# Was Christopher Columbus acting on any tips from prior travellers? **URL:** \ **Category:** Factual Questions\ **Created:** [April 1, 2021, 1:00am UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123 "2021-04-01T01:00:37Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![GreenWyvern](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/greenwyvern/32/2834_2.png) [@GreenWyvern](https://boards.straightdope.com/u/GreenWyvern)\ **Post date:** [April 2, 2021, 6:49pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/22 "2021-04-02T18:49:09Z")
In 1474 the Florentine astronomer Paolo Toscanelli wrote a letter to King Alphonso V of Portugal suggesting that a westward voyage to Japan and China was possible. He based this on a miscalculation of the land width of Asia, and also placed Japan very much further east and south than it actually is. He thought that Japan was almost where Central America is. Nothing came of that letter, but Toscanelli later corresponded with Columbus in the years before his first voyage. Columbus then added his own mistaken idea about the diameter of the earth, which made the voyage seem more possible. Both Columbus’ son Ferdinand (or Fernando), and Bartolomé de las Casas, who lived in Hispaniola for several years from 1502, say that Toscanelli was the first person to come up with idea of sailing west to China. If there had been any other stories or sources of information, there was no reason not to mention them, so it seems unlikely that there were. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [April 2, 2021, 6:50pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/23 "2021-04-02T18:50:03Z")
Pretty sure Cabot would have gone in 1497 or maybe earlier, but some say he only went due to Columbus. Bristol had already sent several expeditions to look for Hy-Brasil as early as 1480. > **[John Cabot](https://en.wikipedia.org/wiki/John_Cabot)** > > Pages for logged out editors learn more > > > > > John Cabot (Italian: Giovanni Caboto \[dʒoˈvanni kaˈbɔːto\]; c. 1450 – c. 1500) was an Italian navigator and explorer. His 1497 voyage to the coast of North America under the commission of Henry VII of England is the earliest-known European exploration of coastal North America since the Norse visits to Vinland in the eleventh century. > To mark the celebration of the 500th anniversary of Cabot's expedition, both the Canadian and British government... _Cabot went to [Bristol](https://en.wikipedia.org/wiki/Bristol) to arrange preparations for his voyage. Bristol was the second-largest seaport in [England](https://en.wikipedia.org/wiki/Kingdom_of_England). From 1480 onward it had supplied several expeditions to look for the mythical [Hy-Brasil](https://en.wikipedia.org/wiki/Brasil_(mythical_island)). According to [Celtic](https://en.wikipedia.org/wiki/Celts) legend, this island lay somewhere in the Atlantic Ocean.[[27]](https://en.wikipedia.org/wiki/John_Cabot#cite_note-27) There was widespread belief among merchants in the port that Bristol men had discovered the island at an earlier date but then lost track of it.[[28]](https://en.wikipedia.org/wiki/John_Cabot#cite_note-alwyn-28)[[29]](https://en.wikipedia.org/wiki/John_Cabot#cite_note-hunter-29) Ruddock had contended in a private letter to a colleague, Quinn, that she had found evidence in Italian archives that Bristol men had discovered North America pre-1470.[[30]](https://en.wikipedia.org/wiki/John_Cabot#cite_note-30) As the island was believed to be a source of [brazilwood](https://en.wikipedia.org/wiki/Brazilwood) (from which a valuable red dye could be obtained), merchants had economic incentive to find it.[[31]](https://en.wikipedia.org/wiki/John_Cabot#cite_note-31)_ ---
**Author:** ![Elmer\_J.Fudd](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/elmer_j.fudd/32/1211_2.png) [@Elmer\_J.Fudd](https://boards.straightdope.com/u/Elmer_J.Fudd)\ **Post date:** [April 2, 2021, 7:37pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/24 "2021-04-02T19:37:19Z")
> [@Darren\_Garrison](#): > > Then why no disease resistance in the Native Americans? Unlike missionaries and settlers, fishermen would have little desire to confront natives. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [April 2, 2021, 7:58pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/25 "2021-04-02T19:58:22Z")
Eratosthenes measured the distance between Syene and Alexandria. When the sun illuminated the bottom of a well in Syene, a stick in Alexandra had a seven degree shadow. He paid some poor SOB to walk between the two cities and measure the distance, 575 miles. So he did the math and calculated a remarkable accurate circumference of the Earth. How did he communicate over 575 miles to know it was noon in Syene when it was seven degrees in Alexandria? ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [April 2, 2021, 8:08pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/26 "2021-04-02T20:08:44Z")
