Scientific Investigation and Reasoning

Scientific Investigation and Reasoning Scientific Investigations

Observations

Scientific investigations often begin with observations. An observation is information that you obtain through your senses, such as sight, sound, and touch.

Hypotheses

Scientific investigations often begin with a problem or questions about an observation. A hypothesis is a possible explanation for a set of observations or a possible answer to a scientific question. A hypothesis is often a prediction of what will happen if you introduce a change in a system or process.

For a hypothesis to be valid, it must be testable. This means that you must be able to carry out investigations and gather evidence that will either support or disprove the hypothesis.

Hypotheses are often based on cause-and-effect relationships and written as "If..then.." statements. For example, a valid hypothesis could be, "If salt is added to water, then the freezing point of the water will decrease."

Variables and Controlled Experiments

Investigations are designed to test a hypothesis. All factors that can change in an experiment are called variables. An experiment in which only one variable is changed at a time is called a controlled experiment.

The variable that is purposely changed to test a hypothesis is called the manipulated variable. Manipulated variables are also sometimes called independent variables.

The factor that may change in response to the manipulated variable is called the responding variable. Responding variables are also sometimes called dependent variables.

Scientists carefully control their variables so they can understand how the variables affect the system as a whole. This makes the data collected from an experiment meaningful.

However, sometimes scientists collect data that is contradictory or unusual. When this happens, the scientist should carefully go over the investigation’s design to make sure that there is only one manipulated variable in the experiment. Types of Scientific Investigations

Scientific investigations are organized attempts to seek out, describe, explain, and predict natural phenomena. Scientific investigations are often performed to explore new phenomena, verify the results of previous investigations, test theoretical predictions, and discriminate between competing theories.

There are many different types of scientific investigations that may be performed. The type of scientific investigation that is chosen depends on the question that is being asked in the investigation. Also, scientists sometimes combine aspects of more than one type of investigation. Different types of investigations include:

 making models  performing a controlled lab experiment  performing a field-based investigation  observing and describing objects, organisms, or events

MAKING MODELS

Making a model of something that is too large, rare, complex, or dangerous to fully observe in person can help scientists understand how it works.

For example, scientists can use a computer simulation program to predict weather patterns. By entering past and present weather conditions and phenomena, scientists can collect data from a large span of time and attempt to predict future weather patterns.

PERFORMING A CONTROLLED LAB EXPERIMENT

If the conditions of an experiment must be very precise, or if an object or organism is not being studied in its natural setting, it may be beneficial to perform a laboratory experiment. Conditions can be controlled in a lab experiment.

In a controlled lab experiment, there should be an independent variable, a dependent variable, and a control. The independent variable is the factor in the experiment that is manipulated by the researcher. The dependent variable is the factor in the experiment that changes in response to the independent variable. Controls in an experiment are used as comparison factors, and they can help determine the magnitude of the experiment's results.

PERFORMING A FIELD-BASED INVESTIGATION

If an object or organism needs to be studied in its natural setting, a field-based investigation will be performed. Field-based investigations are often the best way to learn how things work in nature. It is important to tamper with a natural setting as little as possible when performing these investigations.

OBSERVING AND DESCRIBING OBJECTS, ORGANISMS, or EVENTS

Some investigations focus mainly on observations and collecting large amounts of data. The main purpose of these investigations is to thoroughly describe specific aspects of nature. For example, a scientist might collect specimens of a particular kind of insect from many locations. By documenting observations about the specimens, the scientist can precisely define several general aspects of the insect, such as its color, leg length, head size, etc. Investigations like this provide a solid base from which more specific, experimental investigations can develop. Collect & Interpret Data Making observations and collecting information are a large part of a scientist’s job. Once this information is collected, it must be organized and presented in a clear and concise way. Tables and graphs are tools that scientists use to organize and present information.

Collecting information for scientific investigations is a very important task. Collecting data can be done in many different ways, such as:

 observing  measuring or counting  asking questions  performing an experiment

Once information has been collected, it should be interpreted. Most of the time, when data needs to be interpreted, it is placed into tables or graphs.

Tables allow a lot of information to be presented in a small space by organizing data efficiently. The information found in tables can be interpreted to form conclusions about the data and the topic of the investigation.

