0:00:34 > 0:00:36We start our journey here in Galway...
0:00:41 > 0:00:45For centuries, Galway was an important link in a chain
0:00:45 > 0:00:48of commercial ports that ran from Iceland down to Spain.
0:00:50 > 0:00:53But sometimes, things are washed ashore here
0:00:53 > 0:00:55that have come from far further afield.
0:00:55 > 0:00:57What do you make of these?
0:00:57 > 0:01:01They look like props for the latest Hollywood remake of Jack And The Beanstalk or something.
0:01:01 > 0:01:05And in fact, these ARE beans, and for centuries they've puzzled the people
0:01:05 > 0:01:08who found them washed up on our shores,
0:01:08 > 0:01:11not just here in Ireland but all along the Atlantic seaboard,
0:01:11 > 0:01:19and these are one of the clues that led to THE most successful accidental discovery in history -
0:01:19 > 0:01:20America.
0:01:23 > 0:01:26In 1477, a young Genoese sailor landed here in Galway.
0:01:26 > 0:01:32He already knew of the strange beans, even exotic trees that were washed ashore after westerly gales
0:01:32 > 0:01:38and had started to suspect that out there, to the west, there must be a great continent.
0:01:38 > 0:01:40And that continent had to be...
0:01:40 > 0:01:42Asia.
0:01:42 > 0:01:45But what he himself observed here in Galway
0:01:45 > 0:01:51turned suspicion into conviction and prompted one of the greatest voyages of discovery in history.
0:01:51 > 0:01:56That early visitor to Galway was none other than Christopher Columbus.
0:01:56 > 0:02:00I've met up with historian Nicholas Canny to find out more.
0:02:02 > 0:02:07What was it about Galway that inspired Columbus on his journey of discovery?
0:02:07 > 0:02:12Well, during the course of his diary, Columbus makes reference to a series of incidents,
0:02:12 > 0:02:18which convinced him that he could get access to Asia
0:02:18 > 0:02:20by sailing westwards into the Atlantic.
0:02:20 > 0:02:24The most compelling of all, that he said when he was in Galway
0:02:24 > 0:02:29in Ireland that he saw the bodies of two people, a man and a woman
0:02:29 > 0:02:36with oriental appearance being brought ashore on a piece of wood and this satisfied him
0:02:36 > 0:02:43that the distance to Asia must be quite short if bodies could be carried across in that fashion.
0:02:43 > 0:02:46He surely could be forgiven for thinking that maybe
0:02:46 > 0:02:49just beyond the visible horizon was their point of departure.
0:02:49 > 0:02:51That is correct.
0:02:51 > 0:02:57Of course, Columbus didn't find Asia by sailing west, he found a completely different continent.
0:02:57 > 0:03:02So his celebrated discovery of America was, in reality, a comedy of errors.
0:03:02 > 0:03:04You can imagine it, can't you?
0:03:04 > 0:03:08"Very sorry, folks. I haven't found a westerly route to China after all.
0:03:08 > 0:03:12"I seem to have discovered some other vast lump of land instead."
0:03:12 > 0:03:14It's ironic, isn't it?
0:03:14 > 0:03:18By the time Columbus stumbled on the continent, it was inhabited by about 7m people.
0:03:18 > 0:03:22But until he, a European, discovered it, it didn't really exist.
0:03:24 > 0:03:28But the really neat trick that Columbus pulled off
0:03:28 > 0:03:33wasn't getting to America by sailing west, it was getting back, and knowing how.
0:03:33 > 0:03:37Although Ireland and the UK lie broadly at the same latitude
0:03:37 > 0:03:40as Warsaw, Moscow, Southern Alaska and Newfoundland,
0:03:40 > 0:03:43our winters are nothing like as cold as theirs
0:03:43 > 0:03:47thanks to a huge body of water that moves rapidly from west to east
0:03:47 > 0:03:51across the Atlantic - the Gulf Stream.
0:03:51 > 0:03:57Columbus himself, describing the power of the Stream, said, "It moved like the skies."
0:03:57 > 0:04:03Warmed by the Caribbean, the Gulf Stream divides just north of the Gulf of Mexico and one section,
0:04:03 > 0:04:07the North Atlantic Drift, as it's called, makes a beeline for Europe.
0:04:07 > 0:04:11Offshore, the prevailing south-westerly winds blow over it,
0:04:11 > 0:04:17hijacking its warmth and bringing it to land, an equivalent of a million power stations' worth of heat
0:04:17 > 0:04:21that warms our climate by between five and eight degrees.
0:04:21 > 0:04:26Cold winds from the Arctic can intercept these Westerlies, though, and depressions form, bringing rain.
0:04:26 > 0:04:29A lot of rain.
0:04:30 > 0:04:36But without this rain, there would be no "Emerald Isle", there would be no fertile "green and pleasant land."
0:04:38 > 0:04:44It's also the Gulf Stream that explains how those huge beans make the astonishing journey
0:04:44 > 0:04:46to our shores all the way from Costa Rica.