He didn’t. He knew when it was noon in Alexandria. His map showed that Syene was directly south of Alexandria so it would be noon at the same time. [https://www.maa.org/press/periodicals/convergence/eratosthenes-and-the-mystery-of-the-stades-meridian-of-alexandria-and-syene](https://www.maa.org/press/periodicals/convergence/eratosthenes-and-the-mystery-of-the-stades-meridian-of-alexandria-and-syene) This isn’t correct Alexandria is 29.9 East and Syene is 32.9E. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [April 2, 2021, 8:13pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/27 "2021-04-02T20:13:38Z")
How would he know when it was noon in Syene when he measured the seven degree shadow in Alexandria? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 2, 2021, 8:15pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/28 "2021-04-02T20:15:03Z")
He didn’t even need both measurements to be at the same time, merely on the same date (specifically, the northern solstice), and both at local noon (which is, of course, very easy to determine locally). ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [April 2, 2021, 8:43pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/29 "2021-04-02T20:43:00Z")
There was trivia floating around that the bottom of the well in Syene was illuminated by the Sun on only one day of the year. Being a well and thus fairly deep, that meant the Sun was exactly overhead on that day, which meant the day was the Summer Soltice and Syene was on the Tropic of Cancer. So Eratosthenes just had to measure the angle of a shadow on the Summer Soltice at Alexandria. The north-south distance between them was gotten from survey records and he was librarian at Alexandria where those records were kept. He didn’t have to hire someone to walk between the two places. ---
**Author:** ![filmstar-en](https://avatars.discourse-cdn.com/v4/letter/f/50afbb/32.png) [@filmstar-en](https://boards.straightdope.com/u/filmstar-en)\ **Post date:** [April 3, 2021, 1:42am UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/30 "2021-04-03T01:42:01Z")
Columbus sailed to Bristol in England and Galway in Ireland in his youth on a trade mission. Later his some wrote of him having also visited Iceland. Where he might have learnt the lost land to the west called Vinland… This documentary considers the evidence. It suggests that the proximity of Iceland to Vinland could have influenced his belief that America was a similar distance at more southerly latitudes of Spain and it was not just his poor calculations and his confusion over measurements by other geographers. Maybe…maybe not. [![](https://img.youtube.com/vi/bHEoHbSjsI4/maxresdefault.jpg "Did Columbus & Europe know about Vinland? - Short Documentary") ](https://www.youtube.com/watch?v=bHEoHbSjsI4) ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [April 3, 2021, 1:54am UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/31 "2021-04-03T01:54:34Z")
> [@Elmer\_J.Fudd](#): > > Unlike missionaries and settlers, fishermen would have little desire to confront natives. That’s not a strong argument. When the Pilgrim Fathers landed, they were lucky enough to be helped out by a local _who spoke English_ through contact with whalers/sealers, and the population was already decimated from contact. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [April 3, 2021, 3:44am UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/32 "2021-04-03T03:44:18Z")
> [@dtilque](#): > > He didn’t have to hire someone to walk between the two places. Awww. I’d pictured some guy in sandals pushing one of those wheel-clicker things. The question I’ve had is what method or calculations did CC use to arrive at his smaller diameter? ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [April 3, 2021, 3:57am UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/33 "2021-04-03T03:57:49Z")
