# On Discussing Formulas During Presentations

During a recent lecture to the Warren Astronomical Society, a presenter went over a couple mathematical formulas in *great* detail - several audience members were lost almost immediately, most of the rest after just a minute or so. Afterwards, I talked with *one* audience member who not only understood all the math and physics presented, he absolutely LOVED it - but this particular fellow had studied under Carl Sagan, and is a complete Braniac, so his "math tolerance threshold" is a bit higher than most...

I remember *loving* my differential equations class at Michigan Tech, I also remember struggling *mightily* with Calculus; I've completely forgotten both after 30 years of disuse - and I've had more math than most of the general public I lecture to.

During my lectures, I occasionally include *a little bit* of math; I show relevant formulas, and let the audience know that there is math involved, but that's about all. When it comes to astronomy though, there's mathematics *all over the place*, and it is *very* important.

How do *you* present math and formulas during your presentations, without losing your audience? Do you simply not talk about math when presenting to the general public, and reserve it for presentations to educational and professional groups? How do you present the math and physics on a level that the general public can understand?

The ultimate question is always, “does the formula help tell the story?” Even scientific papers presented orally at meetings rarely show formulae; the point of the oral talk is to advertise the work and encourage people to read the paper (where the formulae are found). You’ve got to have a really compelling reason to show a formula.

And if it really is compelling, then it will be worth the effort to spend time explaining what each of the parts signify. The nicest advice I ever got was to explain a formula as if it were a sentence in a language; the equal sign is the verb, the stuff to the left of the equal sign is the subject of the sentence, the stuff to the right is the direct object with all its adverbs and adjectives modifying each piece.

I am a bit surprised to realize, now that you ask, that I very rarely show formulae in my talks. I guess I instinctively avoid them when putting together a presentation for a popular audience. (The Drake equation has turned up in a couple of my talks on extraterrestrial intelligence, more because of its historical role than because it is necessary to explain the subject.)

(I do show plenty of graphs. I get a little anxious if one or both axes are logarithmic. Then I point out the logarithmic nature and I walk the audience through the quantities marked on the graph. I haven’t gotten negative feedback from people who don’t understand such graphs, so perhaps I’m doing it right.)

The scientist-to-scientist talks I attend commonly make use of formulae. Unlike the short conference talks to which Brother Guy refers, the talks I hear are usually one-hour seminars, so the speaker can develop the background more fully. At a conference, one might have ten or fifteen minutes, so must gallop ahead to the results.