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The Composition of the Visible Universe: Beyond Ordinary Matter
The Composition of the Visible Universe: Beyond Ordinary Matter
Our exploration of the visible universe begins with the building blocks familiar to us: protons, neutrons, and electrons. These elements, combined into atoms, form the stars, planets, and galaxies that make up the cosmos we observe. However, a profound and surprising discovery of the 20th century revealed that ordinary matter, or baryonic matter, accounts for less than 5% of the mass of the universe. This revelation challenges our understanding of the composition of the visible universe and leads us to question what comprises the remaining 95%.
Defining the Undefinable
The search for an answer to the composition of the universe extends beyond the physical sciences. Philosophers like Georg Wilhelm Friedrich Hegel, in his work Science of Logic, propose that the unseen governs the seen. Hegel suggests that the observable universe is a manifestation of an underlying, pure, or absolute spirit. While this answer may not be tangible, it offers a profound perspective on the nature of existence. Similarly, ancient Greek philosopher Anaximenes of Miletus posited that the air (or aether) is the root substance of all things, even providing a simple, yet profound, model for the composition of the universe.
Visible vs. Invisibly Abundant
When we look through a telescope, we see a vast array of galaxies, stars, and planets, but the majority of the visible universe is made up of hydrogen. This is not just a mere coincidence; hydrogen is the crucial element that fuels the fusion reactions in stars. The energy released from hydrogen fusion is what powers the stars, and thus, the vast majority of the luminous universe is made of hydrogen.
However, if we are interested in quantity rather than visibility, the most prevalent forms of matter in the universe are not what we can see. Scientists estimate that ordinary matter, which includes hydrogen and helium, only makes up about 5% of the total mass-energy content of the universe. The rest is dominated by dark matter and dark energy. Despite the elusive nature of these forms of matter and energy, they play a crucial role in the structure and dynamics of the universe.
The Elemental Composition of the Universe
Considering the known elements that make up the universe, hydrogen reigns supreme. According to the Abundance of the Chemical Elements table, about 75% of the universe is hydrogen by mass. Helium follows, making up about 24%. All other elements, including oxygen (which comes next in abundance), account for less than 1% of the universe's mass.
This vast abundance of hydrogen has significant implications. The universe's galaxies, stars, and all the luminous matter we can observe are composed primarily of hydrogen and helium. However, the unseen dark matter and dark energy dictate the large-scale structure and evolution of the universe. While dark matter does not emit, absorb, or reflect light, it interacts gravitationally with the rest of the universe, shaping the cosmos in ways we can only infer.
Conclusion
The visible universe, a fascinating mirror of the cosmos, is a result of the ordinary matter that we can see. But the universe extends far beyond the visible, with the majority of its mass-energy content being dark matter and dark energy, which remain mysterious and elusive. As we continue to explore and understand the universe, we must remain open to the ideas that both ordinary matter and the unseen forces contribute to the intricacies of existence.