ferente to the screen. Audiences are especially scornful of speake speaker who rambles on after the timer has sounded. who load their presentations with equations because of a Even in less formal settings, a speaker who ignores the prescribed time limit will quickly alienate nearly every cheguided belief that the mathematics alone will imbue eir work with a more scientific or rigorous flavor yut Talk is lll time. To do so is extremely egotistical, and even if your au- impress your audience with your proficiency in doing dience is courteous enough to let you continue, they will algebra. There is seldom any need to drag your audience 芝 step by step through a derivation or the solution to an But in, say, 10 minutes, how can you possibly convey n. Audiences will happily assurme that you can the significance of the work that you sweated over for the solve equations, so forget the algebra and focus instead on past two years? Rest assured that all speakers wrestle the assumptions that led to the equation, the technique with this problem. The key principle is that virtually ar that you used to solve it and a careful explanation of the topic can be presented in any amount of time. One cor relevance of the solution to your to compress the history of the world into 30 seconds if And finally, keep in mind that audiences need a bit of necessary, or stretch out a treatise on the eating habits of extra time to assimilate mathematics, so try to make their the flea to a yearlong series of weekly lectures. (Admitted- job as for them as possible. It's particularly s hard to imagine either commanding a very large important to dehne any unfamiliar symbols and to avoid audience. umbersome notation. If you're only going to use the Speakers often erroneously assume that very short scalar form of an equation, then write it out using that no time limits mean they must emphasize generalities and tation and leave the generalized tensor version for the gloss over specifics. However, you ll almost always give a textbooks. And dont just plunk down the equation and more lively and interesting talk if you narrow rather than then stand there like a tombstone for 60 seconds while widen the scope of your remarks. Thus if you' re giving a your audience studies it. You should always talk through lecture to the local astronomy club, it's better to spend any equation you show your audience. For example, as your 30 minutes speaking on"The Rings of Saturn"than you're writing out E=me the blackboard, you should on‘ The Planets of th by the sq weed out relentlessly any extraneous subject matter. Any of the speed of light tables or figures or equations that dont contribute specifically to the one or two points you're making must Be sensible about transparencies go, no matter how interesting they may be in their own The overhead projector has in the past decade become the prop up their talks with diverting little sidelights. transparencies for a talk-typically 3 to 6 for a 10-minute Unfortunately, the effe 10 to 15 for a half-hour talk. Al But what should you do if you' ve got 30 minutes worth you should allow several minutes for an audience to absorb of in formation to ust never do is attempt to squeeze your talk into the overwhelm your audience. permitted time slot by speaking rapidly, flashing through You needn't write out full sentences on your transpar. your slides and frantically scribbling on the blackboard. a encies (although you should certainly speak in full w years ago i attended a department colloquium during ntences). In other words, if you re planning to say our which the speaker, a candidate for a faculty position, easurements showed that the period of the pendulum ipped through more than 60 transparencies. I cant was independent of the mass of the emember now what his talk was even about, but I can your transparency should read, "Period was independent easily recall how irritated I felt and how I never wanted to mass. But don't get carried away. It has lately become Use mathematics and equations sparingly often sees transparencies that are meaningless lists of words, abbreviations and sentence fi It is not difficult to integrate equations, into your talk if eral rule is that the transparency text should be absolutely certain that the a ple precautions. First, make enough to be self-explanatory but no more than t tions are necessary, and if Learn where the light switch, focus control and harder pointer are located before your talk. Also give some to understand, they slow the pace and the ought to where you'll stand, because you'll ofter creating confusion. If overdone, they al resent- blocking the view of part of the audience if you stand beside nent; one literally will hear groans from an audience the projector, if that's the case, stand next to the screen and when a speaker flashes an equation-filled transparency on use a pointer. Make sure you've got a table to set your PHYSICS TODAY JULY 1991 43