Some of these are not problems so much as they are proposed solutions to problems: > Dark flow: Is a non-spherically symmetric gravitational pull from outside

Some of these are not problems so much as they are proposed solutions to problems: > Dark flow: Is a non-spherically symmetric gravitational pull from outside the observable universe responsible for some of the observed motion of large objects such as galactic clusters in the universe? I'd like separate lists of the problems (observations that don't fit understanding) and proposed solutions (Dark matter, Dark flow, etc).