Blue flashes in he sky

Interesting theory Frank.

However, the blue flashes I saw were witnessed by someone else observing with me and occured at a variable frequency, which was much longer than a human heartbeat. Also, they cast a shadow.

I wonder by any chance do these originate from some-body using a Flash Camera in the vicinity. If the light were scattered by residual dust or moisture partivles in the air would it result in only the Blue end of the spectrum being refracted back to the ground- whilst in the forward direction (at altitude ) the flashes would appear to be Redder?

I wonder by any chance do these originate from some-body using a Flash Camera in the vicinity. If the light were scattered by residual dust or moisture partivles in the air would it result in only the Blue end of the spectrum being refracted back to the ground- whilst in the forward direction (at altitude ) the flashes would appear to be Redder?

Again an interesting theory but given my observing location it seems very unlikely ... unless someone a few miles away had thermo-nuclear flash in their camera

Rice,
there have been instances where a good deal of distance has been observed with some of these flashes. I myself actually had an incident where it orignated in the sky. It was not like a small lightning flash or anything, my guess was a large piece o space garbage reflecting Moon/Sun light. Read about it here .

Seanie.

I wonder by any chance do these originate from some-body using a Flash Camera in the vicinity. If the light were scattered by residual dust or moisture partivles in the air would it result in only the Blue end of the spectrum being refracted back to the ground- whilst in the forward direction (at altitude ) the flashes would appear to be Redder?

Again an interesting theory but given my observing location it seems very unlikely ... unless someone a few miles away had thermo-nuclear flash in their camera

Is there something those physics students in NUIM are doing which they shouldn't?

Regarding the brightness
'Thermonuclear flashes'
I know you're exaggerating (just a little bit!) but remember when your eyes have adapted to very low level light conditions and your iris is fully open then even a slight temporary alteration in ambient light may seem very bright. Your light sensitivity will be at its most sensitive and so what you percieve to be very bright is only relative to the ambient very dark level. In other words very small changes will seem comparatively large and so very little actual light will be required to give the effect.

To add my own experiences - many years ago I saw flashes on clear summer nights while looking out over the Irish Sea but in my case I would definitely put them down to distant lightening - they tended to be low on the horizon and and had a distinct zone of origin.

There is a very old rule of thumb: distance to the horizon in miles= 1.1 times the square root of h , where h is in feet. So if an aircraft at say 10,000ft were to flash a beacon it is possible it could be seen 130 miles away at its horizon - so a lightening flash over Limerick could just be visible over Dublin.