FIRST REACTIONS: Isaacson calls spacetime a "fabric!"

THURSDAY, FEBRUARY 25, 2016

Part 4—The Beatles called it Arthur: For the last time, we're going to show you what Walter Isaacson said.

In almost all settings, Isaacson is an extremely clear writer. In his best-selling book, Einstein: His Life and Universe, the passages about Einstein's life are lucid, clear, interesting, intriguing.

Then we come to the passages—and the chapters—concerning "Einstein's universe," by which we mean his science. Below, we once again see an early attempt at explaining a famous part of that science.

Granted, we're still in Chapter One of Isaacson's best-selling book. That said, how many readers had any idea what this passage meant?

ISAACSON (pages 3-4): [I]n 1915, [Einstein] wrested from nature his crowning glory, one of the most beautiful theories in all of science, the general theory of relativity. As with the special theory, his thinking had evolved through thought experiments. Imagine being in an enclosed elevator accelerating up through space, he conjectured in one of them. The effects you'd feel would be indistinguishable from the experience of gravity.

Gravity, he figured, was a warping of space and time, and he came up with the equations that describe how the dynamics of this curvature result from the interplay between matter, motion, and energy. It can be described by using another thought experiment. Picture what it would be like to roll a bowling ball onto the two-dimensional surface of a trampoline. Then roll some billiard balls. They move toward the bowling ball not because it exerts some mysterious attraction but because of the way it curves the trampoline fabric. Now imagine this happening in the four-dimensional fabric of space and time. Okay, it's not easy, but that's why we're no Einstein and he was.

How many readers had any idea what Isaacson was talking about in that passage? Just for starters, we'll offer this guess:

Roughly essentially none.

By that, we mean this: We'll guess that very few readers could answer even the simplest questions about the various statements made in the passage. To consider the various sources of confusion in those two paragraphs, click here to peruse Tuesday's post.

In the good-natured jest at the end of that passage, Isaacson himself seems to say that this passage is perhaps quite unclear. A fair-minded person would want to see if Isaacson unpacks this confusion in the later chapters he devotes to the science.

(Examples: Chapter Six, Special Relativity. Also, Chapter Nine, General Relativity.)

Is the work in those chapters clear? We'll set that aside for another day. For today, let's look at Kevin Drum's first reaction to the puzzles offered here.

We do so because Drum is smart. Also, because a few of his commenters were so dittoheaded that they reacted as such figures will typically do—by saying the whole thing is perfectly clear, and that you'd have to be an ass to challenge our exalted professors, who have been nice enough to hand us the metaphors we should recite for the rest of recorded time.

The dittoheads are always with us—and yes, they even exist over here, in our own self-impressed tribe. That said, Drum is not a dittohead, and he undertook, in last Saturday's post, to address a question we had raised about the presentation of this material in best-selling books, even on the front page of the New York Times.

Last Thursday, we commented on the sources of confusion found in Isaacson's passage. In the process, we apparently offered this deathless remark, spoken on behalf of the shlubs of the world:

No one has the slightest idea what Isaacson means when he refers to "the four-dimensional fabric of space and time." We all can picture that trampoline—but none of us knows how to imagine that "four-dimensional fabric!" Nor does Isaacson give us the tools to do so, or notice that he has failed.

In a perfectly sensible way, Drum undertook to explain what "the four-dimensional fabric of space and time" actually is. He offered this presentation, whose accuracy and completeness we aren't equipped to assess:

DRUM (2/20/16): As it turns out, explaining the "fabric" of spacetime isn't hard. Yes, it's four-dimensional. But all this means is that you define it using four numbers. If you described me via my age, weight, height, and IQ, that would be a "four-dimensional" representation of Kevin Drum. It's not a big deal.

Now suppose you want to describe an event. You need to specify where it happened and when it happened. Take, for example, the airplane crashing into World Trade Center 1. It happened at 40.71º latitude, -74.01º longitude, and 6,371 kilometers (relative to the center of the earth) at 13:46:30 GMT on 11 September 2001 (relative to the common era calendar). As an event in spacetime it's represented by an ordered 4-tuple:

(40.71, -74.01, 6371, 2001.09.11.13.46:30)

There are other events that happened at the same time in other places (me saying "oh shit" in California); at the same place in other times (breaking ground on WTC 1 in 1966); and entirely different times and places (the Battle of Gettysburg). If you collect every possible location of an event ever—that is, every combination of four numbers specifying times and places in the universe—that's all of spacetime. Physicists are likely to call it a manifold or a Minkowski space.

"This is all pretty simple," Drum goes on to say. As presented, we'll agree with that statement.

In fairness, it isn't clear why someone would want to "collect every possible location of an event ever—that is, every combination of four numbers specifying times and places in the universe."

It isn't clear what you'd do with this collection once you were done, if you ever could be.

But if that's all Isaacson meant by "the four-dimensional fabric of space and time," it seems that he was working with some fairly simple concepts. Only one question remains:

Why did he use the word "fabric?"

