Page 46 - Curriculum Visions Dynamic Book

We began this book with a brief introduction to the Universe. It gave us a framework for understanding the stars and galaxies that make up the Universe. Now we can look in more detail at what the Universe itself is like.
Asking what the Universe is like and how it came to be that way is the most fundamental of questions. We still do not have an answer to match all of our observations. Perhaps we never will. In fact, the more we find out about space, the more curious it becomes.
New rules
There is a fundamental problem. When you look over
the vast distances and huge time spans that exist in the Universe, with objects moving very fast, the laws, or rules, that we use on Earth do not hold true.
The laws we have developed are approximations of the truth and are good enough for use on Earth. But, as Albert Einstein showed with his theory of relativity (see page 48), it is a different matter when you look out into space.
Einstein was concerned with gravity. He showed that photons of light, even though they always apparently traveled in straight lines, would return to where they started from without ever coming to an edge or boundary. It is gravity that produces this effect. The fact that
gravity can bend light locally can even be seen in many observations of the way light moves when it is close to massive stars.
This new set of rules is called relativity. Using the arguments of relativity, it is possible to think of almost unimaginable things, such as a Universe that has no edge and space that is curved.
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