The gravitational pull of the moon and the sun causes the tides in the earth’s oceans. Because the sun is so far away and the moon so close, the moon’s effect is about three times that of the sun. When the sun and moon are in line, at the times of new moon and full moon, their combined effect causes the highest tides, the spring tides; and when they are opposed to each other, in the first and last quarter of the moon, the tides are lowest, or neap tides.
Because it once was believed that the moon also caused tides in the human brain, we have the word “lunacy,” meaning madness, from the Latin word for moon. Some people still believe that the moon’s phases have an effect on crops, and they plant by the moon’s phases. The moon on the increase is supposed to favor crops that grow above the ground; the moon on the decrease, past full moon, to favor those below the ground, root crops.
The sun is the star around which the earth and other planets of our particular system revolve. It is only a medium-sized star, as stars go, but is twice as big as the orbit of the moon, more than a hundred times the diameter of the earth. The earth’s orbit around the sun is elliptical, but the average distance between the two is about 93,000,000 miles. Paradoxically, the earth is about 3,000,000 miles closer to the sun in January than in July.
Celestial distances are almost inconceivable. The next nearest star to us is about 300,000 times as far away as the sun, some twenty-six million million miles. Since miles lose their meaning, out there in space, astronomers measure distances in light-years—the distance light will travel in a year. Since light travels 186,000 miles per second, a light-year is nearly six million million miles. Sirius, the brightest star beyond the sun, is 8.7 light-years from us. Some other stars are millions of light-years away.
On a brilliantly clear night a person with good eyesight can see about 2,000 stars in the sky at one time. Different stars are visible at different seasons, but the total number visible to the naked eye over the entire year is only about 6,000. An astronomical telescope reveals literally millions more, and the total number in the universe is estimated in the billions. And each star is a sun somewhat like our own, the center of its own system of planets and other satellites.
The solar system to which we belong consists of the sun, nine planets, thirty-one known moons or other satellites, thousands of minor planets and asteroids, dozens of comets, and millions of meteors. In the order of their distance from the sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. Earth and Venus are about the same size, Mars a little over half the diameter of the Earth, Saturn nine times as big, and Jupiter eleven times as big. Mercury, which is only 36,000,000 miles from the Sun, is the smallest of the family, less than half the Earth’s diameter. We have so far discovered that Jupiter has twelve moons, Saturn nine, Uranus five, Mars and Neptune two each.
Mercury, Venus, Mars, Jupiter, and Saturn are what we know as our Morning and Evening Stars. Their positions vary in the sky and they are visible only when they are in a position, like our own moon, to reflect the sun’s light. All of them are, by turn, visible in early morning or early evening, their positions varying from season to season and year to year. Their schedules can be found in a good almanac. Mars always appears to have a reddish glow. Saturn has a ring, a flattened belt, which can be seen through a small telescope; this ring apparently consists of fragments of meteoric material or disintegrated satellites. Jupiter’s moons can also be seen through a small telescope. Some details of all the visible planets and many details of the moon’s surface can be seen through a good pair of binoculars, the ones you may use for watching birds.
The stars appear to move from hour to hour and even from night to night. The apparent movement is a consequence of the earth’s rotation and seasonal shifting of position, but the visual effect is that the heavens wheel from east to west as though pivoted on the North Star, which moves so little and so slowly that we can rely on it for a directional guide. Among the stars there are fixed patterns which ancient man recognized and named as constellations. The old names persist, and the fables about the constellations have endowed many of them with fancied resemblances—The Big Dipper, as an example, and Draco the Dragon and Cygnus the Swan. Some of these names and identifications of form are difficult to believe, but they do help the amateur to find his way about in the starry heavens. And their relative positions are sufficiently constant to be guides as long as any of us are going to look at them. The stars even in the fixed constellations are changing position, but so slowly that those the early Greeks named are still the same shape and in the same relative position that they were thousands of years ago.
Someone who knows a little about the stars can help the beginner a great deal, but anyone can start to learn the constellations with a star chart or handbook. I would start with the North Star, which is not really a brilliant star but can be found any time after it has been identified. From it, one can easily find Ursa Minor, the Little Bear (or the Little Dipper) whose tail-tip is the North Star itself. On a Summer evening the Little Bear will be standing on his tail above the North Star. And off to the left of him will be the Big Dipper, with the two stars at the end of the bowl pointing toward the North Star. The Big Dipper will be standing on its head, handle up toward the zenith. Near the horizon, almost on a line from the tip of the Big Dipper’s handle through the North Star, will be the irregular “W” of Cassiopeia.
With those constellations to begin with, it is easy to go on with a star chart, for you have a starting point and known groups to guide by. Draco the Dragon winds its tail between the Big and Little Dippers. Lyra is just to the east of Draco, and Cygnus the Swan is just below Lyra.
Summer is the most comfortable time to watch the stars, but the Summer skies are less interesting to me than those of late Fall and Winter. By November the Big Dipper is down on the horizon in the northeast in mid-evening, Cassiopeia is high in the sky, the Pleiades are almost overhead, and Orion, with its three unmistakable “belt” stars, is well up in the southeastern sky. To see the Seven Sisters of the Pleiades, which are quite faint, I look somewhat away from them and catch them in the corner of my eye, as it were. Then they are clearly visible. The Pleiades are not visible on a Summer evening; they are still hidden below the eastern horizon and do not appear until late at night.
