How can a loving God send someone to hell, especially someone who has never heard about Christ?

Paul says God has revealed himself in creation to all people. And yet people reject even the basic knowledge of God.

Rom. 1.18 But God shows his anger from heaven against all sinful, wicked people who push the truth away from themselves.* 19 For the truth about God is known to them instinctively.* God has put this knowledge in their hearts. 20 From the time the world was created, people have seen the earth and sky and all that God made. They can clearly see his invisible qualities-his eternal power and divine nature. So they have no excuse whatsoever for not knowing God.

All people have an inner sense of what God requires, but they choose not to live up to it. If people suppress God's truth in order to live their own way, they have no excuse. They know the truth, and they will have to endure the consequences of ignoring it.

Some people wonder why we need apostles if people can know about God through nature (the creation). The answer:

(1) Although people know that God exists, their wickedness blinds them to the truth. Apostles sensitively expose their sin and point them to Christ.

(2) Although people may believe there is a God, they refuse to commit themselves to him. Apostles help persuade them by sharing God's Word and by pointing out dangerous consequences to their actions.

(3) Apostles help th church obey the great commission of our Lord (Matthew 28.19,20).

Anyone who has never heard of Christ, if that person looks up at the mountains and the stars and believes in God who did it, then surely if they were presented Christ, they would believe in the Son of God.

Mat 28:19 Go ye therefore, and make disciples of all the nations, baptizing them into the name of the Father and of the Son and of the Holy Spirit:
Mat 28:20 teaching them to observe all things whatsoever I commanded you: and lo, I am with you always, even unto the end of the world.

(4) Most important, although nature reveals God, peopel need to be hold about Jesus and how, through him, they can have a personal relationship with God.

Knowing God exists not enough. Even the demons know that much. People need to learn that God is loving and that he sent his Son to demonstrate his love for us.

Rom 5:8 But God shows his love for us in that while we were yet sinners Christ died for us.

And see how to accept God's forgiveness of our sins.

Rom 10:14 How then shall they call on him in whom they have not believed? and how shall they believe in him whom they have not heard? and how shall they hear without a preacher?
Rom 10:15 and how shall they preach, except they be sent? even as it is written, How beautiful are the feet of them that bring glad tidings of good things!