It's difficult to definitively declare one experiment as the "shortest" in scientific history, as "short" can be interpreted in various ways: duration, complexity, or the number of steps involved.

However, there are a few contenders for the title:

* Michelson-Morley experiment: While this experiment itself took several weeks to complete, the key measurement that proved the non-existence of luminiferous aether was conducted in a single day. This single day's observation had profound implications for our understanding of light and the universe.

* Rutherford's gold foil experiment: This experiment demonstrated the existence of the atomic nucleus, and while the setup and data analysis took time, the actual scattering of alpha particles occurred in a very short period.

* The experiment that "disproved" the existence of N-rays: This experiment, conducted by Robert Wood, took mere seconds to disprove a claimed scientific phenomenon that had been the subject of extensive research for years.

Ultimately, the "shortest" experiment depends on how you define "short". It's worth noting that even the shortest experiments can have profound implications for science and our understanding of the world.