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Old February 19th 21, 08:21 AM posted to alt.astronomy
R Kym Horsell[_2_]
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Default 'STUNNING ADMISSION' Pentagon admits it has been testing wreckage from UFO crashes

Daniel65 wrote:
R Kym Horsell wrote on 18/02/2021 11:33 pm:
Daniel65 wrote:
R Kym Horsell wrote on 18/2/21 6:04 pm:
Daniel65 wrote:
R Kym Horsell wrote on 17/2/21 11:37 pm:
In alt.astronomy Andrew W wrote:
...
Bragalia said it was a "stunning admission" from the US government and the
documents reveal that some of the retrieved debris possesses "extraordinary
capabilities" including the potential to make things invisible or even slow
down the speed of light.
It's disheartening to hear this last bit.
Many materials "slow down the speed of light". E.g. glass. The "refractive
index" of various glases on which optical instruments depend is the ratio of
the speed of light in the material to the speed of light in air.
Slowing down the speed of light in a vaccum would be the trick.
.... whereas slowing down the speed of light with a sheet of Lead is
quite easily done!!
What is lead's refractive index?
Umm!! At a guess, I'd say "Infinity" or very, very, close!!


They dope glass with lead to increase its refractive index (usually
written as symbol "n").
Making compound lenses for optical instruments from flint and lead glass
was a bit of a dark art when I was in school.
I presume these days it's all about selecting the right sensor
from an online catalog.
Scientists measured the refractive index of lead around 2.
I.e. the speed of light inside the metal is around 50% of the vaccum speed.

The "opacity" (usu written as symbol "k") of lead which I think you're
thinking of is a different but related issue.

Having done, and taught, a little bit of Radio propagation theory in a
past incarnation (over twenty-five years ago!!), 'Refractive Index' was
an indication of how far a radio wave (which light consists of) is bent
towards/away from the normal as it passes from one medium to another.

As light does not pass through Lead, I guessed it would have a high
refractive index.


That would be factually inaccurate. Light can pass through most
substances if it is strong enough.

So-called "transparent" objects have substances that interact very
little with light photons. For an interaction to happen the photon
normally must have a frequency/wavelength with the energy of an orbital
electron in the substance. Very high energy photons can interact with
the nucleus.

X-rays and gamma rays are a form of light. They are known to regularly pass
through lead.

Sometimes you bet right .... sometimes you bet wrong!! ;-P


Sure. What would I know about physics?