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Hello, hello, hello and welcome to English Learning for Curious Minds by Leonardo English, the show where you can listen to fascinating stories and learn weird and wonderful things about the world at the same time as improving your English.
I'm Aleister Budge and today we are going on a journey to the bottom of the ocean.
Or rather, we aren't going on a journey, but we will be talking about the fascinating history of humans trying to travel underwater and understand what lies beneath the surface.
It's an amazing tale of bravery, marvellous inventions, strange creatures and, as we will discover, it is a story that has barely even got started.
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Okay then, let's not waste a minute and learn about the history of underwater exploration.
For as long as we humans have walked on the land, we have also built boats, canoes and rafts to travel on water.
People have explored rivers, lakes and seas, crossed oceans to far off lands.
The seas and oceans have always been a subject of intrigue and mystery, with their storms, high waves and strange creatures that lurk beneath the surface.
In practically every culture with some history of seafaring, there are stories of mysterious sea monsters, beasts from the deep.
After all, it is hardly surprising.
People knew that there were animals down there, because they could throw nets or hooks into the sea and pull them out.
Fish, octopus, squid, sharks, whales, creatures of all shapes and sizes.
Clearly, there was an abundance of life beneath the surface.
But, compared to the life on earth, the ocean and its inhabitants were very poorly understood.
For starters, for thousands of years, there was not even agreement on whether the deep sea ever finished, whether there was a flaw to the ocean, or whether it was an eternal abyss of water.
After all, you couldn't see the bottom, and there was no possibility of going there.
So, did the sea continue forever or not?
In 1521, a man called Ferdinand Magellan did attempt to answer this question.
Now, you might know about Ferdinand Magellan already, or you might remember him from episode 196.
Long story short, he was a Portuguese explorer, and the first person to sail all the way around the world.
Well, whether it was actually Magellan or someone else is another question that you can hear about more in that episode.
But the point is that he was an explorer, who was the first or one of the first people to ever sail all the way around the world.
Anyway, in 1521, he was a couple of years into his expedition, and he was in the middle of the time.
How he did this was by attaching a cannonball to a piece of long rope, and then lowering it off the side of the boat.
As the men lowered the cannonball, they measured how much rope had been used, with the idea that when the rope went slack, when the line was no longer tight, this meant that the cannonball had hit the bottom.
The men lowered and lowered and lowered it, but after 732 metres, it was still just as tight as before.
And they had run out of rope.
Magellan concluded that, and I'm quoting directly, the ocean was immeasurably deep, too deep to be measured.
This might sound like a relatively basic way of measuring the depth of a body of water, but it works very well, and had been the way in which people measured the depth of water for thousands of years, and it was still the main way people measured depth for much of the 20th century.
Now, of course, there is a big difference between knowing how deep a body of water is and knowing what is actually going on beneath the surface.
To state the obvious, there is a hard limit of how deep a human can dive below the surface, on their own, without any kind of assistance.
Just going down 10 metres below the surface doubles the pressure upon the body, which is why you feel that discomfort in your ears, and why you need to blow holding your nose to equalise the pressure if you are diving.
So, there's the question of pressure, but there's also the more important question of running out of breath.
Even the most seasoned divers, people from communities where they would dive for pearls or sponges, they can typically only get to depths of 20 or 30 metres, and hold their breath for around 10 minutes.
Sure, that is very impressive, but it really is only a tiny fraction of the depth of the ocean.
And even going back thousands of years, people knew what they needed to explore the deep – some kind of container and source of air.
One of the first mentions of this kind of contraption dates back to Aristotle in the 4th century BC.
But this was just from a theoretical perspective – there is no evidence that any such object was ever built.
Yet, the idea captured imaginations for centuries to come.
By the Middle Ages, tales from French and German poetry spoke of a hero using a diving bell to explore the ocean's depths.
One of the most famous legends linked this invention to Alexander the Great, who supposedly descended underwater in a glass bell alongside a few animal companions – a dog, a cat, and even a chicken.
While there is no historical proof that Alexander attempted such a dive, the story has persisted, blending myth and ambition in the pursuit of the deep.
The first use of what we now call a diving bell came much later, in the 16th century, invented by the Italian Guillermo del Urana.
Together with a colleague, Francesco de Marchi, del Urana sought to go to the bottom of Lake Nemi, just to the south of Rome.
