Out of curiosity, what is the benefit to doing it the other way. Is it for clarity, or is there another reason?
Id say for clarity.
It sure will make it easier to work with in the long run.
Use const for input parameters in functions that you know wont change.
Example "void UpdateWorld(const float deltaTime);"
For example in your planet constructor you have a int objtypes, thats a perfect case for where it should be const.
Const can be abit tricky to see the point of in the beginning. But for me, its really great. It makes the code more clean and it prevents mistakes.
That's not the best example though, since deltaTime is already copied by value (so const here might have some meaning to the programmer such as "there is no reason to ever modify the deltaTime variable inside UpdateWorld" and some people like to do it for this reason, while others think it's ridiculous, but it can't possibly affect the function's behaviour). There is no real consensus on this use of const.
You are correct Bacterius, it was a bad example. Thanks for clarifying.