Spiritual realities changing the physical world.

Why do we make a Purim Seuda, when the source of the problem on Purim was that the Jews went to the Seuda of Achasveiros.  The answer is that when the Jews did Teshuva from Ahavah. it was counted as if they did a mitzvah and not an aveirah.  This shows us not just the importance of Teshuvah, but that physical things can change from spiritual realities.

from a Shiur by Rebbetzin Heller about Purim on Aish.com