There's an excellent anecdote of Maxwell[0] and Thomson[1] looking at some experimental apparatus the former had built, and when the former says to just look through the eyepiece here, the latter asks him what the deuce the little man dancing in the corner is for.
— For? For fun, of course.
[0] I'm fairly sure; consider https://clerkmaxwellfoundation.org/html/zoetrope.html
[1] as he was then — not so sure that I recall this participant correctly