Cerenkov Light: What is it?

[willbirful]

This is a great video

[lduych]

@fermilabvms

(1-2)

"The ratio between c and the speed v at which light travels in a material is called the refractive index n of the material (n = c / v). For example, for visible light the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200,000 km/s; the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 90 km/s slower than c."

~Wikipedia

cont...

[lduych]

@fermilabvms

(2-2)

The refectory index of water is n ≈ 1.33881 which is NOT less than one.

There is no known medium with a refractive index less than 1, therefore your statement:

"Actually, the particles ARE moving faster than the speed of light in a medium (pure oil or water) "

is false.

My source:

refractiveindex [dot] info

[lduych]

Assuming c is the cosmological speed limit (and especially as the neutrino is not massless). Cerenkov Light, as defined in this video, can never have been observed. But 'Cerenkov Light' has been observed. Therefore the mechanism presented here as to how Cerenkov Light is caused cannot be correct. If it were correct, then the existence of ftl-neutrinos would not be a supposed anomaly recently detected(maybe) by OPERA but, rather, an already well established, observable fact. But it isn't. FAIL.

[Shadowfax913]

that awkward moment when a duck swims by, effectively ruining your experiment, while you're demonstrating cerenkov light with pebbles and a body of water

[Tan070]

Completely skipped over the main point of this video - Cerenkov light. Are the light particles being produced from the charged particle exciting and then de-exciting the water molecules or is being given off directly from the charge particle?

Other than that analogies were excellent...especially the fact you used unusual (the duck and bullet) as well as usual ones too.

[evgsin]

Cherenkov was not the first who explained this phenomenon, he was the first to observe it. The theoretical explanation of the phenomenon was given by I. Tamm and I. Frank in 1937.

[Iwilldiesome]

very nice and almost self explainatory

[Hughdapu]

this music sounds at the start reminds me of shenmue.

fuck i miss my dreamcast for tht game

[sudoLinux666]

Very nice, and easy explanation, and the analogies were terrific! Thank you for uploading.

-Nick

[AttemptingReason]

This video is fantastic, it makes me feel smarter =D

[fatihkhider]

I liked this vidio VERY much. The explanation is simpler and clearer than it ever be!!? very few can explain phenomena as simple as this. the auther explained the sonic boom and Cherenkov radiation with a single stone!! I would say just BRAVO!!

[brockunc]

There is a problem with the explanation. Particles can not move faster than the speed of light. Other than that good demo but you need to to think about rewording those parts.

[fermilabvms]

@brockunc Actually, the particles ARE moving faster than the speed of light in a medium (pure oil or water). You may know light travels different speeds in different media. The maximum speed of light is the speed of light in a vacuum. In these experiments particles are moving close to the speed of light in a vacuum, and suddenly they are in a vessel of oil or water, where the speed of light is slower. Cerenkov light is emitted because they are traveling faster than light in the oil or water.

[SkeksisRule]

@brockunc You can move faster than the speed of light if you slow down the light, which can be achieved through a medium. So yes, it is possible to move faster than light as long as you are not in a vacuum.

[DarkStar1O9]

THANK YOU!

[AluminumStudios]

One weak spot of the explanation, at 4:00 the narrator says that particles produced are traveling faster than the speed of light in the water or oil.

He should explain that the speed of light is slower in some mediums (like water or oil). The particles aren't actually going faster than "the speed of light" but rather faster than the light can go in the liquid medium.

[fermilabvms]

@AluminumStudios , Actually, the narrator *does* say "If a charged particle is traveling faster than the speed of light in that medium, ... ", which is exactly what is happening. But I can understand how a more thorough explanation might make the concept more apparent.

[derenkoff]

lol my family name is derenkov

[ductonius]

Very good explanation.

[AukraNET]

Nice clip! Thanx :)

[warriorsoul28]

cute ducks

[warriorsoul28]

i ve seen it for real

[TrippnTroll]

Loved this video! Many thanks!

[IvanStrelnikov]

This helped explain the 'why' and 'how' of Cerenkov radiation, but to the layman, the 'what' is totally unaddressed. Thirty seconds of the Penn State or the Advanced Test reactor explaining that there are no light sources on in the pool, yet the core glows brightly due to Cherenkov Radiation would have accomplished this. Tack it on to the beginning and you're all set.