Reading [this question](https://mathoverflow.net/questions/54818/consistency-strength-needed-for-applied-mathematics), and the [Wikipedia page](http://en.wikipedia.org/wiki/Reverse_mathematics) on reverse mathematics, I wonder whether one needs more than the subfield $\mathcal{P} \subset \mathbb{C}$ of periods for applied mathematics, or indeed weak forms of pure mathematics.

Edit: This was the sort of question one poses to friends over a coffee, and be quickly reminded that _again_, somehow, one forgot that periods only form a ring. With some time passed, I think I shall vote to close it and leave it as a warning to others: this is not a good MO question!