how do I enter science center and crustacean empire I finished celestia please help
You asked "how do I enter". If you just need to know "where" the entrances are, this might help.
For the Science Center, when you are in the Base Camp for Celestia, go towards the Sun School Trainer (on the right side of the Base Camp). There is a ramp near the trainer, and that ramp leads to the Science Center.
For the Crustacean Empire (Crab Empire), again, when you are in the Base Camp for Celestia, go towards the sigils that take you to The Trial of The Spheres. On the right side of those sigils, you will see another ramp, and that ramp leads you to the Crustacean Empire.
Here is a map for the Base Camp in case you need it:
Your title for your post reads "Lounging Lizards". Just in case you need help finding the lizards, this link to one of the fansites shows detailed pictures with the locations of each lizard. There is a green arrow on the pictures showing where to find them.