The Non-Expanding Universe

FQXi ^ | 25 Aug 2009 | Kate Becker

[BGHater]

Time doesn’t exist. The universe isn’t really expanding. And if you want a theory of quantum gravity, look to the man who inspired Einstein, says Julian Barbour.

For someone who believes time doesn’t exist, Julian Barbour sure has a head for dates. He remembers exactly when he started to have doubts about time: It was October 18, 1963, and he was reading the newspaper. He spotted an article about the physicist Paul Dirac and his quest for a theory of quantum gravity—a theory linking Einstein’s ideas about gravity to the clashing doctrine of quantum mechanics.

Today, Barbour is on that same mission to unite gravity with quantum mechanics. In order to succeed, he believes that we not only need to re-examine our understanding of time, but also question the conventional wisdom that the universe is expanding.

Happily for me, Barbour doesn’t take advantage of his skepticism about time to shrug off appointments. After picking up the phone precisely on time for this interview, he asked for seven minutes exactly to finish the remaining third of his cup of coffee, and was ready and waiting for my call, coffee cup drained, 560 seconds later.

Off the Clock

Barbour’s certainly not the first physicist to question our understanding of time; Einstein was a skeptic, too. If Barbour had told Einstein to give him a call back in seven minutes, Einstein might have asked: Your minutes or mine? If Barbour had been calling, say, from a spaceship moving at close to the speed of light, or one perched at the lip of a black hole, Einstein would find that each of Barbour’s minutes would last far longer than his. There is no universal reference clock that both Barbour and Einstein could agree on.

But, asks Barbour, what if it isn’t just time that has no universal reference? What if position is all relative, too? Ernst Mach—the multi-talented scientist who discovered the sound barrier and gave his name to the eponymous numbers—suggested something similar in the late 1800s, rejecting "absolute" measurements and replacing them with relative, or relational, ones.

To get a handle on Mach’s viewpoint, imagine a particle spinning out in space. If there were no stars forming a backdrop against which to measure the particle’s motion, can we really say that the particle is moving? To Mach, the answer was no, in an empty space there is no distinction between the particle spinning and the particle being stationary.

"The Anatomy of God"

If this doesn’t seem revolutionary, try seeing it from Isaac Newton’s perspective. When Newton penned his laws of motion, Barbour explains, "He thought he’d seen ’the anatomy of God.’" And to Newton, God looked pretty much like three-dimensional graph paper. On top of this invisible coordinate grid, balls rolled, apples dropped, planets orbited.

To Newton, our particle could definitely be said to be spinning, because it was moving relative to the fixed grid of space. All one needed to understand the universe was full knowledge of where each object was on the grid, and when, according to the ticking of an invisible absolute clock.

Newton’s "theory of change" was "phenomenally successful," says Barbour. But it had a weakness, "the invisible background grid and clock."

"My life’s work has been about finding an alternative theory of change," says Barbour, one that is purely "Machian"—that is, a theory that does away with the grid and clock. Such a theory, he believes, might open the door to quantum gravity.

Going Off Grid

Einstein took a big step in deconstructing Newton’s old grid. In his theory of General Relativity, Einstein reimagined the grid as pliable, allowing space itself to arch and flex under the influence of gravity. And because objects are in constant motion, Einstein saw the grid as dynamic, changing with time as gravity adjusted its grip. Einstein even coined the term "Mach’s Principle" to describe the ideas that inspired him.

But for a "Machian" thinker, there is a problem: Following astronomer Edwin Hubble’s measurements in the 1920s and 1930s, which showed that other galaxies seem to be receding from ours, Einstein accepted that the universe is expanding. Yet, with no absolute ruler to measure that expansion, how would it be possible to know that the universe is any bigger today than it was yesterday?

"When you look at General Relativity, it is beautifully Machian," says Barbour. "But the expansion of space that it allows presupposes an absolute ruler. That’s a surprising vestige of Newton’s absolute grid."

Barbour explains with a geometrical analogy. Suppose the whole universe just consisted of a triangle. You could measure the angles of the triangle with respect to each other and classify the triangle as equilateral, isosceles, or scalene (providing, that is, that you remembered your seventh-grade geometry). You could say, hey, the angles of a triangle add up to 180 degrees! But if you wanted to judge the size of the triangle, you’d need a second triangle to make a comparison.

Barbour’s conclusion: "Shape is much more fundamental than size. I conjecture an alternative cosmology in which the universe is merely changing its shape—becoming more structured—and not doing that as well as expanding."

