diff --git a/README.md b/README.md
index d13be4f..26f317d 100644
--- a/README.md
+++ b/README.md
@@ -8,3 +8,5 @@ $ python3 nav.py mars
 ```
 
 Requires Python 3.9 or newer; no further dependencies.
+
+All routes start at Earth. Getting back is your own problem.