PDF KEY CONCEPT Science is an ongoing process. - ClassZone

KEY CONCEPT

Science is an ongoing process.

Sunshine State STANDARDS

SC.H.1.3.1: The student knows that scientific knowledge is subject to modification as new information challenges prevailing theories and as a new theory leads to looking at old observations in a new way. SC.H.1.3.2: The student knows that the study of the events that led scientists to discoveries can provide information about the inquiry process and its effects. SC.H.2.3.1: The student recognizes that patterns exist within and across systems.

VOCABULARY

hypothesis p. 6 law p. 6

BEFORE, you learned

? Science is a way to explore the natural world

? Science is based on objective observation

? Scientific ideas can be tested

NOW, you will learn

? What processes scientists use ? How scientists use patterns ? How scientific ideas change

with time

EXPLORE Assumptions

Can you recognize your assumptions?

PROCEDURE

1 Use the six toothpicks to make an equilateral triangle, one in which all three sides are the same length.

2 Now use the same six toothpicks to make two equilateral triangles.

3 Use the same six toothpicks to make four equilateral triangles.

MATERIALS

6 toothpicks

WHAT DO YOU THINK? ? What did you assume, or take for granted, about the

triangles you were forming? ? Were you able to do step 3? If not, try to think of more

assumptions you may have unknowingly made. Is there any reason to believe these assumptions are true?

Science is a process.

You can think of science as a continuous process of asking questions about the world and seeking answers to those questions. Scientists use many processes. Typically, scientists studying a topic ask questions, determine what is known about the topic, investigate, interpret their results, and share their results. As more knowledge becomes available, scientists also see how this new knowledge affects their ideas. Scientists are always building on old knowledge and interpreting results in different ways on the basis of new knowledge.

Check Your Reading List five steps that scientists usually take as part of the scientific process.

Chapter 1: The Nature of Science 5

Scientists make observations and try to figure out what factors affect the things they observe. They try to come up with explanations, or hypotheses, to account for what they notice. A hypothesis is a tentative explanation for an observation. A hypothesis often explains the relationship between two or more different variables. A scientific hypothesis is testable--it leads to a prediction that can be confirmed by new observations.

VOCABULARY Make a description wheel in your notebook for law.

Scientists look for patterns.

When scientists develop hypotheses, they often do so to explain patterns that they have noticed. Scientists look for the rules behind patterns they observe. Patterns come in many forms. A pattern can be a cycle, such as the changing seasons. It can be a relationship, such as how the volume of a gas changes as the temperature changes. It can be a geometric pattern found in nature, such as the sunflower shown below on the left that resembles the mathematical pattern on the right.

Patterns can also help scientists understand natural laws and processes. In science, a law is a principle or rule that describes a physical relationship. Laws always work the same way under the same conditions and can be discovered by finding patterns in relationships.

When scientists understand the forms of natural laws and processes, they can then develop hypotheses that explain the patterns they observe. But even if scientists cannot explain why a certain pattern exists, they can still use the pattern to help them in their investigations.

check your reading How can scientists use patterns?

The seeds in this sunflower form a geometric pattern.

6 Chapter 1: The Nature of Science

This mathematical pattern resembles the natural pattern in the sunflower.

Patterns

Are patterns easy to notice?

PROCEDURE 1 Decide on a simple rule that determines which letter of the alphabet can fol-

low another letter in a sequence you are making. For example, your rule might be that a small letter must follow a capital letter. Write down your rule, but keep it secret as you follow the next two steps. 2 Write down a starting letter. Have your partner suggest a letter. If the letter can come next in your sequence, add it to your sequence. 3 Have your partner suggest more letters. Each time, place the letter in your sequence if it follows your rule, or say that it does not fit the rule. Continue until your partner thinks he or she knows the rule. 4 Now have your partner pick a secret rule, and repeat the procedure. Did each of you figure out the other's rule?

WHAT DO YOU THINK? Were both rules equally easy to determine?

CHALLENGE How was figuring out your partner's rule similar to using a prediction to test a hypothesis?

