What Is The Universe Made Of?

The universe contains all that we know to exist. Every planet, moon, star, and galaxy is contained within the known universe. However, what is all of this made of? Things like planets and stars look tremendously different from each other, and certain celestial objects are made of different elements and compounds. Overall, what is the universe made of?

Matter And Energy

Galaxy
Visible matter in the universe is composed mostly of hydrogen and helium, with only small amounts of all other elements. Image credit: NASA/ESA

Technically, one could argue that the universe is made of only two ingredients: matter and energy. However, we can actually take this a step further and say that energy is the only ingredient of the universe. That’s because, as Einstein showed with his famous equation E=MC^2, all matter is just a form of condensed energy. When the universe began in the Big Bang some 13.8 billion years ago, all that existed for the first second of time was pure energy, which eventually condensed to form the first forms of matter. Matter itself is composed of all the known elements on the periodic table. The periodic table contains 92 naturally occurring elements. Of those 92 elements, only two make up nearly all forms of visible matter. Hydrogen is the most abundant element in the cosmos, comprising a staggering 73% of all elements. Meanwhile, 25% comes in the form of helium. That means that only 2% of all the matter we can see is composed of every element other than hydrogen and helium. When we look out into space, all the planets, stars, and galaxies are primarily composed of just hydrogen and helium. Furthermore, nearly every element contains protons, neutrons, and electrons. 100% of elements are composed of some variation of these particles. Protons and neutrons themselves are composed of quarks, and so all visible matter is composed of basically just quarks and electrons. 

The Universe We Cannot See

Galaxy cluster
Galaxies are held together by dark matter, while dark energy is causing most galaxies to move away from each other. Image credit: NASA/ESA

Although all that we can see is composed of only a few ingredients, there is more to the story. All the visible matter in the universe comprises a mere 5% of the total amount of stuff in the cosmos. The remaining 95% of the universe is made of dark matter and dark energy. Dark matter makes up roughly 27% of the universe, and dark energy makes up the remaining 68%. This means that the stuff that makes up most of the universe is completely invisible to our eyes. In fact, neither dark matter nor dark energy interact with light or visible matter. The only reason dark matter is known to exist is because of its gravitational pull, while dark energy is causing the universe itself to expand. Thus, the universe is mostly composed of dark matter and dark energy, and even the small amount of visible matter is made almost entirely of quarks and electrons. 

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