Matter can pass through dark matter without colliding because dark matter particles are thought to interact only weakly with other particles, including normal matter particles.
While normal matter particles such as protons and electrons interact with each other through the electromagnetic force, dark matter particles are believed to interact only through the weak nuclear force and gravity. This makes dark matter particles much less likely to collide with normal matter particles, since the electromagnetic force is much stronger than the weak nuclear force.
Furthermore, dark matter particles are believed to be “non-relativistic,” which means that they move relatively slowly compared to the speed of light. This makes them less likely to interact with normal matter particles, which are typically moving at much higher speeds.
Although dark matter is thought to be abundant and to have strong gravitational effects on the motion of normal matter in the universe, its weak interactions with other particles make it difficult to detect directly. Researchers use a variety of techniques, such as observing the effects of dark matter on the rotation of galaxies or the large-scale structure of the universe, to infer its presence and properties.
In summary, matter can pass through dark matter without colliding because dark matter particles are thought to interact weakly with normal matter particles, and because they are typically moving at much lower speeds than normal matter particles.