 Planar Kakeya neighborhood lower bound

Choose $M\asymp {\delta }^{-1}$ angularly separated unit segments in a bounded Kakeya set, and let $F$ sum the indicators of their Kakeya tubes. Then $\int F\asymp 1$. Two tubes at angular separation $\alpha$ intersect in area at most $C{\delta }^2/(\delta +\alpha )$, so summing each harmonic angular row gives $\int F^2\lesssim \log (2/\delta )$. The Cauchy-Schwarz inequality on their union proves the displayed neighborhood lower bound. Since $|E_{\delta }|\lesssim {\delta }^2{N}_{\delta }(E)$, both planar Minkowski dimensions equal two.