So when you die, and assuming there is no God, how would you know?
That's a hard one. Taking your assumption there is no God, then there is no heaven or God's home. Also there is no such thing as good and evil, and there is no such thing as the soul as everything is only physical. If there's no God or existence later, then all the believers, those that mankind revered as good, Billy Graham etc. will be in the same nothingness as Hitler, Himmler, Pol Pot, Stalin or Bin Laden. For these reasons I cannot assume there's no God.
My belief in God is not based on any scientific argument or data or rationalizing. To me there is no argument, either you believe or not. Why does person X believe and person Y not believe, I don't know. When you believe you just know.
As I said some do, some don't, some will and some won't. Even if the alternative to eternal life in God's home is say an eternal Disneyland or Playboy Mansion, I'll take real life in God's home any day.
I don't condemn anybody for not believing as it's their free will. All I know is where my real home will be after this life. How joyous it is when you know that you approach real life faster with very passing day, instead of worrying about this worldly life we're losing as the calendar passes.
Probably my above remark based on faith which defines my opinion is not satisfactory to you, but if you honestly want your question answered, then the best thing is to discuss this with a pastor.