How did physicists detect particles in the past?
Cloud chambers or bubble chambers
How do cloud or bubble chambers work?
These detectors produce tracks when particles pass through them.
You can work out the type of particle from the type of track it made.
In 1936, two Americans discovered a particle like an electron, but bigger. What sort of particle was this?
For over 100 years now, how have scientists tried to detect particles?
They accelerate small particles and collide them into matter. By looking at what came out of the collisions, they work out what is inside matter.
This work is similar to Rutherford’s experiments. What did Rutherford fire at gold foil?
Positive alpha particles.
What did Rutherford discover?
The positively charged nucleus (containing protons and neutrons) at the centre of an atom.
What is the largest particle accelerator in the world called?
The Large Hadron Collider (LHC) in Switzerland.
How does the LHC accelerate particles?
With a very strong electric field.
How fast can these particles be accelerated?
Close to the speed of light (300 000 000 m/s)
What are the detectors at the LHC?
Made of semiconductors that detect the mass and charge of a particle.
When scientists smashed protons and electrons together, what did they find?
They found that some electrons bounced off particles much smaller than a proton. This is similar to alpha particles in Rutherford’s experiment
They found particles inside protons and neutrons. What are these called?
In 2012, they discovered a particle that gives everything mass. What is this called?
The Higgs boson
Compare how particles are detected today with Rutherford’s experiment.
In both, particles were accelerated, and collided with an object (nucleus or other particles).
However, Rutherford worked out what is in an atom, the LHC was looking for a new particle.