Earth Science: The Science of Planet Earth

 

 

Alfred Wegener proposed his theory of continental drift in the early 1900s; it was based on indirect evidence. During his lifetime, he could not find enough evidence to convince most other Earth scientists that continents move over Earth’s surface. However, new evidence gathered by other scientists working 50 years later gave renewed support to his ideas. Today, plate tectonics, as the theory is now known, is supported by precise measurements of the changing positions of the continents. This is a good example of how the efforts of many scientists resulted in a new way of thinking about how our planet works. Science can therefore be defined as a universal and continuous method of gathering, organizing, analyzing, testing, and using information about our world. Science provides a structure to investigate questions and to arrive at conclusions. The reasoning behind the conclusions is clear, and the conclusions are subject to continued evaluation and modification. The body of knowledge of science, even as presented in this article, is simply the best current understanding of how the world works.

 

 

WHAT IS SCIENCE?

 

Science is a way of making and using observations. The applications of science have played a central role in the advancement of civilization. The Latin origin of the word science (scire) can be translated as “to know.” While some people might think of scientific conclusions as unchanging facts, our understanding is never complete. As the understanding of nature grows, old ideas that no longer seem to fit our observations are discarded. The so-called facts of science are often temporary while the methods of science (observation and analysis) are permanent.

 

Science often attempts to answer questions such as: Why is the sky blue? Why do we see the moon on some nights, but not on others? What causes clouds to form? Why are there violent storms, earthquakes, and volcanoes? How can people protect themselves from these disasters? How can people wisely use Earth’s resources and still preserve the best features of a natural environment? Understanding Earth and how it changes is essential for human survival and prosperity. Great works of art are valued, in part, because they have strong emotional impact. However, unlike works of art, scientists generally want their work to be as free of bias and individual judgments as possible. Rational thought and clear logic support the best scientific ideas. Scientists often use numbers and mathematics because mathematics is straight forward, logical, and consistent. These qualities are valued in scientific work. Scientific discoveries need to be verifiable. This means that different scientists who investigate the same issues should be able to make their own observations and arrive at similar conclusions. When a climate prediction is supported by the work of many scientists or by computer models, the prediction is considered to be more reliable. In fact, the ability reproduces results or verify ideas is a significant characteristic of science.

 

 

GOOD SCIENCE AND BAD SCIENCE

Sometimes it is easier to understand science if you look at what is not science. Tabloids are newspapers that emphasize entertainment. They publish questionable stories that other media do not report. Bring your teacher an article from a questionable news source that is presented as science. Your teacher will display the stories for the class to discuss. What are the qualities of these stories that make them a poor source of scientific information?

 

WHAT IS EARTH SCIENCE?

 

The natural sciences you study in school are generally divided into three branches: life science (biology), physical science (physics and chemistry), and Earth science. (See Figure -2.) Earth science generally applies the tools of the other sciences to study Earth, including the rock portion of Earth, its oceans, atmosphere, and its surroundings in space. Earth science can be divided into several branches. Geology is the study of the rock portion of Earth, its interior, and surface processes. Geologists investigate the processes that shape the land, and they study Earth materials, such as minerals and rocks. (See Figure -3.) They also actively search for natural resources, including fossil fuels. Meteorology is the study of the atmosphere and how it changes. Meteorologists predict weather and help us to deal with natural disasters and weather-related phenomena that affect our lives. They also investigate climatic (long-term weather) changes. Oceanography is the study of the oceans that cover most of Earth’s surface. Oceanographers investigate ocean currents, how the oceans affect weather and coastlines, and the best ways to manage marine resources.

 

Fig 2

 

Figure - 2 Earth sciences study the major parts of the planet by using other branches of science, such as biology, chemistry, and physics.

 

 

Fig - 3

Astronomy is the study of Earth’s motions and motions of objects beyond Earth, such as planets and stars. Astronomers consider such questions as: Is Earth unique? How big is the universe? When did the universe begin, and how will it end? Many Earth scientists are involved in ecology, or environmental science, which seeks to understand how living things interact with their natural setting. They observe how the natural environment changes, how those changes are likely to affect living things, and how people can preserve the best features of the natural environment.

 

 

HOW IS EARTH SCIENCE RELATED TO OTHER SCIENCES?

 

One important feature of Earth science is that it draws from a broad range of other sciences. This helps present an all-encompassing view of the planet and its place in the universe. Earth scientists need to understand the principles of chemistry to investigate the composition of rocks and how they form. Changes in weather are caused by the energy exchanges at the atomic level. By knowing the chemical properties of matter, scientists can investigate the composition of stars. Knowledge of biology allows Earth scientists to better interpret the information preserved in rock as fossils. The movements of stars and planets obey the laws of physics regarding gravity and motion. Physics helps us understand how the universe came about and how stars produce such vast quantities of energy. Density currents and the circulation of fluids control the atmosphere, the oceans, and even changes deep within our planet. Nuclear physics has allowed scientists to measure the age of Earth with remarkable accuracy. The Earth sciences also make use of the principles of biology and, in turn, support the life sciences. Organic evolution helps us understand the history of Earth. At the same time, fossils are the primary evidence for evolutionary biology. The relationships between the physical (nonliving) planet and life forms are the basis for environmental biology. Only recently have people grown to appreciate how changes in Earth and changes in life forms have occurred together throughout geologic time.

