In Cixin Liu's novel Death's End, an alien creature that goes by the name Singer measures time in "grains of sand". How much is this unit in human time?


2 Answers 2


Excerpt from Death's End:

Nine time grains after the first three communications, another record appeared: The Star-Pluckers plucked their star again to send out another broadcast ... a set of coordinates!

The "first three communications" refers to the first message sent from Earth to the Trisolarans, the warning response, and the response to that message that doomed Earth. The message that came "nine time grains" later was the spell Luo Ji put on 187J3X1.

Ye Wenjie sent the first message in autumn of 1971.

The pacifist Trisolaran sent a warning response immediately upon receiving the message in early 1976.

Ye Wenjie responded immediately to that response in 1980.

Luo Ji cast his spell in Year 8 of the Crisis Era. The Crisis Era began somewhere in the 2010's according to the table of eras at the beginning of Death's End. If we split the difference and say the Crisis Era began in 2015, Luo Ji cast his spell in 2023.

The span of time between Luo Ji's spell and Ye Wenjie's last message to the Trisolarans is 43 years. 43 years divided by 9 grains gives an answer of 4.78 years per grain.


There are two answers to this. First one is fairly simple: the last message sent by Ye Wenjie was sent in 1980 and Luo Ji broadcasted his spell in year 8 of the Crisis Era, and the Crisis Era started somewhere in the 2010s. So to arrive to year 2272 (that's when Gravity/Blue Space broadcasted the location of Trisolaris) it means that the time Luo Ji broadcasted his curse was around mid-2019. This means that one grain is 4,344 years. (60 x 4,344 + 2011,5 = 2272). This also means that the Crisis Era started in mid-2011.

The second one is pure sci-fi/spe-fi. As we later learn the universe has been shrinking down in dimensions and the universal laws of physics won't apply as we know them since there are so many mini-universes and highly advanced civilizations use things like 2-dimensional "letters" as weapons. So all that being said, we can't really be sure about how long it took for the gravitational waves, radio waves, or light itself to travel to certain places. So from Singer's perspective "a grain of sand" could be a fluctuating way of measuring the time given the different parameters or it could be stable resulting in errors. We will never know but I would like to believe that the most advanced civilizations took these changing parameters into account when deciding if or how to destroy entire solar systems.

  • 2
    Hey, welcome back! Thanks for coming back and fixing up the math.
    – DavidW
    Commented Feb 24, 2021 at 20:55
  • Hey person! No problem and thanks for the edits!
    – Riku Salo
    Commented Feb 24, 2021 at 21:06

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