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Reading Selection, Lesson 1

Where Did Matter Come From?

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Aborigines creating a dreamtime image
These Australian Aborigines are painting images of their Dreamtime story.

Where did all the stuff in the universe —Earth, the sun, rocks, plants, animals, even you— come from? Was it made at a certain time? If so, how long has it been around? Has it always been there? People have asked these questions since the earliest times.

Most cultures have stories of how the universe was created. For instance, Australian Aborigines tell a story about the sun, moon, and stars sleeping beneath the ground. Their ancestors also slept there. One day the ancestors woke up and came to the surface. The Aborigines call this the Dreamtime. During the Dreamtime, the ancestors walked the Earth as animals such as kangaroos, lizards, and wombats. Out of beings that were half animal and half plant, the ancestors made people. They then went back to sleep. Some went underground, but some became objects such as trees and rocks. The Dreamtime is an important part of Australian Aboriginal culture.

The Cosmic Background Explorer (COBE) satellite at launch.
This background radiation map of the universe was produced using data collected by the Cosmic Background Explorer or COBE (see photo below). The purple spots represent energy at the farthest edges of the expanding universe, giving a “picture” of the universe about 1 million years after the Big Bang. This image shows that even then, “structures” were being formed.

Scientists have also tried to answer the question of how the universe began. When scientists try to answer questions, they sometimes make observations of what happens and collect data. Scientists use their observations and data to try to explain the phenomena they are studying. One important part of science is the ability for different scientists to make the same observations and collect the same data when they are studying the same phenomena. When many scientists have made the same observations over a period of time, their explanations of these observations are called theories. As new knowledge is gained, theories are tested and retested. Sometimes the theories don’t stand up to the new information. These theories are then replaced with new theories.

Over the years, as scientists have gained new knowledge about the universe, new theories have replaced old theories. Currently, many scientists think the universe started with the “Big Bang.” The Big Bang theory suggests that all the matter and energy in the universe exploded out from one point. As the explosion occurred, energy and matter spread outward and formed the universe. The matter from the Big Bang formed clouds of gas. As these gases cooled and condensed, stars, galaxies, and eventually planets and other “structures” that make up the universe were formed.

The Cosmic Background Explorer (COBE) satellite launching.
The Cosmic Background Explorer (COBE) satellite was launched in 1989. Its mission: Find out more about the origins of the universe by looking for background radiation left over from the Big Bang.

Even now, billions of years after the Big Bang, the universe is still spreading out. By looking at light from distant stars and galaxies, scientists can observe and measure this expansion. Using special apparatus, they can also detect some of the background glow of invisible energy left over from the Big Bang.

Illustration of the Big Bang.

Many scientists think that at the start of time, all matter and energy were contained within a single point. The point exploded in the Big Bang. The energy of this explosion caused the matter to spread out in all directions, forming galaxies, planets, and other objects. Using specialized instruments, scientists are able to measure the expansion of the universe.

Space telescopes, such as the Hubble telescope and X-ray telescopes in orbit around Earth, are constantly making new and exciting observations. Ideas about the formation of the universe and the Big Bang may change as these instruments are used to discover more about our evolving universe.

QUESTIONS

1. Use information from this reader and any other information you can find from books, CD-ROMs, or the Internet to list the evidence for the Big Bang theory.

2. In science, the term "theory" has a special meaning. Find a definition of this term and give two examples of other theories that are used in physical science.

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