（Contributed by Ana)
Time – Part 1: Time Dilation
Time is an interesting concept. After all, we all know that we have a past, a present and a future. We know that time is passing non-stop, and that we can measure it with clocks and calendars. Yet, it is elusive in nature because we cannot experiment with it, and we can’t study it under a microscope. The arrow of time just happens.
To measure time, ancient people used nature, such as the movement of the Earth around the Sun. Nowadays, we use more precise forms of time-keeping such as atomic clocks. We also know that even if we stopped measuring time, it would continue, and that it is something universal.
The idea of absolute time being measurable, and the same by all observers was expressed by Newton: “absolute, true and mathematical time, of itself, and from its own nature, flows equably without regard to anything external.”
From our everyday experiences, Newton’s statement certainly seems to be true. How can it be anything different? Yet, Newton’s statement is not correct.
Einstein’s special theory of relatively showed that there isn’t a universal time. This is because your time, and my time, can be different if we move differently. In a nutshell, the time duration between two events can vary dependent on how fast we are moving. This is called time dilation.