Part 2—Much heat, little light: Last November, Nova set out to make Einstein easy again.
Its hour-long program, Inside Einstein's Mind, was timed to mark an anniversary.
It had been a hundred years since 1915, when Albert Einstein brought forth the general theory of relativity. To commemorate this important event, Nova became the millionth professor, publisher or broadcast org which seemed to think that it knew how to make Einstein easy.
At about the nine-minute mark in its program, Nova began its first attempt at explaining the revolution in physics Einstein created. At roughly that point, it began to trace the first of "the crucial thought experiments that led to his great discoveries."
More precisely, Nova presented the "thought experiment" which led to Einstein's presentation of "special relativity" in 1905, when he was just 26. It would be ten more years before Einstein produced the paper describing general relativity. But in 1905, Einstein's "miracle year," special relativity constituted a huge major step on the way.
Yesterday afternoon, we presented the transcript from the chunk of the program in which Nova described the thought experiment which led to special relativity. To peruse that transcript, click here.
Today, we'll review the very elementary physics involved in Einstein's thought experiment. Tomorrow, though, we'll present an awkward fact:
Nova's presentation doesn't justify the "mind-blowing," semi-metaphysical statements the program derives from that famous thought experiment.
Nova's physics is very basic. Its "metaphysics" fails.
Starting around the nine-minute mark, Nova describes the thought experiment which led to special relativity. This thought experiment comes straight from Einstein himself. As Nova describes it, it involves a man standing on a railway platform; a woman passing by on a very fast train; and a pair of lightning strikes.
The physics involved in this thought experiment concerns the speed of light. That physics is extremely easy, even if Einstein isn't.
Here's how the physics plays:
Light travels at a very high rate of speed, but it does take time for light to travel from one place to another. For that reason:
If Person A is closer to a lightning strike, and Person B is farther from that lightning strike, the light from the strike will reach Person A before it reaches Person B.
That's extremely simple stuff. As presented by Nova, it turns into a major ball of confusion.
Below, you see the transcript from the part of the show where Nova discusses the thought experiment in question. For the fuller transcript, see yesterday afternoon's post. To help you picture what is occurring, you can watch the full Nova program (links below).
Having said that, let us also say this:
When we watched Nova in November, we thought what follows was perhaps the worst non-explanation explanation we had ever seen.
We haven't changed our mind about that. Having said that, here's the part of the transcript in which the thought experiment is described:
From Nova, Inside Einstein's Mind:For reasons we'll discuss tomorrow, that's a terrible non-explanation. In fairness, let's clarify a couple of points the Nova presentation obscures.
WALTER ISAACSON: [Einstein] realized that any statement about time is simply a question about what is simultaneous. For example, if you say the train arrives at 7, that simply means that it gets to the platform simultaneous with the clock going to 7.
NARRATOR: In a brilliant thought experiment, he questions what "simultaneous" actually means, and sees that the flow of time is different for an observer that is moving versus one that is standing still.
He imagines a man standing on a railway platform. Two bolts of lightning strike on either side of him.
The man is standing exactly halfway between them, and the light from each strike reaches his eyes at exactly the same moment. For him, the two strikes are simultaneous.
Then, Einstein imagines a woman on a fast-moving train traveling at close to the speed of light. What would she see?
As the light travels out from the strikes, the train is moving towards one and away from the other. Light from the front strike reaches her eyes first.
For the woman on the train, time elapses between the two strikes. For the man on the platform, there is no time between the strikes.
This simple thought has mind-blowing significance. Simultaneity, and the flow of time itself, depends on how you're moving.
CARROLL: If there's no such thing as simultaneity, then there's no such as absolute time everywhere throughout the universe, and Isaac Newton was wrong.
NARRATOR: This concept, that time and space as well are relative, became known as "special relativity." It led to remarkable results, such as the famous equation relating energy to mass.
First: It makes best sense to picture these two lightning strikes occurring at a great distance from the man on the platform.
(As specified by Nova, "the man is standing exactly halfway between them.")
It makes best sense to picture these two lightning strikes occurring at a substantial distance. Einstein articulates this point in Chapters 8 and 9 of his 1916 book, which Nova's presentation tracks. By way of contrast, Nova's graphics make it look like the lightning strikes hit very close to the man. This doesn't negate the basic logic of the thought experiment, but it's easier to grasp the logic if the strikes are farther away.
Second, and crucially important: The lady on the fast-moving train is immediately adjacent to the man on the platform when the lightning strikes occur.
(Einstein specifies this in his book. Nova doesn't articulate this point in its transcript, although this point is suggested by its visual presentation.)
Because her train is moving at extremely high speed, the lady quickly moves closer to the one lightning strike, and farther away from the other. But in the example, she is directly adjacent to the man on the platform when the strikes occur.
The physics of this homely example is extremely simple. To wit:
Because the man is standing exactly halfway between the two lightning strikes, light from the two lightning strikes will reach him at the same time. On the other hand:
Because the woman quickly moves toward the one lightning strike and away from the other, she will have a different experience. The light from the one lightning strike will reach her sooner than the light from the other strike.
For the man, there will be no lapse of time between the arrival of the light from the two lightning strikes. For the woman, there will be a lapse of time between the arrival of light from the one strike and the arrival of light from the other.
This is very basic stuff. It's related to our own (un-confusing) everyday experiences, even to our experiences concerning lightning strikes.
The basic physics is simple and clear. That said, Nova takes that simple, homely example and creates a ball of confusion.
In the transcript we've posted above, Nova derives a set of "mind-blowing" conclusions from this homely example. (We'd almost be inclined to describe them as "metaphysical" statements.) As stated by the narrator, one of them goes like this:
"Simultaneity, and the flow of time itself, depends on how you're moving."
We're sorry, but that homely example doesn't explain, support or justify that "mind-blowing" statement, which is extremely fuzzy.
Under even the simplest questioning, very few PBS viewers could explain what that statement means. Those viewers shouldn't feel bad about that. We doubt that the author of Nova's program could explain what that statement means, or how it derives from that homely example.
When we watched Nova's program in November, we thought the passage we have posted constituted one of the worst non-explanation explanations we had ever seen.
We've watched the program many times since then. It utterly fails to justify the many dramatic, "mind-blowing" statements it derives from the example of the man on the railway platform and the lady on the very fast train.
Tomorrow, we'll show you why we say that. In our view, our society's culture of incoherence emerges from that transcript in all directions, producing more heat than light.
To watch the Nova program: We've been linking you to Nova's site to watch last November's program.
You can still watch the program there. To do so, just click here.
Yesterday, we noticed that some extremely annoying ads have been inserted into the program at completely random places. One such ad interrupts the passage we've posted above.
To watch the program without interruption, you can just click here.