Tables should include all the important data in an experiment, especially the independent and dependent variables. It is easiest to see patterns in the data in a table if the data is put in order instead of randomly ordered. For example, the data could be put in order according to the size of the independent variable or the dependent variable.

For example, if Kolbe is measuring the resistance of various materials, he put the materials in his table in order of increasing resistance.

Sample ID: Material Length Resistance B4 red/gold metal 1.5 cm 0.5 Ω A1 silver metal 1.5 cm 2.1 Ω C10 golden metal 1.5 cm 8.3 Ω F23 green leaf 1.5 cm 1,275 Ω

Putting the data in this order makes it clear that metals tend to have low resistances. However, there is one problem with this table: Kolbe did not need to include the length of each sample.

While tables are used for organizing information, graphs are used to present information visually. Different types of graphs are used for presenting information in different ways.

Circle Graphs

Circle graphs are best used to show how a whole is divided into parts (or percentages of a whole).

Circle graphs, or pie charts, are circular-shaped graphs that are broken into sections. The sections represent different parts of the whole, and all of the sections combined should add up to the total. Section sizes in the graph correspond to the percentage or amount of the whole that it represents. For example, a section that represents 50% of the total should take up half of the graph.

Good examples of questions that may use circle graphs include:

 percentages of students in different classes (out of students in the school)  number of people that reside in each continent (out of entire population)

Example 1:

Anna has a bag of one hundred pieces of candy, which are either purple, blue, red, yellow, or green. She wants to know which color of candy she has the most of in her bag. She counts the candy and records her results. From her results, she makes the following graph.

Which color of candy does Anna have the most of?

From looking at the graph, you can tell that Anna has more pieces of blue candy than any other color.

Bar Graphs

Bar graphs are best used to show how a number of objects or events compare in relationship to a single property.

A bar graph uses bars to compare one property of different objects or events. Each bar represents one object or event, and there can be two or more bars present on one graph. The bar for each object is a certain length, which is determined by the amount or occurrence of the property being compared in relation to the other bars. Thus, the longer the bar, the greater the amount of the object or frequency of the event.

Bar graphs consist of a horizontal and a vertical scale. One scale identifies the objects to be compared and the other scale is numerical. The numerical scale must be consistent. A graph can be misleading or difficult to read if the wrong scale is chosen.

Good examples of questions that may use bar graphs include:

 the favorite color of students in a class  number of each type of animal in an area

Example 2:

Mr. Ward wants to know how much each student in his class participates on a certain day. He decides to test this by counting the number of times that each student raises his hand during class. Mr. Ward records his results and makes the following bar graph.

Which student participated the most in class? Using the number of times a student raised his hand in class to measure the amount of participation, Ashley participated most in class on that day.

Line Graphs

Line graphs are best used to show a relationship between two measured quantities, usually as a trend over time.

Line graphs are usually made up of data points on a graph, with a line that connects them or is drawn to best fit the most points. There are two axes on a line graph. The x-axis, or the horizontal axis, is where the independent variable (manipulated by the experimenter) is placed. The y-axis, or the vertical axis, is where the dependent variable (not manipulated by the experimenter) is placed. Line graphs are often used to see trends over time, with the time normally being the independent variable.

Good examples of questions that may use line graphs include:

 plotting plant growth vs. days  plotting temperature vs. time of day  plotting the year vs. number of animals present in an area

Example 3:

Angie is growing a plant. She measures the plant each week for ten weeks and records the height of the plant. After the ten weeks, Angie makes a line graph of the information that she collected.

How tall was Angie's plant after 5 weeks? Angie's plant was 25 inches tall after five weeks.

Scatterplots

Scatterplots are best used to find out whether two variables are related.

A scatterplot is used to examine two sets of data and to investigate the possible relationship (or correlation) between two variables. The pattern of the points suggests how closely the data are related.

Example: This scatter plot is used to determine the correlation between the number of hours a student studied and the scores on his tests.

Calculating Mean Value When interpreting scientific data, often it is useful to find the central tendency or "middle" of a data set. The mean is one way to calculate the central tendency of a set of data.

Calculating Mean: Add up the numbers then divide by the number in the set to get the mean.

