I have no doubt that every educator is familiar with the following situation:
"Are there any questions?"
"What is a harmonic oscillator?"
"What is the difference between a metal and an insulator?"
etc.
We ask an (open-ended) question to engage our students and start looking around at their faces in the lecture hall or classroom. Most students seem to look down at their desk or simply stare into space. After what feels like eternity, we decide to break the awkward silence and answer the question ourselves -- or, in the case of the "Are there any questions?"-question, we would say something along the line of "No? Great, let's move on to the next chapter."