Well, the firmament would trap in heat like a greenhouse, so we'd all be cooked. 
You think God doesn't know what He is doing? You think God can't create a Sun with the right heat output to avoid destroying the earth?
Maybe the Sun isn't as big as NASA says it is, is much closer, and doesn't have enough heat output to cook everything under the Firmament. Which is what, in fact, we observe.
Accept it. God is our Creator, and He has us creatures in His snow-globe. We are like fish in a fishbowl; there is no escaping the container, or escaping His hands in any way. That thought doesn't bother me.