Example: Find the mean of the following: { 66 m, 72 m, 83 m, 89 m} 66 m + 72 m + 83 m + 89 m Mean = 4 310 m Mean = 4 Mean = 77.5 m

Units of Measurement

A variety of properties can be used to help identify and classify matter. The major measurable properties of matter are shown below. When measuring matter, it is important to use the correct measurement units.

Measurable Properties of Matter

Property Definition Common Units mass the amount of matter in an object milligrams, grams, kilograms weight the force exerted upon an object due to gravity ounces, pounds, newtons millimeters, centimeters, meters, length the measure of how long an object is kilometers volume the amount of space an object takes up milliliters, liters the measure of "hotness" or "coldness" of an object temperature degrees Celsius or environment density the amount of matter in an object per unit volume kg/L, g/mL

Lab Tools

Laboratory tools are used to make measurements and gather data in lab. Knowing how to use these tools is important for making precise and accurate measurements.

Common laboratory tools include a science notebook, triple beam balance, graduated cylinder, test tube, beaker, measuring cup, petri dish, hotplate, ruler, spring scale, compass, microscope, binoculars, hand lens, telescope, stopwatch, and thermometer. A science notebook, which may also be called a journal, is an important tool for controlled laboratory Science experiments and also for doing fieldwork. The Notebook or hypothesis, procedures, data, and observations for Journal each investigation should be recorded using words, pictures, or data tables in the notebook.

A triple beam balance is used to measure the mass of solid objects. It has three beams that each Triple Beam measure mass to a different unit place (ones, tens, Balance hundreds). Units of mass include milligrams, grams, and kilograms.

A graduated cylinder is used to measure the volume of liquids in milliliters (mL) or liters (L). It is read by Graduated looking at the very bottom of the curve of liquid in Cylinder the cylinder. This curve of liquid is called a meniscus.

A test tube is a long, narrow type of glassware in which liquids can be stored and heated. Test tubes Test Tube have round bases and are stored in test tube racks or mounted on test tube stands.

Beaker A beaker is a type of glassware. It can be used to store liquids, heat liquids, and measure the volumes of liquids. Beakers have broad, flat bases. Beakers usually measure liquid volumes in milliliters (mL).

A measuring cup is used to measure the volume, or amount, of a liquid. To measure how much liquid is in a measuring cup, look at the lines in the front, Measuring Cup and see what line the top of the liquid is at. Measuring cups can measure volume in metric units, such as milliliters (mL), or in U.S. system units, such as ounces and cups.

Petri dishes are most often used for growing cultures Petri Dish of microorganisms, such as bacteria or mold. They may also be used as containers in the lab.

A hot plate is a type of lab equipment used to heat Hot Plate substances (usually liquids). It has a flat platform where a beaker containing a liquid can be placed.

Rulers, meter sticks, and tape measures are used to Ruler, Meter measure length. These tools usually have two edges Stick, and Tape —one that measures in metric units (millimeters, Measure centimeters, and meters), and one that measures in U.S. system units (inches and feet). A spring scale is used to measure the weight, or gravitational force, of an object. It is used by Spring Scale attaching an object to the hook at the end of the scale, then the weight is displayed on the tube of the scale in Newtons (N) or pounds (lb).

A compass is a tool that detects magnetic fields. When no local fields are present, a compass will detect Earth's magnetic field. The arrow of a Compass compass generally points North, so a person using a compass can tell which direction (North, South, East, or West) he or she is facing.

A microscope is used to view objects that are too Microscope small to be seen with the naked eye, such as cells.

Binoculars are used for seeing objects that are Binoculars distant, but not as far away as space. A hand lens is used to look at objects up close. It Hand Lens makes objects appear larger.

A telescope is used to view objects that are very far Telescope away, such as planets and moons.

A stopwatch is used to measure time in seconds and Stopwatch minutes.

A thermometer is used to measure temperature in either Thermometer °C or °F. A thermometer is read by looking at the number that is displayed at the top of the red line inside of the thermometer.

Computers & Calculators in Science It is sometimes useful to use a computer or a calculator to analyze, interpret, or communicate data from a scientific investigation.

Calculators

Calculators are tools that are used for simple math-related tasks, such as

 basic calculations—addition, subtraction, multiplication, and division

 finding the mean or average of numbers

Computers

Computers are tools that can be used for complex tasks, such as

 calculations with multiple steps

 creating graphs and charts of data

Weather Tools

Meteorologists are scientists who study weather. Meteorologists use several different types of tools to measure different characteristics of weather.

