Slowing Light to 38 mph - Exploring Refraction & Einstein's Theory

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In summary, the conversation discusses an experiment where scientists were able to slow light to 38 mph, contradicting Einstein's theory that light travels at a constant speed of 3x10^8. The conversation also delves into the concept of the speed of light in a vacuum and how it is not fundamentally the same as the speed of light in matter. The possibility of light having a rest mass is also mentioned, along with relevant resources for further reading.
  • #1
1MileCrash
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I was just checking out an article that talked about scientists who were able to slow light to 38 mph. they went on to say that "einstien said that light could only travel at 3x10^8, but he never said it couldn't go slower!"

this seems plainly wrong to me. in my understanding, current theory would be violated if something were able to "cross the threshold" something that could travel the speed of light, or below it, or above it. if a particle were found that traveled faster than the speed of light, theory would still be applicable unless that same particle were able to slow down to lower than the speed of light (if i am incorrect here, please educate me)

even when we say "light travels slower through air than through a vacuum" this is essentially because refraction causes the light to travel further, thus making it appear to travel more slowly.

so how is this experiment explained? is it the same case as traveling through air?
 
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  • #2
It's the speed of light in a vacuum that is fixed according to relativity, not the speed of light in matter. Light goes about 2x10^8 m/s in water, but that has nothing to do with relativity. The following FAQ may also be relevant.

FAQ: Is the c in relativity the speed of light?

Not really. The modern way of looking at this is that c is the maximum speed of cause and effect. Einstein originally worked out special relativity from a set of postulates that assumed a constant speed of light, but from a modern point of view that isn't the most logical foundation, because light is just one particular classical field -- it just happened to be the only classical field theory that was known at the time. For derivations of the Lorentz transformation that don't take a constant c as a postulate, see, e.g., Morin or Rindler.

One way of seeing that it's not fundamentally right to think of relativity's c as the speed of light is that we don't even know for sure that light travels at c. We used to think that neutrinos traveled at c, but then we found out that they had nonvanishing rest masses, so they must travel at less than c. The same could happen with the photon; see Lakes (1998).

Morin, Introduction to Classical Mechanics, Cambridge, 1st ed., 2008

Rindler, Essential Relativity: Special, General, and Cosmological, 1979, p. 51

R.S. Lakes, "Experimental limits on the photon mass and cosmic magnetic vector potential", Physical Review Letters 80 (1998) 1826, http://silver.neep.wisc.edu/~lakes/mu.html
 
  • #3
Although neutrinos go slower than the speed of light, photons do not (in a vacuum)..
 
  • #4
mathman said:
Although neutrinos go slower than the speed of light, photons do not (in a vacuum)..

I assume this is in reply to "The same could happen with the photon"? In that case, take a look at the Lakes paper, which is about setting an upper limit on the mass of the photon.
 
  • #5
The material absorbs and re-emits photons, which takes a while, therefore the light appears to move more slowly through the material. The photons that come out are not really the same ones that came in (although that may be a philosophically debatable issue).
 

1. How is it possible to slow light down to 38 mph?

Slowing light down to 38 mph is achieved through a phenomenon called "refraction." This is when light passes through a medium, such as water or glass, and its speed is reduced. By carefully controlling the material and conditions, scientists have been able to slow light down to extremely low speeds.

2. What is the significance of slowing light to such a slow speed?

Slowing light down to such a slow speed allows scientists to better understand the properties and behavior of light. It also has practical applications in technologies such as fiber optics and quantum computing.

3. How does slowing light down relate to Einstein's theory of relativity?

Einstein's theory of relativity states that the speed of light is constant and cannot be exceeded. Slowing light down to 38 mph is a demonstration of how even light, which is typically thought of as the fastest thing in the universe, can be manipulated and controlled under certain conditions.

4. Can light be slowed down to speeds even slower than 38 mph?

Yes, scientists have been able to slow light down to speeds as slow as 38 miles per hour. However, with advancements in technology and the understanding of light, it is possible that even slower speeds could be achieved in the future.

5. What other experiments have been conducted to explore light's behavior and properties?

Aside from slowing light down, scientists have also conducted experiments such as splitting light into its component colors, measuring its wavelength, and testing its polarization. Other experiments involve manipulating light through devices like lenses and prisms, and using it to create images and transmit information.

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