Creation by Adam Rutherford

Author:Adam Rutherford
Language: eng
Format: mobi, epub
Publisher: Penguin Group US
Published: 2013-05-09T21:00:00+00:00

CHAPTER 9

Logic in Life

“If it was so, it might be; and if it were so, it would be; but as it isn’t, it ain’t. That’s logic.”

Tweedledee

Flick the switch, the light comes on. This is the simplest useful electrical circuit. The parts are designed and created to follow one single instruction: the switch is a gap when open, but when closed, electrical energy surges through the circuit. The filament in the bulb converts some of the electrical energy into a form that we can detect with the cells in our eyes, and so enlightenment occurs. The function is clear, the instruction pure, the logic is unimpeachable, the light comes on.

At the other end of the scale, you watch a video streamed over the Internet on a laptop. Billions of electrical signals will have been created, modified, and transmitted in order for that moving image to play. The circuits have been designed in intricate detail with each one obeying a logical pattern determined by the hardware and software in your mouse, your computer, the servers that host the file, and so on. The logic is also perfectly clear, but the complexity of the pathway makes it all but inscrutable to almost everyone, and occasionally unpredictable. And yet we use the output of this tangled circuit every day without care or understanding of the millions of decisions that have been made to put a moving image on your screen.

Recall, if you can bear to, some of the electrical circuitry you learned at school. A lightbulb connected to a battery with a simple switch has a binary output: ON or OFF. You might have then added other devices into the circuit to introduce finer levels of control, such as diodes—electrical valves that turn a wire into a one-way street. If you added, for example, a thyristor, you’d have a dimmer switch. Possibly the greatest invention, certainly the most enabling technology, of the twentieth century was the transistor, which allowed the ability to control and modify multiple electrical signals. Interconnected transistors make up what are known as logic gates, which modify the input signal to produce a specific but different output. With the introduction of logic gates, circuits of ever-increasing complexity can be designed and built. For example, an AND gate acts as a positive conjunction: if two electrical inputs feed into an AND gate, both must be ON in order for the output to also be ON (in electronic engineering, capital letters indicate logical calculations, rather than merely bellowing for emphasis). A microwave oven uses this logic. It will only cook if the door is closed and the start button has been pressed. If either of the two crucial signals is negative, then the output is negative.

Electrical circuitry relies on logic, on following pathways determined by the component parts. From the light switch all the way up to the machine I am typing on, the route of information takes the form of digital questions with digital answers: if I press the on switch, the

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.