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Refraction of light at the interface between two media.
The refractive index or index of refraction of a substance is a measure of the speed of light in that substance. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium.[note 1] The velocity at which light travels in vacuum is a physical constant, and the fastest speed at which energy or information can be transferred. However, light travels slower through any given material, or medium, that is not vacuum. (See: light in a medium).
A simple, mathematical description of refractive index is as follows:
n = velocity of light in a vacuum / velocity of light in medium
Dr Mattia Negrello, of the Open University and lead researcher of the study, explained, "Our survey of the sky looks for sources of sub-millimetre light. The big breakthrough is that we have discovered that many of the brightest sources are being magnified by lenses, which means that we no longer have to rely on the rather inefficient methods of finding lenses which are used at visible and radio wavelengths."
The Herschel-ATLAS images contain thousands of galaxies, most so far away that the light has taken billions of years to reach us. Dr Negrello and his team investigated five surprisingly bright objects in this small patch of sky. Looking at the positions of these bright objects with optical telescopes on the Earth, they found galaxies that would not normally be bright at the far-infrared wavelengths observed by Herschel. This led them to suspect that the galaxies seen in visible light might be gravitational lenses magnifying much more distant galaxies seen by Herschel.
Interesting. It's likely I've brought up this idea or something closely relating to it elsewhere. Also ties into Fizeau's experiment which is interesting in its own regard.
It had me wondering some things about light, particularly the nature of why c is considered the limit of how fast things can go. And yet the nature of c seems a little funky or paradoxical in some ways.
Light or photons is supposedly massless for all practical purposes. Yet gravity bends it. I think the nature of why gravity bends it has to do with the distortion of time within the gravitational field.
Speed is distance per unit time, so if you change what the unit of time is the speed will change in respect to that. A difference in speed for a beam of light passing through a gravitational field should be similar to a difference in speed when light passes through materials of different optical density.
Another interesting thing is that relativity shows that identical ideal clocks operating while traveling at different speeds or in differing gravitational fields show time dilation. That is, although the ability to measure time for clocks is the same, the actual time measured by them is not. Yet if you do an experiment to measure the speed of light under those circumstances, you will get the same value for c. Going back to speed being distance over time, that would also indicate that the measurement of c is also relative.
As the passage of the time in each case is not uniform. So if c is a relative measurement, how does it work as a universal constant?
Time dilation in regards to relativity seems indicative that there's no such thing as a universal clock. (Isn't that something that frustrated Einstein and had him rewrite some stuff a few times?)
It looks like the limit is always going to be c+(whatever your speed is) not matter how fast you're going. The "gaining mass" explanation seems funky, because to me it seems that the progression of time is what will shift in order to keep c as c within a relative frame of reference. The thing is, wouldn't one still cover more distance as they encounter "higher values" of c? It also leads me to question the use of light-years as a "yardstick" if the concepts of c and years are as variable as the gravitational fields one would encounter on a route covering such distances.
Seems some other funky ideas spring out knowing that E=mc^2. It would work out that E=m(d/t)^2 or E=m (area/time^2) and fiddling around with that m=E*time^2/area... Of course that's roughing it out loosely, since the ratio between distance and time is fixed by the c constant. However the values for d or t may not be constant, it's the ratio between the two that is c. It's funny that it works out as an area and not a volume, and the only other phenomena that I can think of involving time^2 is acceleration. Which then ties into either inertia or gravity. But that makes some sense into regards to mass.
The problem is, I'm not much for doing math. At one point I did some more advanced stuff, but I've burnt-out on the subject and haven't kept in practice. Still I'm wondering if I'm noticing any loopholes that may be related to c or the phenomena of gravity with such a basic approach. Practical applications of such loopholes are very intriguing if conditions for them exist.
Does anything I mentioned make any sense? Or is that as crazy an idea as seeing quantum effects possibly as a real world phenomena relating to the modulo operation?