In my book I classify scientific presentations according to the following scheme:

a)  speaker has no goal apparently
b)  speaker wants to prove he is smarter
than anybody in the audience
c)  speaker wants to give listeners a flavor
of new developments in his field
d)  speaker wants to teach some new
science to the listeners.

In the book I discuss talks of type a), b) and d) to some length, but I say noting about talks of type c). The basic reason being that talks of this type are very difficult to deliver.

Flavor of new developments
If you do not talk to specialists and you do want to drown your audience you have a very difficult task. In the first place be honest to your audience how difficult the subject is. Feynman says in his set of lectures
QED, The Strange Theory of Light and Matter about calculating (Feynman) diagrams: “It takes seven years to train our physics students to be able to do that trick.”
So you must separate those concepts that your audience can understand and those they cannot understand. Make clear that it is not your intention to impress them and that they must accept the fact that a number of things you present they cannot understand (you can make them plausible, though). Furthermore be very modest. Do not overload them with too much new information.

Use as many analogs from the daily life of your audience as possible (kitchen, billiard balls, apples, …).
Feynman is our great example here. The conservation law of the number of particles is brilliantly explained by Feynman with his amusing story of Dennis the Menace who is always mischievously hiding his toy building blocks from his mother.

Admit that there are a number of developments you, as speaker, do not understand yourself. Emphasize over and over again that the pleasure is in fundamental understanding and not in possible applications.
I give below some characteristics of talks of type b) to show what you should *not* do if you want to give your audience a flavor of your field.

Bad example: talks of type b)
Speaker comes with chaotic – but intimidating – slides, in false colors and with a lot of impressive formulas. He utters a lot of one-liners that are popular in the media. The orator speaks fast to extremely fast. There is no chance for the listeners to understand anything. The speaker gives two or three talks rather than one. He goes way over his time. He is abusing the question period to deliver the remaining part of his presentation. Any real question is received as an insult. The prevailing opinion in the audience is: “This guy is extremely smart and very enthusiastic. I wish I was that smart.”

Try it
Giving talks of type b) is so simple and requires so little preparation that many speakers cannot resist the temptation. I think you should see it as a real challenge and you should have the guts to, at least try, to give your lay audience a realistic insight in your field, rather than drowning them.

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