Time, The Martian 
(Spoilers)
    I think a lot about how we measure time. In this novel, time is primarily measured in sols. This describes the Martian day, which is about 40 minutes longer than ours. Which is interesting to think about because this conception of time is completely arbitrary. The way that we time the revolution of the Earth around the Sun is measured by a unit we invented. Our entire conception of time is ticked of farcically by the minute. 

     The Martian  is measured not only in sols but activities, hours,accomplishments, even years. Mark does not have society and other people to enforce our collective conception of time, so his experience of time becomes completely his own. Through his blog we see that his time is marked by survival, the twelve hours to charge the various batteries, months for the potatoes to grow, counting down the days until his supplies run low or how many accomplishments  until he can reach Schiaparelli and the Ares IV.

     In this book time also is seemingly a character. It is one of that antagonists in a story that largely only follows one character.  Time is, in conjunction with other natural occurrences, Mark's adversary. The sols, hours, and minutes become as real an obstacle to his survival as any other factor, will he make it enough time before the potatoes grow, can he handle the interminable solitary sentence he receives, can he get rid of the time between him and rescue without losing his sanity first? The more I dwell on it the more I realize that time truly became the antagonist of the story, right down to the end of the novel where a story of insurmountable time is decided by the smallest possible intervals of the same subject.