The longest-running scientific experiment in the world is a pitch drop experiment that began in Queensland, Australia, in 1927 (described in this post). The setup is basically putting pitch in a funnel and see if it drips out. The point is to prove that pitch is a viscous liquid that will flow, instead of a solid. The problem is that it takes years for a drop to actually drop, and has never been witnessed. A similar experiment was begun in 1944 at Trinity College in Dublin, Ireland. Now, for the first time, a drop has been recorded!
Over several decades a number of drips did form in the funnel and fall into the jar, giving credence to the hypothesis that pitch is indeed viscous.
However, the dripping was never witnessed or captured on camera, which would have definitively proved the theory.
A number of weeks ago, scientists in the department noticed that a drip had formed.
In order to finally and definitively end the experiment, they set up a webcam to video the experiment around the clock.
Last Thursday, the drip finally dropped into the jar, and was captured on camera.