The atmosphere forms a gaseous, protective envelope around Earth. It protects the planet from the cold of space, from harmful ultraviolet light, and from all but the largest meteors. After traveling over 93 million miles, solar energy strikes the atmosphere and Earth’s surface, warming the planet and creating what is known as the biosphere, the region of Earth capable of sustaining life. Solar radiation in combination with the planet’s rotation causes the atmosphere to circulate. Atmospheric circulation is one important reason that life on Earth can exist at higher latitudes because equatorial heat is transported poleward, moderating the climate.

An upsurge of new research suggests that animals have a much higher level of brainpower than previously thought. If animals do have intelligence, how do scientists measure it? Before defining animals’ intelligence, scientists defined what is not intelligence. Instinct is not intelligence. It is a skill programmed into an animal’s brain by its genetic heritage. Rote conditioning is also not intelligence. Tricks can be learned by repetition, but no real thinking is involved. Cuing, in which animals learn to do or not to do certain things by following outside signals, does not demonstrate intelligence. Scientists believe that insight, the ability to use tools, and communication using human language are all effective measures of the mental ability of animals.

Light pollution is a growing problem worldwide. Like other forms of pollution, light pollution degrades the quality of the environment. Where it was once possible to look up at the night sky and see thousands of twinkling stars in the inky blackness, one now sees little more than the yellow glare of urban sky-glow. When we lose the ability to connect visually with the vastness of the universe by looking up at the night sky, we lose our connection with something profoundly important to the human spirit, our sense of wonder.

Photosynthesis is the process that plants use to convert sunlight into the food that they need to survive and grow. Most plants create some form of sugar from the sunlight, and this sugar is used by the plant as its primary food source. Plants actually need only three things to create this sugar: sunlight, carbon dioxide, and water. The sunlight reacts with the plant’s chlorophyll, a green chemical which is used to convert water and carbon dioxide into sugar. As a general rule, photosynthesis occurs in a plant’s leaves. The leaf contains chlorophyll, which reacts when sunlight strikes the leaf. It is also the chlorophyll which gives the leaf its typical green color, since photosynthesis absorbs most light rays except green, which are reflected outwards. The process of photosynthesis produces more than just sugar, however. One byproduct of the process is oxygen, which is “exhaled” by the plant into the atmosphere. In fact, plant photosynthesis is one of the primary sources of oxygen generation on our planet, making plant life essential to almost all living things on earth.

For centuries, time was measured by the position of the sun with the use of sundials. Noon was recognized when the sun was the highest in the sky, and cities would set their clock by this apparent solar time, even though some cities would often be on a slightly different time. Daylight Saving Time (DST), sometimes called summer time, was instituted to make better use of daylight. Thus, clocks are set forward one hour in the spring to move an hour of daylight from the morning to the evening and then set back one hour in the fall to return to normal daylight. Benjamin Franklin first conceived the idea of daylight saving during his tenure as an American delegate in Paris in 1984 and wrote about it extensively in his essay, “An Economical Project.” It is said that Franklin awoke early one morning and was surprised to see the sunlight at such an hour. Always the economist, Franklin believed the practice of moving the time could save on the use of candlelight, as candles were expensive at the time.

Businesses today routinely keep track of large amounts of both financial and non-financial information. Sales departments keep track of current and potential customers; marketing departments keep track of product details and regional demographics; accounting departments keep track of financial data and issue reports. To be useful, all this data must be organized into a meaningful and useful system. Such a system is called a management information system, abbreviated MIS. The financial hub of the MIS is accounting. Accounting is the information system that records, analyzes, and reports economic transactions, enabling decision makers to make informed choices when allocating scarce economic resources. It is a tool that enables the user, whether a business entity or an individual, to make wiser, more informed economic choices. It is an aid to planning, controlling, and evaluating a broad range of activities. A financial accounting system is intended for use by both the management of an organization and those outside the organization. Because it is important that financial accounting reports be interpreted correctly, financial accounting is subject to a set of stringent guidelines called “generally accepted accounting principles” (GAAP).

Despite their similarities, the pyramids of Egypt and Mesoamerica seem to be unrelated because of distinct differences in the time of construction as well as their design and function. Historians have discovered that the construction of the pyramids in Egypt and Mesoamerica are separated by over 2,000 years. The Egyptians used only cut stone quarried many miles away from the pyramid sites—a construction method that enabled them to construct sturdy buildings that could withstand the test of time. On the other hand, the pyramids of Mesoamerica were not built to withstand the ravages of time. Rather, the step pyramids rose in tiers, on the top of which a small temple was erected. Unlike the Egyptians, they used irregular stones.

Arteries of the heart blocked by plaque can reduce the flow of blood to the heart possibly resulting in heart attack or death. Plaque is actually fat and cholesterol that accumulates on the inside of the arteries. The arteries of the heart are small and can be blocked by such accumulations. There is a medical procedure that creates more space in the blocked artery by inserting and inflating a tiny balloon into the blood vessel. It is called coronary balloon angioplasty. Angioplasty means “blood vessel repair.” When the balloon is inflated, it compresses the plaque against the wall of the artery, creating more space and improving the flow of blood.

