Talk:2205: Types of Approximation
- In that What-If, the rounding formula for Fermi problem estimation is given as "Fermi(x) = round10(log10(x))". log10(pi) (Google search, shows calculator) is roughly .4971... so close enough that someone could do a "Fermi rounding" to either 1 or 10 and not really care one way or another. 126.96.36.199 21:19, 20 September 2019 (UTC)
As a physics Phd (though not working in astrophysics), approximating pi to 1 is not all that bad. Especially when the measurable quantities that go into the calculation usually have huge error bars.--188.8.131.52 21:03, 20 September 2019 (UTC)
Using natural units (setting c=hbar=1) is different from setting pi to 1. Using different units is always allowed and not an approximation. Setting pi to 1 on the other hand, is an approximation and is only justifiable if the other quantities in the calculation have huge uncertainty. --184.108.40.206 21:07, 20 September 2019 (UTC)
In curved spaces, size of a circle also matters a lot. Small circles will always have circumference/diameter ratio closer to pi than larger circles, no matter where they are.