Scientists often discover patterns that can be written down as mathematical formulas. In the early 1600s, German astronomer Johannes Kepler was trying to find a simple way to describe how planets moved. Most scientists of the time thought that the planets moved in perfect circles. Kepler had inherited a large amount of data on the positions of the planets that had been collected by a Danish astronomer named Tycho Brahe (TEE-koh BRAH). Kepler searched for circular patterns in the data.

When he found that the data did not fit

any circular patterns, he started looking for the

actual pattern. He discovered that he

could explain the positions of the planets by

assuming that the planets orbited the Sun in

slightly flattened circles, or ellipses. Kepler also

discovered a mathematical relationship

Sun

between a planet's distance from the Sun and

the time the planet takes to move around the

Sun. Kepler's formulas, however, only described

the patterns. They did not explain why the

patterns existed. That explanation would

come later.

SKILL FOCUS

Inferring

MATERIALS

? pencil ? paper

TIME

30 minutes

Earth 365 Earth days Mars 693.5 Earth days

Chapter 1: The Nature of Science 7

RESOURCE CENTER



Learn about another case of new information expanding and changing old ideas.

Scientists often build on previous ideas.

Scientists do not work in isolation. They are part of a community that shares its results. Scientists also have access to many ideas that other scientists have already investigated. They can take an existing hypothesis or theory and extend it to discover something new. They can also use data that have already been collected and think of new explanations for the patterns and rules that others have found.

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You will learn more about gravity in Chapter 4.

Sir Isaac Newton, an English scientist and mathematician of the late 1600s, built his theories on both his own observations and the work of other scientists. It was Newton who provided an explanation for the laws of planetary motion that Kepler had discovered. Newton reasoned that a force acted between the Sun and the planets. He also reasoned that this was the same force that caused objects to fall to Earth--the force of gravity.

Kepler's laws enabled Newton to make inferences about the nature of gravity. Newton wondered what properties gravity would have if it were the force responsible for planetary motion. He determined that the force of gravity between two objects must depend upon the masses of both objects and the distance between them. In other words, Newton's law of gravity explained why the motion of the planets could be described by Kepler's formulas.

By studying the work of previous scientists, Newton was able to develop a set of theories that explained why planets move as they do. Newton acknowledged that he could not have made his discoveries without the work of previous scientists. He wrote, "If I have been able to see further, it was only because I stood on the shoulders of giants."

Newton's Law of Gravity

The force of gravity between two objects depends on their mass and the distance between them.

Objects attract each other because of their masses.

Sir Isaac Newton 1642?1727

8 Chapter 1: The Nature of Science

The greater the masses, the greater the force of gravity.

The greater the distance, the smaller the force of gravity. The length of the arrows represents the size of the force. How do the arrows relate to the captions?

Scientific understanding can change with new information.

As scientists learn more about the universe, the information they collect can challenge existing ideas. Similarly, new ideas can shed light on existing data. When the data do not agree with a well-established and tested theory, scientists usually check both the data and their assumptions about the theory. Often, it turns out that they did not take into account some factor when analyzing the data. Sometimes, however, it is the theory that needs to be reconsidered.

Old Ideas and New Information

Sometimes new observations do not agree with the predictions that can be made based on a hypothesis or theory. Newton's formulas for gravity and motion allowed scientists to make very specific predictions about the motions of the planets. For the most part, these predictions proved to be accurate. However, during the mid-1800s, scientists discovered a very small difference between Mercury's predicted motion and its actual motion around the Sun. Because the motions of the other planets were so accurately predicted, scientists were puzzled by Mercury's motion.

Scientists looked for reasons to explain why Mercury's motion did not agree with Newton's theories. One hypothesis was that another planet, so close to the Sun that it could not be seen, was affecting Mercury's orbit. But no such planet was found. Other possible causes were suggested, such as the existence of dust between Mercury and the Sun, but no evidence of these causes was ever found.

check your reading Why did scientists question Newton's law of gravity?

New Ideas and Old Information

The mystery of Mercury's motion was not fully explained until the early 1900s, when German-born physicist Albert Einstein developed a new way of understanding gravity. Newton had viewed gravity as a force by which objects attract each other because they have mass. Einstein instead thought that perhaps mass distorted space and time. His idea was that an object moving through curved space would also curve.

Mercury, shown here, had an orbit that could not quite be predicted by Newton's laws.

Chapter 1: The Nature of Science 9

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