There are five or ten comets that appear in the skies every year, but most of them are so faint that they can be seen only with a telescope. Halley’s Comet is the most famous of all we know. It was reported as early as 240 B.C. and has made periodic appearances every seventy-six years since. Few people will see a large, spectacular comet more than once in their lifetime. Comets are now believed to be members of the solar system, closely related to meteors but traveling in regular, predictable orbits. They have long, glowing tails, probably of gas and meteoric dust. Those tails appear to be harmless. The earth has passed through the tail of Halley’s Comet without being scorched or in any way affected. Halley’s Comet’s next visit to the earth’s vicinity will be in 1986.
There are countless meteors or shooting stars. They streak across the night skies, often visible, and occasionally fragments of one strike the earth. There are large craters in Arizona, near Hudson Bay, in Siberia, and in Estonia where large meteors once struck the earth. The one which made the Arizona crater is estimated to have weighed 50,000 tons. Most meteors burn up in the atmosphere before they reach the earth. There are predictable meteor “showers” of considerable intensity. These periodic showers are named from the constellations from which they appear to come. Among them are the Lyrids in April, the Perseids, most spectacular of all, about August 10, the Leonids in mid-November, the Andromedes in late November, and the Germinids about December 10-13.
And now, a few final notes:
There are two Equinoxes each year, the Autumnal and the Vernal. The Autumnal Equinox occurs on or about September 21, the Vernal about March 21, at which time day and night are supposed to be equal (but aren’t exactly) and the sun stands direct
ly overhead at midday and rises due east, sets due west.
There are two Solstices each year, the Summer and the Winter. The Summer Solstice occurs on or about June 21, the Winter Solstice on or about December 21, traditionally the year’s longest and shortest days, though not actually so by a matter of a few minutes. The Summer Solstice marks the point of the sun’s apparent movement to its farthest point north and the Winter Solstice the sun’s farthest apparent movement south. The span of daylight decreases after the Summer Solstice and increases after the Winter Solstice.
The Solstices and Equinoxes mark the changes from Spring to Summer, Summer to Autumn, Autumn to Winter, and Winter to Spring—by the almanac and calendar, but not by the weather and the birds and plants, which only approximate those seasonal dates.
The solar day is exactly twenty-four hours, though the actual spans of daylight and darkness vary with the season and the latitude. The lunar day is twenty-four hours and fifty minutes, which is responsible for the moon’s phases described earlier.
Twilight and dusk in the Northeast vary in length from about an hour and a half in Winter to more than two and a quarter hours in Summer.
Rainbows are always seen in that part of the sky opposite the sun and are never seen when the sun is near midday. They are caused by a combination of refraction and reflection of sunlight on raindrops. On rare occasions moon-bows are seen, the parallel phenomena caused by moonlight on raindrops.
Sundogs are streaks of rainbow color, one on each side of the sun, usually seen at or soon after sunrise in the Winter. Apparently they are created by ice crystals in the air which refract the sunlight like prisms. Occasionally they occur at midday, when they are a part of a halo type of phenomena; sometimes the halo is complete, a circle of rainbow color. Both sundogs and the halo can on occasion occur with the moon, also in Winter. Then, of course, they are moondogs.
The Aurora Borealis, or Northern Lights, can be spectacular and are so varied in form and color that no general description suffices. They may be white, yellow, green, red, or yellow, or all colors. They may be rays that seem to radiate from the northern horizon or writhing streamers or nothing more than a suffused glow. I have seen Northern Lights that looked like the sky glow of a tremendous fire beyond the horizon, I have seen them look like a giant fan of green and yellow and white, and I have seen them like rippling ribbons in the northern sky. Often they have the appearance of faint neon light. Scientists say they seem to be caused by electrically charged particles in empty space as much as 600 miles above the earth. The earth’s magnetic poles seem to emphasize the phenomenon, which is why Northern Lights are typical of the polar latitudes. A friend of mine who spent some time in both the Arctic and the Antarctic tells me that the Aurora is even more spectacular in the South Polar area than in the Far North. We frequently have brilliant Northern Lights in the Autumn, especially, where I live.
Chapter 11
Biotopes and the Lay of the Land
Soil, climate, and the prevailing winds determine which forms of life will thrive and which will perish in any area. He who would know the botany and biology of his homeland must first know where he lives in those fundamental terms. He must know his own biotope.
IN THE TERMS OF science, the word “biota” means the organic life, the plants and animals, of a particular region; and a “biotope” is an area of uniform environment for life. So we all are part of the “biota” of our own regions, and each of us lives in a “biotope.” Man, being an adaptable creature with the means of warming or cooling his own habitation and the ability to import food from a distance, can live in many different kinds of environment. Few other animals can. And plants have to live where they sprout and take root and find hospitable growing conditions. So the biota, the plant and native animal life, of any particular region is more or less predictable.