For example:

 A thermometer is used to measure temperature.  An anemometer is used to measure wind speed.  A wind vane is used to measure wind direction.  A barometer is used to measure air pressure.  A rain gauge is a tool used for measuring the amount of rain that falls in a given period of time.

A thermometer is used to measure temperature in degrees Fahrenheit or Celsius. Thermometer Snow Gauge

A snow gauge is used to measure the amount of snow that falls in a given period of time.

Anemometer

An anemometer is used to measure wind speed in one area.

Wind Vane

A wind vane is a tool used for measuring wind direction.

A rain gauge is a piece of equipment designed to measure the amount of rain that Rain Gauge falls in a given period of time. ..

Barometer

A barometer is used to measure air pressure.

Spectroscopes

Spectroscopes are devices that separate electromagnetic radiation into different wavelengths. These devices can be used for many purposes. In astronomy, spectroscopes are used to determine what planets, stars, and other objects are made of. For example, scientists use spectroscopes to separate visible light from stars into bands of color. By comparing patterns in these bands with known patterns of various elements, the scientists can determine the stars' compositions.

But stars and planets aren't the only objects that can have their emission patterns analyzed with spectroscopes. Virtually anything that emits or reflects light can be analyzed with a spectroscope. While the Sun emits light of almost every visible color (which makes its emission spectrum nearly continuous), most human-made objects emit only certain types of light.

The spectrum of light emitted by an incandescent light bulb can be determined with a spectroscope. Its emission pattern is shown on the right. This spectrum is very nearly continuous, making it similar to sunlight. The spectrum of light emitted by a florescent light bulb can be determined with a spectroscope. Its emission pattern is shown on the right. This spectrum is not continuous, since it shows individual bands of light.

Laboratory and Field Safety

The following rules are essential for keeping you and your classmates safe in the lab:

General Lab Safety

 Read the entire lab procedure before you begin an experiment.  Only perform the assigned experiment when the teacher has given you permission to do so, and when the teacher is supervising.  Know where all the safety and emergency equipment (e.g. eyewash station, fire extinguisher, fire blanket, first-aid kit, etc.) is located in the lab.

 Only bring necessary materials into the lab area; keep your work area uncluttered.

Personal Safety

 Always wear closed-toe shoes, safety goggles, a protective lab apron or lab coat, and protective gloves when working in the lab.  If possible, wear clothes made of cotton. Synthetic materials can melt onto your skin if they catch fire.  If a chemical gets in your eye(s), go to an eyewash station and flush your eyes with water for at least 15 minutes. Notify the teacher.  Tie back long hair, and roll up loose sleeves.  Never eat, drink, or apply makeup in the lab.

 Do not touch your face or eyes while conducting an experiment.  If you have to cut something, cut in a direction that is away from your body.  Wash your hands thoroughly with soap and water after completing experiments.

Chemical Safety

 Never taste any chemicals in the lab.  Avoid contaminating stock solutions; never return unused chemicals to their original container.  Do not directly inhale any gas or vapor; use your hand to waft the fumes toward your nose.  Always pour an acid or base into water, not vice-versa. Use the mnemonic A&W to help you remember that you should add Acid to Water, not water to acid.  Report any chemical spill to your teacher immediately.

Glassware, Heating, and Electrical Safety

 Do not use glassware with cracks and chips; ask the teacher for a replacement.  Never insert glass tubing into a rubber stopper without teacher permission.  Never use electrical equipment with a damaged cord.  When heating chemicals in a test tube, point the opening of the test tube away from yourself and others.  Use tongs or insulated gloves to hold or pick up hot objects. Field Safety

 Notify the teacher of any allergies or medical conditions that you may have prior to going into the field.  Don't touch any plants or animals without the teacher's permission.  Never put any part of a wild plant in your mouth.  Don't drink unpurified water.  Wear long pants, long sleeves, socks and closed-toe shoes

 Don't wander off alone.  Wash your hands after being in the field.

