What was your favourite historical scientific experiment and why?

Question

What was your favourite historical scientific experiment and why?

Answer 1

Rutherford's scattering experiment.  It's my favorite because he didn't ignore the outlying data points and was smart enough to recognize they meant something.  It also led to a huge advancement in understanding of atomic structure.  Ironically, the experiment for which he is most know for, was not the research that won him his Nobel Prize.  The scattering experiment was done in 1911, his Nobel Prize (in Chemistry) awarded in 1908.  

Answer 2

The genetics and botanical inheritance experiment of Gregor Mendel - - he is a great scientific exemplar because he was so systematic and thorough - - his work outshines Watson & Crick of the shape of DNA in that he did work away from the glare of publicity and reward and a typical need for fame/awards:

"Earlier scientists had noticed the disappearance and reappearance of traits in hybrid plants. What Mendel did differently was count. And count. And count. Mendel used mathematics to draw conclusions about what was happening deep inside the cell.

Mendel concluded that every trait must be controlled by two “elements” (what we now call genes) that are present in every pea plant. As part of sexual reproduction, these elements separate and only one is passed down to the offspring. Whether a plant has green or yellow peas depends on the combination of elements that it received from its parents. If a plant receives two dominant elements, its trait will be dominant (i.e. yellow peas). If it receives two recessive elements, its trait will be recessive (i.e. green peas). If it receives one of each element, the dominant trait will mask the recessive trait. This is what caused all the green peas to disappear in Mendel’s first generation of plants."