 

 

WHY STUDY EARTH SCIENCE?

 

Although some readers of this article may become professional geoscientists, it is more likely that you will find work in other areas. Regardless of the career you choose, Earth science will affect your life. Everyone needs to know how to prepare for changes in weather, climate, seasons, and earth movements. Natural disasters are rare events, but when they occur, they can cause devastating loss of life and property. To limit loss, people can prepare for hurricanes, tornadoes, floods, volcanic eruptions, earthquakes, and climate shifts.

Humans can survive the effects of cold and drought if they plan ahead, but they need to know how likely these events are and how best to avoid their devastating consequences.

 

How will humans be affected by general changes in climate? Can it be prevented? Will a large asteroid or comet strike Earth, and how will it affect Earth’s inhabitants? Our civilization depends on the wise use of natural resources. Freshwater, iron, and fossil fuels are among the great variety of materials that have supported a growing world economy. These resources have brought us unprecedented wealth and comfort. How much of these materials are available for use? What will happen if these materials run out? What is the environmental impact of extracting, refining, and using these resources These issues affect all of us regardless of our profession. As citizens and consumers, we make decisions, and as citizens, we elect governments that need to consider these issues. How can you, as one individual among millions in the United States, among billions in the world, make a difference? Environmental activists have a useful way of thinking about this, “Think globally, but act locally.” If you consider broad issues as you conduct your daily life, you can contribute to solving global problems. One person conserving resources by reusing and recycling materials has a very small impact. But when all people contribute their small parts, the beneficial effects are multiplied. One person buying a more fuel-efficient car or using mass transportation has a small impact. However, when these practices become widespread through public education, they can become powerful forces.

 

 

OBSERVATIONS, MEASUREMENT, AND INFERENCES

 

You gather information about your surroundings through your five senses: sight, touch, smell, taste, and hearing. The processes and interpretations made by scientists depend on making use of information gathered using their senses. These pieces of information are called observations. Some observations are qualitative. Relative terms, such as long or short, bright or dim, hot or cold, loud or soft, red or blue, compare the values of our observations without using numbers or measurements. Other observations are quantitative. When you say that the time is 26 seconds past 10 o’clock in the morning you are being very specific. Quantitative comes from the word quantity meaning “how many.” Therefore quantitative observations include numbers and units of measure. Scientists use measurements to determine precise values that have the same meaning to everyone.

Fig - 3

Measurements often are made with instruments that extend our senses. Microscopes and telescopes allow the observation of things too small, too far away, or too dim to be visible without these instruments. Balance scales, meter sticks, clocks, and thermometers allow you to make more accurate observations than you could make without the use of instruments. People accept many things even if they have not observed them directly. An inference is a conclusion based on observations. For example, if Liz meets a friend late one afternoon, and he appears tired and is carrying a baseball, bat, and glove, Liz would probably infer that her friend had been playing baseball. Although Liz never saw him playing, this inference seems reasonable. When many rocks at the bottom of a cliff are similar in composition to the rock that makes up the cliff, it is reasonable to infer the rocks probably broke away from the cliff. Scientists often make inferences. When scientists observe geological events producing rocks in one location and they find similar rock in other locations, they make inferences about past events, although they did not witness these events. No person can see the future. Therefore, all predictions are in ferences. In general, scientists prefer direct observations to inferences.

 

 

Exponential Notation

 

Scientists deal with data that range from the sizes of subatomic particles to the size of the universe. If you measure the universe in subatomic units you end up with a number that has about 40 zeros. How can this range of values be expressed without using numbers that are difficult to write and even more difficult to work with? Scientists use exponential numbers, sometimes called scientific notation, which uses powers of ten to express numbers that would be more difficult to write or read using standard decimal numbers. Numbers in exponential notation take the form of c X 10e, where c is the coefficient (always a number equal to or greater than 1 but less than 10) and e is the exponent. Being able to understand and use exponential notation is very important. Any number can be changed into exponential notation in two steps.

 

Step 1: Change the original number to a number equal to or greater than 1 but less than 10 by moving the decimal point to the right or left.

Step 2: Assign a power of 10 (exponent) equal to the number of places that the decimal point was moved.

 

A good way to remember whether the power of 10 will be positive or negative is to keep in mind that positive exponents mean numbers greater than 1, usually large numbers. Negative exponents mean numbers less than 1, which are sometimes called decimal numbers. Once you get used to it, it becomes easy. Let us see how this is done. The mass of Earth is 5,970,000,000,000,000,000,000,000 kilograms. Move the decimal 24 places to the left to get 5.97. The power of 10 is therefore 24 Expressed in exponential notation this number is 5.97 X10²⁴ kilograms.

