How Science Develops

Models, Theories & Laws

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Introduction

• Today, the amount of scientific knowledge is huge. It covers topics ranging from matter’s smallest particles to the whole universe. How did that knowledge develop? Over the years, as scientist studied the natural world, they did more than collect facts. They developed more complete explanations for their observations.

Getting knowledge

• Scientists – use models & – Develop, theories &

laws

• to increase people’s understanding of the natural world.

What is a Scientific Model?

Describes the phenomena

Scientific models

• Sometimes, it may be impossible to observe certain objects and scientific processes. So a scientist will make a model. A model is a picture, diagram, computer image, or other representation of an object or process.

Scientific models

• Physical models, such as a representation of the solar system, may look like the real thing.

• Other models can be generated by computers, such as the flight plan of a space vehicle.

Scientific models

• Still others can be mathematical equations or words that describe how something works.

• Certain models, such as models of atoms (the particles that make up matter), have been especially important in building up our understanding of science.

The Kinetic Molecular Model

• Particles are in constant motion. – In solids the particles are

close together and have limited motion.

– In a liquid some of the attraction between particles is overcome which allows the particles more freedom of movement.

– In a gas particles attraction between particles is minimized and the particles move freely throughout the container.

What is a Scientific Theory?

Explains the phenomena

Scientific Theories

• In some cases, many observations can be connected by one explanation. This can lead to the development of a scientific theory.

• A scientific theory is a well-tested explanation for a wide range of observations or experimental results.

Four elements

• Since time immemorial people have been trying to understand what the Universe is made of. One of the earliest theories said that everything could be built from just four elements, Earth, Air, Fire and Water.

• This was a great scientific theory because it was simple. But it had one big drawback: it was wrong.

Four elements

• The Greek philosopher, Leucippus of Miletus and his follower Democritus set the scene for modern physics in 5th century B.C. Athens when they considered what would happen if you chopped up matter into ever smaller pieces. There would be a limit, they said, beyond which you could not go. And they called their fundamental particles “atoms” (indivisible).

Atomic Theory

• Now we use the atomic theory, that states all substances are composed of tiny particles called atoms.

• The atomic theory helps explain many observations, such as where does electricity comes from.

Sun around Earth: A Scientific Theory

• Based on observations of sunset and sunrises, ancient people theorizes that the sun revolved around Earth. New evidence led scientists to abandon that ancient theory.

• Today scientists know that Earth, along with the other planets in the solar system, revolves around the sun.

Evolution: Just a Scientific Theory

Scientific Theories

• Scientists accept a theory only when there is a large body of evidence that supports it.

• However, future evidence may not support the theory. If that happens scientists may modify the theory or discard it altogether.

• This illustrates the ever-growing and exciting nature of the scientific knowledge.

What is a Scientific Law?

Predicts what is going to happen in phenomena.

Scientific laws

• Have you ever heard someone say “What goes up must come down”?

• When scientists repeatedly observe the same result in specific circumstances, they may develop a scientific law.

• A scientific law is a statement that describes what scientists expect to happen every time under a particular set of conditions.

Scientific laws

• A scientific law describes an observed pattern in nature without attempting to explain it.

• You can think of a scientific law as a rule of nature. For example, the law of gravity states that all objects in nature attract each other. This law has been verifies over and over again.

Gravity Law

• According to the law of gravity, this sky diver will eventually land back on Earth.

Newton’s Gravity Law

Discussion questions

1. What is a Scientific Model?

2. What is a Scientific Theory?

3. What is a Scientific Law?

4. How do Scientific Theories differ from Scientific Laws?

7 Wonders of the Natural World

Each of the following sites captures the imagination with its natural power and

beauty. And they have one thing in common: Nothing made by humans can approach their majestic dignity.

1. Grand Canyon National Park • The Grand Canyon in northwestern Arizona was formed by the

erosive power of the weather and the Colorado River and its tributaries as they scoured away billion-year-old rocks. Although known to Native Americans for thousands of years, the vast gorge was not discovered by the first Spanish explorers until 1540.

