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.
BEFORE, you learned
NOW, you will learn
• Science is a way to explore the
natural world
• Science is based on objective
observation
• Scientific ideas can be tested
• 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.
MATERIALS
6 toothpicks
2 Now use the same six toothpicks to
make two equilateral triangles.
3 Use the same six toothpicks to make
four equilateral triangles.
VOCABULARY
hypothesis p. 6
law p. 6
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.
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.
VOCABULARY
Make a description wheel
in your notebook for law.
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
SKILL FOCUS
Are patterns easy to notice?
Inferring
PROCEDURE
1
MATERIALS
Decide on a simple rule that determines which letter of the alphabet can follow 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.
• pencil
• paper
TIME
30 minutes
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
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.
Sun
Earth
365 Earth days
Mars
693.5 Earth days
Chapter 1: The Nature of Science 7
RESOURCE CENTER
CLASSZONE.COM
Learn about another
case of new information
expanding and changing
old ideas.
FLORIDA
Content Preview
reminder
You will learn more about
gravity in Chapter 4.
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.
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.
The greater the masses, the greater the force of gravity.
Sir Isaac Newton
1642–1727
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?
8 Chapter 1: The Nature of Science
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
If you roll a marble across a flat rubber sheet that is stretched out
like a trampoline, the marble will travel in a straight line. If you put a
heavy weight on the rubber sheet, the sheet will stretch and curve, as
shown in the illustration below. If you roll a marble across the sheet
now, its path will be affected by the curve in the sheet. The effect on
the marble is similar to the effect gravity has on moving objects.
Einstein used his new ideas about gravity to calculate and predict the
motions of the planets. Einstein’s theory accurately predicted the orbit
of Mercury. Because Mercury is closer to the Sun than the other planets, the curve of space and time has a more obvious effect on its orbit.
Einstein’s formulas predicted this effect accurately.
In Newton’s theory, light could not be affected by gravity. Einstein’s
theory, however, predicted that gravity should affect light as well as
matter. In 1919 scientists observed that light was in fact affected by
gravity, and Einstein’s ideas became widely accepted.
Einstein’s Theory of Gravity
An object moving through curved space will curve. If gravity is
viewed as a curving of space and time, Mercury’s motion can be
fully explained.
Space with No Mass
Space with Mass
If there is no curve to space, an
object moves in a straight line.
Mass curves space and time, so a moving
object has a curved path near a mass.
What would a more massive object do to the curve in the rubber sheet?
10 Chapter 1: The Nature of Science
Using Old and New Ideas
Although Einstein’s view of gravity is now accepted as
a more complete way to understand gravity, Newton’s
theories about gravity are still taught. This is because
Newton’s formulas are easier to understand and work
with and, in most cases, they predict the correct
motions. Only where gravity is very strong do
Newton’s formulas stop giving accurate results. It was
Newton’s formulas, and not Einstein’s, that were
used to send humans to the Moon.
check your reading
Why are Newton’s formulas still used today?
Scientists do not usually discard old theories
that still work. They are, however, now aware that
Albert Einstein 1879–1955
those theories are limited and work only under
specific circumstances. But when scientists look at the extreme ends of
Einstein’s formulas give
the same answers as
things, new theories are often absolutely necessary. For example, the
formulas for motion must be modified for objects traveling close to the Newton’s formulas under
most normal conditions.
speed of light. Many physical laws must also be modified as scientists
study objects as tiny as atoms and molecules.
Scientists are also aware that with new technology and new information, even topics they thought were very well understood can hold
surprises. Our understanding of gravity may still not be complete.
As some of our early spacecraft approach the outer reaches of our solar
system, their motion is different from what scientists had predicted.
While there may be explanations for this that are consistent with
Newton’s or Einstein’s theory, some scientists are looking once again at
the current theory of gravity to see if it may need more modification.
KEY CONCEPTS
CRITICAL THINKING
1. What part do hypotheses play
in the scientific process?
4. Synthesize Recall when
something you learned about a
scientific topic changed the
way you thought about it.
How did the new information
change your ideas?
2. Why do scientists look for
patterns?
3. Explain how a scientific idea
can change with time.
5. Analyze What evidence could
you use to convince a young
child that the world is really
shaped like a ball?
CHALLENGE
6. Infer Ella discovered that
1 cm3 of a liquid had a volume
of 2 g. She also found that each
time she doubled the volume of
the liquid, the mass also doubled. How could Ella express
her findings as a mathematical
formula?
Chapter 1: The Nature of Science 11