At the bottom of this lake lay two huge ancient barges that had been built as floating palaces for the Roman Emperor Caligula in the 1st century AD.
They most probably couldn't be seen from the surface, but there were plenty of historical records and local stories.
People knew they were there, only 18 metres below the surface.
But this was sufficiently far down that people couldn't dive and properly explore them.
However, Guillermo del Urana invented a device that allowed him to spend hours at a time exploring the ships, meaning he could return to the surface with treasures from ancient Rome.
Now, how this device actually worked is still a bit of a mystery, because his diving partner, de Marchi, the man who later wrote an account of the adventure, took a vow of secrecy.
What we know is that it was basically a large wooden barrel with a small piece of crystal for a window.
This would be put on the diver's head, and there must have been some way of getting the exhaled air out of the bell and pumping fresh air into it.
But, as the writer was sworn to secrecy, we don't know exactly how this was achieved.
But we know that it worked, there is little doubt about this.
In fact, in his account, de Marchi would write that the limit to how long a diver could stay underwater with this invention was nothing to do with how much air there was left, but rather, how long the diver could withstand the cold of the water and the fatigue of wearing this heavy contraption on their
head. It was a cunning system indeed, and did allow these men to complete what has been described as one of the first instances of underwater archaeology.
But it had its limits.
20 metres, after all, is not very deep.
Throughout the 16th, 17th and 18th centuries, inventors continued to tinker away on new versions of this technology, trying to solve the problem of how to get rid of exhaled air, have enough capacity for fresh air and maintain the right pressure at the same time.
And they weren't all doing this only out of scientific curiosity, or out of an innate desire to understand the marine biology of the seas.
The major objective was allowing people to dive down and recover valuables from shipwrecks.
By this point in time, there were hundreds of known shipwrecks with valuable treasure, from ancient Roman shipwrecks through to ships that had only sunk the previous year.
In some cases, they were known to contain today's equivalent of tens of millions of euros worth of perfectly usable gold.
It was just a question of being able to get down there and pick it up.
And with this very real monetary incentive, diving bell technology did increase dramatically, and divers were able to go down to depths of 20 or so metres and stay there for extended periods of time, supported either by tubes or sealed buckets of fresh air delivered from the surface.
But in 1620, just under 100 years after De Lorena and Demarche's trip to the bottom of Lake Neimi, a Dutch inventor named Cornelis Drebbel would design something that would go on to surpass the diving bell – the submarine.
He was working in London at the time, having been contracted by the British to work on all sorts of weird and wonderful inventions that might aid the British navy.
And the design for a submarine was one of them.
Now, his submarine was very different from modern submarines.
It was made of wood and leather.
It had all to propel it.
And air was supplied by two tubes that went up to the surface.
But it worked, sort of.
He continually improved the machine, building bigger and better versions of it.
By the time he had finished, it was able to travel all the way from Westminster to Greenwich in London, a distance of more than 10 kilometres.
Underwater, I should add.
It travelled at a depth of four metres.
And he even took King James I of England for a spin, giving him the unusual title of being the first ever monarch to travel underwater.
Now, unfortunately for Drebbel, the submarine was not considered to have any practical military value.
So the project was scrapped.
But it was an important development in underwater technology.
The next important step came a century and a half later, during the American War of Independence, when an American inventor, called David Bushnell, created the turtle.
This was a sort of large wooden ball, three metres long and two metres wide, which could fit one person inside.
Importantly, it was self -powered.
So the person inside could pedal with their feet, like a bicycle, to move the submarine forwards.
Its objective was a military one.
Remember, this was an American invention created during the American War of Independence.
The idea was to creep up undetected on British ships and plant a bomb on the ship's hull, the side of the ship, and then rush away before the bomb exploded.
It was a similar idea to a submarine firing a torpedo.
But the main difference being that it had to pedal up to the ship with the to the side, rather than firing it from a distance of several hundred metres, or even kilometres.
It sounded perfectly good in theory, but in practice it never actually worked.
The currents were too strong, so it got pushed around too much, and it couldn't hold enough air to stay underwater for long enough, so it never actually completed a successful mission.
Fast forward to the late 19th century, and submarine technology had improved dramatically.
