Every website starts somewhere. This one started with a podcast.
In an episode of The Rest Is Science, the show presented by Hannah Fry and Michael Stevens, there is a conversation about π. The episode is called "Earth Is A Cradle But Not A Grave", and the π part starts at 38:00. Somewhere in it, the two of them get talking about a question that almost everyone has wondered about at some point: is my phone number hidden in the digits of π?
They looked. In the first 2 billion digits, their numbers weren't there.
We are big fans of the show, and that sounded like a challenge.
Why 2 billion digits isn't enough
2 billion digits sounds like a lot, and it is: printed in a normal book, it would fill about a million pages. But a phone number is a ten-digit number, and there are 10 billion of those. Even if π's digits are perfectly random, a particular ten-digit number has less than a one in five chance of turning up in the first 2 billion digits. Only 18% of them have appeared by then. About 8.2 billion are still missing.
So the presenters weren't unlucky. They were just a little early.
What if you looked further? The maths says that a typical ten-digit number first turns up around 7 billion digits in, and that if you could search 100 billion digits, 99.995% of all ten-digit numbers would be in there. The full calculation is in why your phone number is (probably) in π.
From a question to a website
Searching 100 billion digits by reading them one at a time would be far too slow for a website. So we did it the other way round. We took the digits that Google Cloud computed in 2022, slid a ten-digit frame along the first 100 billion of them and wrote down where every ten-digit number first appears. The result is one enormous table, with one line for every possible number. Any search is now a single look-up. You can read the whole trick in how we search the digits.
Then things got a little out of hand, in the best way. If numbers work, why not names, spelled on a phone keypad? Why not birthdays? Why not see how far apart two names sit, or let them fight? Why not a daily game about guessing where a word hides? Most of what you see here grew out of that first question.
A note on privacy
The question in the episode was about their own phone numbers, and that's exactly the kind of thing people should be careful with. So from the very beginning, the rule here has been: we never keep what you type. Your search travels inside the request, never in the web address, and it isn't logged or stored. The position where it turns up isn't stored either, because a position can give a number away just as easily as the number itself.
So, Hannah and Michael: your numbers are almost certainly in here. We will never print them, but you are very welcome to come and look.
Thank you
This site was inspired by The Rest Is Science. It is an unofficial fan project. It isn't affiliated with or endorsed by The Rest Is Science, Hannah Fry, Michael Stevens or Goalhanger, the company that produces the show. We just enjoyed the conversation enough to build something out of it.
If you've never listened, the episode above is a fine place to start. There is also a longer thank-you note on this site.
Where to next
- Find your own number in the first 100 billion digits.
- Read is every number really in π? for the honest answer.
- Visit the nerd corner for more about π.
Sources
- The Rest Is Science: "Earth Is A Cradle But Not A Grave", from 38:00.
- The Rest Is Science on YouTube
- Google Cloud: Calculating 100 trillion digits of pi on Google Cloud, where our digits come from.