Wilson Hall at the Department of Energy’s Fermilab, USA. <em>Photo: Reidar Hahn, Fermilab</em>
What do we know?
Particle physics explores the undiscovered universe from the vast extremes of space to the tiniest particles.

Wilson Hall at the Department of Energy’s Fermilab, USA. Photo: Reidar Hahn, Fermilab

This much we know.

That the universe is vast and bounded only by the limitless confines of space and time. That particles of matter fill this space and time, and that forces bring structure to it all. This much we know.

The science of particle physics explores the relationship between space, time, matter and forces. Its ambition is no less than to illuminate our world and the universe we inhabit at the most fundamental level. Particle physics, the science of the very small, teams up with cosmology, the science of the very large, using observation and experiment to navigate the undiscovered universe from the vast extremes of space to the tiniest particles.

Looking out into space, we observe that at the largest scales, matter is organized into structures like galaxies. Studying the world around us, we find that at smaller scales, it is organized into stars, planets, people and atoms. And using the tools of particle physics to look deep into inner space, we discover the nuclei of atoms and the fundamental particles and forces that are the building blocks of everything.
Particle physics experiments have shown that, at the most basic level, all the variety of matter that we see around us, from the flowers in the field to the stars in the sky, consists of just a handful of fundamental particles and four forces acting among them. It’s a simple and elegant picture. At the largest scales, the force of gravity is master, corralling matter into beautiful swirling galaxies. Stars, planets, people and atoms dance to the tune of electromagnetism, which holds electrons in orbit around atomic nuclei and gives structure to everything we see. At the smallest scales, nuclear forces, strong and weak, take over. The strong force binds nuclei together, while the weak force drives the stellar furnaces that bring light and energy to us all.

A centuries-long journey of discovery has shown us that the Earth is round, that apples fall from trees for the same reason that Earth orbits the sun, that we can master natural phenomena like electricity and magnetism to the benefit of all. Particle physics and cosmology beckon us onward in the next phase of our journey.

Advances in these fields have let us voyage back in time to the point when the universe became transparent. We have witnessed the birth of the first galaxies and the ignition of the first stars. By studying fundamental particles, we have pieced together a detailed understanding of particles and forces. Along the way we have fostered new technologies in fields as diverse as medicine and information technology.

This much we know. But there’s one more thing our research has told us: we have much more to learn.
From the flowers in the field to the stars in the sky, matter consists of fundamental particles and forces.