 Lab Materials When working with materials in the laboratory, it is important to store or dispose of the materials correctly. This will help avoid injuries, damage to the environment, and damage to equipment.  Laboratory Tools

Most laboratory tools can be reused for many experiments, as long as the tools are not damaged. For example, glassware can be reused as long as it is not cracked or broken. Even if a tool has come into contact with a harmful material, it can usually be cleaned using a variety of methods.

Sometimes lab materials break or become unusable for some other reason. If a material is recyclable, such as most plastics, metal, glass, and paper, it should be recycled—but only when it cannot be reused. A cracked glass beaker or a broken plastic petri dish are two examples of lab equipment that could be recycled.

Equipment and tools that have been used in the lab should never be reused as food or drink containers.

Disposal of Materials Scientists should try their best to reduce the amount of waste generated during an experiment. Not only does this save money, but it also makes the lab a safer place and helps protect the environment. Because some waste is unavoidable, it important to know how to dispose of it properly.

Waste materials that cannot be reused for another lab may be disposed of in many ways. Some of the main ways are shown below. Always ask your teacher before disposing of any laboratory material.

Trash Can - The trash can is usually used for the disposal of dry, harmless materials that cannot be reused or recycled.

Sink - The sink is usually used for the disposal of water. Some chemicals shoud not go in the sink even though they are not dangerous. For example, corn starch and oil are not dangerous chemicals, but they will eventually solidify and clog the drain pipes. You should only put chemicals into the sink if your teacher has told you that it is safe to do so.

Waste bottles - Chemicals should be used sparingly. Any chemical waste should be placed in its appropriate waste bottle (with a lid) for the teacher to dispose of at the proper time. Different types of chemical waste should not be mixed together unless a teacher gives specific instructions to do so. Some chemicals can form toxic fumes or even expolde when they are mixed.

Biohazard container - After a biological material (such as bacteria) is used in an experiment, it should be sealed and placed in a biohazard receptacle. The teacher will dispose of the stored waste at the proper time. Scientific Evidence

The goal of any scientific experiment is to answer a question or to better understand a process or system. After an experiment is complete, scientists must analyze the data, draw conclusions, and communicate their results using evidence from the experiment.

ANALYZING DATA

Scientists perform investigations because they are curious. That is, they want to learn more about something. When an experiment is complete, the scientist studies the data to find out what it means. The scientists tries to understand how one factor, or variable, in the study affected another. For instance, imagine a scientist planted 20 bean seeds in each of 7 cups. She placed the cups in each of 7 different temperatures. If the scientist had gathered the following data:

Temperature Number of Sprouted (in °F) Bean Seeds 55 2 60 5 65 7 70 12 75 15 80 9 85 4 she might determine that temperature affects the sprouting rate of bean seeds, and that more of these bean seeds sprout at 75° than at 55°.

DRAWING CONCLUSIONS

After gathering and interpreting data, a scientist draws conclusions about the hypothesis. The evidence may prove that the scientist's hypothesis was correct. The evidence could also prove the hypothesis was incorrect. Either way, the scientist has learned something.

Scientists must check conclusions they and other scientists draw and check each others’ hypotheses, experiments, and conclusions to make sure that they are accurate.

Checking work is made easier through the keeping of honest, careful records about observations and experiments. These records should never be changed or altered to fit a conclusion or idea or to hide something. When reporting what is learned during an experiment, it is important to offer reasons for all of the findings and to make sure all conclusions are supported by the evidence, and are not made from hope or guesses.

USING EVIDENCE TO COMMUNICATE RESULTS

Scientists show openness when they are willing to provide all of the information about their experiments to others. This allows the other scientists to review the work. Sometimes other scientists will disagree about how to interpret data collected during an investigation. When scientists review the results of another scientist’s experiment, they are often skeptical. That is, they question the validity or reality of the data. The scientists may try to learn if the results are reliable by asking the following questions:

 Was the sample size large enough?  Was the experiment controlled?  Are the findings reliable?  Can the data be interpreted in a different way?

 Evaluating Models Models are objects, drawings, or ideas that are very similar to the real thing, but are different in some ways.  A globe, for example, is a model of the planet Earth.

A globe is a good model of planet Earth. Both objects are round, and have land and oceans shown on them. However, the model globe is much smaller than the real planet Earth, and it is made of different materials.  Although models are always a little different from the real thing, they are very useful for helping people learn about the real thing.

Another example of a model is a plastic model of a human's inner organs.

