Criticality accident
http://en.wikipedia.org/wiki/Criticality_accident

It has also been proposed by some, that the blue flash
is produced when beta radiation from the criticality
event enters the eye of the observer and causes the
emission of Cherenkov radiation as it traverses the
vitreous humor of the eye. Though this effect is possible
and was in fact noted by Apollo astronauts during their
trip to the moon when they closed their eyes, the effect
observed by the Apollo astronauts was due to exposure
to very high energy cosmic rays, not beta particles. ...

In addition, the flashes seen by the Apollo astronauts
were almost always described as being white with only
one event described as being "blue with a white cast,
like a blue diamond" while descriptions of the blue light
accompanying criticality events is almost universally
described as being "a blue glow".

On Apr 6, 9:53 am, ca314159 wrote:
Criticality accidenthttp://en.wikipedia.org/wiki/Criticality_accident

It has also been proposed by some, that the blue flash
is produced when beta radiation from the criticality
event enters the eye of the observer and causes the
emission of Cherenkov radiation as it traverses the
vitreous humor of the eye. Though this effect is possible
and was in fact noted by Apollo astronauts during their
trip to the moon when they closed their eyes, the effect
observed by the Apollo astronauts was due to exposure
to very high energy cosmic rays, not beta particles. ...

Why would that rule out Cerenkov radiation? All that
matters is that you have a charged particle moving
faster than c/n, the speed of light in the medium.

In addition, the flashes seen by the Apollo astronauts
were almost always described as being white with only
one event described as being "blue with a white cast,
like a blue diamond" while descriptions of the blue light
accompanying criticality events is almost universally
described as being "a blue glow".

OK, I see. The Wiki article is making a case that the
blue light seen at criticality incidents is not
Cerenkov.

What was your reason for posting this quote?

- Randy

Dear ca314159:

On Apr 6, 6:53 am, ca314159 wrote:
Criticality accidenthttp://en.wikipedia.org/wiki/Criticality_accident

It has also been proposed by some, that the blue flash
is produced when beta radiation from the criticality
event enters the eye of the observer and causes the
emission of Cherenkov radiation as it traverses the
vitreous humor of the eye. Though this effect is
possible and was in fact noted by Apollo astronauts
during their trip to the moon when they closed their
eyes, the effect observed by the Apollo astronauts
was due to exposure to very high energy cosmic rays,
not beta particles. ...

Consider that the reason they did not include massive "radiation
shielding" in the spacecraft is because any shielding we could loft
would only serve to increase the numbers of energetic particles
produced, without much affecting the total energy. If you look at the
decay of K40, there is a "clean" beta decay, and a *very dirty*
positron decay with about 30 identified daughter photons... all very
energetic.

Apollo astronauts most likely saw many scattered energetic electrons
few cosmic rays... rather than the rays themselves.

In addition, the flashes seen by the Apollo astronauts
were almost always described as being white with only
one event described as being "blue with a white cast,
like a blue diamond" while descriptions of the blue light
accompanying criticality events is almost universally
described as being "a blue glow".

Rods are active / activated with eyes closed. They do not perceive
color, only "shades of grey". The cones perceive color, but require
more light than can be had with the eyes closed... unless fatal
amounts of energetic electrons are being beamed at them.

I often wonder if my million curie Co-60 gamma source would have
glowed a different color, had it been kept under 20 feet of ethanol...
of course, I had an operator that I think would have drunk the pool
dry were that the case.

But the characteristic Cherenkov radiation color is evident even from
our own atmosphere.

David A. Smith

On Apr 6, 6:53 am, ca314159 wrote:

Criticality accident
thttp://en.wikipedia.org/wiki/Criticality_accident

It has also been proposed by some, that the blue flash
is produced when beta radiation from the criticality
event enters the eye of the observer and causes the
emission of Cherenkov radiation as it traverses the
vitreous humor of the eye. Though this effect is possible
and was in fact noted by Apollo astronauts during their
trip to the moon when they closed their eyes, the effect
observed by the Apollo astronauts was due to exposure
to very high energy cosmic rays, not beta particles. ...

In addition, the flashes seen by the Apollo astronauts
were almost always described as being white with only
one event described as being "blue with a white cast,
like a blue diamond" while descriptions of the blue light
accompanying criticality events is almost universally
described as being "a blue glow".

These flashes were also observed by the Gemini astronauts. Maybe the
Mercury astronauts as well. The argument is the frequency and
intensity which translates into noticeability by these astronauts. As
I understand it, the Gemini and the Apollo missions only reported them
as nuisance which only occurs relatively infrequent compared with that
high-altitude space shuttle mission in which these flashes with their
eyes closed became somewhat unbearable.