This goes into detail about Columbus’ multiple miscalculatons: > **[Columbus’s Geographical Miscalculations](https://spectrum.ieee.org/tech-talk/at-work/test-and-measurement/columbuss-geographical-miscalculations)** > > Columbus based his ‘Enterprise of the Indies’ on three massive metrological errors. > Eratosthenes calculated the circumference of the earth to within one percent of its actual girth. He figured that one degree of latitude was equal to 59.5 nautical miles. > In making his own calculation, however, Columbus preferred the values given by the medieval Persian geographer, Abu al Abbas Ahmad ibn Muhammad ibn Kathir al-Farghani (a.k.a. Alfraganus): one degree (at the equator) is equal to 56.67 miles. That was Columbus’s first error, which he compounded with a second: he assumed that the Persian was using the 4 856-foot Roman mile; in fact, Alfraganus meant the 7 091-foot Arabic mile. (This is, of course, the sort of confusion of units that sent the Mars Climate Orbiter into its terminal swan dive in September 1999.) > Taken together, the two miscalculations effectively reduced the planetary waistline to 16,305 nautical miles, down from the actual 21,600 or so, an error of 25 percent. > And then there was the third error. “Not content with whittling down the degree by 25 percent,” Morison writes, “Columbus stretched out Asia eastward until Japan almost kissed the Azores.” Through a complicated chain of reasoning that mixed Ptolemy, Marinus of Tyre, and Marco Polo with some “corrections” of his own, Columbus calculated that he would find Japan at 85º west longitude (rather than 140° east)—moving it more than 8,000 miles closer to Cape St. Vincent. > All in all, he figured, the Indies were just 68 degrees west of the Canary Islands. Calculated travel distance: 3080 nautical miles. Actual distance from Tenerife to Jakarta: 7313 nautical miles. Margin of error: 58 percent. SO a combination of error, willful blindness, and pig-headedness. Plus, maybe he heard that the Basques (or Bristolians) had seen land over there, assumed it was evidence of the other end of Asia. As for the Basques (and Bristol and the Irish). The Basques may have preferred not to talk about their secret fishing hole, like modern anglers, but it’s pretty hard to hide the fact that ships would come back laden with plenty of cod. I’m sure it was a shared secret among the hundreds of Basque fishermen, local merchants, pub owners, etc. This: > **[English Voyages before Cabot](https://www.heritage.nf.ca/articles/exploration/bristol-explorers.php)** > > Although the re-discovery of Newfoundland is credited to John Cabot, we know that as early as the 1480s, English ships were venturing into the unknown Atlantic Ocean. If you wonder why they did not want to share, I recommend Farley Mowat’s book _Sea of Slaughter_ describing the Gulf of St. Lawrence and surrounding lands, and the description of the earliest explorers - schools of cod so thick you could practically walk in the water; cod 10 feet long was a common occurrence. Anyone fishing there knew that spreading the word would (a) lead to overcrowded conditions as every fisherman in Europe headed there and (b) consequently severely depress the price so nobody could make a living fishing. As it was, they had a secret motherlode. Like the article says, they could claim it was from Iceland, but anyone who knew things knew Icelanders were not letting others fish in the area if they could help it. There is evidence in Labrador of Basque fish camps where pottery remains indicate they put ashore to dry and salt fish, fairly close to contemporaneous with Columbus. As for China and Japan and Indonesia (Spice Islands). They were well described in Polo’s memoirs. Plus, as was beaten to death in another thread, China and the Mediterranean world have known about each other since the Roman times at least. (IIRC they even exchanged ambassadors with Rome). The silk road, which also traded spices, was a lucrative business. Daniel Boorstin in _The Explorers_ describes the evolution of modern exploration. The kingdoms along the silk road each took their tax on the cargoes, and jealously prevented westerners from travelling to see the source of the goods. When Genghis Khan conquered Asia, from China to the Mediterranean, he created an empire where he allowed free travel. For about 200 years, until the empire fell apart, travel was unhindered and people like Polo and has father and uncle could travel to China and back without being harassed. Then it all closed up again, but now Europeans knew where all these spices were coming from, with tales of how shiploads of precious spices could be gotten for a pittance if only one could sail there. Think of it as that era’s equivalent of the search for the map of the lost gold mine. the Portuguese monopolized the “around Africa” method, so Spain was willing to give westward a try against the advice of the scholars who knew it was a mistake. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [April 3, 2021, 2:18pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/34 "2021-04-03T14:18:08Z")