Even though a model of a human's inner organs is different from a real human, it is useful for helping people to understand where these organs are located in a real body. History of Science & Technology

"If I have seen further than other men, it is because I have stood on the shoulders of giants." —Sir Isaac Newton

This famous quote from a letter to Robert Hooke by Isaac Newton expresses how one scientific discovery or technological advance leads to another. In a very real way, humankind owes everything it has accomplished in the field of science to every scientist over several thousand years. Below is a small sample of some of these "giants" in chronological order.

Nicolas Copernicus was born in 1473 to German parents in what is now Poland. At the time when he began his study of astronomy, the widely accepted theory of how planets and stars moved had stayed basically the same for over 1,300 years. This ancient model of the universe originated with the idea that everything should move in perfect circles about the Earth, and it was adapted to resemble the actual motions of the planets and stars. Based on his observations and solid mathematical calculations, Copernicus came up with a model for the universe in which all the planets including the Earth revolved around a central point, the Moon revolved around the Earth, and the Earth rotated on its axis. Other people followed Copernicus's lead in conducting scientific investigation through observation and mathematics, eventually culminating in the Renaissance.

Harmonia Macrocosmica by Andreas Cellarius

Galileo Galilei was born in Italy in 1564. He made an improved telescope and used it to study astronomy. He discovered the first moons orbiting other planets—moons of Jupiter. Galileo conducted systematic experiments in kinematics, studying gravity and how it accelerated different objects. His support of Copernicus' theory that the Earth was a moving planet like the other planets was vehemently opposed by major Christian leaders including Martin Luther, John Calvin, and Pope Urban VIII. Copernicus's theory was considered to oppose verses from the Christian Bible such as "He [God] has made the world firm, not to be moved." (1 Chr 16:30)

Robert Hooke was born in 1635 in England. He contributed to many different fields of science and technology. He has a law of physics named after him, was a known rival and opponent to Sir Isaac Newton, and he later confirmed Anton van Leeuwenhoek's microbiological discoveries.

Hooke built a compound microscope—a microscope that used two lenses. He published his observations in 1665 in the popular book Micrographia. This book may have inspired van Leeuwenhoek to begin building microscopes.

Using his microscope to examine cork, Hooke became the first to observe cells and gave them their name.

Image from Micrographia by Robert Hooke, 1665

Anton van Leeuwenhoek was born in Holland in 1632. He became very skilled at grinding lenses and was able to build simple microscopes that could magnify objects 200 times while still giving a clear image. This was such a vast improvement over earlier microscopes that some people consider him to have invented the microscope. His novel, clear view into the microscopic allowed Leeuwenhoek to observe and describe microorganisms. Because he was the first to study such tiny life in detail, he is sometimes called the father of microbiology. A replica of one of Leeuwenhoek's microscopes is shown below. Image by Jacopo Werther

Isaac Newton was born in 1642 in England. He attended Cambridge University and, while still young, formulated his laws of motion, calculus, and the theory of gravity. He applied the law of gravity to explain tides on the Earth and the motion of planets around the Sun. Newton also contributed to optics and other fields of physics.

James Hutton was born in 1726 in Scotland. His study of geology led him to theorize that the features of the Earth—mountains, hills, rocks, etc.—were continually being formed and worn away by processes such as erosion and deposition. He also realized that processes such as volcanic eruptions and the formation of certain rocks depended on the heat from inside the Earth.

Charles Darwin was born in 1809 in England. His interests and contributions spanned the fields of taxonomy (the classification of living things), geology, paleontology (the study of ancient life forms), and anthropology (the study of humans).

Darwin's time on the ship The Beagle provided him and other scientists with valuable observations and samples which led him to form the theory of evolution by natural selection. Image by José-Manuel Benitos, reproduced under GNU Free Documentation License version 1.2

Gregor Mendel was born in 1822 in Austria. He studied the way physical characteristics of plants were passed down from parents to offspring. In the process, he formulated three laws of inheritance that describe how dominant and recessive traits are passed down through genes. Although Mendel did not use the word genes, he is considered to be the father of modern genetics. From Mendel's Principles of Heredity: A Defence by William Bateson, 1902

Louis Pasteur was born in France in 1822. After demonstrating that yeast was the cause of fermentation—the process by which wine and beer become alcoholic—Pasteur went on to study disease and create vaccines for various diseases. He developed a process, now named after him, for removing microorganisms from foods and drinks. He used this process to provide evidence to support germ theory. George Washington Carver was born into slavery in the United States around 1864. He spent his life in agricultural research, focusing on helping the poorest farmers in the South. He helped educate farmers on how to enrich the soil by growing plants like sweet potatoes and peanuts that put nitrogen back into the soil and by using crop rotation. He developed multiple uses for crops such as peanuts to create a demand for them, changing the economy of the South.

