ForOppenheimer,Cillian Murphyplunged deep into the mind and physicality of an iconic scientist that irrevocably changed our world.

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And thats exactly what you want from any role, really.

Cilliam Murphy in ‘Oppenheimer’

Cillian Murphy in ‘Oppenheimer’Universal Pictures/Everett Collection

Everything was deliberate with him.

He was polymathic in his interests and Bowie was the same.

Now again, these are things that just kind of hover in the background.

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From left:Emily Blunt, director Christopher Nolan and Cillian Murphy on set.Melinda Sue Gordon/Universal Pictures/Everett Collection

Bowie was incredibly slim and Oppenheimer was very, very self-conscious about his physique.

DEADLINE: How did you build the character from there?

You had Nolans very comprehensive, detailed script, but what else were you looking at?

MURPHY: Theres so much out there.

Theres so much text, theres so many books, and I just dove in.

It was a pleasure to read, and firsthand accounts of him were really, really useful to me.

People that knew him, had spent time with him.

And then there are all these images of how he sat in very peculiar ways.

And there are pictures of him like that.

There were lots of pictures of him standing like that I just stole.

And then you work it into the physicality.

It was fascinating and really rich, and there was so much of it.

But we were never going to do an impression.

Those were the kinds of things you didnt choose to include because theyre a little on the nose?

Like you say, you dont want to do an impression, you want to evoke.

But if you put that into a character, its just immediately signaling that someones going to die soon.

So, first off, you just leave that out.

And again, this points to Chris genius.

Oppenheimer is the only character in the film that smokes.

Hes the only character in the film that has a hat.

I really do find all that stuff so rewarding and exciting in the prep period.

What did you make of his attempt to poison his college lecturer with an apple?

He acted in a fairly sociopathic way then, but later he battles with his conscience in other ways.

How did you reconcile those two things?

MURPHY: That to me is just exactly what you want in a character, fictional or not.

That contradiction and complexity is just amazing to play.

I never judge them.

I think thats up to the audience.

DEADLINE: Right, if you did that, how would you play them?

Because they wouldnt do that to themselves.

Thats not how people are.

Its really reductive and not useful.

So, I dont ever do that.

We dont know how the conversations going to go.

We dont know who else is going to walk into that room.

We dont know what information theyre going to give us.

So, for me, in acting, its not an intellectual exercise, its an instinctual one.

DEADLINE: Did it help you at all that youd played a physicist before in the 2007 filmSunshine?

We used to go for dinner and hang out with the most brilliant people in the world.

DEADLINE: What was your takeaway from those brilliant people?

MURPHY: That I dont think its necessarily a gift.

I think it might be a burden.

DEADLINE: Have your teenage sons seenOppenheimer?

Did it spark an interesting moral debate with them?

MURPHY: Yeah, we had lots of great chats.

And we watch a lot of movies together and we have great discussions.

There were people dressing up as Oppenheimer and going to the cinema to watch the movie.

Its so heartening and its such a fantastic result for cinema, I think.