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Comment by memset | Hacker News Reader

Part of my daily internet routine, for the past 4 months, has been to check up on Time. Well, I guess it's back to work now!

(I also feel like I've missed something in the story. The wikis say that the story takes place far into the future. How do they know? Are there other references I've missed? Is this... a larger allegory, or something, that I am missing out on?)

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Well, the main story point is the flooding of the Mediterranean (revealed recently when the protagonists are shown a map of the projected sea level). We know that happened in the past and might happen again. People in the past had no way to produce such accurate maps. Also, the sand castle built in the beginning looks medieval, not prehistoric.

Update: the blurred dialog of the woman in the castle has been partially deciphered and also places the story in the future pretty clearly: http://www.explainxkcd.com/wiki/index.php?title=1190:_Time:_...

We actually placed the story in April 13291 AD via astronomy. There's a section that shows the night sky clearly and the stars have moved slightly from their current positions.

Also interestingly enough Antares has gone supernova in the intervening 11278 years.

See http://xkcd-time.wikia.com/wiki/Astronomy#The.C2.A013291_Hyp...

All is in the giant forum thread (51k posts and counting).

During the night scene several readers tried to use the stars to determine location and date:

* Diurnal motion matches 39.5° north.

* Proper motion and the position within milky way indicate far future.

* Eventually someone matched everything to Tuesday, 10 April 13291 and that estimate stuck (but it could be off by several hundred years).

http://xkcd-time.wikia.com/wiki/Astronomy

The proper motion of some of the faster stars is enough to get a date within about 200 years, and the positions of the planets have been searched exhaustively within that range, so I think the 13291 date must be accurate.

Could it have been by accident? I.e. Randall just happened to draw something that happened to roughly correspond to year ~13300? How unlikely is it? Really interesting!

We can tell it is not an accident because there many independent sources of evidence, all of which point to the same era. In particular, the proper motion of stars (i.e. the shape of constellations) matches exactly in every case. This is very strong evidence because a) unlike axial procession, it isn't cyclical, and b) we can look at any star that moves sufficiently fast relative to us, and use it as independent evidence. There are dozens of such examples in the parts of the sky that are shown in the comic.

For example, in the image below the left-hand image is from the comic, while the two on the right are captured from Stellarium using two different dates, 13291 and 2013.

http://i.imgur.com/PrQgn4k.png

As a side note, it just isn't possible that Randall drew the stars by hand. They were either captured within planetarium software like Stellarium, or generated programmatically.

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