As discussed in some earlier comments, it’s worth asking why physicists still bother flying around and giving talks, since we could easily just record a single example of each talk and make it available on the web for perusal at one’s leisure. Of course, we could say the same thing about, for example, any class you take at school — why bother with live teachers, when we could just play a video of some classic lectures? And why go to concerts if we can listen to recordings of some previous live performance? Or why bother meeting friends for a drink, when we can drink at home while sending email back and forth?
Enough sarcasm — it’s actually a good question, but to me it’s clear that the opportunities for direct interaction make all the traveling quite worthwhile. Still, you can’t always get everyone interesting to come give a talk, which is why it’s extremely useful to have talks online. With that in mind, here is my recent talk on “Why is the universe accelerating?” in various formats — html slides, pdf slides, and an actual video (some of me, but mostly of slides). The video is from the talk at Goddard Space Flight Center, which was marred by a computer glitch, so some of the graphics are missing.
I hope everyone understands what a style-cramping thing it is to give away talks online. Of course people who give a lot of talks will use basically the same slides over and over — no reason not to, if the new audience hasn’t yet heard the talk. More importantly, though, one tends to use the same jokes over and over, usually with some confidence that they’re new to this audience. Now that the whole internet can hear my talks ahead of time, does this mean I have to come up with new jokes?