Not much else to say about that, but it does make me curious giorgiana1976. With regard to coolers, would this same theory hold true, and if so, would coolers be able to keep hot things hot? Or would this not work due to the lack of a reflective surface?
The thermos flask provides thermal insulation because the vacuum created between the 2 thin walls of thermos flask is not a good conductor of heat.
To increase the insulating effect, the surfaces of thermos flask are coated with refelctive substances, therefore the loss of heat by thermal radiation is eliminated.
Due to this double thin wall vacuum principle, the hot or cold liquids inside thermos flasks are keeping their temperatures for hours.