Questacon!!

Questacon!!
This place has really cool exhibits that run for a few months and then change it up, and are always improving their current long lasting ones.
You should try check out the shows as well. They are pretty cool, albeit aimed at a young audience for the most part, but they are still informative and definitely enjoyable.
The staff I see here are often quite happy to come and tell you about what you are seeing or help you out.