How Christopher Nolan recreated nuclear explosion for Oppenheimer

How do you go about recreating a nuclear blast?

Well, unless you fancy pouring billions of dollars into a nuclear programme to enrich uranium to the levels needed for a bomb, then you'll have to find another way.

Now, it might seem an outlandish question but this is precisely the challenge that Christopher Nolan and his team faced on the set of Oppenheimer.

In an industry where CGI has become the norm on movies, you might think that the easiest way to do this would be to do it in post.

But sometimes that isn't the case - remember Dwayne Johnson as the Scorpion King in The Mummy?

No matter how ultra-realistic CGI is, high end practical effects is often better. But it's not the first time Nolan has had to create one, as he explained: "With the Trinity test, what I knew from experience having done a nuclear explosion via computer graphics in The Dark Knight Rises, which worked very well for that film [...].

YouTube / Variety

"It showed me that with a real life event like Trinity [...] the computer graphics would never give you the sense of threat that you see in the real life footage."

So, there was a lot of pressure to get it right.

But just how did they do it?

First, you have to think about the different parts of the explosion.

There's the initial flash, then the shockwave, and finally the mushroom cloud.

And after some 'experiments', they managed to come up with plenty of 'analog methods' that would create the effect as accurately as possible.

To create the flash and cloud, the team put together a special mixture of explosives including gasoline, gunpowder, and aluminium.

The aluminium was responsible for the flash at first, before the gasoline and gunpowder ignited in a sequence designed to create the shape of the mushroom.

Obviously the explosion they created wasn't large enough to create a shockwave by itself.

So instead, they built a device to be placed in front of the camera.

This was a small 'stage' made out of wood, with a wooden bar under the surface which could be pulled along very quickly.

When the top was covered with sand, pulling the bar created a wave of sand along the surface.

But it wasn't just the physical practical effects that helped, but also the perspective of the camera to give off the impression of a catastrophic explosion.

It's the little things that matter.