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Real time
We perceive ourselves in the real spacetime.
Point in time
We usually think of a point in time, or a clock that runs further and further. Seconds, minutes, hours, days, weeks, months, years, forever ...
But actually we do not know at all what time is.
Lifetime
For every human, life begins with birth and ends with death. What was before birth and what comes after death, no one knows. There are many different views. But does life really start with birth, and ends it really at death?
Universe
The universe has not always existed. Most people think that it once emerged (or was created). And it will probably also stop some time. There are many different ideas about it. Was there a Big Bang and will there be a Big Crunch?
Timespan
Time is not a constant factor. With the special theory of relativity, you can calculate this. As speed increases, time runs slower. The maximum speed is the speed of light, that we can never reach, as time would then stand still.