Optical illusions, 2/5
\documentclass[tikz,border=10pt]{standalone}\newcommand{\centercircle}{\filldraw (0,0) circle(0.5);}\begin{document}%% definition of the circle in the center, just to show%% that in both configurations the same one is used\begin{tikzpicture}%% surrounded by big circles (looks smaller)\centercircle\foreach \a in {1,...,5}\filldraw (90+360/5*\a:1.8) circle(1);%% surrounded by small circles (looks bigger)\begin{scope}[xshift=5cm]\centercircle\foreach \a in {1,...,5}\filldraw (90+360/5*\a:0.8) circle(0.2);\end{scope}\end{tikzpicture}\end{document}