Condign volumes 1 to 3

Read from the scan by GLM-OCR; expect the odd misread word.

## PROJECTED SHAPES AND SHADOWS

1. Frequently UAP reports suggest shadow shapes (i.e. objects apparently seen in silhouette). It is believed that a proportion of these are projected shadows from any object which is opaque, or near opaque at the wavelength of the surrounding light. Thus a shadow with a fairly sharp edge is reported, although much closer examination would show that the shadow is not absolutely sharp.

2. The shadows of aircraft and helicopters are frequently seen on the ground, often in film or video taken from the same platform. Less well known (to terrestrial observers) is the projection of aircraft shapes on to cloud layers and the consequent moving shadows seen from beneath the clouds. Further, it is possible for rainbow-like arrays to be produced through sunshine via aircraft windows, which can be projected on to clouds some kilometres distant. These can be reported as UAPs with colours.

## FLUORESCENCE AND LUMINESCENCE

3. Earthlights are seen in the dark but they are not observed by reflected light They actually provide the light energy which the eye receives and be classed as 'fluorescent'whereas, luminescence is visible light, generated by the conversion of energy invisible to the eye. Luminescence is a general term classified according to the means of excitation, examples are:

- Photo-luminescence is that generated by radiant energy.

- Bioluminescence is generated by bio-chemical reaction.

- Cathodo-luminescence is generated by electron bombardment.

Luminescence is called fluorescence or phosphorescence, depending on the rate of decay; phosphorescence persists for some time. Fluorescence ceases when electron bombardment stops (i.e. within $ \sim 1 0^{-8} $ sec.). Therefore to obtain continued fluorescence, continuous electron bombardment is needed. (See also para 6 below).

## ABSORPTION AND SCATTERING

4. When ambient light impinges on a gas its intensity is affected by the absorption and, as a result its velocity will be less in the medium than in free space. The meduim may not reduce the intensity by equal amounts for all wavelengths. No substance is known which absorbs all wavelengths equally, although some can approach this condition over a wide range of wavelengths. Normally one would expect selective absorption to occur.

5. Bodies can cause different effects for transmitted and reflected light. Hence an observer on one side of the body, receiving energy which has passed through a gas may observe one colour, whereas an observer of the same object using reflected (i.e. back-scattered) light can see a different colour. True absorption represents the actual disappearance of light, the energy of which is converted to heat motion of the molecules. In the UAP context there appears to be complete absorption when a totally 'black' shape