Why is Dark Matter essential for understanding the universe?

[bolahab]

Why do we think there is a significant amount of Dark Matter in the
universe?
a) Descibe at least 3 independent situations which require Dark Matter to understand observations.
b) Why don’t we think that Dark Matter is baryonic?
c) What do we think is might be?

 

[Astronuc]

We respectfully request students to apply some effort and attempt an answer first, and show work before asking for assistance.

 

[bolahab]

Yeah for this question i did a lot of work on it, but I am trying to see what i got is right, and if does match what i get from you guys

 

[topherfox]

I think he wants you to show us your answers first, and we can tell you were you went wrong, otherwise, you are getting the smarter kid to do your homework.