Time is an interesting concept. Is it reality? Is it inevitably linked with space in the space-time continuum? We can measure it, but do we know what it is?

There are seven arrows of time as Stephen Hawking defined them. One way markers - why is it that we can go forward but not backward in time? Perhaps we can - but if we change the events of the past, how do our actions affect the present?

Or perhaps it is only a huge hologram like the Holodeck of the fictional Star Trek Next Generations. Are we just players on a world stage?