3 Physics Experiments that Changed the World

3 Physics Experiments that Changed the World, presents you with experiments that have changed everything we know and do.

1. Henry Cavendish Measures Gravity

While Newtons discovery of gravity was amazing, not everyone believed him and it was difficult to prove. In 1797 Henry Cavendish set out to demonstrate what Isaac Newton had been saying for years, that even small masses exert a gravitational force on one another.

To do this he used a torsion ball experiment which sounds super complicated but  is basically a wooden rod suspended on a wire with a small lead ball on either end, then he mounted a much larger ball near each small one. He found that the small ones gravitated towards the big ones allowing him to actually measure the force of gravity, and thus determine the gravitational constant of the universe.

2. Thomas Young made Waves

Young helped revolutionize how we think about light. There was constant debate among physicists at the time as they didn’t know if light moved as beam of particles or as a wave, with most siding with Newtons theory of particles.  Young decided that Newtons beam theory didn’t quite fit properly, like how does it become subject to refraction?

He put the particle theory to the test by covering a window with paper containing a small hole. He bounced the beam coming through off a mirror and then held a thin card up to it and diverted the beam into two. The results, a pattern on the wall that looked very similar to what happens when two ripples of water meet. This was an risky experiment because he had contradicted newton and launched the 200 year debate of what light is. As it turned out they were both equally right and wrong, light is basically both, exhibiting wave-particle duality.

3. Ernest Rutherford Figured out what the atom looked like

By the early 1900’s people still didn’t know fully what  the atom looked like with the current theory at the time being the dreadfully flawed ‘plum pudding’ model. this suggested electrons floated around in a positively charged cloud that held them together, like plums stuck in a pudding.

In 1909 he and his colleagues aimed a beam of alpha particles at a thin layer of gold foil and stated if the plum pudding model was correct than the alpha particles would have passed straight through. While most did as expected, some alpha particles bounced back.

He concluded that atoms must have a solid core containing a slightly positive charge that repelled the alpha particles when they hit them. He then figured that if this was the case then electrons must be surrounding these and moving around them, meaning most of atoms, and everything is just empty space which is how most alpha particles had passed straight through. This is still the model we use today, with a nucleus of protons and neutrons surrounded by orbiting atoms.