# Is 4 the second or third digit of pi

If someone says that they know 10 digits of pi, does that mean that they know ten digits starting with the 3 in 3.14 or with the 1 in 3.14?

• Depends on the speaker; you pretty much have to ask. I careful speaker would say something like I know pi to 64 decimal places (or however many was the case). Aug 26, 2015 at 1:22
• Fortunately, I don't have this problem of ambiguity. I know the digits of $\pi$ in decimal form up until the first zero. It is a convenient place to stop. Aug 26, 2015 at 1:27
• @JMoravitz The next one is a $2$. Now that I've told you this, would you say that you know 2 many? Aug 26, 2015 at 1:33
• @JMoravitz I've always thought the most convenient stopping-point would be after "3.14." Aug 26, 2015 at 4:56
• I know all ten digits that occur in the decimal expansion of $\pi$. I'm pretty sure there aren't any others. Aug 26, 2015 at 11:29

• Another fun fact: If you express the largest distance we can observe (46 million light years) in terms of the planck length (the smallest length that actually makes sense physically), you get that it is about $2.7\cdot 10^{58}$ planck lengths. Thus with $\pi$ to about 60 digits, you should be able to calculate the circumference of every circle in the universe to the accuracy permitted by physics (of course the objection by @MarcvanLeeuwen about GR still applies; even more so, since at that precision, every local object will change the geometry). Aug 26, 2015 at 8:26