Final answer:
Dark matter is invisible because it does not emit or interact with electromagnetic radiation like visible light, radio waves, or X-rays, and its presence is inferred from gravitational effects such as gravitational lensing and the rotational speeds of galaxies.
Step-by-step explanation:
The reason why we can't see dark matter is because it does not emit or interact with electromagnetic radiation in a way that we can detect. Unlike stars and gas clouds that emit light or radio waves, dark matter does not produce its own radiation and thus remains invisible to our telescopes. Dark matter's existence is inferred through its gravitational effects such as gravitational lensing, where light from distant galaxies is bent around invisible objects, indicating the presence of mass that can't be observed through conventional means. It's also indicated by the rotational speeds of galaxies, which are faster than they would be if only visible matter were present, suggesting additional, unseen mass.
Assertions that dark matter only emits infrared radiation and X-rays or that it's blocked by dust lanes are not consistent with evidence. Neither does the idea that all dark matter is simply too far away or doesn't exist aligns with current scientific understanding. The true nature of dark matter is still one of the biggest mysteries in astronomy and particle physics today.