Galactic Ghosts: How Dark Matter Haunts Our Cosmos

Dark matter is one of the greatest mysteries in modern science. Despite being invisible and undetectable by traditional means, it makes up approximately 27% of the universe’s total mass and energy. It does not emit, absorb, or reflect light, making it completely transparent to current observational instruments. However, scientists are certain of its existence due to its gravitational effects on visible matter, radiation, and the large-scale structure of the universe. Its discovery has led to a major shift in our understanding of the cosmos, revealing that most of the universe’s matter remains hidden from our view.

The term "dark matter" was first introduced in the early 20th century, but it wasn’t until the 1970s that astronomers began to recognize its significant role in the universe. In 1933, Swiss astronomer Fritz Zwicky observed the motion of galaxies within clusters and noted that the amount of visible matter in these clusters was insufficient to account for their observed gravitational effects. This led him to propose the existence of an unseen form of matter, which he referred to as "dark matter." Over the following decades, similar observations were made by astronomers studying the rotation of individual galaxies. The rotation speeds of galaxies were found to be much higher than what could be explained by the visible matter in the galaxies. This discrepancy suggested that there was additional, unseen matter providing extra gravitational pull, keeping the galaxies intact and preventing them from flying apart.

Dark matter does not interact with light or other forms of electromagnetic radiation, which is why it cannot be directly observed. It’s not made up of the usual atoms and particles that constitute the familiar matter we see in everyday life. Instead, it seems to consist of particles that do not interact with electromagnetic forces, which is why they are invisible.

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Lydbog: 8. april 2025