There goes for those who call on the dead. Any mortal who passes over is dead to the World. For example, while Jesus of Nazareth is not dead, he is dead to the world because he is not here. How come the dead cannot hear us? Because they don't even know they are dead. And when Judgement Day comes, the unbelievers think they have been dead for only an hour:
They think that even though they have been wrecked to no end when they were dying;
And while they are dead, their souls are brought before the fire in the morning and evening, a nightmare like that haunts the unbelievers until the Day of Judgement:
So, they will think they had an hour of nightmare! For the believers, death is totally different thing. For example, the story of the believer:
Also, we are told in the Quran that the Angels welcome those who died believers;
Therefore, death is not a mystery in Islam. When a Muslim is about to die, he is not clueless, hopefully. Thousands upon thousands of people die each year not knowing where they are going. They expect like a "white" light and so on and so forth. You don't go anywhere except a different dimension. Just like we can't see or hear them, they can't see or hear us.
The funny thing is, millions of people believe in stories about "other" side and Psychics who publish books about such things to dupe people. There is no such connection. The demons(Jinn) who totally live in different dimension can hear us. Such demons who were part of our deceased comes back to psychics and tells all about their thoughts and what not. People fall for it big time!
Death! The only thing every human will experience but is the number one mysterious thing in our World. Death is not a mystery in Islam. The believers and the unbelievers experience it differently. In Islam, as far as the Human is concerned, there are two world; This world and the next. And each cannot cross to the other. For example, if you call out to someone who is dead, they cannot hear you;
If you call on them(the dead) they shall not hear your call, and even if they could hear they shall not answer you; and on the resurrection day they will deny your associating them (with God); and none can inform you like the One Who is Aware. Surrat ul Fater, 35:14
And at the time when the hour shall come, the guilty shall swear (that) they did not tarry but an hour; thus are they ever turned away. And those who are given knowledge and faith will say: "Certainly you tarried according to the ordinance of God till the day of resurrection, so this is the day of resurrection, but you did not know." Surrat ul Rum, 30:55-56
And had you seen when the angels will cause to die those who disbelieve, smiting their faces and their backs, and (saying): "Taste the punishment of Hell." Surrat ul Anfal, 8:50
The fire; they shall be brought before it morning and evening and on the day when the hour shall come to pass: "Make Pharaoh's people enter the severest chastisement." Surrat ul Qhafer, 40:46.
And from the remote part of the city there came a man running, he said: "O my people, follow the messengers; Follow him who does not ask you for reward, and they are the followers of the right course; And what reason have I that I should not serve Him Who brought me into existence? And to Him you shall be brought back; What! shall I take besides Him gods whose intercession, If the Beneficent God should desire to afflict me with a harm, shall not avail me aught, nor shall they be able to deliver me? In that case I shall most surely be in clear error: Surely I believe in your LORD, therefore hear me." It was said(to him, at the time of his death): "Enter the garden." He said: "O would that my people had known of that on account of which my Lord has forgiven me and made me of the honored ones. Surrat ul Yasin, 36:20-27.
Those whom the angels cause to die in a good state, saying: "Peace be on you; enter the garden for what you did." Surrat ul Nahal, 16:32