Sadly, our question is important. When Isaacson refers to "space and time" as a "fabric," it lets him employ the picture of that infernal trampoline, a picture which will be familiar to readers of Einstein-made-easy books.

The problem continues from there. When Isaacson refers to "space and time" as a "fabric," this lets him tell us to picture a bowling ball rolling onto a trampoline, then to imagine something dropping onto "the four-dimensional fabric of space and time" in some similar way. Somehow or other, this is supposed to help us understand gravity, which he has already said is "a warping of space and time."

Alas! It's easy to "picture what it would be like to roll a bowling ball onto the two-dimensional surface of a trampoline." That doesn't tell us why Isaacson then decided to compare "space and time" to that trampoline. It doesn't tell us what he means when he says that space and time constitute a "four-dimensional fabric."

Sadly enough, it doesn't tell us why he referred to space and time as a "fabric" at all! We the readers of simplified books are left on our own with that!

"Okay, it's not easy," Isaacson says, "but that's why we're no Einstein and he was." For ourselves, we'd offer a different explanation. We'd say it isn't easy because Isaacson has made no attempt to explain the peculiar things he has said!

In last Saturday's post, Drum explained what "spacetime" is. This is a step Issacson skipped in the passage we posted.

Let's assume that Drum's account of "spacetime" is accurate and complete. Having done that, let us also ask this:

Even now, do you have any idea why you, or anyone else, should regard spacetime as a "fabric?"

In Drum's account, which is perfectly lucid, "spacetime" sounds like a giant collection of data. So why on earth would someone want to call it a fabric? Why wouldn't you call it "a page full of numbers," or maybe "a vat of ball bearings?"

If we might borrow from the Beatles, why shouldn't we just call it Arthur?

(Reporter: "What would you call that hairstyle you're wearing?" George Harrison: "Arthur." Click here, move to 0:54.)

Why did Isaacson say that "space and time" are some sort of "fabric?" Uh-oh! As readers of Einstein-made-easy books know, this is a common notion.

Indeed, Professor Greene's second best-selling book was called The Fabric of the Cosmos: Space, Time and the Texture of Reality. In Isaacson's "Acknowledgments" chapter, he thanks Greene first among the seventeen different physics professors who helped him craft the science in the book. (Greene "honed the wording of the science passages," Isaacson says.)

That said, here's our question: Does Isaacson ever explain the way in which space and time can be considered a "fabric?" How about Professor Greene? How clearly does he explain this metaphor, concept, description in his own best-selling book?

Following Frost, we'll set that aside for another day. In closing, though, we'll show you one more thing Drum said as he explained spacetime. We'll continue a bit beyond what we posted before. This time around, we'll highlight just one remark by Drum:

DRUM (2/20/16): As it turns out, explaining the "fabric" of spacetime isn't hard. Yes, it's four-dimensional. But all this means is that you define it using four numbers. If you described me via my age, weight, height, and IQ, that would be a "four-dimensional" representation of Kevin Drum. It's not a big deal.

Now suppose you want to describe an event. You need to specify where it happened and when it happened. Take, for example, the airplane crashing into World Trade Center 1. It happened at 40.71º latitude, -74.01º longitude, and 6,371 kilometers (relative to the center of the earth) at 13:46:30 GMT on 11 September 2001 (relative to the common era calendar). As an event in spacetime it's represented by an ordered 4-tuple:

(40.71, -74.01, 6371, 2001.09.11.13.46:30)

There are other events that happened at the same time in other places (me saying "oh shit" in California); at the same place in other times (breaking ground on WTC 1 in 1966); and entirely different times and places (the Battle of Gettysburg). If you collect every possible location of an event ever—that is, every combination of four numbers specifying times and places in the universe—that's all of spacetime. Physicists are likely to call it a manifold or a Minkowski space. For laymen, fabric is fine.

This is all pretty simple. You might not know the mathematics for dealing with arrays of four numbers at a time, but it's well developed. And if you combine that with a few other concepts—like the idea that the speed of light is always constant—you'll eventually end up with the theory of gravitational attraction that's called general relativity.

"For laymen, fabric is fine?" He seems to be saying it's close enough for Einstein-made-easy work!

Our passage from Isaacson turns on the concept that "space and time" can be regarded as some sort of "fabric." Once we've agreed to regard "space and time" that way, we can imagine some counterpart to those bowling balls creating curving and warping.

That said, in what way can "space and time" be regarded as a fabric? Why would anyone say such a thing? Under the circumstances, this seems like an obvious question.

Alas! After explaining nothing, Isaacson simply says the whole thing is hard. After explaining what "spacetime" is, Drum simply says that the "fabric" metaphor, comparison or description is "fine for laymen!"

Copy and recite!

To his credit, Drum accepted the Einstein-made-easy challenge in a pair of posts. Routinely, Drum does excellent work. In this case, though, in the end, even he left us shlubs on our own.

Einstein-made-easy is very hard work! In our view, it's part of a fascinating culture—an upper-end culture of incomprehension. This culture suffuses the failing work of our unhelpful academic and journalistic elites.

Coming next: Nova tackles the plight of the lady on the fast-moving train