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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: * Diu

by phaker 13y ago

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

siddboots 13y ago
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.
- sillysaurus 13y ago
  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!
  - siddboots 13y ago
    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 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.

by phaker 13y ago

siddboots 13y ago

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.

sillysaurus 13y ago
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!
- siddboots 13y ago
  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 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.