United States or Afghanistan ? Vote for the TOP Country of the Week !
Though signaling by flashes of light occurred to the ancients, we have no knowledge that they devised a way of using the light-flashes for any but the simplest prearranged messages. The mirrors of the Pharaohs were probably used to flash light for signal purposes. We know that the Persians applied them to signaling in time of war.
What matters to us here is the validity of the conclusions drawn from Roemer's discovery within the framework of thought in which they were made. Boiled down to its purely empirical content, Roemer's observation tells us solely and simply that within the earth's cosmic orbit light-flashes travel with a certain measurable speed.
The heliograph, which established communication by means of short and long light-flashes, is another important means of signaling to which the Morse code has been applied. This instrument catches the rays of the sun upon a mirror, and thence casts them to a distant receiving station.
In a certain sense Roemer's observations and even those of Bradley rank together with the terrestrial measurements. For Roemer used as optical signals the appearance and disappearance of one of Jupiter's moons in the course of its revolution round the planet; thus he worked with light-flashes, as the experimental investigations do.
It was something to see that collar and handkerchief pin a bevy of quail in a clump of locusts and remain rigid and immovable till we had flushed the birds. Now and again the dog emitted the vari-colored light-flashes I have mentioned. The one thing, Paul explained, which he had not anticipated and which he doubted could be overcome.
Often when they woke at night the air was luminous, and they were convinced that if they remained there long enough it would be easy to devise some telegraphic code of light-flashes by which they could communicate with the spirit world, and so get ideas from the host of spirits that had already solved the problem of life and death, but who were not as yet sufficiently developed to be able to return to the earth.
Word Of The Day