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Building Einstein's universe

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Author Topic: Building Einstein's universe  (Read 68 times)
Deborah Valkenburg
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Posts: 3233

« on: May 04, 2008, 11:19:55 pm »

Building Einstein's universe

A York professor brings precision to a major test of general relativity

Oct 02, 2005 01:00 AM
Peter Calamai
National Science Reporter
Norbert Bartel is already getting the heebie-jeebies over his part in next year's moment of truth for Einstein's general theory of relativity.

Bartel and his small research group at York University are responsible for producing one half of "The Number" that could decide if Einstein's theory continues to rule as a central pillar in our current understanding of how the universe works.

"And I don't want to be the guy who says that after 10 years of analysis I actually made a mistake two or three years ago. That would be absolutely horrible, and that is why I am so nervous now," he says.

By any rational standard, there's no justification for this nervousness. The 55-year-old astronomer was recruited for the most expensive space experiment ever — the $700 million (U.S.) Gravity Probe B — because he and research associate Michael Bietenholz enjoy an international reputation in astrometry, the science of pinpointing the location and movement of stars, supernovas, black holes and other denizens of the cosmos.

(Aficionados of the TV show Star Trek: Voyager may recall scenes in the ship's astrometrics lab.)

Key to this testing of Einstein's universe is a degree of precision unimaginable to most people. But Bartel, born and educated in Germany, has made precision research a life-long quest bordering on obsession.

"I like precision," he says. "It is something that elevates you a little bit. You have the feeling that you come a little closer to nature, that you're communicating a little more intimately with nature."

Bartel, best known to some as the serious talking head in two popular science DVDs he narrated and produced, is by turns passionate, funny and revealing during a two-hour interview in his York office.

"I have a little of the artsy side in me," he confides. "The combination of arts and science is fascinating to me. It's almost like general relativity and quantum mechanics. They speak completely different languages."

It was a fascination with precision that led Bartel to the field of radio astronomy, where arrays of giant dishes can capture far finer details of stellar phenomena than are possible with even orbiting optical telescopes. Supported by Bietenholz, Bartel has carved out a reputation for precision astronomy, including the first "movies" of a supernova explosion and the first ever detection last year of a supernova giving birth to either a black hole or a neutron star.

Yet he still gets nervous thinking about the relativity experiment.

"This is an experiment very different from other experiments NASA supports," he says. "NASA supports the Hubble telescope. You get thousands of pictures. If the data analysis for one picture is a little wrong, nobody cares. They say they just made a blunder and here's a new picture. There's no problem with that.

"Here we are not allowed to do that," he says. "It comes down to this particular moment. This is an experiment where just the one number gives us an indication of whether the predictions are right or wrong."

A lot more than avoiding a black eye for NASA is riding on the experiment to test the general theory of relativity. At stake are not just the millions of dollars and the reputations of scores of distinguished scientists, but also the core scientific legacy of the iconic Albert Einstein.

"Einstein is the quintessential scientist," says Bartel, reaching into a box beside his desk and pulling out a doll with that trademark fly-away white hair. "No other physicist has an action figure."

The force of Einstein's personality helped carry general relativity a long way after he first announced it in 1915. So has the fact that the theory predicted an expanding universe and the existence of black holes, both subsequently confirmed.

Especially attractive to physicists and astronomers — and mostly puzzling to others — is the sheer elegance of Einstein's vision of space-time as some kind of infinite rubbery plain where matter and energy make the surface sag. As a result, light rays and planets trace curved paths rather than straight ones.

In this sense, it is not gravity that pulls our bodies down to the floor but the warping of space-time that pushes them. Einstein was convinced that general relativity's simplicity and elegance would ensnare physicists in an almost-hypnotic spell. "The theory is of incomparable beauty," he wrote.

Says Bartel, "This Einstein theory is such a clean geometric theory that it has to be right. That is the argument of many theoretical physicists — not all of them — and that is the argument of many astronomers, but also not all of them."

Both communities have their doubting Thomases — scientists who point out that general relativity has been experimentally tested only to a precision of one part in a thousand. By contrast, the other pillar of modern physics, quantum mechanics, has been confirmed at the one-part-in-a-billion level.

The prosaically named Gravity Probe B, a van-sized spacecraft that finally went into orbit around the Earth in April of last year, was born 45 years ago from the desire for more precision. Everything about the gravity-probe project hammers home the message that testing Einstein is no ordinary space experiment.

It was initially conceived in 1959. Five years later, NASA provided researchers at Stanford University in California with the first chunk of money to study the idea. Since then the idea has consumed $700 million (U.S.) and been cancelled a half-dozen times, only to be repeatedly reborn. Nearly 100 Ph.Ds have been awarded at Stanford and elsewhere to researchers and engineers who cut their teeth on the project.

Project co-leader Brad Parkinson, a Stanford engineer, calls it "a testimony to perseverance, at the least."

The experiment itself is widely considered a technological marvel. Cosseted inside what amounts to the largest thermos bottle to fly in space are what NASA claims are the four most perfectly spherical objects ever made by humans. If the Earth were as perfectly round, the tallest mountain would rise less than two-and-a-half metres.

These quartz spheres, slightly larger than golf balls, are gyroscopes spinning at 4,300 revolutions per minute. Their chief job is to measure whether and how the rotating Earth twists space-time around itself, something like a child's top spinning in maple syrup.

