Anecdotes_05 ' In the dark '

One of the minerals found in the Cornish mines was/is pitchblende, aka uranium ore. It was mined and supplied to glass manufacturers. Despite its black colour (hence the name) it colours the glass a dense yellow.

Best regards,

Swarf, Mostly!

Hello all

In the 1950's, astronaut John Glenn experienced a total lack of instrument illumination when flying a fighter at night, over the sea during the Korean war. He found the aircraft carrier by following phosphorescence from the carrier's prop.wash for several hundred miles, and landed safely.

Jim

Radon - in some parts of the UK houses over granite have to have extractor fans in their cellars to prevent build up of radon.

Neil

IanP & Martin,

I will let this run for a while as I love a mystery.

All this talk of going into the bowels of the earth reminds me of the time in the Cango Caves near Oudtshoorrn, and the lights being turned off to let us have the experience. The total & utter blackness sudden was not a little daunting at first, but it didn't last long enough for us to experience any peripheral light. Quite an experience though, as well as going through those caves.

Another memorable one was going down the deepest mine in the world, namely Western Deep Levels near Carletonville, and having the heat and humidity hit you like a brick wall.

Geoff - All that took place 50odd years ago. Where the blue blazes has that time gone?

Radon is widely found on the West Coast of the South Island of NZ, there is a large area of minable Uranium in the area, it is also very rich in high quality coal.

About 45 years ago, Kodak, and others had to stop using paper to separate X- ray film (it used to be yellow), it was found to contain enough radiation to fog the film in increasingly shorter and shorter time, this was about the time when trees were maturing after the first of the atomic bomb tests, and the Japanese bombs. Ian S C

Before fast digitization and storage came along fast events were recorded on oscilloscopes with fast photographic film. One off events gave too little light to record on film so "pre-fogging" was used, a very low level light exposed the film so that less light was needed to record the scope trace. Tektronix then built a multichannel electron multiplier into their crt's so that the apparent intensity on the screen could be increased by 1,000 to 10,000 times. This enabled recording one off experiments that were impossible to repeat such as atomic weapons testing. There is a very good museum devoted to atomic testing in Los Vegas, they have very knowledgable staff who really know their atomic physics and instrumentation, just downwind from the Nevada test site.

The multichannel multiplier is now used in some image intensifiers.

X-ray film was very expensive, it had a thick silver containing emulsion, nowdays silicon sensors replace the film, more sensitive, no storage issues and no development needed, the image is produced immediatly and the radiation dose is much smaller.

Billy.

Locally street lighting goes off between midnight and 6 am as an energy saving measure so the sky change is very apparent. In some areas the street lighting electricity is not separately metered, they are charged on the number of lights, estimated consumption and hours on, it's too expensive to wire up metering.

Some towns have a "dark skys" policy, street lighting is directed downwards and of limited power so the stars appear against a velvety black background. When you are getting near some towns at night you can see a foggy dome of light enveloping the town, light spill upwards illuminating dust and mist in the air.

With most people city dwellers they don't get to see a starry dark sky, just a dim fog with a few stars. There are only a few places in the UK where the skys are really dark as you need to be perhaps 20-30 miles from urban areas.

One real weird UK lighting madness is that local councils light side roads with no cars per hour and people inside buildings but very busy Motorways -such as the M25 and A1M - have no lighting in many places.

Billy.

This is safety and security in side roads which is very welcome to women especially. In my home village there is just the one streetlight which makes us very 'grown up' like a real town. Elsewhere in the village a torch or wellies is essential becasue the cattle sheep and horses have free reign ..........

Would sugest that wells and mines could give a better view because only a small part of the sky glow ( from street lighting) would be visible so after a while in real darkness ( with the mine lights off) the human eye would reach high sensitivity. Urban Canyons might not work as well because most buildings loose a lot of heat so there is a lot of thermal turbulance as well as a bright sky and local lighting to contend with.

Some astronomy is done through optical filters which reduce the brightness of the sodium d lines ( the bright yellow ones), that helps quite a bit. The eye is quite sensitive to yellow however if you take a picture under sodium streetlighting it is mostly red.

Perhaps one of the most strange aspects of the human eye and vision is that the retina is not a continuous light sensitive surface, it is covered with many blood vessels yet when we are awake we normally experience no trace that our eyes are not so perfect. Sometimes when you wake in the morning or when you are at the opticians you might glimpse the blood vessels tree trunk appearance but it then dissapears in a flash as it is " computed" out of our perceived vision.

Billy.

When I had to work for a living, at one stage I worked near Edinburgh RAAF base, on the Northern outskirts of Adelaide. RAAF Edinburgh was used as a sort of "base camp" during the nuclear bomb trials (at Woomera) in the 50s. Being an electronics/avionics/defence industry sort of place we used to get a lot of bright eyed, bushy tailed young electronics Engineers.

One evening whilst working late I went to the tea room to make a coffee. Already there was a young Engineer, looking confused. Pointing at the water tap he asked if the water was safe to drink. I said, "....well you will have heard about the nuclear tests, when they used to fly the aircraft through the mushroom cloud? They flew back to the RAAF base and washed the fallout off of the aircraft. The wash water went into the groundwater, which is what comes out of the tap. Some people say that if you use a glass cup, full of water, on a dark night, you can use it to light your way." At this point the young Engineer went pale, emptied his cup down the sink and left.

cheers

Bill

Edited By Bill Pudney on 22/02/2014 01:45:13

I'v not tried it, but it is said that you can, given a clear sky, see the stars in day light from the bottom of a deep shaft/well. Ian S C

Yes, Ian, true, so long as the sun is not to near of course.

Party pooper: **LINK**

Neil

Maybe, but I wasn't looking thru' a cardboard roll, was at bottom of a 90 ft. pot and it was fairly late in late winter. Maybe was snowflakes.

Top marks for your homework!

Ouballie means 'Old Man' in Afrikaans slang, and I'm certainly in that category, being three score and ten later this year.

I do remember, when in in my 20s, wondering if I would see the Millenuim in! At that age of course, anyone over 35 was well past it, and no doubt the same thoughts by the young turks today.

The light I HAVE seen is that things now take forever to do.

Geoff - Still semi-floored from treatment, but improving.

Thanks for clearing that up Geoff even if I had to wait because YOU like a puzzle.

Ian P

" In the dark" ,Maybe this could be combined with the Wills post?