Today's video is about Richard Feynman--

a lot of people's favorite scientist--

and safe breaking.

But I just wanted to point out at the start that most safes,

or secure filing cabinets, actually have one dial.

And if you've got a three number combination, for

example, you'll turn that dial in one direction, then the

other direction, and then back in the other direction.

And that's how you open it.

But the mock up that we've used in this video--

and it is a mock up, I can assure you.

It's about as far from a safe as you could get.

We've used three dials.

That kind of makes things a bit more visual, a bit easier

to understand looking at it in that way.

But in most cases, the sort of safes we're talking about will

actually be using one dial.

I don't want to get all the safe enthusiasts out there too

fired up and angry in the comments section.

But for now, here's Professor Bowley with his pretend safe

and the story of Richard Feynman and his World War II

safe cracking.

PROFESSOR ROGER BOWLEY: I'm talking about Feynman and how

he managed to crack safes when he was working on the atomic

bomb project in Los Alamos in the early '40s.

His wife had died.

So early in the 1940s, his wife died.

And he was stuck in the middle of Los Alamos,

not able to get out.

It was a sort of desert area around there.

He was stuck with lots of other theoretical physicists.

So he needed something for amusement.

And as a hobby, he tried cracking open all the safes in

Los Alamos.

Now, they had new, purpose built safes with locks on them

made by the Mosler lock company.

You can imagine 100 numbers for this, 100 numbers for

that, 100 numbers for that--

a million, a million possible settings.

And if you fiddle them around, it'll take about five

seconds to do it.

So if you tried to crack it, it will take

you about 60 days.

On the average, it'd be 30 days, but 60 days if you screw

up and it takes the last one to open it.

Well, Feynman was a group leader.

So he was given one of these in his office to keep all the

top secret files that he might come up with.

So he knew how this worked mechanically, because he

fiddled around with it.

He'd just fidget with anything.

He wanted to know how it worked.

And he found by trial and error, suppose the number

should be 20, it was set at.

Actually, it started at 25, and a lot of people didn't

change it from 25, naught, 25.

That was the default.

And if he wanted to crack the safe, a lot of times, people

left it in the default setting, because it's the

easiest one to remember.

Suppose he set it at 20.

Now, he found that if he tried to set it at 20 and it opened,

he could also set it to 21 and it would open, or 22.

There was some slack on this.

This was not mechanically perfect.

So there was a bit of tolerance, plus or minus 2 on

every single number, which meant that if you set it at

20, it could be 21 or 22 or 19 or 18--

and the same for this dial and the same for this dial.

So now, if you go through all the combinations, you only

have to do 3, 8, 13 and so on--

every fifth one--

to make sure you cover them all.

Now, there are only 20 settings for this, 20 for

that, and 20 for that.

So automatically, that's gone down, oh, I can't do it.

Can you do it in your head, Brady?

It's really quite difficult.

8,000 different settings--

now, that becomes doable mechanically.

It will take you something like 10 hours

working solidly overnight.

And you could do it.

And he could do that.

He worked out how to do it.

He found out other ways of doing this.

He found that most people will set a birthday, an

anniversary, some well-defined date that--

I don't know, the Independence Day in the United States of

America, whatever.

And it would not be an ordinary number, because if

it's going to be, say, my birthday, which is the 21st of

April if anybody wants to send me presents.

There's the 21st.

04--

04 is there.

And I'm born in 1946, which is down there.

So for the top one, which is the days of the month, there

are typically 30 days in a month.

So let's suppose there are just 30 and never 31.

30 days in the month, you would need to set it in six

different positions.

Now, for the months, there's 12 months in the year, so you

may need not two, but three for that.

So now, we've got six settings here, three settings there.

And for the year--

well, now, the year, if it's some date, it's going to be

something in the past.

So how long back in the past is somewhat arbitrary.

But suppose 45 would do, and then it would be 9.

He was doing it 1942 or '43 or '44.

All right.

So the test would be somewhere around there.

So 45 is a natural number to look at, because then you

don't have to go back into the previous century.

6 for this one, 3 for this one, and 9 for that one.

And you multiply them together.

And you get out 162.

So that's 162 different settings.

Five seconds for each, 162--

that's 800 seconds.

It's about 12 minutes.

So he could go in and if somebody had chosen one of

those dates, instead of having 8,000, he's got 162.

And he can do it in 12 minutes.

On the average, it will be six minutes, because he might be

reach it in the first go or he might

reach it after 12 minutes.

But he would only require 12 minutes.

So he would go in and make a big fuss of going into the

office and say, I'm not going to show the secrets.

These are top secret stuff.

I don't want everybody to know my secrets.

And he'd carry in a bag with tools-- screwdrivers, picks,

all sorts of things that people would think you crack

safes with--

shut the door, and in 12 minutes, he would do it.

He'd take a magazine in with him.

Sometimes, he'd get it done straight away and he'd do some

exercise and wait for 20 minutes just to make everybody

believe it was tough work doing this.

And then he'd come out with a bit of sweat on his brow,

saying, that was hard work.

So those were the main techniques that he used.

162 means that this isn't safe and using your birthday or

anniversary is not safe.

But after that, he learned another trick.

And he got the number down to 20.

Out of all these million, there were 20.

And it turns out that if you open the safe and leave it

open, and there's a little draw on the bottom.

And he goes into somebody else's office.

He chats to them.

And the safe is open.

He fiddles with all the knobs.

And after two years of practice, he got these two

sorted out by fiddling around with the knobs when the safe

was open in somebody else's office.

He'd go back afterwards--

and they don't realize he's been doing this-- and writes

down these two numbers in a little book and

says such and such.

So by the end of the war, he could go

into anybody's office.

He's got the last two numbers.

There are 20 settings.

It takes him a minute and a half to open

the safe, or less.

So he really has to spin it up.

He has a reputation of safe cracking.

And everybody thinks he knows how to use picks.

But he's just used human nature, the tolerance of all

this, and deviousness, just to show how clever he was.

He was doing it just to show how clever he was.

He was obnoxious.

He would like to be one up on everybody else.

But there was a security problem there.

And the guy who he shared a room with was the guy who gave

the secrets of the bomb to the Russians,

which is Klaus Fuchs.

He was a roomie of his.

BRADY HARAN: But for all his showing off about safe

breaking, it turns out the real spy was in

the room with him.

PROFESSOR ROGER BOWLEY: Yes.

But I don't--

well, yes.

When you look at this, now that we live in worlds where

you have a little security code for everything, this

seems unbelievably primitive--

phone hacking and everything else going on.

But people weren't-- if you're a scientist, you're not really

looking at the other guy next door and wondering whether

he's letting all your secrets out.