maybe i should just step out and say it -
no dude, people are not going to hell for not believing the earth is flat, and you are not going to hell for refusing to accept that the earth is not flat.
people go to hell because they reject Jesus Christ -- not because they are ignorant, however willfully, of the natural world. though if they make idols out of it, rejecting the Creator for the created things -- well, ...
God is still sovereign, and He will have mercy on who He will have mercy. but He has said that whoever believes on the Son has eternal life, and who does not believe Christ is condemned already.
the deciding factor is not what you do with physics or with Isaiah's descriptive language. it's what you do with Jesus Christ.