Here is the full list of all 16 Universe Sandbox achievements. It takes around 200 hours to unlock all of the achievements on Windows.
Start Universe Sandbox 10^2 = 100 times
Start Universe Sandbox 10^3 = 1000 times
Start Universe Sandbox 10^4 = 10000 times
Rule over your universe for 24 hours
Rule over your universe for 30.4 days
Rule over your universe for 12 months
Some will know from their childhood; some were not born yet
Capture 100 screenshots
Crash the Earth into the Sun
Result of millions of years of computation
Rule over your universe for 60 minutes
Start Universe Sandbox 10^1 = 10 times
Freeze the Earth by moving it farther from the Sun
Finish five tutorials
Rule over your universe for 60 seconds
Start Universe Sandbox at least once