How far you can sail, walk or fly in a perfectly straight line, from any country and any point on Earth.
A picture goes round social media: you can sail from India to the USA in a straight line without touching a shore.
Here is that line on the map. Straight it is not: it dives under Africa, rounds South America and only then turns north. So which is crooked, the line or the map?
Fold the map into a ball and the line straightens. On a sphere a straight line is a great circle. Cut an orange exactly in half: the edge of the cut is one. On a flat map such circles look like arcs, because the map stretches the Earth.
Look at the line from above: it is straight. And very long.
From India it heads south past Madagascar, under Africa, passes south of Cape Horn and crosses the whole Pacific to Alaska.
29,820 km in all, three quarters of the way round the Earth, and not one shore on the way.
And that is not even the longest straight line over water. The record starts in Kamchatka and ends near Karachi in Pakistan: eight tenths of the way round the Earth.
A Reddit user posted it in 2012; in 2018 Rohan Chabukswar and Kushal Mukherjee checked it by computation. Theirs is 6 km longer because of differences in the coastline data.
Long straight lines over water are not only for records: swell, the waves of a distant storm, runs along them. In 1963 Walter Munk set instruments from New Zealand to Alaska and saw waves from Southern Ocean storms cross the whole Pacific barely weakening.
From the storms south of New Zealand to Alaska it is 12,901 km in a straight line. Surfers, by the way, find their beach's “swell window” like this: wherever a straight line over water reaches it, that's where the waves come from.
In 1960 depth charges went off near Perth, and 3 hours 43 minutes later hydrophones in Bermuda heard them.
Perth and Bermuda lie almost exactly opposite each other on the globe, and there is a straight line over water between them: 20,017 km, half the Earth. The same lines tell what the hydrophones listening for nuclear tests can hear.
The place in the ocean farthest from land. Whichever way you turn, a straight line from here runs at least 2,699 km over water before it meets Easter Island or Antarctica. The other oceans have such points closer to a shore: the Atlantic 2,034 km, the Indian 1,935, the Arctic 1,003, and the Mediterranean only 343.
When the ISS passes over Point Nemo, the nearest people are the astronauts, some 400 km up.
Over land you won't get nearly as far: sooner or later you hit the sea. The YouTuber GeoWizard walks across countries in a perfectly straight line: in 2020 he crossed Norway that way. The longest straight line over land starts in China and ends in Liberia.
It grazes the southern tip of the Dead Sea. A little further north and the lake would cut it.
The Suez Canal is a ditch dug through land, and we count it as land. Count it as water and Africa is cut off from Asia, and the record changes: from China to Portugal, 11,246 km.
That is the line Chabukswar and Mukherjee found: for them water is whatever lies below sea level. Decide differently what counts as water and the record is 2,357 km shorter.
Sometimes there is no straight line at all. The Americas are joined by land, yet every straight line over land from the USA to Brazil ends in the sea.
The closest attempt crosses Mexico and stops on the Pacific coast of Guatemala, 2,633 km short.
Now let's fly. New York and Singapore are joined by one of the longest non-stop flights in the world: 15,339 km in a straight line that passes just 280 km from the North Pole.
On the globe it is plainly a straight line, just one across the Arctic.
Unfold the globe and the same straight line becomes a huge arc: on a flat map the pole is stretched into the whole top edge.
Hence the old question of why a plane from New York to Asia flies over the Arctic. It flies straight; it's the map that is crooked.
Those were the records, but every country has its straight lines.
Pick yours and see where you could sail, walk or fly from it. Or cast lines from any point of the ocean.