The Meaning of Human Existence Read Online Free PDF

winding processes of evolution that created it. Part of the end product is the gradient of size across a dozen orders of magnitude.It ranges from the blue whale and African elephant down to superabundant photosynthetic bacteria and scavenging picozoans of the sea, the latter so small they cannot be studied with ordinary light microscopy.
    Of all the continua mapped by science, the most relevant to the humanities are the senses, which are extremely limited in our species. Vision is based in Homo sapiens on an almost infinitesimal sliver of energy, four hundred to seven hundred nanometers in the electromagnetic spectrum. The rest of the spectrum, saturating the Universe, ranges from gamma rays trillions of times shorter than the human visual segment to radio waves trillions of times longer. Animals live within their own slivers of continua. Below four hundred nanometers, for example, butterflies find pollen and nectar in flowers by the patterns of ultraviolet light reflected off the petals—patterns and colors unseen by us. Where we see a yellow or red blossom, the insects see an array of spots and concentric circles in light and dark.
    Healthy people believe intuitively that they can hear almost every sound. However, our species is programmed to detect only twenty to twenty thousand hertz (cycles of air compression per second). Above that range, flying bats broadcast ultrasonic pulses into the night air and listen for the echoes to dodge obstacles and snatch moths and other insects on the wing. Below the human range,elephants rumble complex messages in exchanges back and forth with other members of their herd. We walk through nature like a deaf person on the streets of New York, sensing only a few vibrations, able to interpret almost nothing.
    Human beings have one of the poorest senses of smell of all the organisms on Earth, so weak that we have only a tiny vocabulary to express it. We depend heavily on similes such as “lemony” or “acidic” or “fetid.” In contrast, the vast majority of other organisms, ranging in kind from bacteria to snakes and wolves, rely on odor and taste for their very existence. We depend on the sophistication of trained dogs to lead us through the olfactory world, tracking individual people, detecting even the slightest trace of explosives and other dangerous chemicals.
    Our species is almost wholly unconscious of certain other kinds of stimuli without the use of instruments. We detect electricity solely by a tingle, a shock, or a flash of light. In contrast, there exist a variety of freshwater eels, catfish, and elephant-nose fish, confined to murky water where, deprived of vision, they live instead in a galvanic world. They generate charged fields around their bodies with trunk muscle tissue that has been modified by evolution into organic batteries. With the aid of electric shadows in the pattern of charges, the fish avoidobstacles around them, locate prey, and communicate with others of the same species. Yet another part of the environment beyond the reach of humans is Earth’s magnetic field, used by some migratory birds to guide them during their long-distance journeys.
    The exploration of continua allows humanity to measure the dimensions of the real cosmos, from the infinite ranges of size, distance, and quantity, in which we and our little planet exist. The scientific enterprise suggests where to look for previously unexpected phenomena, and how to perceive the whole of reality by a measurable webwork of cause-and-effect explanation. By knowing the position of each phenomenon in the relevant continua—relevant continua in ordinary parlance being the variable of each system—we have learned the chemistry of the surface of Mars; we know approximately how and when the first tetrapods crawled out of ponds onto the land; we can predict conditions in both the infinitesimal and near-infinite by the unified theory of physics; and we can watch blood flow and nerve cells in the human brain