Placeholder Image

字幕表 動画を再生する

  • [Dr. Meghan Gray] Today, I'm excited because I'm making a video that I've wanted to make for quite a long time.

  • And it's a subject that's close to my heart, because it's about my hometown.

  • I was born and raised in Halifax, Nova Scotia and as we film this, we're coming up to the hundredth anniversary

  • of one of the most major events in the history of that city. But it's also an event that was marked around the world.

  • Because it was the largest explosion made by human beings in the Pre-Atomic Era.

  • Key to understanding this story is understanding the geography of Halifax as a city.

  • And so I'll sketch it out here. The main part of Halifax is a peninsula.

  • Quite a funny shape. In the wider area,

  • and what made Halifax such an incredible resource, for hundreds of years is...

  • the larger picture and the harbor and how it opens up into the Atlantic Ocean.

  • So you have, next to this peninsula, this deep and sheltered basin called the Bedford Basin.

  • And then, you have this tiny little passage called the Narrows, with a little bump here.

  • And then this beautiful deep Harbor. You've got a few islands here, you've got a big ones here, McNabs Island.

  • You've got a little one here.

  • Out here is the Atlantic Ocean.

  • Over here is the Bedford Basin.

  • This side is a city, the city called Halifax. And on the other side is a city that used to be called Dartmouth.

  • Now they're put together in one Regional Municipality.

  • But we'll call them separate sides to keep everything in track. Key to this story is this narrow little passage here.

  • Which is actually called the Narrows. Let me set the scene for you: 100 years ago, it's

  • 1917 December, World War 1 is fully in force and this is an incredibly strategic point.

  • Hundreds of ships could fit in this nice protected Basin.

  • And then be shepherded over the North Atlantic in convoy to Europe. It's the morning of December 6, 1917.

  • Halifax is waking up. It's a very busy town. It's got a big naval presence. It's got a big army presence.

  • So the night before, every night in fact, submarine nets would have come down across the harbor.

  • To protect all the ships in this part of the basin from U-boat attack.

  • Submarine nets would have gone down across here and across here and limited the traffic in and out of the harbor.

  • And so we now have to introduce two boats to our story.

  • Number 1 is the [SS] Imo, this is a Norwegian registered Belgian relief ship.

  • So this was a neutral ship that was tasked with carrying supplies

  • to give relief to civilians on the continent that had been devastated by war.

  • So this is sitting here in the basin. It's been sitting there for a while and it's getting impatient.

  • It's meant to be leaving on the 5th, but by the night of the 5th,

  • it still hasn't been loaded up with coal and the submarine nets are down.

  • It's stuck, it wants to go to New York. Coming in from New York, is the [SS] Mont-Blanc.

  • And this is a French ship and unbeknownst to almost anyone in Halifax. It's carrying. It's loaded.

  • It's packed to the brim with explosives.

  • So it's also intending to go across the North Atlantic and help with the war effort.

  • It arrives too late

  • to get through the submarine nets, so it spends the night over here, next to McNabs Island.

  • What happens the next morning, these two ships both want to get through the harbor in different directions.

  • According to the "rules of the road", they should be passing port side to port side.

  • Which means they should come across like this (right lane moving) navigating carefully and slowly to get through the Narrows.

  • However, that's not what happens.

  • The Imo takes this corner wide to avoid an oncoming ship (passing on the left).

  • While the Mont-Blanc is keeping its station on the correct side.

  • At this point, there are a few kilometers apart, and remember,

  • it's 1917 and the conventional way of communicating is through whistles.

  • So the Mont-Blanc whistles first, that means by rights,

  • they should retain right-of-way. And they say one whistle, "I'm staying where I am"

  • The Imo, unbelievably,

  • responds with a cross signal, two signals whistles, "No, I'm keeping this station." Now we have a problem. The Imo was moving quite fast.

  • It's not loaded with anything, so it's sitting high in the water.

  • And it's moving probably faster than the speed limit. The Mont-Blanc cuts its speed.

  • Again, one whistle...

  • Even moves over slightly to the starboard side, the Dartmouth side. "I'm staying here." Two whistles from the Imo.

  • "No, I'm staying here." At this point, heads would have turned. The first exchange,

  • people are used to that background noise. The second exchange,

  • people would have known that something unusual was happening. And would have stopped to look. And at that point,

  • it's quite clear that these two ships are

  • heading straight towards each other in this narrow channel, with very little room left to maneuver. Remember how nervous

  • the captain of the Mont-Blanc must be, he knows what's in his cargo. Cuts his engines, says:

  • "Ok, I've got to do something to mitigate this situation," cuts his engines, which causes the ship to drift towards the Halifax side.

  • Had that been the only thing that happened,

  • the situation would have been avoided. It would have been a near miss, but at the same time, the Imo

  • also cuts its engines. And because it's sitting so high in the water, its propeller has really little purchase and it has very little maneuverability.

  • And so now a collision is absolutely inevitable. And so, the Imo impacts the Mont-Blanc broadside (right),

  • like this.

  • Even then,

  • a fairly minor collision in the grand scheme of things. What makes this story really interesting, is to understand fully,

  • what exactly was on the Mont-Blanc. We have a variety of things, all designed to blow up.

  • We have 227,000 kilograms of TNT.

  • Have 1.6 million kilograms of wet picric acid, as well as,

  • 544,000 kilograms of dry picric acid. On top of that, 56,000 kilograms of gun cotton and

  • strapped in barrels to the top of the ship, we had

  • 223,000 kilograms of benzol and monochlorobenzol.

  • So let's talk about what these things actually are, the benzol and the monochlorobenzol,

  • they're petroleum byproducts and they're used, sort of, in the production of picric acid, which let's talk about a minute.

