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Ancestors of E = mc2: E Introduction equals m c squared

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The word energy is surprisingly new and can only be traced in its modern sense to the mid-1800s. It wasn't that people before then had not recognized that there were different powers around—the crackling of static electricity and the billowing gust of wind that snaps out a sail, for example. It's just that they were thought of as unrelated things. There was no overarching notion of "Energy" within which all these diverse events could fit.

One of the men who took a central role in changing this was Michael Faraday. Faraday's work showed a profound link between electricity and magnetism, and helped lead the scientific community to see that every other form of energy was connected. Scientists of the Victorian era came to believe that energy could change its form, but the total amount of energy would always remain precisely the same. The principle was called the law of conservation of energy.

Michael Faraday (1791-1867)

Faraday, the son of a blacksmith, was once a very good apprentice bookbinder. He had no interest, however, in spending his life binding books. When he was 20, a shop visitor offered him tickets to a series of lectures at the Royal Institution. Sir Humphry Davy was speaking on electricity and on the hidden powers that must exist behind the surface of our visible universe.

Davy's lectures captivated Faraday. He crafted an impressive book from his lecture notes, complete with drawings of the demonstration apparatus, and presented it to Davy. Not long after, Davy hired Faraday as a lab assistant.

For years, Faraday's new position was less than ideal. Sometimes Davy behaved as a warm mentor, but at other times he would seem angry and push him away. Faraday's prospects of becoming a great scientist in his own right changed, though, when Davy asked him to investigate an extraordinary finding out of Denmark.

Until then, everyone knew that electricity and magnetism were as unrelated as any two forces could be. Electricity was the crackling and hissing stuff that came from batteries. Magnetism was different, an invisible force that made navigators' needles tug forward. Yet a lecturer in Copenhagen had now found that if you switched on the current in an electric wire, any compass needle put on top of the wire would turn slightly to the side. Davy asked Faraday to work on why this might occur.

The discovery that sparked a revolution

In the late summer of 1821, Faraday designed a landmark experiment. He imagined that a whirling tornado of invisible circular lines swirled around a magnet. If he were right, then a loosely dangling wire could be tugged along, caught in those mystical circles like a small boat getting caught up in a whirlpool. He propped up a magnet next to a dangling copper wire. When he connected a battery to the wire, he had the discovery of the century.

What Faraday invented, in his basement laboratory, was the basis of the electric engine. Ultimately one could attach heavy objects to a similar wire, and they would be tugged along as well. Apart from the countless practical applications, Faraday's work gave science a new concept: electromagnetic rotation.

With Faraday's experiment, the crackling of electricity and the silent force fields of a magnet—and now even the speeding motion of a fast twirling copper wire—were seen as linked. As the amount of electricity went up, the available magnetism would go down. Faraday's invisible whirling lines were the tunnel—the conduit—through which magnetism could pour into electricity and vice versa. The full concept of "Energy" had still not been formed, but Faraday's discovery brought it closer.

A triumph turned sour

It was the high point of Faraday's life—and then Sir Humphry Davy accused him of stealing the whole idea. After a few months Davy backed off, but he never apologized, and he left the charges to dangle. Faraday never spoke out against Davy. But for years after the charges of plagiarism, he stayed warily away from front-line research. Only when Davy died, in 1829, did Faraday resume work on electromagnetism.

Faraday went on to make other important discoveries, including the principle behind the electric transformer and generator, innovations that fueled the Industrial Revolution.

In his day, Faraday was celebrated as a great experimenter, but many elite scientists spurned Faraday's more theoretical notions, particularly his vision that the area around an electromagnetic event is filled with a mysterious "field," and his idea that light itself might be an electromagnetic phenomenon.

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Faraday

Michael Faraday didn't attend Oxford, Cambridge, or even what we call secondary school, yet he became one of England's most prominent scientists.











Faraday apparatus

In Faraday's apparatus, a copper wire hangs with one end near a magnet in a dish of mercury. When Faraday charged the wire with electricity, it began rotating around the magnet. His simple experiment united electricity, magnetism, and motion.

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Magnet with iron filings

Faraday thought the essence of electromagnetic fields was apparent in the curving patterns that iron filings take when they are sprinkled around a magnet.

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