QUES: On the morning of 11 September 2001, 19 men affiliated with al-Qaeda hijacked four airliners all bound for California. Once the hijackers assumed control of the airliners, they told the passengers that they had the bomb on board and would spare the lives of passengers and crew once their demands were met – no passenger and crew actually suspected that they would use the airliners as suicide weapons since it had never happened before in history. The hijackers – members of al-Qaeda's Hamburg cell – intentionally crashed two airliners into the Twin Towers of the World Trade Center in New York City. Both buildings collapsed within two hours from fire damage related to the crashes, destroying nearby buildings and damaging others. The hijackers crashed a third airliner into the Pentagon in Arlington County, Virginia, just outside Washington D.C. The fourth plane crashed into a field near Shanksville, Pennsylvania, after some of its passengers and flight crew attempted to retake control of the plane, which the hijackers had redirected toward Washington D.C., to target the White House, or the U.S. Capitol. No flights had survivors. A total of 2,977 victims and the 19 hijackers perished in the attacks.

Which plane crashed into the White House?
What is the answer?
ANS: unanswerable
QUES: In the last years of the nineteenth century, Planck was investigating the problem of black-body radiation first posed by Kirchhoff some forty years earlier. It is well known that hot objects glow, and that hotter objects glow brighter than cooler ones. The electromagnetic field obeys laws of motion similarly to a mass on a spring, and can come to thermal equilibrium with hot atoms. The hot object in equilibrium with light absorbs just as much light as it emits. If the object is black, meaning it absorbs all the light that hits it, then its thermal light emission is maximized.

Planck studied what problem posed originally by Kirchhoff?
What is the answer?
ANS: black-body radiation
QUES: The Gregorian reform contained two parts: a reform of the Julian calendar as used prior to Pope Gregory XIII's time and a reform of the lunar cycle used by the Church, with the Julian calendar, to calculate the date of Easter. The reform was a modification of a proposal made by Aloysius Lilius. His proposal included reducing the number of leap years in four centuries from 100 to 97, by making 3 out of 4 centurial years common instead of leap years. Lilius also produced an original and practical scheme for adjusting the epacts of the moon when calculating the annual date of Easter, solving a long-standing obstacle to calendar reform.

What calendar was changed by the Julia reform?
What is the answer?
ANS:
unanswerable