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[–]roc 1 insightful - 1 fun1 insightful - 0 fun2 insightful - 1 fun -  (1 child)

Dark matter and dark energy are not undetectable. They are the names for something that clearly influences matter in the galaxy through gravity. For dark matter there are even maps where it is calculated to be more and less dense. This is mostly at the same place as galaxies and clusters. But dark matter and dark energy do not interact through electromagnetism, this is why they are called dark.

Black holes can be very visible through their accretion disks. The black hole in the center of the Milky Way galaxy has not been photographed yet because the center of the galaxy is full of many stars that are a lot brighter than this black hole's accretion disk. But since 10 April we have a picture of a black hole with an accretion disk in the galaxy Messier 87.

About your question: if string theorists are to be believed, there are many hidden dimensions on a very small scale. I don't think string theory is a useful development in theoretical physics, because it has not provided any observable predictions.

[–]zyxzevn[S] 1 insightful - 1 fun1 insightful - 0 fun2 insightful - 1 fun -  (0 children)

Good answer.
String theory gives us indeed lots of invisible dimensions.

[–]zyxzevn[S] 1 insightful - 1 fun1 insightful - 0 fun2 insightful - 1 fun -  (0 children)

Virtual particles - They are mainly a theoretical placeholder.