Kolchin is the sister planet to Earth. Originally they were conjoined, but Kolchin separated herself off in self-preservation, as is told in the Tale of Separation.
Yet Earth and Kolchin are not entirely divorced. It is possible to journey from one to the other by traversing the Transcending Sea, known as the Great Sea on Kolchin and the Atlantic Ocean on Earth, and crossing the Rainbow Bridge over the Rainbow Chasm. But it does not seem that one can cross at all points, only at specific ones, whether in geography, time, or by virtue of spell or incantation or talisman. Or a combination of two or more of these. Whatever it is, not even the wisest have discerned.
Kolchin is almost identical in size to Earth, with a circumference of just under 25,000 miles and a radius of just under 4000. The proportion of land to sea is roughly the same, though the positioning of the continents is very different.
She is also the same distance from her sun, and with a similar make-up of atmosphere and spread of flora and fauna. Kolchin also has only one satellite, called M’y – a diminutive of Mowy-mowy.
For those who are interested in more background to the novels, I include some details of:
- the General Geography of Kolchin, and especially of the fastland;
- Peoples and Places;
- Associated Tales;
- Maps and Posters; and