When we go out for a walk we often see things that we haven't seen before. If we don't know what it is, we can ask somebody, maybe somebody who lives nearby, who has seen it before. Sometimes the things we see can be a bit scary, and often it's best not to touch something or get too close, but we don't have to be afraid of everything new that we see. If we are sure it is safe to do so, we can pick it up or touch it, and perhaps we can guess what it does, or what it's for.
A long time ago people didn't know as much as you do about things like the weather, or what the Sun was, or why things died or were born. And because nobody knew, they didn't have anyone to ask! It wasn't any good asking the man by the river why the water always went the same way, because he didn't know. He had never seen where the river came from. He knew there were fish in it, and he probably knew how to get them out, and that he could eat them, but he didn't know where the water came from.
But just like you, early people watched things, and wondered about them. Sometimes they watched things every day to see how they changed, and by watching like this they learned a bit more. Then they could tell other people, and they could teach their children and grandchildren. Because they didn't have writing or books, they had to tell each other everything, and sometimes thing were forgotten or not passed on. When people started to write things down it was much easier to remember or save information.
Watching very carefully, writing down what we see, and figuring out how things work is called science. When we watch things very carefully over a long time we can learn a lot about them. When early people watched the Sun and the Moon moving, and also the patterns of the stars in a different place every night they drew pictures of them, and it helped them predict the weather, so they knew when to plant crops. Watching the plants grow taught them how to look after the crops they planted.
There really are only two ways to learn about anything. One is to watch things very carefully for a long time yourself, and the other is to have somebody tell you about it all instead. If you study things yourself and have people teach you things too, you can learn even more. Gradually, over a long time, people have learned a lot about so many things that these days we are able to build airplanes that fly all over the planet, and we can talk to each other over long distances using phones. We are able to do things like this because people before us watched very carefully, and wrote things down.
But there's something else sometimes people do when they don't know something. They guess. Guesses can be very useful, and sometimes they are right. If you are digging in your garden and you find a piece of thin stone, shaped like a triangle, with sharp edges, that looks as if somebody had made it on purpose, you can probably guess it was a tool or a weapon. When you show it to an older person, they can tell you it was an arrowhead, so your guess was pretty good! Sometimes even scientists have to make guesses to start with. Then they tell each other about their guesses, and put together a theory. A theory is a very special type of guess, not just any guess. It means you have watched things very carefully, lots of times. You make sure it is always the same.
Sometimes people made guesses, but they didn't have anyone who knew more, to ask if they thought it was right. Sometimes their guesses seemed quite good to other people, and instead of checking it for themselves, they assumed the guess was right. Sometimes they wrote this down. This is very bad science. Writing down guesses is a good way to start, but writing down other people's guesses and passing them on as facts is a bad idea. It can lead to lots of people believing things that are wrong.
A lot of these unchecked guesses were written down a very long time ago. Some people, often called priests, spent all their time telling others what these old books said, and they decided the books could never be changed. As time passed, people watched more, and learned more, and found that some of the guesses in the books were wrong, but when they told the priests what they had learned, they were told to go away. Sometimes they were treated very badly for disagreeing with the guesses in the old books.
Today we know that almost all of the guesses in these very old books are wrong. We have been watching things and learning about them for such a long time now, that we have new books, called science books. With science, when we learn something new, we change the books. In the future we will know even more, and our science books will be replaced with even better ones.
Priests don't change their old books at all, not even one word of them, even when they know the guesses in them are totally wrong. They like their old books so much that some of them think we should be using them instead of science books. This would be a big mistake and would cause a lot of problems.
Priests have lots of other names, such as pastor or minister, and sometimes the people who share the old books are just teachers and other ordinary people you meet. They are not bad people, some are very kind and helpful, but they don't understand science. So, these people cannot teach you science. You should always be polite to them, but you don't have to take any notice of what they say.