And with the invention of the torpedo, the submarine became a viable and deadly military asset.
But these submarines still weren't able to go particularly deep, not much more than a couple of hundred metres.
And what's more, we're talking about deep sea exploration, not warfare here.
At the same time as submarine technology was going through a period of rapid development, there was a greater desire to understand the seas and oceans from a scientific perspective.
Between the years of 1872 and 1876, a British ship called HMS Challenger embarked on a huge mission of scientific exploration, travelling a grand total of 127 ,580 kilometres – the equivalent of going around the world more than three times.
The objective was to understand the seas and oceans, and it was tasked with measuring the depth of the ocean, which it did 492 times, taking samples from the bottom of the ocean, which it did 133 times, pulling huge nets through the water to see what lay beneath, which it did 151 times, and measuring
the temperature of the water, which it did 263 times.
It was a gargantuan mission, and it was hugely important in the growing field of oceanography.
The science of the sea.
To those who had thought the deep sea was inhospitable, unable to sustain life, they were proved to be wholly mistaken.
In its four -year voyage, the Challenger discovered around 4 ,700 new species of marine life.
The crew also discovered the deepest place on Earth, or at least the deepest known place on Earth.
While in the Pacific Ocean, they conducted one of their 492 depth samples, dropping a lead weight to the bottom, and continuing to let the rope down until it hit the bottom – pretty much like Magellan did 350 years before.
They continued for 8 ,184 metres before the rope went slack, indicating that the bottom had been hit.
What they had found was part of what we now call the Mariana Trench – the deepest ocean trench in the world.
Now, they didn't actually find the deepest bit of the trench.
The deepest known part is actually 10 ,984 metres deep, making it more than 2 ,000 metres further from the Earth's surface than the peak of Mount Everest.
But it was a pretty good attempt, and the deepest known part of the trench, and the furthest known distance from the Earth's surface, is named after this ship and this expedition – Challenger Deep.
And, just as standing on the top of the world, and summiting Mount Everest, has become a goal for the world's most adventurous explorers, so has going to the very depths of the Mariana Trench.
But, compared to getting to the top of Mount Everest, getting to the bottom of the Mariana Trench is a lot harder.
The first people to achieve it were the American Don Walsh, and his Swiss oceanographer colleague Jacques Picard, who managed it in 1960.
This iconic descent took place in something called a bath escape, which looks a little bit like an airship – a zeppelin – and consists of a small round pressure sphere at the bottom, where the two men would sit, and a large collection of tanks filled with gasoline in order to keep the device buoyant.
The pressure sphere had to be incredibly strong, so it was made from reinforced steel 9cm thick.
At those sorts of depths, the pressure is so intense, it's more than a thousand times what it is at sea level.
Or, to put it another way, it's like there was a 1 ,250kg weight pushing down on every square centimetre of the craft.
There is absolutely no way a human body could withstand that sort of pressure.
Our organs would be instantly crushed, we would be compressed to a fraction of our normal size, and, to state the obvious, instantly killed.
But, fortunately, the craft had been forged from incredibly strong steel, and the men successfully went to the depths of the Mariana Trench and returned alive and well.
This was more than 60 years ago, but, given the difficulty and expense of going so far deep, few others have managed it.
As of a couple of years ago, there have been only 22 manned descents, and 7 unmanned descents, so compared to the number of people who have climbed Mount Everest, or even the number of people who have gone to space, it is still a tiny fraction.
And, really, although we now have the technology to map the ocean floor without having to drop cannonballs and measure rope, and we can go anywhere in the ocean and have seen weird and wonderful deep sea creatures living at depths people once thought far too great to sustain life, the Earth's seas and oceans
are still among the worst understood parts of the planet.
The legendary French maritime explorer and filmmaker Jean -Michel Cousteau once said that we understand the other side of the moon better than we understand our own oceans.
So, while we know more about it than ever before, the deep sea still is a comparative unknown that holds more questions than answers.
Okay, that is it for today's episode on exploring the deep.
I hope it's been an interesting one, that you've learned something new, and if you are going to a pub quiz and one of the questions is which monarch was the first to travel underwater, you will know the answer – King James I.
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You've been listening to English Learning for Curious Minds by LeonardoEnglish.
I'm Alistair Budge, you stay safe, and I'll catch you in the next episode.
