Hi, I’m Marley, the astronomer here at the H.R MacMillan Space Centre.  

If you’re familiar with astronomy, you probably know gravity is an important force. For a refresher on gravity, take a look at our blog post, How Gravity Works. Because gravity is so widespread, you may think that it is the only force that plays a role in holding things together. In reality, there are four forces that describe every interaction we see in nature. They are the gravitational force, the strong force, the weak force, and the electromagnetic force. These four forces, the fundamental forces, govern the Standard Model of particle physics - the model that explains how the building blocks of matter interact.

In the Standard Model, there is a special kind of particle called a ‘boson’. Particles of matter exchange energy with each other by trading bosons. It is this exchange that causes the fundamental force. Three of the fundamental forces have their own unique type of boson: the strong force has the gluon, the weak force has the W and Z boson, and the electromagnetic force has the photon – the particle of light. The boson for gravity (a graviton) has not been found—yet! The force that we interact with every day, the force that keeps us on the ground, is not explained by the Standard Model, the model we use to explain everything else!  

Getting gravity to work with the Standard Model is quite the challenge. Gravity, while an infinite force, is the weakest of the four. This makes sense! Just the act of lifting our feet off the ground counteracts the force of gravity of the entire Earth. Gravity is a force explained on macro scales, the scales of stars and galaxies. We can see the effects of gravity with the ‘pulling’ of material towards an accretion disk of a black hole or the ‘pulling’ of asteroid towards the planet Jupiter. The other three forces are explained on micro scales. When we discuss these three forces, we are on the scales of the nuclei of atoms! Trying to make the two scales work together mathematically is very difficult. Luckily, at the scale of atoms, the effect of gravity is next to nothing. Weird right?  

The Standard Model works well, but it leaves many questions unanswered. Gravity aside, it also does not explain dark matter or dark energy; both mysteries in astronomy. Despite being difficult, scientists are still trying to solve these mysteries. Particle accelerators like CERN (Conseil Européen pour la Recherche Nucléaire", or European Council for Nuclear Research) and Fermilab are trying to solve these mysteries, and you can help! Check out the playlist below for some projects and activities for you to try.

Particles of the Standard Model (Image: Daniel Dominguez/CERN)



Astronomer's Playlist

Discover more about the Standard Model

Watch Jonathan Butterworth’s TED-Ed talk, What’s the smallest thing in the universe?

For a little extra reading about the Standard Model have a look at this short article for kids and then dive a little deeper with this article from CERN.

Use this interactive to discover more about the particles that make up the building blocks of our universe.

 Have some fun with particle physics and the subatomic world and play this online game. 

Ask yourself: Do you think gravity will ever fit into the Standard Model or will scientists come up with another model to explain how the basic building blocks of matter interact?


Contribute to science with these citizen science projects.

Help scientists look for signs of particles produced in the Large Hadron Collider at CERN with New particle search at CERN

Help measure dark energy of the young universe with Dark Energy Explorers

Ask yourself: How does it feel to help analyze scientific data?


But what about the Higgs boson?

The Higgs boson was discovered in 2012 and the physicists who discovered it were awarded the Nobel Prize. We’d need another blog post to talk about the Higgs boson. If you can’t wait for that watch this short video series from CERN about the discovery of this particle.

Part 1, Part 2, Part 3

Take your own tour of CERN  

 What’s next? Read this short article about five mysteries the Standard Model can’t explain.

Ask yourself: What do you think it would feel like to discover something no one else has discovered before?