September 6, 2023

Tsz Kiu Amanda Leung

9th Grade

Diocesan Girls' School

We live in a world of protons, neutrons, and electrons. However, if we examine the universe as a whole, all light and atoms, “normal matter,” only make up about 5% of the cosmos. If so, what exactly is the remaining 95%, and how do we find it?

A concept first proposed in the 1930s by Fritz Zwicky, dark matter was only confirmed by Vera C. Rubin and her colleagues in the 1960s, making it a very recent discovery. Our universe is mainly dark matter and dark energy, where dark matter makes up about 27% and dark energy roughly 68%. One view of dark matter is that it is non-baryonic - that is, it is not made up of protons and neutrons, but other particles, such as leptons, quarks, or axons. Scientists generally agree that dark matter is a new, invisible type of particle that our sensory equipment cannot pick up. Since light passes through dark matter, we have not seen dark matter directly. Instead, we discovered its existence by analyzing gravitational events and calculations influenced by the mass of dark matter. Another theory is that dark matter can be explained by changing our theories on gravity - perhaps there is another system of gravity that could describe why and how dark matter behaves. 

How exactly do we find the invisible? Scientists study dark matter by observing the gravitational effects of it on visible objects. Gravity bends rays and affects what we can see in space, just as water distorts light. Astronomers use gravitational lensing, which entails observing the gravity of massive galaxy clusters that contain dark matter and affect the light from other galaxies behind the cluster. Using mathematical models, scientists consistently determine that there is about five times as much dark matter as normal matter in the universe. Dark matter also binds galaxies that would otherwise break apart. 

Dark energy is a newer and possibly more groundbreaking discovery. Before its discovery, we thought the expansion of the universe would gradually slow due to the effects of gravity. However, through numerous observations, we found that the cosmos is expanding increasingly over time. Dark energy drives this expansion of the universe against gravity, yet not much more is known. Why dark energy exists also remains a mystery. 

Throughout history, we have sought to discover more about the universe through improving technology. Through Galileo's telescope, we saw parts of the cosmos previously invisible to us, and greatly increased our understanding of space. Modern innovations such as the James Webb Space Telescope by NASA and the Euclid spacecraft mission by the European Space Agency have already greatly advanced our understanding of dark matter, black holes, and energy. As aerospace technologies improve, it is certainly possible to uncover more mysteries of space.