Alfred Wegener was born in 1880 in Germany. Coming upon descriptions of similar fossils found on opposite sides of the ocean, he spent much of his life gathering evidence for continental drift. Geologic formations, fossils, and evidence of ancient climates as well as the shapes of the continents themselves supported his theory that all the Earth's continents used to be grouped together as one "supercontinent" and are in continual motion. Image from This Dynamic Planet, USGS

Rachel Carson was born in 1907 in the United States. She was an accomplished writer on the subject of biology. She is best remembered for her book Silent Spring, which focused on the effects of pesticides on the environment. Her book sparked a public outcry that led to the banning of DDT and the founding of the Environmental Protection Agency. Without Rachel Carson, the bald eagle (among other creatures) would probably no longer be able to survive in the continental US.

Jane Goodall was born in 1934 in England. She spent years observing chimpanzees in Tanzania and was for a time accepted by a troop as a member of their social group. Having not been trained as a scientist before she started her observations, Jane Goodall saw the apes with fresh eyes—less as objects to be studied and more as unique and complex individuals. She has dedicated her life to spreading knowledge of great apes throughout as much of the world's population as she can and works for their preservation.

Impact of Science - Cultural Contributions

Many different types of people, with many different interests, backgrounds, and experiences, have made significant contributions to science.

Conventional scientists working in laboratories are not the only people who have made major contributions to the progression of modern science.

Sometimes the focus of science is significantly changed by popular writing and activism. This was the case with 20th Century author and biologist Rachel Carson and her world famous book Silent Spring. In the book, which was published in 1962, Carson revealed some of the potential threats of using inorganic chemical pesticides in agriculture. The response to Carson's book was so large that a now large and powerful government agency, the Environmental Protection Agency, was created as a direct result.

Another unconventional scientists was Percival Lowell, who had been a successful businessman in the late 19th Century, but then turned virtually all of his attention to astronomy. Lowell established the Lowell Observatory in Flagstaff, Arizona, which was the first observatory ever deliberately built far from civilization and at a high altitude. Lowell is best remembered for his efforts to verify that there are canals carved into the surface of Mars; an idea that has since been disproved. But Lowell's detailed observations and sometimes wild theories eventually led to the discovery of Pluto, formerly considered to be the ninth planet in our solar system. Sometimes scientific discoveries powerfully impact human culture, society, business, and beliefs.

Nicolaus Copernicus was one scientist whose theories about the heliocentric nature of the universe significantly impacted astronomy as well as the dominant beliefs of his time. Copernicus' observations about the movement of the other planets in the early 16th Century led him to believe that the Earth and all of the other planets revolve around the Sun. Copernicus was the first to popularize this model of the universe. It had been previously believed that the Earth was the geometric center of the universe.

In more recent times, some of the more groundbreaking scientific discoveries have come from investigating the world of the very small. Luis Alvarez was a world famous particle physicist and inventor, who won the Nobel Prize in Physics in 1968 for investigating resonant states of atomic nuclei; his findings helped develop the first devices capable of observing the ultra-small quantum properties of nuclei. He also aided in research headed by his son, which led to the modern theory of the dinosaurs' extinction.

Louis' son, Walter Alvarez, became a famous scientist in his own right. Walter conducted research in the 1960s looking into a transition between two geologic periods, which took place about 65 million years ago, the same time the dinosaurs went extinct. This geologic boundary, he found, had extraordinarily high levels of a metal whose presence could only be explained by an asteroid impact with Earth. This discovery led to the now dominant theory that most of the animals alive during the age of the dinosaurs became extinct after a massive asteroid struck the Earth. Antoine Lavoisier & Conservation of Matter

In the late 1700s, Antoine Lavoisier conducted experiments in which he carefully measured the masses of all the substances involved in various chemical reactions, including the gases used and those given off. What he found what that the total mass before and after a chemical reaction was always the same. Antoine Lavoisier was a French scientist who contributed significantly to chemistry. He is partially responsible for developing the law of the conservation of mass/matter in chemical reactions.

