This STEM activity familiarises the student with the important advances in physics during the 1920s, a time when many of the concepts of modern physics were being established. It is not too great a simplification to state that scientists in the century since have largely been engaged in refining these important ideas and principles. The 1927 Solvay conference in Belgium is significant because almost all the key scientists of the age took part. Click on a conference participant for related questions.