Wikijunior:How Things Work/Time
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How does time work?
Time is something around us all the time, yet is difficult to understand.
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[edit] Who invented it?
Time was never invented. It has always been around[citation needed] , and there was never anything before. This is quite something that you might find difficult to understand, but don't worry! A lot of people find it hard. The first people to use and measure time were the Sumerians, the oldest civilisation in the Middle East, around 2000 BCE. Later on the Ancient Egyptians and Romans invented time keeping instruments like the sundial, the water clock and the hourglass. Isaac Newton, a scientist who lived in the 17th century, believed that time was part of the universe itself, and could be measured just like length, height and width are. The famous scientist, Albert Einstein made some remarkable disoveries about how time and space are related (relative) to one another.....he called his theory, The Theory of Relativity.
[edit] How does it work?
Ah! The world knows a little more about this now than 100 years ago. Shortly before you were born it was discovered that time is not fixed. In other words. An hour here is not the same as an hour somewhere else. How can this be?
Well, time has been found to be relative. This is important to know if you are going to go on to college and become a world reknown scientist.
When you move, time slows down. It's true. Unfortunately you can't tell because it doesn't slow down that much. Every time something moves, time slows down for it.
An experiment was performed by an airplane pilot with a very accurate clock in their airplane. The pilot set the clock to the same time as one on the ground and then took off. After flying as fast as they could, they landed and compared the clock to the one on the ground and found that the clock in the airplane had slowed down during the flight. Just a little but still it slowed down.
What that means is that Pilot stayed younger than the people on the ground.
If your teacher was to ride in a vehicle that traveled very close to the speed of light time would slow down for them so much that you would eventially be older than them.
Can time go backwards? Maybe. Can time stop? Maybe. and when did it start anyway?
[edit] How dangerous is it?
Time can be very dangerous.
Take for example the little bit of time that exists when a door is closing and your hand is between the door and the door frame. If the time that the door takes to close is too short for your brain to move your hand, then time is not your friend.
On the other hand, if the time that the door takes to close is quite long, then your brain will have enough time to realize that pain will soon be in your future and perhaps it would be a good time to move your hand. Shortly after, your brain issues a command to your arm muscles to move your hand to a safer place. Time is once again your friend.
[edit] What does it do?
Time is nature's way of keeping everything from happening all at once. - Anonymous
[edit] How does it vary?
Please refer to the discussion of relativity above.
[edit] How has it changed the world?
It would be better to ask "What in the world hasn't changed because of time?"
[edit] What idea(s) and/or inventions had to be developed before it could be created?
This assumes that time came before the creation of the universe. It might have.
Some people believe that time began when Matter and Anti-Matter bumped into each other and created a huge amount of energy and light. If you had been there it would have sounded like a big bang.
Anyway, Matter won the fight and that is what you are made of. If Anti-Matter had won, you would be made of something different.
No one really knows what would have come before time but the universe was probably a very quiet place with nothing to see.
