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What are the building blocks of matter?

What are the most fundamental building blocks of all matter -- the pieces of matter that make up everything from flowers to people to galaxies and cannot be broken down into anything smaller?

Model of a Helium Atom

This helium atom is not drawn to scale. In a real atom, the protons and neutrons are far larger than quarks and electrons, and there would be much more empty space. In fact, if this atom were the size of a large city, each proton and neutron would be the size of a person, and each quark and electron would be smaller than a tiny freckle.

Scientists once thought the most fundamental building block of matter was a particle called the atom. Now we know that the atom is made of many smaller pieces, known as subatomic particles.

Every atom contains a central core called the nucleus, made of particles called protons and neutrons. The nucleus is surrounded by mostly empty space, except for very tiny particles called electrons that orbit the nucleus. Recently, scientists have discovered that protons and neutrons are made of smaller particles known as quarks.

Today, physicists don't know of anything smaller than quarks and electrons, but they don't know for sure whether these are the simplest building blocks of matter.

The Heart of the Matter



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