 

 

EXPONENTIAL NOTATION IN THE REAL WORLD

 

Make a list of 5 to 10 values expressed in scientific notation, document their use, and translate them into standard numbers. Your examples must come from printed or Internet sources outside your Earth science course materials. For each example you bring, include the following:

1. The value expressed in exponential notation. (If units of measure are present, be sure to use them.)

2. What is being expressed. (For example, it might be the size of a particular kind of atom.)

3. The same value expressed as a regular number.

4. Where you found the value. Please give enough information so that another person could find it easily.

 

Over the course of time, different countries developed their own systems of measurements. The inch and the pound originated in England. There were no international standards until the European nations established a system now known as the “International System of Units.” This system is called “SI,” based on its name in French, System International. SI units are now used nearly everywhere in the world except the United States. SI is similar to the metric system. In a temperature-controlled vault in France, a metal bar has been marked at exactly 1 meter. In the past, it was the precise definition of meter, and all devices used to measure length were based on that standard. Everyone knew the length of a meter and everyone’s meter was the same. Today the meter is defined as a certain number of wavelengths of light emitted by krypton-86 under specific laboratory conditions. The advantage of this change is the standard length can be created anywhere and is not susceptible to natural or political events. In everyday life, people often use a system of measures called “United States Customary Measures.” Units such as the mile, the pound, and the degree Fahrenheit have been in use in this country for many years. Most Americans are familiar with them and resist change. As this country becomes part of a world economy, SI units will gradually replace the United States Customary units. Many beverages are now sold in liters. A variety of manufactured goods created for world markets are also measured in SI units. (See Table 1-1.)

 

 

TABLE 1-1. International System of Units

 

 

MAKING ESTIMATIONS

 

Estimation is a valuable skill for anyone, but especially for scientists. If you want to know whether a measurement or calculation is correct, it can be helpful to estimate the value. If your estimate and the determined value are not close, you may need to give some more thought to your procedure. If you were to estimate the distance from your home to the nearest fast-food restaurant, you might say that you can walk there in 30 minutes. If you walk at a rate of 5 kilometers per hour (km/h), in half an hour you can walk 2.5 km. So, your estimate would be 2.5 km. Working in groups, estimate the volume of your classroom or your school building. No measuring instruments may be used. Your group must write a justification of your estimate. Please use only SI (metric) units.

 

USING SI UNITS Density is an important property of matter. For example, differences in density are responsible for winds and ocean currents. Density is defined as the concentration of matter, or mass per unit volume. For example, if the mass of an object is 30 grams and its volume is 10 cubic centimeters,

 

cm³), then its density is 30 grams divided by 10 cm³, or 3 grams/cm³. The formula for calculating density is given in the Earth Science Reference Tables.

 

 

HOW IS DENSITY DETERMINED?

 

Density is the concentration of matter, or the ratio of mass to volume. Substances such as lead or gold that are very dense are heavy for their size. Materials that we consider light, such as air or Styrofoam, are relatively low in density. Objects made of the same solid material usually have about the same density. (Density does change with temperature as a substance expands or contracts.) As shown in the following problem, density can be calculated using the formula given in the Earth Science Reference Tables. Density is generally expressed in units of mass divided by units of volume. Note that the units are carried through the calculation, yielding the proper unit of density: grams per cubic centimeter (g/cm³).

 

SAMPLE PROBLEM

 

 Practice Problem 2

A 105-g sphere has a volume of 35 cm³, what is its density?

 

 

Water, with a density of 1 g/cm 3, is often used as a standard of density. Therefore, the process of flotation can be used to estimate density. If an object is less dense than water, the object will float in water. If the object is denser than water, the object will sink. Most wood floats in water because it is less dense than water. Iron, glass, and most rocks sink because they are more dense than water. The idea of density will come up many times in Earth science and it will be discussed as it is applied in later chapters. The instrument shown in Figure is called a Galileo thermometer. It is named for the Italian scientist who invented it. This thermometer is based on the principle that the density of water changes slightly with changes in temperature. As the water in the column becomes warmer and less dense, more of the glass spheres inside the tube sink to the bottom. Therefore, the number of weighted spheres that float depends on the temperature of the water. Reading the number attached to the lowest sphere that floats gives the temperature. A demonstration of the relative density of liquids can be made by first pouring corn syrup, then water, followed by cooking oil, and finally alcohol into a glass cylinder. Care must be taken not to mix the liquids. They will remain layered in order of density as shown in Figure 1-8. If a rubber stopper with a density of 1.2 g/cm3 were added, it would sink through the water layer. The stopper would remain suspended between the water and the corn syrup. Rubber is more dense than water, so it sinks in water. Corn syrup is more dense than rubber. Therefore, the rubber stopper would float on top of the corn syrup layer.

 

TECHNOLOGY IN EARTH SCIENCE

 

How science is “done” has always depended on the tools available. Some tools have revolutionized Earth science. Computers provide a good example. When they are attached to a variety of other devices, computers can be used for an amazing variety of applications. Computers help us analyze data, produce and edit images, and quickly access information. The first electronic computers filled entire rooms, and were so expensive that only a few research facilities could afford them. Today, a laptop computer can have computing power equal to that of a supercomputer of the 1970s. Connecting computers in networks has progressed to the point where you can almost instantly access information stored in millions of computers all over the world. This is the World Wide Web connected by the Internet. It allows all of us to communicate faster than ever before.