We recently came across this post on Reddit. It references a YouTube video claiming to have discovered the longest straight line that can be sailed without going over land. The video creator calls it the Cooke Passage. However, we have attempted to recreate it in Google Earth, and it appears that it is not actually a straight line.
We have in the past discussed what constitutes a straight line in Google Earth. In this instance, we are interested in great circles, which is what Google Earth uses by default when drawing a path. However, Google Earth always draws the shorter arc of a great circle, so to draw the longer section of a great circle it is necessary to include at least one more point and then adjust it with care. You know you have got it right if you can draw another shorter path on any section of it and it still follows the same path.
Using the above techniques, and locations shown in the video, we have investigated the Cooke Passage and decided that it does not follow a great circle.
It seems the record for the longest straight line that you can sail is a route from Pakistan to Siberia, which you can read more about here or see it featured in the following YouTube video:
We also came across another interesting, though shorter route that goes from Norway to Antarctica by way of the Bering Strait.
To see the various routes discussed in this post in Google Earth, download this KML file