  • They're flammable. They are in danger of catching a fire.

  • What's packed in the holds, however, is something more dangerous.

  • Now TNT at that time, was

  • becoming to be used in the production of munitions. It was largely replacing picric acid as the explosive powder

  • used in munitions, because picric acid is so incredibly volatile and dangerous.

  • So while the new TNT was perhaps less powerful as an explosive, it was

  • relatively speaking, much easier and safer to handle than the picric acid. We've now got our two ships, then they sort of are

  • maneuvered apart. Okay?

  • So they're now separate. The Mont-Blanc

  • drifting towards the Halifax side. In the initial collision, a fire started on deck. Now it may have been from the sparks.

  • Caused by the metal hulls grating against each other. It was likely caused by the the simple,

  • you know detonation, of a few grains of picric acid.

  • But once the fire took hold, all of these flammable things on the top deck

  • started to catch fire. And so now, you've got a ship on fire. [Brady] This is mainly the benzol. [Dr. Meghan Gray] This is mainly the benzol, yeah.

  • It's spewing off thick oily black smoke, and people are starting to become worried, because the ship is drifting towards the Halifax side.

  • It's heading straight for some of the wooden piers that are the heart of the harbour business. Okay?

  • So they're worried that there's gonna be a fire on shore, they're worried about pollution in the harbor from oil.

  • That would be bad enough. On the ship,

  • the crew immediately know that there is absolutely nothing that they can do to stop this ship from blowing up. I should mention that,

  • in sensible non-war times, if you were carrying a ship like that, you would be flying flags all over the place. Saying...

  • You know, "Danger, stay away." For obvious reasons,

  • you don't want to do that in war-time. So very few people actually knew that it was a ship loaded with high munitions.

  • The crew immediately,

  • seeing how futile the situation was, got into their lifeboats. They start moving towards the Dartmouth side.

  • They're shouting all the way, there shouting warnings to people. But the warnings are either not heard or they're not

  • understood because they're in French. So now we've got the situation where the ship is on fire,

  • it's now nestled against pier six on the Halifax side. The fire is raging,

  • the benzol and then later the monochlorobenzol

  • is reaching boiling points. Those barrels are shooting up into the air and exploding.

  • So it's a big spectacle, people are rushing to windows. They're rushing down the streets to see what's going on.

  • What's happening in the hold,

  • it that these are hermetically, they're carefully constructed holds. To hold these high explosives.

  • The fire is raging, the temperatures are increasing, and whether eventually it's from the incredibly high

  • temperatures and pressures inside these sealed compartments, or whether it's an impact from these exploding barrels coming down and hitting the deck.

  • Detonation occurs: the picric acid

  • explodes, sends a shock wave through the neighboring barrels, the hold explodes, sends an air blast the rest of the ship.

  • One by one, the holds full of dry picric acid.

  • The wet picric acid and the gun cotton, which have the water inside them evaporated,

  • turning them into high explosives as well.

  • Detonates as well.

  • You've now got a ship with three kilotons of high explosives,

  • which is now the largest bomb that human beings have ever made and at 09:04 on December 6th, 1917,

  • it exploded.

  • Well instantly, there is a massive fireball that reaches 5000 degrees Celsius.

  • That's nearly the temperature of the surface of the Sun.

  • And it engulfs the neighboring streets.

  • [Brady] But people on the land... [Dr. Meghan Gray] The people on the land, incinerated.

  • The Mont-Blanc, three million kilograms of iron hull,

  • destroyed.

  • White-hot shards of iron are flown through the air. Faster than bullets and rained down on the neighboring area.

  • Most devastating was the air blast.

  • Traveling a 1000 metres per second, through the narrow streets. It causes

  • unimaginable devastation to houses, to human beings, to the whole whole city.

  • Remember that many of these people are standing looking at this spectacle.

  • Lining the steep hills, leading down to the harbor, looking out at the burning ship.

  • When it explodes, all of the windows in the city exploded as well. And most of them are driven inwards.

  • Horrifically injuring people. Everything that wasn't immediately blown up as a structure, catches on fire.

  • It's a huge firestorm throughout the city. As the air blast

  • goes out, and the gas is cool. The air rushes back in again and

  • tornados full of debris, start sweeping through the streets. The 1.4 thousand kilogram

  • anchor of the Mont Blanc was flown

  • kilometres away. Way over on the

  • other side of the city and can still be seen today where it landed.

  • Going back to what happened in the harbor, the expanding gases push the water away,

  • forming a hole in the in the water in the harbor.

  • Just like when you throw something into a pond, and and you see the ripples rebound,

  • caused a huge geyser to appear in the harbor.

  • That sucked water away from the opposite shores and then sent a huge tsunami

  • funneled down these narrow harbor walls, reaching 20 feet in height, causing even more devastation.

  • At the end of that morning, you had 2,000 people dead,

  • 9,000 people severely injured,

  • 12,000 homes destroyed and

  • every single

  • building within a 12 mile radius damaged.

  • [Brady] You can find out more about the Halifax Explosion.

  • Including some links in the video description, and I'll also have details about more from this interview with Dr. Gray.

  • Also thanks to Neil Barnes from our chemistry channel, Periodic Videos for helping out with some of these demonstrations.

  • And you can find out more about Periodic Videos, also in the video description.

[Dr. Meghan Gray] Today, I'm excited because I'm making a video that I've wanted to make for quite a long time.

字幕と単語

動画の操作 ここで「動画」の調整と「字幕」の表示を設定することができます

B1 中級

ハリファックス爆発-60のシンボル (The Halifax Explosion - Sixty Symbols)

  • 0 0
    林宜悉 に公開 2021 年 01 月 14 日
動画の中の単語