WHEN THE USSR TESTED THE BIGGEST NUKE EVER OVER SEVERNY

In 1961, the USSR dropped the biggest ever nuke on Severny. It was a game-changer for humanity.

There was a time in our history that mortal men raced to see who could build the biggest bomb. It was a scary time, but it all started when the United States dropped its atom bombs on Hiroshima and Nagasaki. Those bombs were devastating, levelling both cities, and so big that they caused Japan to surrender, effectively bringing World War II to an end.

Drunk on power, the US continued to develop the atom bomb, making them bigger and bigger each time. But they weren't the only ones, soon, a few other nations climbed on the band-wagon. The United Kingdom made bombs, so did France and a few other countries, but it was the USSR who would become America's most prominent opponent. The fallout of this would be the Cold War, and the World would find itself fearing a nuclear war that could possibly end humankind.

These two giants of bomb-making would go back and forth, testing their new bombs. Eventually, in March of 1954, the US would test a hydrogen bomb over Bikini Atoll. It was called the Castle Bravo test, and its explosion weighed in at an astounding 15-megatons, far more destructive than anything the USSR had achieved. It vaporised three entire islands and turned the sky red. It was so hot, people 50km away felt like someone was applying a blowtorch to their faces. It would also be the last of its kind the US would ever test.

A year later, the USSR also broke the megaton mark, but theirs was only 1.5-megatons. Unfortunately, it still managed to kill two people accidentally; a soldier and a two-year-old girl.

The Soviets were still eager to construct a bomb that would put the Castle Bravo test to shame. In July 1961, Moskow requested nuclear physicist, Andrei Sakharov, to build it. He had just 16 weeks, but the experience he gained from developing their previous bombs helped.

Soon, he had the blueprint for the ultimate weapon. A 100-megaton monster the likes the world had never seen. The Soviet dream had come true. It would be, what he called, a layer cake made up of three layers that would set each other off in sequence. It would be 700-times more powerful than Hiroshima and Nagasaki combined.

But Zakharov was scared that it would be too big. He was concerned that it would cover northern USSR in radiation so, as the deadline approached, he replaced the Uranium layers in the bomb swapped out for lead instead. This would effectively halve the bomb's yield, but it would still be far more potent than that of the Americans.

On October 30th, 1961, the 8-metre long, 27-ton Tsar Bomber was strapped to the bottom of a Tu-95 Bomber, which then flew a thousand miles from the north of Russia to the island of Severny. Even with a 1-ton parachute to slow the bomb's fall, the chances of survival for the plane and its crew was only 50-percent.

At a height of 10km, the Tsar Bomber was released, falling for over a minute. When it reached an altitude of 3,940-metres, it detonated. In an instant, a fireball 8km wide lit up the sky. Its flash was so bright, it could be seen from over 1,000km away. Within seconds, a mushroom cloud 64km high and 100km wide had formed, that's 7-times higher than Mount Everest.

Animals 100km away received 3rd-degree burns, at 160km, wooden buildings were flattened and at 250km away, any living creature looking at the blast, had their eyes severely damaged. Windowpanes 700km away shattered, the shockwave was so incredible, it was felt all the way in Finland.

The Tsar Bomber's shockwave circled the Earth three times, while the plane that dropped the bomb fell 1,000-metres before the pilot regained control. One of those on board later wrote, "At that moment, our aircraft emerged from between two cloud layers, and down below, in the gap, a huge bright orange ball was emerging. The ball was powerful and arrogant like Jupiter. Slowly and silently, it crept upwards, having broken through the thick layer of clouds, it kept growing. It seemed to suck the whole of the Earth into it. The spectacle was fantastic, unreal, supernatural."

The bomb registered a 5 on the Richter scale and knocked out all radio communications for over an hour. By the time it came back on, the world already knew what had happened. It was such a shock that nobody would ever test a bomb of that size again.

Although massive, the Tsar Bomber would never be viable for warfare. The aircraft required to carry it would quickly be shot down from the sky. It was actually one of the cleanest bombs ever, so Severny island remains radio-active free, although it's still uninhabited.

Frighteningly, even though nuclear bombs are heavily controlled, there are still about 14,000 nukes around the world today. That's more than enough to destroy humanity forever. Hopefully, that day never comes.

Find out more in the video below by Geographics host, Simon Whistler.