Antoine Lavoisier helped to develop the idea of the conservation of matter.

The conservation of matter (or mass) principle states that in any isolated system, the total amount of mass in that system will be constant through time.

So when Lavoisier conducted his experiments, he saw chemicals changing into other chemicals, liquids changing to gases, solids changing to liquids, and many other transformations. However, over the course of all of these transformations, even though the type of matter he had changed, the total mass of that matter did not change. The Curies & Radioactivity

Scientists estimate that the Earth's age is nearly 4.6 billion years. This age has been calculated from the radioactive decay of specific radioactive elements.

This age was not immediately arrived at by scientists in the late 1800s and early 1900s. This was because, at this time, different ways for calculating the age of the Earth were yielding different results.

In the late 1800s, William Thomson (known as Lord Kelvin), calculated that the Earth was only about 40- 100 million years old. This calculation was based on the planet's current temperature near the surface. Kelvin assumed that the Earth began as a hot, molten mass of liquid rock. From this initial temperature, Kelvin then was able to figure out how long it would take the Earth to cool to its present temperature. Kelvin's results were not looked upon favorably by a number of prominent scientists of his time, though virtually everyone agreed that he had made no errors in his math. Thomas H. Huxley, for one, argued that Kelvin's result was entirely too short an amount of time to account for all of the biological evolution that had taken place in Earth's history. Geologists also found an age as low as 100 million years extremely difficult to accept.

As it turned out, Kelvin (as well as a number of other scientists) had based his calculations on faulty assumptions. Specifically, until 1896, no one had any idea what radioactivity was, or what role it has played on planet Earth.

DISCOVERY OF RADIOACTIVITY

Radioactivity was discovered by accident by French scientist Henri Becquerel in 1896.

This discovery helped to explain how the Earth could be billions of years old, but still be relatively warm.

Henri Becquerel discovered radioactivity in his laboratory, when he was attempting to show that uranium was phosphorescent. Phosphorescent materials can absorb energy, such as light from the Sun, and then re-emit this energy later. Becquerel found that uranium kept emitting energy, well after it had been exposed to light. This meant that the energy it was emitting must be coming from within.

MARIE AND PIERRE CURIE

After radioactivity was discovered, scientists Pierre and Marie Curie were among those who worked to figure out exactly what it was.

Pierre Curie and Marie Curie in their laboratory in France

The pair isolated two new elements that were the source of most of the radioactivity of uranium ore. They named one radium because it gave off powerful invisible rays, and the other polonium in honor of Marie Curie's country of birth, Poland. The Curies also showed that the amount of radiation that came from these elements changed as the amount of radioactive material was changed. This demonstrated that radioactivity must come directly from each individual atom's nucleus.

For this work, Pierre and Marie Curie won the Nobel Prize in Physics for 1903. Eight years later, Marie Curie became the first person to win a Nobel Prize in two different fields, when she won it again for chemistry.

RADIOACTIVITY AND THE EARTH'S AGE

The discovery of radioactivity and the work of scientists like the Curies helped to explain how the Earth could be billions of years old, but still be relatively warm.

Scientists learned that new heat is continuously produced in the Earth's interior by radioactive elements. Eventually, it was shown that the rate of heat flow from Earth's interior has been relatively constant for a very long time, and that Kelvin's estimate for the age of the Earth was far too low.

Since Kelvin's time, it has been learned that the Earth is not a completely solid rock, but that it has many layers and contains radioactive elements in its interior.

Unlike Kelvin's idea, scientists' understanding of radioactivity has allowed for a much longer expanse of time between the Earth's initial molten state and the present. This is because much of the heat escaping the Earth is not left over from the Earth's initial molten state. Instead, much of the heat is continuously produced by radioactive decay in the Earth's interior.

Studies of specific radioactive elements have provided estimates for the ages of many geologic features, prehistoric events, and the age of the Earth itself.

Based on rates of radioactive decay, the Earth is estimated to be nearly 4.6 billion years old.