The new air world

by Willis L. Moore

How Heat and Light Reach the Earth. The heat of the sun is some forty-six thousand times as intense as is the heat of the earth. The violent agitations of the molecules of the sun’s hot atmosphere impart vibrations to the ether of space, which decrease in effectiveness inversely as the square of the distance; that is to say, that if the earth were twice as far from the sun as it is, the intensity of the solar rays would be one fourth of what they are now. These vibrations are called solar energy. They pass through space without perceptibly warming or lighting it. When they encounter the molecules of the earth’s atmosphere, and the dust and cloud in suspension in the air, or impinge upon the solid matter of the earth, they are transmuted back into molecular agitations, and manifest themselves in a multitude of forms, such as heat, light, chemical rays, electricity, etc.

The Difference between Heat and Temperature. The agitation of the molecules of a substance set up by the absorption of heat is indicated by temperature, which gives no measure of the quantity of heat absorbed, the quantity varying widely for different kinds of matter. The amount of heat necessary to raise one pound of water 1° F. is the heat unit generally employed in commerce; but in scientific research the amount necessary to raise one gram of water 1° Centigrade is the unit of heat best adapted to use. It is called the gram-calorie.

Let us take a glass filled with boiling water. You see the glass and the water because they reflect to the eye light waves received from some source,—possibly the sunlight that is diffused by the dust motes of the air into the room through the window. But the glass and the water radiate other waves to which the eye is not sensible; these invisible long heat waves may be felt by the nerves of the hand. They warm all matter upon which they fall by adding to the agitation of the molecules of which it is composed; but they do not warm all matter equally. The waves that reach dark bodies are broken up; that is to say, absorbed. Their energy is transmuted into sensible heat, and in the place of the waves we have molecular vibrations in the matter, which are made manifest by a rise in its temperature. Dark rough surfaces more completely absorb the waves and therefore rise to a higher temperature than the same surfaces when smooth. When the waves encounter bright and highly polished surfaces the effect is quite different; then most of them are reflected away and therefore warm the matter but little. These reflected waves are not broken up, but on the contrary start off in some new direction, possibly falling upon and warming some matter more receptive to their influence. The higher the polish the more completely are the waves reflected.

Difference between Light Waves, Heat Waves, and Sound Waves. The light and the heat waves of the ether are infinitesimal ripples as compared to the backward and forward pulsations that constitute the sound waves of the air. Within a space of one inch there are sixty-six thousand of the violet waves of light, which are the shortest etheric vibrations to which the human eye responds, and over thirty thousand of the red waves, the longest that affect the eye; while the sound waves of the air vary from about one foot for the shrill notes of the human voice to four feet for the middle C of the pianoforte. A shrill whistle produces waves of about one half inch. There are twenty-two thousand of certain heat waves to the inch, and these, like some of the light waves of the ether, are invisible.

There is also a vast difference between the velocity of vibration of the air waves and those of the ether. The human ear is sensitive to sound waves of somewhere between twenty-nine per second to thirty-eight thousand per second; while the eye responds to light waves of from five hundred million to one billion per second. Some ears are better adjusted to the low vibrations and some to the high, and the ears of no one hear any but a small part of the melody of a great symphony. Tyndall could hear the sharp chirp of thousands of insects that were inaudible to his guide as the two climbed the Alps, but the guide’s ears responded to the long, slow waves that came from the dull tread of the donkey’s hoofs farther up the mountain, which waves the scientist was unable to hear. Likewise some eyes are able to penetrate far into the violet, or the red, or both, and some are unable to distinguish between certain colors.

Chemical Rays of Light. The chemical or photographic rays have still shorter waves than the violet. They produce special physiological effects in vegetable and animal tissues, and, acting upon particular kinds of matter, they cause fluorescence, which is the property possessed by some bodies of giving off, when illuminated, light of a color different from their own and from that of the light that illuminates them. These chemical rays are sometimes called ultra-violet rays.

Invisible Light. From a reading of the immediately preceding paragraphs one may be prepared for the startling statement that there is such a thing as invisible light. Vibrations of the ether that move slower than those that give to the eye the sensation of red are invisible, as are those that move faster than the violet rays, and it is certain that neither the eye of man nor of animal ever will see but a small part of the beauty of a landscape or the delicate coloring of a flower. The eye only takes in and renders sensible to the brain the red, orange, yellow, green, blue, indigo, violet, and their various tints, but the delicate instruments of science reveal many other colors. One sees as through a glass darkly, for the gentle signals that might reveal the beauties of Paradise fall upon the eye unheeded. A keener vision and a more complete appreciation of the beauties and the wonders of the universe await one on the other side of the gauzy veil of immortality. The finger tips of the outstretched arms may span the river of life and the ethereal breath of loved ones may be caressing one’s cheek. The music of the spheres is not a myth; the lily or the rose as it opens its petals to receive the benediction of the morning sun may give forth a veritable pæan of joy. A rose bush may be a grander symphony than anything that Beethoven ever wrote. What to us is the invisible light may be the illumination that guides the sweep of the angels’ wings.

How Heat Moves through or Is Transmitted by Matter. Heat passes by contact from the warmer to the colder molecules of a body. This action is called conduction. When one end of a bar of iron is held in a fire, the end away from the fire soon becomes too hot to hold in the hand, because heat is rapidly transferred from the hot portion of the bar to the cooler portion by conduction, showing that iron is a good conductor. On the other hand, the end of a stick of wood can be held in the fire until it is completely consumed without the other end becoming too warm to hold, indicating that wood is a poor conductor. Metals are the best conductors, silver leading the list, with copper second. Snow and ice and fibrous and porous substances are poor conductors, and are called insulators. Air and water are also poor conductors. The fur of animals and the feathers of birds protect against the rapid loss of heat because they contain numerous interstices filled with air, a poor conductor. Heat is lost by radiation when the molecules of matter set up vibration in the ether. The atmosphere itself performs this function on a large scale when the sky is cloudless, so that radiated heat is not absorbed by the cloud covering and its loss into space restricted. When air or water is not evenly or homogeneously heated a circulation is set up in which the colder part settles down and the warmer rises. This is called convection. The air that is heated by contact with a stove rises and passes along the ceiling to the colder parts of the room, gradually parting with its heat until it is no warmer than the air next adjacent to it, and slowly settling to the floor as the cold air beneath it moves toward the stove, is warmed and sent aloft, the first air finally making a complete circuit and returning to the stove again. In this way the heat is distributed by convection throughout the whole room. When one part of the earth’s surface becomes hotter than another a similar action takes place on a large scale. The region of greater temperature warms the air above it, and the surrounding denser air flows in along the surface, forcing the lighter air to rise, when it in turn is similarly warmed and driven up.

The clear waters of lakes and rivers and of the ocean permit the passage of heat waves to a considerable depth before they are completely absorbed. On a cold day in winter, when the sun is shining brightly, a room with spacious windows may become as warm as though heated by a furnace, simply by the capacity of the glass in the windows to transmit the heat waves of the sun without considerable absorption, and at the same time prevent the escape of the longer heat waves that are radiated from the interior walls of the room. This capacity of matter to transmit heat waves without absorption is called diathermancy. The clear atmosphere is an exceedingly good transmitter, and rock salt is one of the best of all solids.