is 632 991 399.4±0.6 fm. The value for the speed of light is, of course, the product of the frequency and wavelength and is c= 299 792 458.6±0.3 m/s, with a one sigma uncertainty.

with an estimated overall relative uncertainty of ± 1.3×10−10 [which results from an estimated relative standard deviation of 0.44×10−10] apply to the radiation of a He-Ne laser stabilized with a cell of methane, within or external to the laser, subject to the conditions:

The speed of light has intrigued scientists for several centuries and during the short quarter century of the laser it has not been different. The measurement of the speed of light, c, by a group of scientists at the National Bureau of Standards in 1972 [1]1 reported a value for c from the product of the wavelength and frequency of a 3.39 μm He-Ne laser which was limited in accuracy by the uncertainty in the krypton length standard. This definitive measurement for c followed by other confirmative measurements prompted the international scientific community, through the Comité Consultatif pour la Definition du Metre (CCDM), to a new definition for the meter. The new definition for the meter, adopted by the Conférence Générale des Poids et Mesures (CGPM) in October 1983 reads, “The meter is the length of the path travelled by light in vaccum during a time interval of 1/299 792 458 of a second.” [2] This definition for the meter fixes the speed of light to be exactly 299 792 458 m/s. With this definition the meter could be realized from the wavelength of any coherent optical source whose frequency is known, for example, a laser which is stabilized to a narrow atomic or molecular absorption for which the frequency is known. The wavelength λ would be determined from the relation λ=c/v, where c is the fixed value of the speed of light, and v is the measured frequency of the transition. Since the measurement in 1972 there have been four speed of light measurements [3–6]; two at a wavelength of 3.39 μm and two at a wavelength of 9.31 μm. These measurements have been summarized [7], and the average value for the speed of light is 299 792 458.1 m/s with a fractional uncertainty of ±4×10−9 (3σ), which is the recognized uncertainty in the realization of the meter from the krypton definition.

This uncertainty, and the frequency and wavelength values, are based on the weighted mean of only two determinations. The more precise of the two, however, was a measurement dependent only on frequency mixing and multiplication techniques relative to the radiation in 1.1. above.

“that the differences between the national Meters and the international Meter lie within 0.01 millimeter and that these differences are based on a hydrogen thermometer scale which can always be reproduced..;

Perhaps I’m just too limited in my imagination, though. I’m not too proud to steal a good idea if someone comes up with one!

Still, I’m open to seeing what others might do with this UV resin adhesive. (It’s not a particularly new thing, either. UV resin glue pens were being sold more than a decade ago. There were even TV ads that showed it being used to “instantly” repair eye-glasses frames, etc. Our LHS got in a couple of boxes of them that they kept by the cash register and eventually sold them all, but they never re-stocked. My guess is there was no real demand from hobbyists.)

by means of the wavelength in vacuum λ of a plane electromagnetic wave of frequency f; this wavelength is obtained from the measured frequency f, using the relation λ = c/f· and the value of the speed of light in vacuum c =299 792 458 m/s;

I can’t imagine any fine scale modeling use where the “volumetric addition” of the UV resin would be acceptable except as a filler. Adhesives that add volume (or rely on volume to create their bond - the more volume-mass the stronger the bond) are generally not useful except in some limited applications. For example, epoxy-putty that can be sculpted to replicate weld beads as well as functioning as an adhesive. PVA and acrylic adhesives generally lose volume as they dry out, so they can be used for light duty purposes without adding too much objectionable volume to the joint area.

“The meter is the length equal to 1 650 763.73 wavelengths in vacuum of the radiation corresponding to the transition between the levels 2 p10 and 5 d5 of the krypton 86 atom.”

and that in all cases any necessary corrections be applied to take account of actual conditions such as diffraction, gravitation, or imperfection in the vacuum.

In this list, the values of the frequency f and of the wavelength λ should be related exactly by the relation λf=c, with c =299 792 458 m/s but the values of λ are rounded.

Appendices 1 and 2 are taken from NBS Special Publication 330, The International System of Units (SI) and are the official translations from the minutes of the General Conferences on Weights and Measures.

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that wavelengths determined from frequency measurements and a given value for the speed of light have a reproducibility superior to that which can be obtained by comparison with the wavelength of the standard radiation of krypton 86,

The following recommendations for the practical realization of the definition of the meter were adopted by the International Committee for Weights and Measures (Comité International de Poids et Mesures, CIPM) in 1983.

The fractional uncertainty of the meter realized through the new definition and use of a laser stabilized on either this frequency measured iodine transition [8], or another in the yellow region [13] is 10 times smaller than the uncertainty as realized through the krypton definition and would represent a tenfold improvement in accuracy for length metrology. Future frequency measurements in the visible will undoubtedly be even more accurate, ultimately being limited by the time standard itself. In fact, length metrology need not be limited by the frequency measurement of the laser used to realize the meter. Thus, with the new definition, a new era of length metrology is at hand, one in which the uncertainty will not be due to the length standard but with the measurement techniques.

I watched a youtube video of someone who used the glue that hardened with UV light. It gave him the time to get the piece just right then the UV light from his light source cured it in place. I do not recall anyone mentioning using it here. Thoughts, experiences?

Still experimenting with it, as a filler. My intention was to use it to ‘glue/fill’ a badly fitting canopy, but I cracked the canopy too badly to use.

that there is an advantage, notably for astronomy and geodesy, in maintaining unchanged the value of the speed of light recommended in 1975 by the 15th CGPM in its Resolution 2 (c =299 792 458 m/s),

“Considering that the international Prototype does not define the meter with an accuracy adequate for the present needs of metrology, [the CGPM] decides that it is moreover desirable to adopt a natural and indestructible standard.

Each of these radiations can be replaced, without degrading the accuracy, by a radiation corresponding to another component of the same transition or by another radiation, when the frequency difference is known with sufficient accuracy. Details of methods of stabilization are described in numerous scientific and technical publications. References to appropriate articles, illustrating accepted good practice for a particular radiation, may be obtained by application to a member laboratory of the CCDM, or the BIPM.

The product of the frequency and wavelength of the ith hyperfine component of the 11-5, R(127) transition of 127I2 yields a value for the speed of visible red light. This value of c, the most accurate ever measured for visible light, agrees with the value defined in the redefinition of the meter within the 3σ error limits of the krypton length standard.