Introduction

Science is one of the most powerful ways humans learn about the world. It helps us understand everything from the smallest atoms to the largest galaxies, from how our bodies work to how weather forms.

Science is not simply a collection of facts—it is a way of asking questions, gathering evidence, and developing explanations about the natural world.

Every scientific discovery begins with curiosity.

Whether investigating why plants grow, how electricity works, or what causes earthquakes, scientists follow a process that helps them build reliable knowledge based on evidence.

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What Is Science?

Science is the systematic study of the natural world through observation, experimentation, and evidence.

Scientists investigate questions about:

• Living organisms
• Matter and energy
• Earth and space
• Forces and motion
• Weather and climate
• Chemical reactions
• Electricity and magnetism

Science seeks explanations that can be tested and supported by evidence.

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The Natural World

The natural world includes everything that exists in nature.

Examples include:

• Animals
• Plants
• Oceans
• Mountains
• Weather
• Stars
• Planets
• Rocks
• Microorganisms

Science studies natural events rather than opinions, beliefs, or supernatural explanations.

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Observation

Science begins with observations.

An observation is information gathered using our senses or scientific instruments.

There are two main types.

Qualitative Observations

These describe qualities.

Examples:

• The liquid is blue.
• The rock feels rough.
• The flower smells sweet.

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Quantitative Observations

These involve measurements.

Examples:

• The temperature is 22°C.
• The plant is 18 cm tall.
• The object has a mass of 250 g.

Scientists often prefer quantitative observations because they are more objective and easier to compare.

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Questions Lead to Investigations

After making observations, scientists ask questions.

For example:

• Why do leaves change colour?
• Why does metal rust?
• How do birds fly?
• What causes lightning?
• Why do objects fall to the ground?

Good scientific questions can be investigated using evidence.

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Scientific Explanations

Scientists develop explanations based on the evidence they collect.

These explanations must be:

• Supported by observations.
• Tested through investigations.
• Open to further testing.
• Consistent with the available evidence.

If new evidence is discovered, the explanation may be improved or revised.

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Characteristics of Scientific Investigations

Scientific investigations have several important features.

They are:

• Based on evidence.
• Carefully planned.
• Fair and unbiased.
• Repeatable by other scientists.
• Clearly recorded.
• Open to questioning and improvement.

A good investigation allows others to repeat the experiment and obtain similar results.

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Science Changes with New Evidence

One of the most important ideas in science is that scientific knowledge can change.

As new evidence becomes available:

• explanations improve
• theories are refined
• new discoveries are made

This is a strength of science, not a weakness.

For example:

People once believed that Earth was the centre of the Universe.

As better observations became available, scientists discovered that Earth orbits the Sun.

Scientific knowledge became more accurate because of new evidence.

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Science in Everyday Life

Science affects almost everything we do.

Examples include:

• Medicines and vaccines
• Mobile phones
• Computers
• Weather forecasting
• Electricity
• Cooking
• Sports equipment
• Transportation
• Clean drinking water
• Renewable energy

Many everyday technologies exist because of scientific discoveries.

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Science and Other Ways of Knowing

Science focuses on questions that can be investigated using evidence from the natural world.

Some questions, such as those about personal values, ethics, art, or individual beliefs, are important but are answered using other ways of thinking rather than scientific investigation.

Understanding what science can—and cannot—investigate helps us appreciate its strengths and limitations.

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Worked Examples

Example 1

A student notices that one plant grows faster than another.

Is this an observation, a question, or an explanation?

Answer:

An observation.

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Example 2

Which of the following is a scientific question?

• Why do plants grow toward sunlight?

Answer:

This is a scientific question because it can be investigated through experiments and observations.

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Example 3

A scientist performs the same experiment several times and obtains similar results.

Which characteristic of science does this demonstrate?

Answer:

Scientific investigations should be repeatable.

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Example 4

Why might scientific explanations change over time?

Answer:

Because new evidence may lead scientists to improve or revise their explanations.

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Example 5

Give two examples of science in everyday life.

Answer:

Possible answers include:

• Weather forecasting
• Medicine
• Electricity
• Mobile phones
• Cooking
• Transportation

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Did You Know?

The word "science" comes from the Latin word scientia, meaning "knowledge." Today, scientists around the world work together, sharing observations and evidence to improve our understanding of the Universe.

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Key Terms

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Key Takeaways

• Science is a way of understanding the natural world through evidence.
• Scientific investigations begin with observations and questions.
• Good scientific explanations are based on evidence and can be tested.
• Scientific knowledge changes as new evidence becomes available.
• Science plays an important role in everyday life through medicine, technology, engineering, communication, and many other fields.
• Curiosity, careful observation, and evidence are at the heart of every scientific discovery.