You may wonder if there are other examples of static discharge. The answer is yes. Lightning is a form of static discharge. It is much more dramatic than what happens between you and the door knocker, but it is the same principle. You can see how it occurs in the following diagram and animation. You have no doubt seen lightning in a rainstorm. What does lighting have to do with static electricity? As it turns out, everything! During a rainstorm, clouds develop regions of different charges. This happens due to the movement of air molecules, water drops, and ice particles. The negative charges are concentrated at the base of the clouds. The positive charges are concentrated at the top. The negative charges repel electrons on the ground below. The ground then becomes positively charged. Over time the differences increase. Eventually the electrons are discharged. This is what we see as lightning. You can watch an awesome slow-motion lightning strike below.

How is the top of a cloud different from the base of the cloud during a rainstorm?

Early in chapter 5 we introduced, along with Khalid Sheikh Mohammed, two other men who became operational coordinators for al Qaeda: Khallad and Nashiri. As we explained, both were involved during 1998 and 1999 in preparing to attack a ship off the coast of Yemen with a boatload of explosives. They had originally targeted a commercial vessel, specifically an oil tanker, but Bin Laden urged them to look for a U.S.warship instead. In January 2000, their team had attempted to attack a warship in the port of Aden, but the attempt failed when the suicide boat sank. More than nine months later, on October 12,2000, al Qaeda operatives in a small boat laden with explosives attacked a U.S. Navy destroyer, the USS Cole. The blast ripped a hole in the side of the Cole, killing 17 members of the ship's crew and wounding at least 40. The plot, we now know, was a full-fledged al Qaeda operation, supervised directly by Bin Laden. He chose the target and location of the attack, selected the suicide operatives, and provided the money needed to purchase explosives and equipment. Nashiri was the field commander and managed the operation in Yemen. Khallad helped in Yemen until he was arrested in a case of mistaken identity and freed with Bin Laden's help, as we also mentioned earlier. Local al Qaeda coordinators included Jamal al Badawi and Fahd al Quso, who was supposed to film the attack from a nearby apartment. The two suicide operatives chosen were Hassan al Khamri and Ibrahim al Thawar, also known as Nibras. Nibras and Quso delivered money to Khallad in Bangkok during Khallad's January 2000 trip to Kuala Lumpur and Bangkok. In September 2000, Bin Laden reportedly told Nashiri that he wanted to replace Khamri and Nibras. Nashiri was angry and disagreed, telling others he would go to Afghanistan and explain to Bin Laden that the new operatives were already trained and ready to conduct the attack. Prior to departing, Nashiri gave Nibras and Khamri instructions to execute the attack on the next U.S.warship that entered the port of Aden.

Why did the team avert from attacking an oil tanker and attempt to attack a warship?

Fossils can be used to match up rock layers. As organisms change over time, they look different. Older fossils will look different than younger fossils. Some organisms only survived for a short time before going extinct. Knowing what organisms looked like at certain times also helps date rock layers. Some fossils are better than others for this use. The fossils that are very distinct at certain times of Earths history are called index fossils. Index fossils are commonly used to match rock layers. You can see how this works in Figure 2.30. If two rock layers have the same index fossils, then they're probably about the same age.
How are index fossils useful?