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The Longest Straight Path You Could Travel On Water Without Hitting Land (gizmodo.com)
An anonymous reader quotes a report from Gizmodo: Back in 2012, a Reddit user posted a map claiming to show the longest straight line that could be traversed across the ocean without hitting land. Intrigued, a pair of computer scientists have developed an algorithm that corroborates the route, while also demonstrating the longest straight line that can be taken on land. The researchers, Rohan Chabukswar from United Technologies Research Center Ireland, and Kushal Mukherjee from IBM Research India, created the algorithm in response to a map posted by reddit user user kepleronlyknows, who goes by Patrick Anderson in real life. His map showed a long, 20,000 mile route extending from Pakistan through the southern tips of Africa and South America and finally ending in an epic trans-Pacific journey to Siberia. On a traditional 2D map, the path looks nothing like a straight line; but remember, the Earth is a sphere.
Anderson didn't provide any evidence for the map, or an explanation for how the route was calculated. In light of this, Chabukswar and Mukherjee embarked upon a project to figure out if the straight line route was indeed the longest, and to see if it was possible for a computer algorithm to solve the problem, both for straight line passages on water without hitting land or an ice sheet, and for a continuous straight line passage on land without hitting a major body of water. Their ensuing analysis was posted to the pre-print arXiv server earlier this month, and has yet to go through peer review. "There would be 233,280,000 great circles to consider to find the global optimum, and each great circle would have 21,600 individual points to process -- a staggering 5,038,848,000,000 points to verify," the researchers wrote in their study.
Anderson didn't provide any evidence for the map, or an explanation for how the route was calculated. In light of this, Chabukswar and Mukherjee embarked upon a project to figure out if the straight line route was indeed the longest, and to see if it was possible for a computer algorithm to solve the problem, both for straight line passages on water without hitting land or an ice sheet, and for a continuous straight line passage on land without hitting a major body of water. Their ensuing analysis was posted to the pre-print arXiv server earlier this month, and has yet to go through peer review. "There would be 233,280,000 great circles to consider to find the global optimum, and each great circle would have 21,600 individual points to process -- a staggering 5,038,848,000,000 points to verify," the researchers wrote in their study.
Or you could use a nice globe and a piece of string.
If you think I voted for Trump because of this post, you're wrong. I voted for Dr. Jill Stein of the Green Party. Again.
As straight as you can get on a sphere, anyway.
Or, expressed differently: start sailing in a particular direction, and do not deviate left or right from that (locally) straightline path until you hit land again.
It took me a few seconds to see how the path shown on the map is straight. Sure, straight lines on the Earth will look curved on a map, but that path heads very much South, then turns and heads very much North. How can that possibly be straight?
Then it dawned on me. If you're near the South Pole and you head South, toward the pole, then keep going PAST the South Pole, you'll be headed North - all the while going straight.
Where the path goes South of South America, it's near the pole. What looks like a turn North is actually going straight across Antarctica and up the other side.
Huh? If you look at TFA, the line clearly has an endpoint on the western edge of the Indian subcontinent, and does not approach western Europe at all..
Man, some people will do *ANYTHING* to avoid Russia!
The longest great circle route they found on land is like the one Christopher Priest used in his science fiction story Inverted World in 1974. Perhaps it's obviously the longest route when you spend some time poring over a globe.
// DevsVult: The Machines Will It
"The path covers an astounding total angular distance of 2883523, for a distance of 32 089.7 kilometers.
This path is visually the same one as found by kepleronlyknows, thus proving his assertion."
the path looks nothing like a straight line; but remember, the Earth is a sphere.
It's not a sphere. It can be approximated as an oblate spheroid with roughness. The faux editors here have no background in science, and the brash generalizations are rampant.
This type of flagrant error goes over their heads. There is certainly enough "unspheriness" of the earth to potentially throw off the result if the calculation were done with a spherical projection.
Take, for instance, the Kola borehole. It is not the deepest borehole on earth, but it is the closest borehole to the core of the earth.
That 'roughness' still meets the qualifications of a billiard ball.
Dontcha mean "apples to pancakes"?
Table-ized A.I.
If you look at TFA (Figure 9), the longest straight line that can be taken *on land* indeed starts in Portugal. You're both correct.
In spherical geometry:
That last one is the rule you've come across.
I don't think these researchers dug deep enough into the history of this. For those who are interested, here is the reddit post:
https://www.reddit.com/r/MapPorn/comments/15mwai/the_longest_straight_line_you_can_sail_almost/
Here's another reddit thread that he cross-posted to from five years ago; it seems that the researchers didn't dig deep enough:
https://www.reddit.com/r/todayilearned/comments/15mxxp/til_you_can_sail_almost_20000_miles_in_a_straight/
Apparently he learnt it from a Wikipedia article, where it is also reported (without citation) that the longest distance only on land is 13,573 km (8,434 mi).
The edit was added with this revision by Wikipedia user Muh1974 (who doesn't have a Wikipedia user page). The Talk page around that time has unreferenced "I remember reading somewhere" speculation about the longest great circle. My guess is that Muh1974 checked (somehow) that this path was valid, and had a distance at least comparable to the other ones mentioned in the wikipedia article, but that's where the trail goes cold for me.
Ask me about repetitive DNA
You are privileging Euclidean geometry. If a straight line is defined as the shortest distance between two points, then on the surface of the Earth, a straight line is the same thing as a great circle.
All I want is a secure system where it's easy to do anything I want. Is that too much to ask ~~ Randall Munroe
Lines of latitude aren't straight.
All I want is a secure system where it's easy to do anything I want. Is that too much to ask ~~ Randall Munroe