2. The Context of Cybersecurity: Cyberspace 15 To start, all three of the switches, labeled, “Exotic Animals?”, “Fine Dining?”, and “Sea Shells?”, are set to “No” (0 in binary), and the light bulb is off because the wires connecting it to the battery do not form a closed circuit. For a given candidate destination, imagine flipping the three switches appropriately and then turning the power switch on. If an acceptable destination is identified, the wires will complete the circuit, and the lightbulb will light up indicating a winner. Table 2.4 below shows the values of the switches and their effect on the lightbulb for some candidate destinations. Table 2.4 Sample results of the simple computer’s computations. It is easy to see that the “calculation” happens quickly—flip the appropriate switches, turn on the power switch, and instantly, the lightbulb either comes on or not. In this simple case, our brains can solve the problem just as fast. To help us think more about the power and potential of computers, imagine instead of just one person deciding where he wants to go on vacation, there is a room full of people each with their own vacation preferences. For each person, a circuit can be constructed similar to the one in Figure 2.4. If we needed to consider vacation preferences that worked not just for one person, but for all the people in the room, it would be possible to take all of the separate circuits and wire them together in a circuit with a single battery and a single lightbulb (see Figure 2.5). This large circuit would be a complicated and tangled mess of switches and wires, but it could encode the logic of the vacation destination choice for the entire group. Just like the simple computer, this larger computer could be programmed with all of the different preferences for all of the different people by flipping the individual switches. And just like the simple computer, once the programming is done, the power can be turned on, and the lightbulb would either come on or not, revealing the answer. Electricity flows through wires at rates close to the speed of light. This is incomprehensibly fast. For example, even if this more complex computer used enough wire to stretch all the way from New York to Los Angeles, when the power switch is flipped, if a circuit is formed the light bulb would come on in about one hundredth of a second—the time it takes electricity to travel 2,500 miles. To our senses, this is indistinguishable from the amount of time it would take for electricity to travel the few inches in Figure 2.4. There-
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