Chapter 25 of 'Einstein' - all chapters at www.bryantwieneke.com/blog
25. Christian Doppler was an Austrian mathematician and physicist who discovered something very interesting about the nature of sound and light.
Doppler noticed and documented that the frequency of a sound or light wave changed depending on the position of the observer. For instance, the sound of an on-rushing train was different as it approached than after it passed. Specifically, according to Doppler, the pitch was higher when the source of the sound was approaching than when it was leaving. The same principle applied to light waves. Or, as Albert might point out, that aspect of light that behaved as a wave. The so-called “Doppler Effect” was apparent through the observation of celestial objects. When a star and the earth were moving toward each other, the frequency was higher and the wavelength was shorter; therefore, light observed from earth appeared violet. When a star and the earth were moving away from each other, the frequency was lower and the wavelength was longer; therefore, light observed from earth appeared red. The position of the observer played an important role in Doppler’s discovery. Einstein wanted to apply the same principle to light that Doppler had applied to sound. The process was initially straightforward. Albert used his now-standard technique of moving equations around between coordinate systems to get the mathematics right. But as he stretched the mathematics to determine how the Doppler Effect might apply at speeds approaching the speed of light, he was pleased by the results. They showed that the effect was true up to the speed of light. At that point, the math fell apart, suggesting the Doppler Effect no longer applied. Albert was pleased again because he had expected this result. It was additional support for the idea that the speed of light was the last remaining absolute, a barrier that nothing could cross. He sat back and took a deep breath. He had made progress, but there was more work to do. For instance, he had not yet dealt with energy, and he knew he had to show that relativity was consistent with recent discoveries about the nature of energy. Despite his fatigue Albert dove right into it, and the equations, which built on the proof’s previous ones, spun off his pencil as easily as the allegro portion of a familiar concerto rolled off his violin. He worked out the calculations for light energy measured in motion and the same energy measured at rest. When he had finished, he wrote the following: “Lorentz’s theory on the electrodynamics of moving bodies agrees with the principle of relativity.” Implicit in that conclusion was that Lorentz’s equations did not agree with classical physics. It was a momentous blow to the greatest scientist of the past two hundred years. While Albert would hesitate to say that Newton was wrong, he now knew there was more to mechanics than any 17th-century scientist – even one as brilliant as Newton – could imagine. Albert considered the statement again:
Lorentz's theory of the electrodynamics of moving bodies agrees with the principle of relativity. By ridding his proof of absolute notions, except the speed of light, Einstein had successfully reconciled Lorentz's equations. The equations were no longer a problem or an outlier in physics. They were no longer an unexplained phenomenon with disturbing implications. They were now an explainable, predictable, and reasonable part of a principle of relativity. He muttered only two words to himself in a soft voice at this important moment. “Mazel tov.”
Albert turned down the lamp in his study and made his way through the sitting room into the hallway. After stopping in the bathroom, he turned the lamp down there as well and continued into the bedroom. It was dark, but he knew how to avoid Hans Albert’s crib. He heard the sound of the baby’s breathing as he passed.
He made almost no noise as took his nightshirt from the hook on the back of the door. In the chill of the early morning, he quietly removed his clothes and pulled on the nightshirt. It was flannel, and it bunched slightly as he carefully lay down in the bed, pulling the heavy blanket over him. He was exhausted. Lying on his back and closing his eyes, he allowed the fatigue to wash over him, but he did not forget what he had done that evening. He knew the potential implications of his proof, both for what he had disproven with his logic and mathematics and what he had verified. It was not just that he had successfully negotiated a proof. He had solved one of the most difficult problems of physics by taking it from abstraction to reality, step-by-step until a new foundation was established.
Einstein had thrown his net as far as he could. He had addressed the most problematic areas of mechanics and electromagnetism and shown that a relativity principle could explain the previously unexplainable activity. His hypothesis worked. It was valid. There was no longer any doubt in Albert's mind that he had laid out a new fundamental theory of mechanics. Relativity. He had finally found the answer to the thorniest questions plaguing classical physics. While it was inevitable that many scientists – and thinkers in other fields such as philosophy, for that matter – would suggest that a world without absolute notions of space and time was unthinkable, Einstein would argue otherwise. The demise of absolutes did not mean that the world was less organized; on the contrary, the relativity principle provided flexibility, a rubbery texture that allowed the world to adjust while maintaining its basic form. In Albert Einstein's mind, there was a balance and symmetry to the shapelessness of relativity that was missing in all the strictness of Newton’s absolutes. The world was simply more malleable than classical physicists ever imagined. The principles of physics needed to be adjusted to recognize this malleability and accommodate the activity in the far reaches of space and the tiny world of the atom, as well as the world around us every day.
Albert had done it.
And he had done it without an academic appointment, without any of his professors from the ETH guiding him, and without any other prominent figure in the field recognizing his talent. He was a stubborn and independent Jewish boy from a Catholic school, who never showed the type of promise that would lead one to believe he could solve such a complex and pervasive problem.
He had done it as a scientist who could not get anything other than temporary fill-in jobs upon leaving the university and now occupied a full-time job testing other people's patent applications. He was a young man with a wife, a one-year-old child, and no standing whatsoever in the scientific community.
While Einstein knew he had not found the unified theory of the universe – the one that tied all of nature's quirks, idiosyncrasies and magnificence together – he also knew that he had done what no one else could.