Dark matter is a form of matter that makes up about 27% of the universe, far more than the 5% made of normal matter like stars, planets, and people.

Like normal matter, dark matter has mass and occupies space. However, it differs in a key way: it does not interact with light. It does not emit, absorb, or reflect light, which makes it completely invisible.

Even though it’s invisible, we know dark matter exists because it interacts with gravity. While light does not reveal dark matter directly, gravity does. Its presence can be detected through the way it influences the motion of galaxies and galaxy clusters.

Although its effects are well measured, the true nature of dark matter remains unknown—making it one of the greatest open questions in modern physics.

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