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EXPLAIN BITCOIN LIKE I’M FIVE


IF YOU STILL CAN’T FIGURE OUT WHAT THE HECK A BITCOIN IS…

Nik Custodio

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Published in

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6 min read
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Dec 12, 2013

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We’re sitting on a park bench. It’s a great day.

I have one apple with me. I give it to you.

You now have one apple and I have zero.

That was simple, right?

Let’s look closely at what happened:

My apple was physically put into your hand.

You know it happened. I was there. You were there. You touched it.

We didn’t need a third person there to help us make the transfer. We didn’t need
to pull in Uncle Tommy (who’s a famous judge) to sit with us on the bench and
confirm that the apple went from me to you.

The apple’s yours! I can’t give you another apple because I don’t have any left.
I can’t control it anymore. The apple left my possession completely. You have
full control over that apple now. You can give it to your friend if you want,
and then that friend can give it to his friend. And so on.

So that’s what an in-person exchange looks like. I guess it’s really the same,
whether I’m giving you a banana, a book, or say a quarter, or a dollar bill….

But I’m getting ahead of myself.




BACK TO APPLES!



Now say, I have one digital apple. Here, I’ll give you my digital apple.

Ah! Now it gets interesting.

How do you know that that digital apple that used to be mine, is now yours, and
only yours? Think about it for a second.



It’s more complicated, right? How do you know that I didn’t send that apple to
Uncle Tommy as an email attachment first? Or your friend Joe? Or my friend Lisa
too?

Maybe I made a couple of copies of that digital apple on my computer. Maybe I
put it up on the internet and one million people downloaded it.

As you see, this digital exchange is a bit of a problem. Sending digital apples
doesn’t look like sending physical apples.

Some brainy computer scientists actually have a name for this problem: it’s
called the double-spending problem. But don’t worry about it. All you need to
know is that, it’s confused them for quite some time and they’ve never solved
it.

Until now.

But let’s try to think of a solution on our own.


LEDGERS



Maybe these digital apples need to be tracked in a ledger. It’s basically a book
where you track all transactions — an accounting book.

This ledger, since it’s digital, needs to live in its own world and have someone
in charge of it.

Say, just like World of Warcraft. Blizzard, the guys who created the online
game, have a “digital ledger” of all the rare flaming fire swords that exist in
their system. So, cool, someone like them could keep track of our digital
apples. Awesome — we solved it!




PROBLEMS

There’s a bit of a problem though:

1) What if some guy over at Blizzard created more? He could just add a couple of
digital apples to his balance whenever he wants!

2) It’s not exactly like when we were on the bench that one day. It was just you
and me then. Going through Blizzard is like pulling in Uncle Tommy(a
third-party) out of court(did I mention he’s a famous judge?) for all our park
bench transactions. How can I just hand over my digital apple to you, like, you
know— the usual way?

> Is there any way to closely replicate our park bench, just you-and-me,
> transaction digitally? Seems kinda tough…




THE SOLUTION



What if we gave this ledger — to everybody? Instead of the ledger living on a
Blizzard computer, it’ll live in everybody’s computers. All the transactions
that have ever happened, from all time, in digital apples will be recorded in
it.

You can’t cheat it. I can’t send you digital apples I don’t have, because then
it wouldn’t sync up with everybody in the system. It’d be a tough system to
beat. Especially if it got really big.

Plus it’s not controlled by one person, so I know there’s no one that can just
decide to give himself more digital apples. The rules of the system were already
defined at the beginning. And the code and rules are open-source. It’s there for
the smart people to contribute to, maintain, secure, improve on, and check on.

You could participate in this network too and update the ledger and make sure it
all checks out. For the trouble, you could get like 25 digital apples as a
reward. In fact, that’s the only way to create more digital apples in the
system.


I SIMPLIFIED QUITE A BIT

…but that system I explained exists. It’s called the Bitcoin protocol. And those
digital apples are the “bitcoins” within the system. Fancy!

So, did you see what happened? What does the public ledger enable?

1) It’s open source remember? The total number of apples was defined in the
public ledger at the beginning. I know the exact amount that exists. Within the
system, I know they are limited(scarce).

2) When I make an exchange I now know that digital apple certifiably left my
possession and is now completely yours. I used to not be able to say that about
digital things. It will be updated and verified by the public ledger.

3) Because it’s a public ledger, I didn’t need Uncle Tommy(third-party) to make
sure I didn’t cheat, or make extra copies for myself, or send apples twice, or
thrice…

> Within the system, the exchange of a digital apple is now just like the
> exchange of a physical one. It’s now as good as seeing a physical apple leave
> my hand and drop into your pocket. And just like on the park bench, the
> exchange involved two people only. You and me — we didn’t need Uncle Tommy
> there to make it valid.

In other words, it behaves like a physical object.

But you know what’s cool? It’s still digital. We can now deal with 1,000 apples,
or 1 million apples, or even .0000001 apples. I can send it with a click of a
button, and I can still drop it in your digital pocket if I was in Nicaragua and
you were all the way in New York.

I can even make other digital things ride on top of these digital apples! It’s
digital after-all. Maybe I can attach some text on it — a digital note. Or maybe
I can attach more important things; like say a contract, or a stock certificate,
or an ID card…



So this is great! How should we treat or value these “digital apples”? They’re
quite useful aren’t they?

Well, a lot of people are arguing over it now. There’s debate between this and
that economic school. Between politicians. Between programmers. Don’t listen to
all of them though. Some people are smart. Some are misinformed. Some say the
system is worth a lot, some say it’s actually worth zero. Some guy actually put
a hard number: $1,300 per apple. Some say it’s digital gold, some a currency.
Other say they’re just like tulips. Some people say it’ll change the world, some
say it’s just a fad.

I have my own opinion about it.

That’s a story for another time though. But kid, you now know more about Bitcoin
than most.



Additional Reading (Updated 2022)

“Web3 isn’t about owning. It’s about Possessing”

“You Don’t Understand Bitcoin Because You Think Money is Real” by Maria
Bustillos

You can also read more about Ethereum and Smart Contracts here. Enjoy!





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Bitcoin
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PUBLISHED IN WE’VE MOVED TO FREECODECAMP.ORG/NEWS

587K Followers
·Last published May 23, 2019

We’ve moved to https://freecodecamp.org/news and publish tons of tutorials each
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WRITTEN BY NIK CUSTODIO

2.1K Followers
·43 Following

Every few years I write.

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RESPONSES (129)



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Also publish to my profile

Kai Katschthaler

about 9 years ago

Oh for fuck’s sake! Why has no one ever explained it to me like this? Thank you so much!!! :D

185

1 reply

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Leigh Anne Cappello

about 9 years ago

Thanks so much Deb! I SERIOUSLY did not get it the first time I heard it, and now I do. Now, can you explain how to turn the Smart TV my husband just bought on and off? Arghhh.

72



Reply

Zhao Yu

over 8 years ago

Hi, Nic. Thanks for writing this great article for us to understand bitcoin better.
I am a bitcoin lover from China, and I would like to ask your permission to let me translate this article to Chinese. I will post the Chinese version on my blog and…...

Read More

51

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