Equation in stained glass

In the southwest corner of the Church of the Holy Spirit in Heidelberg there is a stained glass window containing Einstein’s equation E = mc² near the bottom.

Most of the windows in the church are much lighter, both in color and in content. This window is not prominent; I only noticed it the second time I was in the church.

I think the text at the top of the window quotes 2 Peter 3:10 and Isaiah 54:10. The date is the day the atomic bomb was dropped on Hiroshima.