- What happened in that initial instant we call the Planck Era (0 to 10-43 seconds)? Our current physics does not allow for measurements of such small periods of time and space.
- What was the mechanism for galactic formation? Cosmologists seem to be getting some resolution on this issue.
- Where is the Dark Matter? Dark Energy?
- Where did the initial matter and radiation come from? Who did it – or did anyone?
- What is the age of the Universe? Yet this issue seems to be less and less of a question among physical cosmologists, given a much better defined number for Hubble’s constant (Ho) and other supplementary cosmological data.
Technically, physical cosmologists do not see any of these issues as unsolvable, even the question of where did everything come from since they are mostly concerned with what happened after the Big Bang. Cosmologists look at three technical but important problems:
- The horizon problem
- The flatness problem
- The magnetic monopole problem
The scope and detail of these problems is beyond this course.