What is Pi? The Circle Constant Explained
Pi (π) is the ratio of a circle's circumference to its diameter. No matter the size of the circle, this ratio is always the same: 3.14159265358979...
Why is it always the same?
If you measure the circumference of any circle and divide it by the diameter, you always get pi. A bicycle wheel, a planet, a coin: the ratio never changes. This is a consequence of the geometry of flat space.
Pi never ends
Pi is irrational, meaning it cannot be written as a fraction of two whole numbers. Its decimal expansion continues forever without repeating. Mathematicians have computed over 100 trillion digits. No pattern has ever been found.
Where pi appears
- Euler's identity: e^(iπ) + 1 = 0
- Normal distribution: the bell curve contains √(2π)
- Fourier transforms: used in audio processing and MRI machines
- Wave equations: describing light, sound, and quantum probability
Key facts
| Fact | Value |
|---|---|
| First 10 digits | 3.1415926535 |
| Proven irrational | 1761 (Lambert) |
| Proven transcendental | 1882 (Lindemann) |
| Current record | 105 trillion digits (2024) |
| Pi Day | March 14 (3/14) |
How to memorise pi on MemorisePi
MemorisePi groups pi into blocks of 6 digits, each mapped to a finger path on a numpad. After a few sessions, your fingers know where to go before your conscious mind catches up.
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