Another way to put it: "We swim in nothing," says Barbour. Not in a rigid grid; not with an absolute clock and ruler. "But," he asks, "precisely how do we swim in nothing?"

Back to Mach

To answer that question, Barbour set out to reformulate physics, this time leaving out both the absolute size and the universal clock. With his hands thus mathematically tied, he began at the beginning, with Newton and the law of inertia ("objects at rest tend to stay at rest, objects in motion tend to stay in motion"—you remember).

Barbour likes to start with his intuition, and then dig in to the math with help from collaborators like Bruno Bertotti at the University of Pavia, Italy, and Niall Ó Murchadha at University College Cork, Ireland. "I’m very much an intuitive thinker," says Barbour. "I was never much good at mathematics—wasn’t in the class of the superstars." (Of course, you’ll want to take this with a grain of salt—he did receive his degree in mathematics from Cambridge with honors.)

Barbour’s first insight was that Newton’s laws of motion could, indeed, be completely rewritten without absolute time or absolute distance. Then, he and his collaborators showed that general relativity is perfectly relational—except for the niggling problem of that un-Machian expansion.

But his search for an alternative explanation that does away with the expansion of the universe has been met with skepticism: "I have been taken much more seriously saying time doesn’t exist than that the universe isn’t expanding!"

Then, of course, comes quantum mechanics. Barbour’s dream is that elimination of expansion might reveal a new route to quantum gravity. He’ll investigate this possibility with the help of a $99,563 grant from the Foundational Questions Institute, and his collaborators Joseph Silk at the University of Oxford, UK, Edward Anderson at the University of Cambridge, UK, and Hans Westman and Sean Gryb, at the Perimeter Institute (PI) in Waterloo, Ontario. Barbour admits it’s a long shot—he estimates the probability he’ll turn out to be wrong is greater than 90%. "But should I be right, I would be assured a place in history," he laughs.

Lee Smolin, a theoretical physicist at PI, says that Barbour has already carved out a comfortable place in the history of quantum gravity. Smolin calls Barbour a scientific "seer," adding that he has provided the rigorous mathematical structure upon which to build clock- and ruler-less theories.

Olaf Dreyer, a quantum gravity researcher at the Massachusetts Institute of Technology, in Cambridge, sits on the opposite side to Barbour on the debate over time, but he salutes his work: " is one of the few people who really thinks about the foundations of general relativity," which Dreyer describes as nearly "virgin territory."

Barbour isn’t counting on a speedy payoff. "I don’t believe there will be a quick breakthrough," he says. "It will keep the young people busy all their lives." To pass some of his knowledge on to those young people, Barbour is also in the process of writing a book which, he says, "will present more or less everything that I think I have learned about two basic questions: What is time? What is motion? The answers to these two questions permeate the whole of modern physics in a way that few researchers realize." It will be "a new perspective that they won’t find in any textbook."

[Huck]

I've never been able to grap these deep physics arguments. Just because we don't have an absolute God-approved clock to check against doesn't mean there is no such thing as time. Things happens in a sequence. If I put a pot of water on to boil, it doesn't instantly boil. I have to wait until it reaches boiling temperature. That waiting period is clearly time. You can argue about whose clock measures that time the best, but you can't argue that there was a period of time bewteen setting the pot on the stove, and the point when it started to boil.

Likewise with the "grid" concept. The grid is a construct to measure space. The grid might be inaccurate, but it doesn't mean space doesn't exist. And even if the Universe is expanding, or if it's a triangle, it pretty much solves nothing, because of infinity. That triangle, or that expanding Universe, exists within space. But isn't there more space outside that space? I can't fathom nothingness. Even empty space is something, isn't it?

[Huck]

PS— I do find it quite entertaining and amazing to consider how little we know about where we are, when we are, why we are. We do well getting by on earth, but the big picture remains a mystery.

[SunkenCiv]

Julian Barbour site:freerepublic.com

Google

Thanks BGHater.

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[SunkenCiv]

Julian Barbour’s web site
http://www.platonia.com/

[BGHater]

Well, there are certain things constant in the Universe, of course, death and taxes.

[EGPWS]

If Barbour had told Einstein to give him a call back in seven minutes, Einstein might have asked: Your minutes or mine? If Barbour had been calling, say, from a spaceship moving at close to the speed of light, or one perched at the lip of a black hole, Einstein would find that each of Barbour’s minutes would last far longer than his. There is no universal reference clock that both Barbour and Einstein could agree on.