> [@Melbourne](#): > > When the Pilgrim Fathers landed, they were lucky enough to be helped out by a local _who spoke English_ through contact with whalers/sealers, “contact” is a very neutral term for being kidnapped, sold into slavery, escaping to live in England for years, then being brought back. By _colonists_ at one of the other existing colonies. There was little luck in it, Tisquantum was very familiar with the English already, and not through casual contact with whalers. It was he who encouraged Samoset, who _had_ leaned his English from fishermen, to make first contact. But Tisquantum was the one who “helped out” the colonists. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 3, 2021, 5:53pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/35 "2021-04-03T17:53:29Z")
In other words, whalers found it profitable to make sufficient contact with the natives that they could have passed on disease. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [April 3, 2021, 6:24pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/36 "2021-04-03T18:24:10Z")
> [@md-2000](#): > > SO a combination of error, willful blindness, and pig-headedness. Thank you for that, and it pretty well matches what I had suspected. ---
**Author:** ![SCAdian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/scadian/32/3292_2.png) [@SCAdian](https://boards.straightdope.com/u/SCAdian)\ **Post date:** [April 3, 2021, 7:47pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/37 "2021-04-03T19:47:21Z")
Columbus could also have gotten information from/about Corte-Real. ---
**Author:** ![GreenWyvern](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/greenwyvern/32/2834_2.png) [@GreenWyvern](https://boards.straightdope.com/u/GreenWyvern)\ **Post date:** [April 3, 2021, 7:52pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/38 "2021-04-03T19:52:43Z")
> [@SCAdian](#): > > Columbus could also have gotten information from/about Corte-Real.   How so, since Corte-Real only started his voyages of exploration in 1500? ---
**Author:** ![SCAdian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/scadian/32/3292_2.png) [@SCAdian](https://boards.straightdope.com/u/SCAdian)\ **Post date:** [April 3, 2021, 8:55pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/39 "2021-04-03T20:55:11Z")
> [@GreenWyvern](#): > > How so, since Corte-Real only started his voyages of exploration in 1500? Wiki: > [@](#): > > **João Vaz Corte-Real** (c. 1420 – 1496) was a Portuguese sailor, claimed by some accounts to have been an explorer of a land called _Terra Nova do Bacalhau_ ( _New Land of the Codfish_ ), speculated to possibly have been a part of North America. For his efforts, Corte-Real was offered the Donatário-Captaincies of São Jorge and Angra, respectively. ---
**Author:** ![Elmer\_J.Fudd](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/elmer_j.fudd/32/1211_2.png) [@Elmer\_J.Fudd](https://boards.straightdope.com/u/Elmer_J.Fudd)\ **Post date:** [April 3, 2021, 10:18pm UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/40 "2021-04-03T22:18:53Z")
> [@GreenWyvern](#): > > How so, since Corte-Real only started his voyages of exploration in 1500? You’re thinking of his sons Gaspar and Miguel who explored the coast of Labrador. ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [April 4, 2021, 4:53am UTC](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123/41 "2021-04-04T04:53:37Z")
> [@SCAdian](#): > > > [@GreenWyvern](#): > > > > How so, since Corte-Real only started his voyages of exploration in 1500? > > Wiki: > > > [@](#): > > > > **João Vaz Corte-Real** (c. 1420 – 1496) was a Portuguese sailor, claimed by some accounts to have been an explorer of a land called _Terra Nova do Bacalhau_ ( _New Land of the Codfish_ ), speculated to possibly have been a part of North America. For his efforts, Corte-Real was offered the Donatário-Captaincies of São Jorge and Angra, respectively. So some people were willing to “spill the beans” on the secret Basque cod goldmine. We’ll probably never know if Columbus heard of this, or specifically read his book but it does demonstrate the knowledge was not at the level of double-plus super top secret. Did it trigger Chris’s obsession that the Indies must be not far west of Spain, or did it simply confirm an idea he already had? Perhaps several of the intelligentsia heard about these stories too, but figured that a few outlying islands west of Greenland were pretty useless and likely to be already claimed by the Icelanders. Also keep in mind that without the internet to guide them, information propagation and lookup for the 15th century intelligentsia was slow, erratic, incomplete, and unreliable. Plus, the upper classes of the time were likely quick to discount uneducated peasants’ rambling stories of fantastical places and sights. We’ll never know the answer to the OP definitively. [Previous page](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123.md?page=1) [Next page](https://boards.straightdope.com/t/was-christopher-columbus-acting-on-any-tips-from-prior-travellers/939123.md?page=3)