Mars is a small planet, with about half the diameter of Earth and about one-tenth Earth’s mass. The force of gravity on the surface of Mars is about one-third of that on Earth. Mars has twice the diameter and twice the surface gravity of Earth’s Moon. The surface area of Mars is almost exactly the same as the surface area of the dry land on Earth. The Martian day is about a half an hour longer than an Earth day and is sometimes called a sol. Its year is about two Earth years long. Mars has two moons, Phobos and Deimos, which are named after the dogs of the Roman god Mars. These tiny bodies are heavily cratered dark chunks of rock and may be asteroids captured by the gravitational pull of Mars. Phobos appears to rise in the west and set in the east. Deimos rises in the east and sets in the west.

There are many ways to tell a story. Some stories start in the middle and flash backward to the beginning; a few start at the end and tell the story in reverse. In media res is a technique in which the author begins a story in the thick of a conflict or the middle of the story and then flashes back to the key events leading up to the present situation or conflict. The difference between a flashback and simply remembering a past event is that in a flashback a character is actually viewed reliving the past event as if it were occurring in the present. Most of the time, however, stories start at the beginning. Writers often begin with what happened first and then tell what happened next, and next, and so on, until the end. When writers tell a story in this order, from beginning to end in the order in which things happened, they are telling it in chronological order. Chronology is the arrangement of events in the order in which they occurred.

Manatee is common name for each of three species of a large walrus-like water mammal popularly called a sea cow. This mammal grazes on marine grasses and other water plants. They live in small family groups, although they occasionally travel in herds of fifteen to twenty. Manatees are characterized by two front flippers and bristly muzzle hairs. These portly marine mammals can grow to four meters in length, weigh up to a metric ton, and consume about 45 kg of seaweed a day. They inhabit sea grassbeds in shallow inlets along the Gulf and Atlantic coasts and have the distinction of being designated Florida's state marine mammal. Manatees die because of red tides, habitat destructions, and collisions with boats.

Most reality TV shows center on two common motivators: fame and money. The shows transform waitresses, hairdressers, investment bankers, counselors, and teachers, to name a few, from obscure   figures to household names. A lucky few successfully parlay their 15 minutes of fame into celebrity. Even if you are not interested in fame, you can probably understand the desire for lots of money. Watching people eat large insects, reveal their innermost thoughts to millions of viewers, and allow themselves to be filmed 24 hours a day for a huge financial reward makes for interesting entertainment. Whatever their attraction, these shows are among the most popular on television, and every season, they proliferate like weeds in an untended garden. The networks are quickly replacing more traditional dramas and comedies with reality TV programs, which earn millions in advertising revenue.

Acquired Immunodeficiency Syndrome (AIDS) is a human viral disease that ravages the immune system, undermining the body’s ability to defend itself from infection and disease. Caused by the human immunodeficiency virus (HIV), AIDS leaves an infected person vulnerable to opportunistic infections and rare cancers. Opportunistic infections are harmless in healthy people, but in those whose immune systems have been greatly weakened, they tax the weakened immune system, and prove fatal. Although there is no cure for AIDS, new drugs are available that can prolong the life spans and improve the quality of life of infected people. Infection with HIV does not necessarily mean that a person has AIDS. Some people who have HIV infection may not develop any of the clinical illnesses that define the full-blown disease of AIDS for ten years or more. Physicians prefer to use the term AIDS for cases where a person has reached the final, life-threatening stage of HIV infection.

Several hundred million years ago, plants similar to modern ferns covered vast stretches of the land. Some were as large as trees, with giant fronds bunched at the top of trunks as straight as pillars. Others were the size of bushes and formed thickets of undergrowth. Still others lived in the shade of giant club mosses and horsetails along the edges of swampy lagoons where giant amphibians swam. A great number of these plants were true ferns, reproducing themselves without fruits or seeds. Others had only the appearance of ferns. Their leaves had organs of sexual reproduction and produced seeds. Although their "flowers" did not have corollas these false ferns (today completely extinct) ushered in the era of flowering plants. Traces of these flora of the earliest times have been preserved in the form of fossils. Such traces are most commonly found in shale and sandstone rocks wedged between coalbeds. Today only tropical forests bear living proof of the ancient greatness of ferns. The species that grow there are no longer those of the Carboniferous period, but their variety and vast numbers, and the great size of some, remind us of the time when ferns ruled the plant kingdom.

The conservatism of the early English colonists in North America, their strong attachment to the English way of doing things, would play a major part in the furniture that was made in New England. The very tools that the first New England furnituremakers used were, after all, not much different from those used for centuries – even millennia: basic hammers, saws, chisels, planes, augers, compasses, and measures. These were the tools used more or less by all people who worked with wood: carpenters, barrel makers, and shipwrights. At most the furniture makers might have had planes with special edges or more delicate chisels, but there could not have been much specialization in the early years of the colonies.