“What is the smallest thing in the Universe that actually exists?”
— Mimi, age 12, Abeokuta, Nigeria
To find an answer, we asked physicist Omololu Akin-Ojo, who teaches this subject. A physicist is someone who studies physics. Physics is the science of energy, forces and particles. We study physics in order to be able to manipulate energy, forces and particles for our benefit. For example, to create electricity or motion to move a car.
So, what’s the smallest thing in the universe?
Thank you for your question.
Take a piece of anything, cut it into tiny pieces, cut the tiny pieces into tinier pieces (at this point you might need a magnifying glass or microscope to see what you are cutting), and continue to cut them into yet tinier pieces. After a point, you will not be able to see the particles, even with microscopes. Suppose we can continue this process until we get to a point where we cannot cut the tiny pieces into tinier pieces any longer.
Then we have reached the level of the atom. An atom is so small you can’t see it, but atoms are everywhere.
To start with, what is an atom?
The word “atom” is from the Greek word atomos, which means “uncuttable”. This is the smallest particle in the universe that behaves “normally”. Normal behaviour for a particular atom means that it is neutral (not electrically attracted to other particles) and still retains chemical properties from the substance from which it was cut.
However, scientists have found that the atom is made up of even tinier particles: electrons and the nucleus.
The electron is one of the tiniest particles that exists.
Inside the nucleus, we have protons and neutrons and inside these there are quarks. Quarks are as tiny as electrons. When atoms break up, other particles, called neutrinos, may be released. Although they are not tinier than electrons, neutrinos might weigh less than electrons – we are not certain.
Scientists have also been able to smash particles together by giving them a lot of energy and making them collide with one another. When particles smash into each other, sometimes we get other particles that are as tiny as electrons but weigh more than electrons. Their names are muons, tauons and pions. We cannot see them with our naked eyes, but scientists have been able to create environments such that when these particles move in them, we can see their paths.
So, Mimi, the electron is the tiniest particle. Then there are neutrinos, which are as small (but may or may not weigh more). Then we have quarks (which are found inside protons or neutrons) and also we have muons, tauons and pions, which are as small as electrons but weigh more.
Everything in the world is made up of all these tiny pieces. They’re everywhere.
Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.
And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.
This article is republished from The Conversation under a Creative Commons license.
