When we think of space, we usually imagine stars, planets, and galaxies. However, most of the universe—the space between these celestial objects—is almost completely empty. In fact, on average, there are only a few atoms in each cubic meter.
The most common atoms in that average cubic meter space are hydrogen and helium, which constitute the majority of the intergalactic medium. These atoms are not neutral, but rather exist in an ionized state, forming a plasma. This plasma is created due to the high energy levels present in space. The vast distances and low densities in space mean that reactions occur at much slower rates than we observe on Earth, making it fill like nothing is happening.
However, behind the cover, space is teeming with activity on both macroscopic and microscopic scales, with quantum field fluctuations, virtual particles, and cosmic rays. Quantum field fluctuations are temporary changes in energy that occur in empty space due to the uncertainty principle, while virtual particles are short-lived particles that pop in and out of existence as a result of these fluctuations. Cosmic rays are high-energy particles, mostly protons, that travel through space at nearly the speed of light and originate from sources like supernovae or distant galaxies.
Ultimately, the emptiness of space highlights how exceptional it is for complex structures, like stars, planets, and even life, to form. In a universe filled with so much emptiness, each piece of matter stands out as something rare and precious.
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