I was under the impression that we were mento come on earth anyway, meaning that God knew Aadam would sin, but only placed Aadam in heaven to let him learn this lesson for when he is on earth, i.e. that Shaytan is gonna try trick him.
This topic is very important and can be long I will try to shorten it. It may not be short so I apologize.
Adam (as) was moulded by Allah (swt) in heaven and Bani Adam (sons of Adam) are trying to be accepted to Paradise. Heaven and paradise are different places. Let me explain...
In Heaven there were Angels, Shaytan (Iblis who earned the rank to be amongst angels), and Adam in one place worshipping Allah (swt). In heaven a person has the ability to sin, like shaytan and Adam did. They both disobeyed Allah while in heaven. The difference is that Adam (as) repented and out of the arrogance/pride of shaytan (Iblis) he did not repent to Allah. He, Iblis, falsely attributed his misguidance to Allah. We must note that one of the main reasons of Allah creating us is that he could show this attribute of "Al-ghafoor, Rrraheem" (the Most forgiving, the most merciful) to all his creation. Allah wants to show this attributes to his creation so we could recognize it, and ask for forgiveness.
The evidence of that can be found in hadith of Prophet (saw) when Ayesha asked the Prophet (saw) about a man who was extremely pious, he helped the poor and the needy and had good character. Ayesha asked if he will be admitted to paradise the Prophet (saw) said No, because he never once said Allah forgive me.
Also, the mercy of Allah (swt) is the reason that Allah (swt) sends His believers to Paradise on the Day of Judgment. The prophet (saw) said: "None of you will enter Paradise with his deeds", They said: "Not even you, oh Messenger of Allah?!", He said: "Not even me unless Allah bestows His mercy upon me."
The other evidence that Allah wants to show his mercy to his creation can be found in this hadith.
Imam Muslim reported that the prophet (saw) said: "When Allah created the heavens and the earth, he created one hundred mercies, each one can cover what is between the earth and the heaven. He allocated to the earth only one, with which the mother is compassionate with her child; the beast and the bird are compassionate with their babies. When the Day of Judgment comes, Allah will complete His mercy." (Meaning Allah will use 100 parts of his mercy to judge us)
Allah (swt) also said about His mercy in surat Al-‘Araf, (verse 156), what can be translated as, "…And My mercy embraces all things…"
The Mother of all books "Al lawin mahfooth".. The last words Allah said in the book was "My mercy prevails my wrath."
To be kicked out of heaven and sent to earth was a test for bani Adam. Adam (as) first fell into trap of shaytan and he did not despair from ther mercy of Allah. He passed the test of asking for forgiveness after he made the mistake. That is as soon as he fell into Iblis's trap he immediately repented he quickly made dua...
They said, "Our Lord! We have wronged ourselves; so if You do not forgive us and have mercy on us, then surely, we are of the losers."
Read Surah Al Araf and you will understand more about what happened in heaven.
http://www.usc.edu/dept/MSA/quran/007.qmt.html
The Prophet (saw) said "All of bani Adam (son of Adam) are sinners and the best of sinners are those who are at-tauwabun (the repenters).
Repenting has conditions so go through that. Don't want to go off topic.
This world is a test to see who will be the friends of Allah and who will be the friends of shaytan. Another words who will obey Allah and his Messenger and who will obey arrogant/prideful like shaytan. the enemy of Allah and enemy of man.
Adam (as) was given the amanah, this trust that all the creation refused except the greedy Insan, who forgot the trust given to him. The trust is if you obey Allah and his messenger he will give you paradise and if you disobey Allah you will be thrown to hell-fire.
In this paradise you cannot sin and the test is passed. In Paradise only a select people who obeyed Allah and recognized the mercy and forgiveness of Allah will be admitted into the "Gardens underneath which rivers flow."
The Prophet (peace and blessings of Allah be upon him) said: “No one will enter Paradise who has an atom’s-weight of pride in his heart.” A man said, “What if a man likes his clothes to look good and his shoes to look good?” He said, “Allah is beautiful and loves beauty. Pride means denying the truth and looking down on people.”
That is what a Muslim does. He eliminates all types of arrogance and submits his will for the will and obedience of Allah (swt) his Creator/Sustainer.
"Turn unto Him repentant, and surrender unto Him" Surah al-Zumar: 54.