Bright white light moving at light speed with comet like tail, leaving cone shaped trail at source.The object was a bright light source like a helicopter landing light with a large and downwardly expanding cone of brightness which looked like a searchlight but did not reach to the ground. I guessed the source to be at about 1000m high. The object was silent throughout the period. I called my wife who was outside at the house and she saw this and the following. The light source rapidly moved outwards from the initial point. It had a definite and prominent tail as it appearded to accelerate away, moving at "light" speed, and disappearing in 8-10 seconds into space about half way between Jupiter and the Big Dipper, to the west of us. Meanwhile the cone of "gas-light" was disapating in the light easterly wind during the remaining 8-9 minutes. The sky was completely clear with a full moon. Many dozens reported the light fenomenon throughout Portugal.((NUFORC Note: Report appears to have been submitted from Portugal, although the return e-mail address was defective. PD))