Longitude by Dava Sobel Summary
Overview of Longitude
Before GPS, sailors died by the thousands. "Longitude" chronicles John Harrison's 40-year quest to solve navigation's deadliest puzzle, winning a king's ransom and changing history. Shortlisted for the Pulitzer Prize, this slim bestseller inspired a BBC series that captivated millions.
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Key takeaways
The Invisible Grid That Changed the World
Imagine being stranded in the middle of the vast ocean with no way to determine your exact position. This was the reality for sailors for centuries, leading to countless shipwrecks and lost lives. While determining latitude (north-south position) was relatively simple-sailors could measure the height of the sun or North Star-longitude (east-west position) presented an entirely different challenge. The world is wrapped in these invisible lines that converge at the poles like segments of an orange. Unlike latitude, longitude has no natural starting point, and is fundamentally linked to time. Since Earth rotates 360 degrees in 24 hours, each hour represents 15 degrees of longitude. To know your longitude at sea, you needed to know what time it was at a reference point while also knowing your local time. This seems simple enough today, but on rolling ships in the 18th century, pendulum clocks couldn't maintain accuracy amid the pitch and roll of ocean voyages. Without accurate time, sailors were literally lost at sea, relying on educated guesswork-"dead reckoning"-with often deadly consequences. What's remarkable is how long this problem persisted and how its solution would eventually come not from established scientists but from a humble, self-taught clockmaker.
Blood and Treasure: The Cost of Navigational Ignorance
The Race for a Solution
The Clockmaker Who Changed the World
H-1 to H-4: The Evolution of Precision
Triumph and Betrayal
A Legacy That Circles the Globe
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"BeFreed turned my commute into learning time. 20-min podcasts are perfect for finishing books I never had time for."
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"It is great for me to learn something from the book without reading it."
"The themed book list podcasts help me connect ideas across authors—like a guided audio journey."
"Makes me feel smarter every time before going to work"
From Columbia University alumni built in San Francisco
"Instead of endless scrolling, I just hit play on BeFreed. It saves me so much time."
"I never knew where to start with nonfiction—BeFreed’s book lists turned into podcasts gave me a clear path."
"Perfect balance between learning and entertainment. Finished ‘Thinking, Fast and Slow’ on my commute this week."
"Crazy how much I learned while walking the dog. BeFreed = small habits → big gains."
"Reading used to feel like a chore. Now it’s just part of my lifestyle."
"Feels effortless compared to reading. I’ve finished 6 books this month already."
"BeFreed turned my guilty doomscrolling into something that feels productive and inspiring."
"BeFreed turned my commute into learning time. 20-min podcasts are perfect for finishing books I never had time for."
"BeFreed replaced my podcast queue. Imagine Spotify for books — that’s it. 🙌"
"It is great for me to learn something from the book without reading it."
"The themed book list podcasts help me connect ideas across authors—like a guided audio journey."
"Makes me feel smarter every time before going to work"
"Instead of endless scrolling, I just hit play on BeFreed. It saves me so much time."
"I never knew where to start with nonfiction—BeFreed’s book lists turned into podcasts gave me a clear path."
"Perfect balance between learning and entertainment. Finished ‘Thinking, Fast and Slow’ on my commute this week."
"Crazy how much I learned while walking the dog. BeFreed = small habits → big gains."
"Reading used to feel like a chore. Now it’s just part of my lifestyle."
"Feels effortless compared to reading. I’ve finished 6 books this month already."
"BeFreed turned my guilty doomscrolling into something that feels productive and inspiring."
"BeFreed turned my commute into learning time. 20-min podcasts are perfect for finishing books I never had time for."
"BeFreed replaced my podcast queue. Imagine Spotify for books — that’s it. 🙌"
"It is great for me to learn something from the book without reading it."
"The themed book list podcasts help me connect ideas across authors—like a guided audio journey."
"Makes me feel smarter every time before going to work"
"Instead of endless scrolling, I just hit play on BeFreed. It saves me so much time."
"I never knew where to start with nonfiction—BeFreed’s book lists turned into podcasts gave me a clear path."
"Perfect balance between learning and entertainment. Finished ‘Thinking, Fast and Slow’ on my commute this week."
"Crazy how much I learned while walking the dog. BeFreed = small habits → big gains."
"Reading used to feel like a chore. Now it’s just part of my lifestyle."
"Feels effortless compared to reading. I’ve finished 6 books this month already."
"BeFreed turned my guilty doomscrolling into something that feels productive and inspiring."
"BeFreed turned my commute into learning time. 20-min podcasts are perfect for finishing books I never had time for."
"BeFreed replaced my podcast queue. Imagine Spotify for books — that’s it. 🙌"
"It is great for me to learn something from the book without reading it."
"The themed book list podcasts help me connect ideas across authors—like a guided audio journey."
"Makes me feel smarter every time before going to work"
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