Exactly!

It frustrates me to no end that some people miss this important part of physics.

I get flack for not getting the lawn cut yet, when in effect, on MY time it is already cut!

I constantly have to make people realize that their time is simply different than mine.

[Quix]

Hmmmmmmmmmmmm

Things that make one go Hmmmmmmm in the night . . .

Thanks.

[mikrofon]

He’ll investigate this possibility with the help of a $99,563 grant from the Foundational Questions Institute

The Institute claimed they gave him $100K -- relativity, y'know...

[brytlea]

From a Christian standpoint not having time as a real thing makes perfect sense. It would explain how God knows what is going to happen—it already has. But I’m not physics smart enough to understand this stuff. We are concrete beings and to us, time DOES exist just as beginnings and endings exist. Except, I also can’t grasp the concept that everything didn’t ALWAYS exist (that is, it has a starting point) because seems that if there was nothing there would never have been anything. OK, now my head hurts!

[trussell]

I get flack for not getting the lawn cut yet, when in effect, on MY time it is already cut!

Who's giving you flack? I'll kick their butt! ;~)

[Michael Barnes]

You still alive and kicking? This is up your alley, right?

[Michael Barnes]

Quix! How ya been?

[aruanan]

"My life’s work has been about finding an alternative theory of change," says Barbour, one that is purely "Machian"—that is, a theory that does away with the grid and clock. Such a theory, he believes, might open the door to quantum gravity.

Grid is Dead?

[Quix]

Up to my usual and getting the new semester off in good form.

Will be interesting to see what happens in such a setting when the

poo HTFan

GOD HAVE MERCY ON US ALL.

Missed seeing you much . . . What’s new in your neck of the woods?

Anything interesting to report from your connections?

What’s your sense, feel, impressions from your perspective?

Do you expect as so many seem to . . . that things will fall utterly apart in great trauma within 30-60 days?

or is it ho hum status quo as far as the eye and senses can see and sense in your sphere?

[aruanan]

Of course, against Barbour's huge pile of words, we have Mills's actually existing hydrinos. He seems to have a much better grasp of physics than Barbour does and it doesn't have to invoke quantum silliness.

[count-your-change]

One can measure the depth of the world's economic depression by the number of books written on esoteric theories that no one reads but are praised to the heavens.

[PIF]

A Time Experiment

Step outside:

Now prove which way a sequence went...

cool water in kettle;
burner lit;
kettle boils;

or

kettle boils;
burner lit,;
cool water in kettle...

Or to put it another way:
If you have a ping pong ball bouncing off two walls - can you prove which wall the ball began bouncing from? There's an article in a very very old Scientific American on this example.

What happens in the middle is called time, but that time may be something subjective and particular only to humans. James Maxwell Clerke posited things happen in fields not vectors (current theoretical physics models). In those theorems, time is simultaneous everywhere. Everything happens at once - we are just incapable of understanding or perceiving it that way.

The perception than time runs forward is an illusion in physics, but one that makes sense to us as humans. However, in a different universe, it might be possible to say that those humans would find the reverse makes more sense for them.

And it is simply a theory that the universe is expanding. While the steady state universe was disproved, it does not mean with all the problems and uncertainties in theoretical physics that it will remain so.

My favorite one is the oft repeated “nothing escapes from a black hole, not even light”. Yet it very clear that something does escape somehow.

Since modern astronomy posits a black hole at the center of every galaxy, nothing should be emitted, but look at any UV/IR image and there indeed is something coming out of the very center of galaxies where nothing should be. No one talks about this wee problem.

Outer space is not empty, but filled with radiations of all kinds. There is nothing we currently know of that actually contains absolutely nothing. We may not be able to graps any of this in our real lives, but it is fun - to me at least - to play with them. :)

[samtheman]

Lee Smolin, a theoretical physicist at PI

This might be off-topic to this thread but the mention of Lee Smolin inspires me to mention that I just read one of his books (The Trouble With Physics) in which he goes to great lengths explaining how the entire grant, job, funding and tenure system conspires to basically lock all non-string-theorists out of the Physics Establishment (at least for a few decades) and I couldn't help thinking as I read that that I bet the EXACT SAME THING is happening in Climate Change (aka Global Warming).

[eldoradude]

Interesting article, thought provoking. Thanks for posting.