Part 3—Einstein just isn't that easy: Was Nova's program, Inside Einstein's Mind, able to make Einstein easy?
Let's restate that question. Did last November's hour-long broadcast make the work of this intellectual giant understandable at all?
We're going to say that the answer is no. Let's return to the non-explanation explanation which occurs near the start of the program.
At roughly its nine-minute mark, the Nova program begins to discuss the "thought experiment" which led to "special relativity," the famous theory Einstein unveiled in 1905.
As described by Nova, Einstein's thought experiment involved a man on a railway platform; a woman on a fast-moving train; and a pair of lightning strikes. Below, you see the transcript of the part of the program which describes this thought experiment.
Nova's visuals will help you picture the scene. To watch the full program, click here:
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.For a slightly longer chunk of that transcript, see Tuesday afternoon's post.
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.
PROFESSOR 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.
The homely example described in that passage involves very basic physics. The man is standing exactly halfway between the two lightning strikes. For that reason, "the light from each strike reaches his eyes at exactly the same moment."
As you can see from Nova's simulation of the thought experiment, the woman is directly adjacent to the man when the two strikes occur. But because she's on a fast-moving train, she moves toward one of the lightning strikes and away from the other.
By way of contrast, the man on the platform just stands there.
Because of her very rapid movement, the woman is soon closer to the one strike, farther away from the other. For this reason, light from the strike which she is approaching reaches her eyes before the light from the strike she is moving away from.
This is a very simple example. Based on this homely example, Nova viewers were quickly deluged with a set of statements we'd almost call "metaphysical."
It's implied that these are "mind-blowing" statements. We can tease seven such statements from just that small chunk of text. Essentially, these are direct quotations from the Nova transcript:
Mind-blowing statements:We'll note that statements 2 and 4 don't go together real well. For what it's worth, we're also told this:
1) The flow of time is different for an observer that is moving versus one that is standing still.
2) Simultaneity depends on how you're moving.
3) The flow of time depends on how you're moving.
4) There's no such thing as simultaneity.
5) There's no such as absolute time everywhere throughout the universe.
6) Time is relative.
7) Space as well is relative.
"The concept that time and space are relative is known as 'special relativity.' "
In effect, viewers are told that a revolutionary theory has now been explained to them in a way they can grasp and explain. That suggestion is utterly silly.
In fact, none of those seven statements follow in any obvious way from the homely example Nova has sketched. In the rest of today's post, let's start explaining why:
Let's start with a suggestion. Let's ignore the mind-blowing statements which deal with "the flow of time."
That particular phrase is extremely fuzzy. Later in our course of study, we'll return to that particular type of murky locution, drawing on Wittgenstein's work.
For today, let's focus on this apparent nugget: "Simultaneity depends on how you're moving."
Although that statement is also quite fuzzy, it seems to be the key take-away from Nova's homely example. Because of its fuzziness, it's hard to paraphrase that statement. But it sounds like Nova is saying this:
The man and the woman have different experiences because they're in relative motion.
It also sounds like Nova is saying something like this: Because the man and the woman are in relative motion, the events are simultaneous for the man but not for the woman. Or something like that! Truth to tell, Nova makes little attempt to explain what its key nuggets actually mean.
In truth, Nova's attempt at explanation moves almost as fast as that fast-moving train. Let's do the best we can with its presentation, which is very sketchy.
In conventional terms, the man on the platform is stationary. The woman on the very fast train is moving very fast.
Expressed in a more rigorous way, the man and the woman are in motion relative to each other. In this particular example, this leads to our mind-blowing outcome:
The light from the two lightning strikes reach the man at the exact same time. By way of contrast, the light from the strike the woman is approaching reaches her before the light from the other strike.
Even that doesn't explain Nova's nugget about simultaneity. As we'll note tomorrow, the woman on the train may yet judge and declare that the two lightning strikes were simultaneous.
In our own lives, we make such judgments quite routinely. That said, let's put that off till tomorrow.
For today, let's restrict ourselves to simpler observations. For starters, let's launch a second thought experiment!
In this case, let's imagine that a second man is standing on that (very long) railway platform. (In his 1916 book, Einstein specifically says that the train in this thought experiment is "a very long train.")
We'll call this new fellow Man B. We'll imagine that he is standing all the way down at the end of the very long platform. He's off at the end of the platform which lies in the direction the very fast train is going.
Our original man, who we'll call Man A, is right where he ever was. Let's picture this new scene:
Man A is standing where he always was, in the center of the very long railway platform. Man B is standing all the way down at the end.
Can you see where this second situation takes us? In conventional terms, neither of these men is in motion. Expressed more rigorously, they aren't in motion relative to each other.
Motion plays no role in this second thought experiment, but so what? Because he's way down at the end of the platform, the light from the nearer lightning strike reaches the eyes of Man B before the light from the other lightning strike.
For Man A, it's just as it always was. Quoting Nova, "The light from each strike reaches his eyes at exactly the same moment."
According to Nova's clumsy formulations, the lightning strikes are simultaneous for Man A. But it isn't like that for Man B! Continuing with Nova's formulations:
"For [the man at the end of the very long platform], time elapses between the two strikes." But this is precisely what will occur for the woman on the fast-moving train.
Motion played no role in this second thought experiment, the one involving Man A and Man B. There is no motion here at all! Each man is standing still on the same railway platform.
Motion plays no role in what happens here. For Man B, time elapses between the arrival of light from the two lightning strikes--but it does so because he's closer to the one lightning strike and farther away from the other. It's just as simple as that.
Of course, that's why the woman on the train will have the same experience! By the time the first light reaches her, she too is closer to one lightning strike and farther away from the other.
In her case, that wouldn't have happened if her train had suddenly stopped moving. But it's hard to see what point is being made when we're simply told, full stop, after just that one example:
"Simultaneity depends on how you're moving." Amazingly, that statement is fuzzy in two different ways, as we'll note tomorrow.
"Simultaneity depends on how you're moving?" What was Nova trying to say when it stressed that formulation? How would you paraphrase, elucidate or explain that portentous, mind-blowing statement?
In Nova's lone thought experiment, two people who were in relative motion had a different experience of two lightning strikes. But as we showed you today, two people who aren't in relative motion could differ about the two lightning strikes in the exact same way.
For ourselves, we have no idea what Nova was trying to say with that formulation. But neither did anyone else who was watching that show last November. It wouldn't be easy to explain what Nova meant by that formulation, or by the other "mind-blowing" statements in our list of seven.
For our money, it's hard to see what we're supposed to learn from the man on the platform and the woman on the train. Tomorrow, we'll ask you to imagine a second woman on that train, all the way back in the train's caboose.
Despite her very rapid motion, she'll experience the two lightning strikes in the same way Man A does. Meanwhile, as lightning strikes all around us, we find ourselves left with an obvious thought:
Einstein simply isn't as easy as Nova was willing to say.
Tomorrow: A woman in the caboose of that train! Also, lightning versus thunder