Einstein’s Thought Experiments, or, Cinema for the Mind

When he was in his early teens, Albert Einstein received a gift from a family friend: a series of illustrated science books with the catchy title of Naturwissenschaftliche Volksbucher (People’s Books on Natural Science), by Aaron Bernstein. In Einstein: His Life and Universe, Walter Isaacson quotes Einstein as having later described it as “a work which I read with breathless attention.”

In the first volume of Bernstein’s popular science series, he asked the reader to imagine a bullet shot through the window of a fast-moving train. Bernstein postulated that anyone examining the bullet’s exit on the opposite side of the train would conclude the bullet must have been shot at an angle.

Bernstein’s point was that, because the earth is hurtling through space, light would exhibit the same refracting properties going through a telescope lens as the bullet passing through the train windows. And that this outcome would always be the same regardless how fast the source of the light was traveling.

Bernstein wrote, “Since each kind of light proves to be exactly of the same speed, the law of the speed of light can well be called the most general of all nature’s laws.” (I think we can all agree Einstein went on to do a pretty good job chasing down this idea.)

In a later volume, Bernstein had his readers imagine the effects of traveling through space as a passenger on a wave of light. At sixteen, a young science nerd like Einstein was fascinated by these creative challenges. In retrospect, we can see the seeds of Einstein’s famous ‘thought experiments,’ where he meditated on complicated physics problems through striking visualizations.

This was partly out of necessity, given the limitations of turn of the century technologies. It was difficult to conduct literal experiments in the burgeoning field of physics prior to nuclear accelerators. Especially since manipulating a solar system ‘under lab conditions’ was and is a pretty tall order for even the brightest and most determined physicist.

Taking advantage of the basal ganglia’s ability to run simulations, and the brain’s inherent visual strengths (remember, 50% of brain activity appears to be devoted to decoding images), Einstein eventually found himself applying Bernstein’s approach to some of the toughest physics problems of his day.

In essence, this allowed Einstein to watch a movie version of the physics problem as it played out in his head. And the beauty of this technique was that he had the power to edit, readjust, and rerun the footage over and over as he sought to uncover the underlying principles of space and time. Before the days of particle accelerators and NASA telescopes, Einstein was already making use of the best tools nature had to offer.

There was, however, one small problem: his thought experiments might go off without a hitch inside his own mind, but he still had to demonstrate the results to the greater scientific community.

To prove one of the tenets of his Theory of General Relativity, that light bends when it passes near a very heavy body, Einstein used not a lab but a total solar eclipse. When the moon passes in front of the sun, the moon shields some of the sun’s intensity, allowing us to observe distant stars, and to measure their light for refraction. Luckily for Einstein, in May of 1919, English astronomer Arthur Eddington agreed to travel to the Island of Principe off the west coast of Africa to take telescopic photographs of stars during an upcoming eclipse.

From Einstein’s point of view, Eddington’s task couldn’t have been more simple: to demonstrate that starlight would be bent by the warped space around the sun’s mass. In reality, Eddington risked life and limb, and given the weather conditions, was barely able to snag the needed photographic evidence. But Eddington got the needed shots, and his subsequent calculations proved out Einstein’s theory and turned him into the intellectual rock star he still is today, nearly 100 years later.

In 1945, French mathematician Jacques S. Hadamard asked Einstein to describe the essence of his thought experiments. Einstein replied with the following letter:

My Dear Colleague: 

In the following, I am trying to answer in brief your questions as well as I am able. I am not satisfied myself with those answers and I am willing to answer more questions if you believe this could be of any advantage for the very interesting and difficult work you have undertaken. 

(A) The words or the language, as they are written or spoken, do not seem to play any role in my mechanism of thought. The psychical entities which seem to serve as elements in thought are certain signs and more or less clear images which can be “voluntarily” reproduced and combined. 

There is, of course, a certain connection between those elements and relevant logical concepts. It is also clear that the desire to arrive finally at logically connected concepts is the emotional basis of this rather vague play with the above-mentioned elements. But taken from a psychological viewpoint, this combinatory play seems to be the essential feature in productive thought – before there is any connection with logical construction in words or other kinds of signs which can be communicated to others. 

(B) The above-mentioned elements are, in my case, of visual and some of muscular type. Conventional words or other signs have to be sought for laboriously only in a secondary stage, when the mentioned associative play is sufficiently established and can be reproduced at will. 

(C) According to what has been said, the play with the mentioned elements is aimed to be analogous to certain logical connections one is searching for. 

(D) Visual and motor. In a stage when words intervene at all, they are, in my case, purely auditive, but they interfere only in a secondary stage, as already mentioned. 

(E) It seems to me that what you call full consciousness is a limit case which can never be fully accomplished. This seems to me connected with the fact called the narrowness of consciousness (Enge des Bewusstseins).

In other words, it seems that Einstein’s thought experiments, or self-described ‘combinatory play,’ started with a concept and then proceeded to the mental movie adaptation, with subtitles as generally an afterthought. This was pretty much the winning Hollywood formula in the years before ‘talkies’ took over.

The difference? Einstein’s brand of ‘mind cinema’ has never ceased to amaze, even a century later.