Introduction to Elementary Particles

Cosmological Research on Elementary Particles and Forces

Particle Accelerator

Near Geneva, on the Swiss-French border, lies the Large Hadron Collider (LHC). The LHC is an underground particle accelerator, 27 kilometers in circumference, located about 100 meters below ground. Scientists use this accelerator to study tiny particles called protons, which are parts of hydrogen atoms.

Scientists speed up these protons to nearly the speed of light. At this speed, protons travel around the 27 km ring 11,000 times per second.
Scientists then collide the protons with other protons going the opposite way. These collisions happen inside large detectors that work like digital cameras.
The detectors can capture conditions as they were less than a billionth of a second after the universe began, up to 600 million times per second. Scientists use big magnets to measure the speed of the particles.

The goal is to create mini Big Bangs to understand how everything is made and connected. This includes molecules, humans, the Earth, the Sun, and all stars in our galaxy and the universe.

Elementary Particles and Forces

When cosmologists look back in time, they find the universe was hotter, denser, and simpler. In the early universe, matter and space were very simple.
Today, the universe is made up of twelve elementary particles held together by four fundamental forces.

From Atoms to Quarks

Quarks are particles that make up protons and neutrons, which are found in all atomic nuclei.
Electrons are particles that orbit the atomic nucleus. They are held in orbit by the electromagnetic force, carried by photons. Quarks are held together by gluons.

Image A: The Atom Analyzed.

The Fundamental Forces

One of the four forces, the 'weak nuclear force', is less known. The Sun shines by emitting particles called neutrinos.
About 60 billion neutrinos pass through every square centimeter of your body every second, but you don't feel them due to the weak nuclear force. This force works over short distances and is very weak, allowing neutrinos to pass through your body.

Most particles were discovered in the last century. The electron was found in 1897, and the tau neutrino in 2000.
The biggest scientific achievement of the 20th century is discovering the patterns of elementary particles and the laws of particle physics. This is called the "standard model," which is a complex mathematical equation.

Diagram A: Twelve Elementary Particles and 4 Forces.

Cosmology helps us understand the universe and our place in it by studying these tiny particles and the forces that hold them together.