Turning Points in Physics

Observed that the gas glows and that the area of fluorescence can be moved by a magnet. Also, that the tube gets hot

Cathode rays must be negatively charged due to the way that they are deflected by a magnetic field

Shows that rays are emitted perpendicular to the cathode. If the cathode was concave, the rays could be directed at a point

Showed that the gas inside the tube changed the colour of the glow. Eg. Neon was red and oxygen was a faint purple

Showed that cathode rays can pass through thin metal foil without puncturing it, so they must be much smaller than atoms.

Put a metal can in the tube, connected to a negatively charged electroscope. The leaf rises further - providing conclusive proof of negatively charged particles.

Measured the specific charge of an electron, and is usually credited with their discovery

Measured the charge on an oil drop and observed that their charges were always multiples of 1.6x10^-19, hence discovering the charge on an electron.
This meant that mass could also be calculated using Thomson's specific charge

Huygens believed that light was made of waves.
His evidence is that when two rays of light cross, they do not scatter, instead they emerge unaffected (like waves)
He proposed that space is filled with an invisible medium called the Ether, through which light can travel.
He predicted that light would move slowed in water than in air

Newton believed that light consists of streams of corpuscles travelling in straight lines
His evidence is that light casts sharp shadows, doesn't diffract (later disproven) and that no wave can travel through a vacuum, but light can.
He predicted that light would move faster in water than in air