4 Senses Animals Have That Humans Dont

4 Senses Animals Have That Humans Don't Radar guns, magnetic compasses, and infrared detectors are all man-made inventions that enable humans to stretch beyond the five natural senses of sight, taste, smell, feel, and hearing. But  these gadgets are far from original. Evolution equipped some animals with these extra senses millions of years before humans evolved. Echolocation Toothed whales (a family of marine mammals that includes dolphins), bats, and some ground- and tree-dwelling shrews use echolocation to navigate their surroundings. These animals emit  high-frequency sound pulses, either very high-pitched to human ears or completely inaudible, and then detect the echoes produced by those sounds. Special ear and brain adaptations enable these animals to build three-dimensional pictures of their surroundings. Bats, for example, have enlarged ear flaps that gather and direct sound toward their thin, super-sensitive eardrums. Infrared and Ultraviolet Vision Rattlesnakes and other pit vipers use their eyes to see during the day, like most other vertebrate animals. But at night, these reptiles employ infrared sensory organs to detect and hunt warm-blooded prey that would otherwise be completely invisible. These infrared eyes are cup-like structures that form crude images as infrared radiation hits a heat-sensitive retina. Some animals, including eagles, hedgehogs, and shrimp, can also see into the lower reaches of the ultraviolet spectrum. Human beings are unable to see either infrared or ultraviolet light with the naked eye. Electric Sense The omnipresent electric fields produced by some animals function like senses. Electric eels and some species of rays have modified muscle cells that produce electric charges strong enough to shock  and sometimes kill their prey. Other fish (including many sharks) use weaker electric fields to help them navigate murky waters, home in on prey or monitor their surroundings. For instance, bony fish (and some frogs) possess lateral lines on either side of their bodies, a row of sensory pores in the skin that detect electrical currents in the water. Magnetic Sense The flow of molten material in the earths core and the flow of ions in the earths atmosphere generate a magnetic field that surrounds the planet. Just as compasses point humans toward magnetic north, animals possessing a magnetic sense can orient themselves in specific directions and navigate long distances. Behavioral studies have revealed that animals as diverse as honey bees, sharks, sea turtles, rays, homing pigeons, migratory birds, tuna, and salmon all have magnetic senses. Unfortunately, the details about how these animals actually sense the earths magnetic field are not yet known. One clue may be small deposits of magnetite in these animals nervous systems. These magnet-like crystals align themselves with the earths magnetic fields and may act like microscopic compass needles.   Edited by Bob Strauss

How the Persian Wars Started

How the Persian Wars Started During the Archaic Age, one group of Greeks pushed another from the mainland, resulting in a sizeable Hellenic population in Ionia (now Asia Minor). Eventually, these uprooted Greeks came under the rule of the Lydians of Asia Minor. In 546, Persian monarchs replaced the Lydians. The Ionian Greeks found Persian rule oppressive and attempted to revolt- with the aid of the mainland Greeks. The Persian Wars lasted from 492-449 B.C. Ionian Greeks The Athenians considered themselves Ionian; however, the term is now used a bit differently. What we consider Ionians were the Greeks the Dorians (or descendants of Hercules) pushed off mainland Greece. Ionian Greeks, who were in contact with the civilizations to their East, including Mesopotamia and ancient Iran, made many important contributions to Greek culture- especially philosophy. Croesus of Lydia King Croesus of Lydia, a man of fabled wealth, was said to have acquired his wealth from the man with the Golden Touch- Midas, son of the man who had created the Gordian Knot. Croesus is said to have been the first foreigner to come into contact with the Greek settlers of Ionia, in Asia Minor. Misinterpreting an oracle, he lost his kingdom to Persia. The Greeks chafed under Persian rule and reacted. The Persian Empire King Cyrus the Great of Persia conquered the Lydians and put King Croesus to death.* By acquiring Lydia, Cyrus was now king of the Ionian Greeks. The Greeks objected to the strains the Persians put on them, including the draft, heavy tribute, and interference in local government. A Greek tyrant of Miletus, Aristagoras, first tried to ingratiate himself with the Persians and then led a revolt against them. The Persian War The Ionian Greeks sought and received military help from mainland Greece, but once the more distant Greeks came to the attention of the African and Asian empire-building Persians, the Persians sought to annex them, too. With many more men and a despotic government going for the Persian side, it looked like a one-sided fight. King Darius of Persia Darius ruled the Persian Empire from 521-486. Going east, he conquered part of the Indian Subcontinent and attacked tribes of the Steppe, like the Scythians, but never conquered them. Nor was Darius able to conquer the Greeks. Instead, he suffered a defeat in the Battle of Marathon. This was very important for the Greeks, although fairly minor for Darius. Xerxes, the King of Persia A son of Darius, Xerxes, was more aggressive in his empire building. To avenge his fathers defeat at Marathon, he led an army of about 150,000 men and a 600-ship navy into Greece, defeating the Greeks at Thermopylae. Xerxes destroyed much of Athens, from which most of the people had fled, gathering together with other Greeks at Salamis to face their enemy. Then Xerxes suffered defeat in the battle off the island of Salamis. He left Greece, but his general Mardonius remained, only to be defeated at Plataea. Herodotus Herodotus History, a celebration of the Greek victory over the Persians, was written in the mid-fifth century B.C. Herodotus wanted to present as much information about the Persian War as he could. What sometimes reads like a travelogue, includes information on the entire Persian Empire, and simultaneously explains the origins of the conflict with references to mythological prehistory. The Delian League After an Athenian-led Greek victory over the Persians at the Battle of Salamis, in 478, Athens was put in charge of a protection alliance with the Ionian cities. The treasury was at Delos; hence the name for the alliance. Soon the leadership of Athens became oppressive, although, in one form or another, the Delian League survived until the victory of Philip of Macedonia over the Greeks at the Battle of Chaeronea. *For conflicting accounts of the death of Croesus, see: What Happened to Croesus? by J. A. S. Evans. The Classical Journal, Vol. 74, No. 1. (Oct. - Nov. 1978), pp. 34-40. Sources A History of the Ancient World, by Chester StarrThe Outbreak of the Peloponnesian War, by Donald KaganPlutarchs Life of Pericles, by H. Hold