Recently I had the opportunity to give a blackboard talk. I’ve talked before about the value of blackboards, how they facilitate collaboration and can even be used to get work done. What I didn’t feel the need to explain was their advantages when giving a talk.
No, the blackboard behind me isn’t my talk.
When I mentioned I was giving a blackboard talk, some of my friends in other fields were incredulous.
“Why aren’t you using PowerPoint? Do you people hate technology?”
So why do theorists (and mathematicians) do blackboard talks, when many other fields don’t?
Typically, a chemist can’t bring chemicals to a talk. A biologist can’t bring a tank of fruit flies or zebrafish, and a psychologist probably shouldn’t bring in a passel of college student test subjects. As a theorist though, our test subjects are equations, and we can absolutely bring them into the room.
In the most ideal case, a talk by a theorist walks you through their calculation, reproducing it on the blackboard in enough detail that you can not only follow along, but potentially do the calculation yourself. While it’s possible to set up a calculation step by step in PowerPoint, you don’t have the same flexibility to erase and add to your equations, which becomes especially important if you need to clarify a point in response to a question.
Blackboards also often give you more space than a single slide. While your audience still only pays attention to a slide-sized area of the board at one time, you can put equations up in one area, move away, and then come back to them later. If you leave important equations up, people can remind themselves of them on their own time, without having to hold everybody up while you scroll back through the slides to the one they want to see.
Using a blackboard well is a fine art, and one I’m only beginning to learn. You have to know what to erase and what to leave up, when to pause to allow time to write or ask questions, and what to say while you’re erasing the board. You need to use all the quirks of the medium to your advantage, to show people not just what you did, but how and why you did it.
That’s why we use blackboards. And if you ask why we can’t do the same things with whiteboards, it’s because whiteboards are terrible. Everybody knows that.
4 gravitons 
Yes, blackboard are great – but have you tried out an interactive white board. Using them all the while when teaching – can use great combination of prepared slides, software and ‘write on board’ all in one.
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I’ve taught on one once. They’re quite handy, I’ll agree, and give you a lot of versatility in the classroom. I wouldn’t use one for collaborating or giving a blackboard-style talk, though, for essentially the same reasons I don’t like whiteboards, because writing on them tends to strike me as crude and cartoonish.
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The best thing about a blackboard talk is that it forces the speaker to *slow down* instead of using 24 slides/second…
Whiteboards are an invention of the devil.
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“Using a blackboard well is a fine art, and one I’m only beginning to learn. You have to know what to erase and what to leave up, when to pause to allow time to write or ask questions, and what to say while you’re erasing the board. You need to use all the quirks of the medium to your advantage, to show people not just what you did, but how and why you did it.”
These are the reasons why I, too, prefer giving blackboard talks. Blackboard talk provides a good opportunity to demonstrate a theoretical work in a lucid way. Presentation based on slides does not/ can not capture the essence of equations (i.e flow of logic). I don’t have any problems with whiteboard though.
Also I find the combination of slides and blackboard to be quiet effective.
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