In 1927, a researcher at the University of Queensland in Australia began what's widely recognized as the longest-running experiment ever, the so-called "pitch drop." It's a simple set up: fill a flask with tar pitch and let it ooze out the bottom to see how quickly it flows, and eventually it makes a proper drop that falls down — about once every ten years or so. Tar pitch is a substance that appears to be solid, but in fact is actually a slowly flowing liquid. However, since the beginning of that experiment human eyes have never actually seen the pitch drop from the bottom of the flask — the last time the Queensland experiment dropped, the webcam that was set up to see it failed at precisely the wrong moment.

Fortunately, another experiment was also set up in 1944 at Trinity College in Dublin, Ireland. At 5PM local time on July 11th, the drop finally happened and was caught on video. You can see a time-lapse video of the event below, or tune in to the live view of the original experiment at the University of Queensland to wait for the next drop. Fair warning: it'll be awhile. If you're interested in learning more about the experiment, Radio Lab did a show on the subject this past February.