In July 1945, scientists detonated Trinity, the world’s first nuclear bomb.
At the time, no one was sure what was going to happen.
But the test was a terrifying success, and it led to an international arms race.
The United States conducted over 200 atmospheric weapons tests for two key reasons: grandstanding
and fine tuning.
They wanted to prove their military might, and make better, more powerful nuclear weapons.
So, they tested out new designs in the air, on the ground, and at sea.
All of these massive fireballs were captured by strategically placed cameras around a test
site, and then analyzed by scientists.
The big number they were all after?
The yield, or the amount of energy released.
These films hold the best scientific data we have of our nuclear potential.
That is, until a weapons physicist decades later found out the data from these films
might be off a bit.
About 10 years ago, I was asked by my boss to write this computer code that would predict
nuclear fallout, and I couldn't seem to get the answer to agree no matter what I did.
That’s Greg Spriggs, a weapons physicist with the Lawrence Livermore National Laboratory.
I kept saying, "I'm not doing anything wrong in my computer code."
Typical scientific answer right, it's always somebody else's fault, not yours."
For weapons physicists like Greg, computer codes are everything.
They’re used to verify the thousands of thermonuclear warheads on standby all across
the country.
And the original data for those codes came in part from these films.
That's the benefit of the data.
It provides ground truth to us , the reality, and it gives everybody a warm fuzzy feeling
back in Washington.
If it ever comes to a point that we have to use a nuke, it better work.
So Greg is working on a special project to scan and reanalyze all of the old films, and
make sure the data is up to snuff.
To do that, he had to track down thousands of Cold War era film canisters.
They’d been sitting in high security vaults for decades and hadn’t been seen by the
public.
Some of the films had decomposed to the point where they had turned to dust.
The only way to accurately study these films is to digitally scan them.
And Greg needed an expert in film preservation.
So he brought in Jim Moye.
For Jim, each film is a mini time capsule.
It's kind of cool to be opening something and having no idea what's there.
Jim processes each nuclear film with this Hollywood-style scanner.
So far, they’ve digitally scanned over 4,000 films.
Then came the work of analyzing them.
There are four major effects.The first one I'll call prop radiation.
Greg spends a lot of time watching bombs explode.
These are the prop neutrons or the prop gammas that are coming off of the fission process.
We’re looking at Housatonic 120256, the last nuclear shot before all atmospheric testing
came to a complete stop in 1962.
The next major effect is what's called the shockwave//a big, high-density air region
that is moving through the atmosphere at very high speed.
Measuring the size of a shock wave over time can reveal how much energy a bomb releases.
So this shockwave is moving very, very fast. and when it hits something ... You could imagine
standing in a hurricane, having that wind blowing at you at 200 miles an hour, well
this is much higher speed.
Back in the 1950s though, the shockwave was calculated by hand using a device called a
kodagraph.
They projected the film onto a grid and advanced it frame by frame.
Scientists we’re doing this manually and very quickly, a process prone to human error.
we found that some of those yields could be off by as much as 20% or 30%.
But now, with these films digitized, Greg can analyze every single pixel in the fireball’s
edge.
This means for the very first time, we’re able to get a more accurate sense of a bomb’s
yield.
The next effect was the thermal blast.
When the shock wave moves through the atmosphere it also heats the air, and that hot air then
starts to radiate thermal energy.
Two pulses emerge from a fireball.
The first pulse happens within 81 milliseconds and has 0.6% of thermal radiation.
The second carries about 99% of total thermal radiation energy from the blast.
Then the fourth major effect, of course, is nuclear fallout.The films can’t measure
nuclear fallout, but measuring the cloud height can give experts a sense of the extent of
the damage.
I found that those cloud heights could be off by as much as 10% or 15%, which makes
a big difference in nuclear fallout.
By pinpointing more precise yields, Greg can update computer models to estimate the damage
from a bomb in different scenarios.
Ultimately, they’re perfecting data for nuclear weapons that will hopefully never
be used.
Still, the pursuit is worth it.This is something new, this is what scientists live for, is
to kind of push the frontier forward just a little bit.
There’s something unnerving about watching these mushroom clouds.
And while we aren’t testing nuclear weapons anymore, these films stand as a terrifying
reminder of our nuclear past and potential.