Broadly speaking, the northern and eastern parts of the United States consist of only a few major biotopic regions—the seashore, the inland valleys, the hill country and mountains, and the lake areas. But within each of these regions there are lesser “biotopes” or relatively uniform environments. For instance, although I live in the hill country of western New England, a biotope in itself, I have within short walking distance of my house four smaller biotopes, each rather specialized in the wild life it supports. In my dooryard is the river, with flowing water and damp banks. Behind the house is the pastureland, the meadow, an area of brooks and grassland. Beyond the pastures is the mountainside, rocks and woodland. And down the road a mile or so is a small bogland, stagnant water and marginal muck.
Each of these four areas has its own assortment of life, some of it specially adapted to or characteristic of the river, the meadow, the hillside woodland, or the bog. There is a good deal of overlapping, since the climate is the same for all four areas, but there are no rabbits in the river, no catfish in the meadows, no woodchucks in the bog, and no snapping turtles in the woods. So to find a particular plant or animal, I must go to the right place; and when I am in a certain place I can rightly expect to find certain plants or types of animal life.
Man sometimes thinks he has changed the face of the earth tremendously, and in limited areas he has. His ax and his plow and more recently his bulldozer have removed forests, stripped the grass from the plains, and cut sizable gashes across the countryside. His dams have created lakes and his channels have diverted rivers and drained swamps. But the major changes have come in the wake of man’s doing, and most of them have been the results of erosion. Top-soil has been washed or blown away, rivers have become silted, lowlands have been flooded, marshes have dried up, shorelines have been altered, underground water levels have been lowered disastrously. Natural environments have been irrevocably changed, and not always to man’s benefit.
But even these effects, unhappy in too many instances, are minor in comparison to fundamental changes that have been going on since time began. Nature not only made the continents and lifted the mountain highlands; it created hill and valley, plain and tableland. And the essential elements of geography as we know them were created long before man invented the first stone ax. Change is still going on, but so slowly that we are scarcely aware of it.
This part of New England where I live, for example, was shaped substantially as it is today long before the first white man, or the first Indian, for that matter, saw it. As a land, this area is probably among the older places on earth and its geologic history is somewhat typical, certainly of the eastern part of the United States.
Parts of this area were thrust up from the primeval seas about half a billion years ago, back in the Cambrian era, in the form of very high mountains. The core of those mountains was limestone and marble, formed of sediments which had settled in the oceans over the eons. That is where Vermont marble comes from, and the fine-grained limestone that crops out in many parts of New England. Those mountains are now worn down into the Berkshire Hills and the Green Mountains, relatively low upthrusts, but in the beginning they probably were as high as the Andes, possibly the Himalayas.
Over the eons those high ridges were eroded away. There were more upheavals. Deep valleys were formed, new hills thrust up, valleys filled again. But apparently some part of the New England mountains remained above the oceans through all that time. Finally most of New England was worn down to a vast high plain that sloped gradually into the still-warm sea, at the margin of which was a broad tidal marsh. Lush vegetation grew there. We know this because in succeeding ages some of it turned to low-grade coal which is still found in the vicinity of Boston and Narragansett Bay.
Then, in another of the earth’s vast convulsions, the Rocky Mountains were thrust up, and in the continental upheaval the whole New England area was lifted several hundred feet above the ocean. With this new tilt of the land, the rivers that had wound sluggishly across the plain became hurrying streams again and gouged deep canyons in their rush to the sea. The land became scarred and rugged. And finally, about a million years ago, the first of the gr
eat Ice Ages began. Tremendous ice sheets formed in the North and flowed down across the land. The ice was more than a mile deep in places, a tearing, gouging, rending plow of ice that slowly sliced southward.
There appear to have been four waves of ice across New England and most of northern United States. At one time or another, ice covered all of New England, reached southern New Jersey, flowed down both sides of the Alleghenies, covered much of New York State, reached down the Ohio River almost to its mouth, covered all the upper Mississippi valley, and reached as far west as the Dakotas. All these areas still show the marks of the glaciers.
Each wave of ice melted back before the next one came, always with great flooding and deep erosion. The last Ice Age ended, perhaps 12,000 years ago, with what might be called The Big Melt. We speak of the ice “retreating,” but it didn’t actually retreat in the sense of moving back north. It melted where it was, the southern edge first, of course. And in the melting, the hilltops and mountains were the first to be ice-free. Once the ice was gone from them, they were wide open to all the forces of erosion, wind, rain, frost, water. As they eroded, the debris was carried into the valleys. The ice was laden with all kinds of geologic trash, picked up on its way south—rocks, sand, silt, all kinds of scrapings from the land. This debris was dumped as the ice melted, and it formed hills and ridges, dammed valleys, created new features on the land. The tremendous volume of water from the retreating ice created surging rivers and huge lakes. Some of those lakes were soon filled with silt and created what man, when he arrived, called plains—the patches of flat, plainlike land here in the East, not the high plains of the West. Elsewhere the debris from the ice settled on the bedrock where the ice dumped it, a miscellaneous collection of sand, silt, clay, gravel, and boulders, the “glacial till” of today, which is characteristic soil in many parts of New England.