• Grand Canyon National Park was established in 1919, preserving the more than 1.2 million acres of colorful cliffs and waterways that are home to 75 species of mammals, 50 species of reptiles and amphibians, 25 species of fish, and more than 300 species of birds. The canyon stretches 277 miles, with some sections reaching a mile deep and 18 miles across.

• More than five million visitors view the canyon annually, often hiking or riding mules down to the canyon floor, while the more adventurous opt for boating or rafting the Colorado River through the canyon.

1. Grand Canyon National Park

With an elevation of 8,000 feet, the Grand Canyon's North Rim is about 1,000 feet higher than its South Rim.

2. Aurora Borealis (Northern Lights)

• The aurora borealis (also called the northern lights) consists of awe-inspiring twirls of light in the sky, caused by "solar wind" -- electrically charged particles interacting with Earth's magnetic field.

• The aurora borealis can be up to 2,000 miles wide, but it fluctuates in size, shape, and color, with green being the most common color close to the horizon while purples and reds appear higher.

• Named after Aurora, Roman goddess of dawn, and Boreas, Greek god of the north wind, these ribbons of color are best viewed in northern climates like Alaska but have been seen as far south as Arizona.

2. Aurora Borealis (Northern Lights)

The aurora borealis is also called the northern lights and is best viewed in northern climates.

3. Mount Everest

• Mount Everest, part of the Himalayan Mountains between Nepal and Tibet, was formed about 60 million years ago due to the shifting of Earth's rocky plates. Named after Sir George Everest, a British surveyor-general of India, Everest is the highest mountain on Earth, looming some 29,035 feet high and growing a few millimeters every year. Climbing Everest isn't easy, due to avalanches, strong winds, and thin air.

• Nevertheless, in 1953, Edmund Hillary and Sherpa Tenzing Norgay were the first climbers to reach the peak. More than 700 others have done so since, with at least 150 persons dying on their quest.

3. Mount Everest

4. Paricutin

• Paricutin provides one of nature's best lessons in how volatile Earth is.

• Exploding out of a Mexican cornfield in 1943, Paricutin was the first known volcano to have witnesses at its birth. Within a year, the cone had grown to more than 1,100 feet high.

• The flow eventually spread over 10 square miles, engulfing the nearby towns of Paricutin and San Juan Parangaricutiro. The eruptions ceased in 1952, and the cone now soars 1,345 feet high.

4. Paricutin

5. Victoria Falls

• Victoria Falls, originally called Mosi-oa-Tunya ("smoke that thunders"), was named after Queen Victoria of England in 1855.

• The raging waters of the Zambezi River pour 19 trillion cubic feet of water per minute into a gorge that is 1.25 miles wide and 328 feet deep, making this the largest curtain of falling water in the world.

• Located between Zambia and Zimbabwe, Victoria Falls is flanked by national parks and is now one of the world's greatest tourist attractions, with resorts, hiking trails, and observation posts springing up around it. White-water rafting at the foot of the falls makes for a thrilling adventure.

5. Victoria Falls

6. Great Barrier Reef

• The Great Barrier Reef blankets 137,600 square miles and extends a dramatic 1,242 miles along Australia's northeastern coast, making it the largest group of reefs in the world.

• The reef began forming more than 30 million years ago and is made up of the skeletons of marine polyps.

• Four hundred species of living polyps can also be found there, along with 1,500 species of fish, as well as crabs, clams, and other sea life. The area is an Australian national park and is visited by two million tourists a year.

6. Great Barrier Reef

7. Giant Sequoia Trees

• Ancient giant sequoia trees are nature's ever-growing wonders. Giant sequoias grow naturally on the western slopes of California's Sierra Nevada Mountains at elevations from 5,000 to 7,000 feet. Some are as tall as a 26-story building, with their trunks spanning up to 100 feet and the bark on the older specimens reaching two to four feet thick.

• California's Sequoia National Park is home to several noteworthy giants, including the General Sherman, which is the world's largest tree by volume, measuring 274.9 feet high, almost 103 feet around, and comprising 52,508 cubic feet of wood. Giant sequoia trees are estimated to be between 1,800 and 2,700 years old. Depending on the tree and where it is situated, giant sequoias can grow up to two feet in height every year, producing almost 40 cubic feet of additional wood each year.

7. Giant Sequoia Trees