Knowing

In 1959, student Lucinda Embry (Lara Robinson) hears whispers as she stares at the Sun. When her class is chosen to contribute to the school's time capsule, each child is asked to draw what they believe the future will look like. Lucinda writes a page of seemingly random numbers and adds it to her elementary school's time capsule, which is set to be opened in 50 years. Lucinda's teacher calls for the pupils to finish but Lucinda continues before her teacher takes it off her desk unfinished. Lucinda then goes missing after the time capsule is dedicated, and is found by her teacher, Mrs. Taylor (Danielle Carter), in a utility closet scratching numbers into the door with her fingernails bleeding.
In 2009, Caleb Koestler (Chandler Canterbury) is a pupil at the same elementary school. When the time capsule is opened, Caleb is supposed to read and write about some of the capsule's contents. He's given the page of numbers written by Lucinda. His widowed father John (Nicolas Cage), a professor of astrophysics at MIT, notices the numbers have a specific set of sequences, with some digits referring to the dates and death tolls of major disasters over the last 50 years, including 911012996 (the date and death toll of the 9/11 attacks). The last three sets of digits on the page are dated in the immediate future.
In the following days, a car drives by the family home with two strangers. They give Caleb a small smooth stone. Caleb later dreams of one of the strange men, who points to the window showing the world on fire with burning animals running out from a forest.
John witnesses a plane crash on a freeway on the day that the paper had next predicted that a disaster would occur. He then learns that the remaining unexplained digits on the paper are the geographic coordinates of the location of each disaster predicted on the paper.




Copy of MatthÃ¤us Merian's engraving of Ezekiel's "chariot vision" (1670)
John tracks down Lucinda's daughter Diana (Rose Byrne) and granddaughter Abby. Though initially apprehensive and scared, after seeing one of the number sets result in another disaster (a major derailment on the New York City Subway, which John had tried to prevent), Diana decides to help John. She says that her mother used to hear voices and that the next (and also last) date in the document, October 19, was the day Lucinda always said Diana would die. Searching Lucinda's mobile home, they find pictures of the disasters she predicted, a copy of MatthÃ¤us Merian's engraving of Ezekiel's "chariot vision", and a pile of small smooth stones near Lucinda's bed. The last number in the document appears to be "33" but they notice that it is really "EE" written backwards. They figure out that EE means "Everyone Else," representing an Extinction Level Event that no one will escape.
The next day, Abby shows John that she has coloured in the sun on the Ezekiel's "Chariot vision" engraving and John has a sudden realisation that this could be how the world ends. He rushes them to the MIT observatory, where he discovers that a massive solar flare will soon reach Earth, making it uninhabitable. John and Diana argue over what is best to do to prepare for the incoming solar flare. After the argument, Diana leaves with both children. While Diana stops for gas, an emergency broadcast is transmitted to alert the world of the solar flare. While on the phone with John, the strangers take the children. Diana chases after them but her car is hit by a truck. John, rushing to catch up with them, arrives just as Diana dies at exactly midnight of October 19 and finds the smooth, black stone in Diana's hand. He goes back to Lucinda's mobile home, finding the children and the strangers waiting in a dry river bed covered with the similar black stones. A space ship descends from the sky. John is refused entry and the ship departs with the children. A distant shot shows many similar space ships leaving Earth.
The next morning John drives to his estranged father's home. John and his family embrace as the flare sets the entire planet ablaze, destroying everything and killing all life still on the surface. Caleb and Abby are deposited by the beings on an Earth-like planet. In the final scene, they are seen running through a beautiful field of wheat towards a giant white tree which resembles the Tree of Life. In the distance other ships are seen leaving suggesting the other children have also been deposited on their new world.

Question: What does John discover that will make the Earth uninhabitable?
Answer: A massive solar flare.