@Francis,
I will just give my opinion to those who need more depth in this issue:
The question of whether or not there is life after death does not fall under the field of science, because science is only concerned with the classification and analysis of recorded data. Moreover, man has been busy with scientific enquiries and research, in the modern sense of the term, only for the last few centuries, while he has been familiar with the idea of life after death since times immemorial. All the prophets of God called their people to worship God and to believe in life after death. They laid so much emphasis on the belief in life after death that even a slight doubt in it meant denying God and made all other beliefs meaningless.
Did they realize the truth through experiencing it? Not so, as the perceptual experience of life after death is impossible. Actually, God has given man, besides perceptual consciousness, rational, aesthetic and moral consciousness too. It is this consciousness that guides man regarding realities that cannot be verified through sensory data. That is why all the prophets of God, while calling people to believe in God and the life hereafter, appealed to the aesthetic, moral and rational sides of man.
The explanation that the Qur'an gives about the necessity of life after death is what the moral consciousness of man demands. Actually, if there is no life after death, the very belief in God becomes irrelevant, or even if one believes in God, that would be an unjust and indifferent God: having once created man only to be unconcerned with his fate. Surely, God is just. he will punish the tyrants whose crimes are beyond count: having killed hundreds of innocent persons, created great corruptions in the society, enslaved numerous persons to serve their whims, and so forth. Man, having a very short span of life in this world, and this physical world, also, not being eternal, punishments or rewards equal to the evil or noble deeds of persons are not possible here. The Qur'an very emphatically states that the Day of Judgment must come and God will decide about the fate of each soul according to his or her record of deeds:
Those who disbelieve say: The Hour will never come unto us. Say: Nay, by my Lord, but it is coming unto you surely. (He is) the Knower of the Unseen. Not an atom's weight, or less than that or greater, escapes Him in the heavens or in the earth, but it is in a clear Record. That He may reward those who believe and do good works. For them is pardon and a rich provision. But those who strive against our revelations, challenging (Us), theirs will be a painful doom of wrath. (Al-Qur'an 34:3-5)
The Day of Resurrection will be the Day when God's attributes of Justice and Mercy will be in full manifestation. God will shower His mercy on those who suffered for His sake in the worldly life, believing that an eternal bliss was awaiting them. But those who abused the bounties of God, caring nothing for the life to come, will be in the most miserable state. Drawing a comparison between them the Qur'an says:
Is he, then, to whom we have promised a goodly promise the fulfillment of which he will meet, like the one whom We have provided with the good things of this life, and then on the Day of Resurrection he will be of those who will be brought arraigned before God? (Al-Qur'an 28:61)
The Qur'an also states that this worldly life is a preparation for the eternal life after death. But those who deny it become slaves of their passions and desires, and make fun of virtuous and God-conscious persons. Such persons realize their folly only at the time of their death and wish in vain to be given a further chance in the world. Their miserable state at the time of death, and the horror of the Day of Judgment, and the eternal bliss guaranteed to the sincere believers are very beautifully mentioned in the following verses of the Qur'an.
Until, when death comes unto one of them, he says, 'My Lord, send me back, that I may do right in that which I have left behind!' But nay! It is but a word that he speaks; and behind them is a barrier until the day when they are raised. And when the Trumpet is blown there will be no kinship among them that day, nor will they ask of another. Then those whose scales are heavy, they are successful. And those whose scales are light are those who lose their souls, in hell abiding, the fire burns their faces and they are glum therein. (Al-Qur'an 23:99-104)
The belief in life after death not only guarantees success in the Hereafter, but also makes this world full of peace and happiness by making individuals most responsible and dutiful in their activities.