This bizarre phenomenon, called frame-dragging, was predicted in 1918 by two Austrian physicists working from the equations in Einstein's still-new theory. The predicted effect near the Earth is so small that it has never been measured directly.

(The probe is also measuring another gravitational distortion predicted by relativity, called the geodetic effect, but it is a hundred times larger than frame-dragging and has already been measured by timing signals from the Cassini mission to Saturn.)

Exotic technology helps the probe's gyroscopes make the necessary super-sensitive measurements: a niobium coating so the gyroscopes can transmit signals about their spin to detectors called squids; cooling of the entire apparatus by liquid helium to two degrees above absolute zero (about -271 C); and a superconducting lead bag that blocks external magnetic fields.

But most of all, the gravity-probe team must know exactly where the gyroscopes are pointing. Or more correctly, where the imaginary axis around which each gyroscope spins is pointing.

If Einstein's theory is correct, during a year-long orbit, frame-dragging should twist the spin axis sideways by one hundred-thousandth of a degree — about the thickness of a human hair viewed from 350 metres away.
This is where Bartel and Bietenholz step in with their expertise in tracking the movement of stars.


The gravity probe spacecraft has a modest optical telescope, 14 centimetres in diameter, that always points to the same guide star during flight, a fixed reference point in space. The spin axes of the gyroscopes are also initially lined up with this star through the telescope.

Then all that's necessary is to measure if and how the spin axes shift out of alignment with the guide star, called IM Pegasi. The problem is that IM Pegasi is a mere 300 light years away, so it's not really a fixed point in space. (For comparison, the centre of our Milky Way galaxy is about 27,000 light years distant.)

In fact, says 46-year-old Saskatchewan native Bietenholz, IM Pegasi appears to be moving in three different paths — along a nearly straight line as the Milky Way galaxy slowly turns, a sideways wiggle because it's orbiting as a binary star, and an oval path from parallax, an apparent visual displacement created by the Earth's yearly passage around the sun.

Using a worldwide network of 15 radio telescopes, the York researchers gather signals from IM Pegasi and three quasars. The quasars, thought to be super-bright black holes, are distant enough that they, unlike IM Pegasi, really do act like lighthouses, providing a stationary reference against which the movement of IM Pegasi can then be plotted.

Each observation requires handling tens of thousands of gigabytes of information. Bietenholz likens the experience to watching a photograph suddenly appear in a darkroom tray.

"You do it all blind. It can take a couple of weeks to go through a data set, and all that time you don't know if you'll actually be able to see what you're looking for.

"Then, like magic, an image pops up."
The York University researchers have been tracking the motion of IM Pegasi since 1997 in anticipation of the gravity-probe launch. The most important measurements cover August last year to August this year, a 50-week span when the spacecraft was sending back readings about the orientation of the gyroscopes' spin axes.

That data, being analyzed at Stanford, will eventually produce a number that measures how much the spin axes deviated from alignment with IM Pegasi. Bartel and Bietenholz will produce another number that measures how IM Pegasi moved during the same period. A group at Harvard University is also producing a second guide star number, using the same radio telescope reading but a different way of manipulating the data.

Neither Stanford nor York-Harvard knows what numbers the others are coming up with, meaning they can't possibly tweak their efforts to make the final answer come out right. This double-blind approach is just part of the extraordinary care being taken to make the result as scientifically bulletproof as possible.

And then comes the moment of truth, when those two numbers come together to produce "The Number," the answer that will decide whether frame-dragging lives or dies and, with it, the fate of Einstein's general theory of relativity.

The fateful meeting will take place next summer at Stanford, although detailed arrangements are still undecided. Yet already Bartel is imagining himself sitting across a table from gravity probe's principal investigator, Francis Everitt, an English-born physicist who joined the gyroscope team in 1962 when he was just 28.

"And then the moment of truth comes. I always pictured it as Francis Everitt will say, `Here's our number... and what do you astronomers get?' And we pull out our number. And he takes out a calculator that you buy from Radio Shack for $12 and says, `Let's put in these two numbers.'"

In his office at York, Bartel pretends to enter a number on his calculator, complete with sound effects for key tapping.

"Dah, dah, dah, dah, dah. Is that one correct?" he asks, now holding up the calculator as Everitt might.

"And now the other number, dah, dah, dah, dah, dah. And now we just subtract or add or do this very simple calculation and only then will we know, have we measured the effect of general relativity as predicted by Einstein?"

If the measured deviation agrees with theoretical predictions, Bartel has a shopping list of new astronomical challenges, some of which he is exploring during his current sabbatical.

But what if "The Number" differs by as much as one two-hundred-millionth of a degree, which Bartel calls a "significant discrepancy"?

He grins. "Then the seat would get very hot."
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Skepticism is good, but when you reach a certain level where
you're grasping at straws and making little sense... it's not
called skepticism.  It's called ignorance.

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Deborah Valkenburg
Superhero Member
Posts: 3233

« Reply #1 on: May 04, 2008, 11:22:45 pm »

A celebration of a man and his scientific genius

Einstein: The former patent clerk who invented E=mc2 bursts to life at a Waterloo festival featuring a can of `brain drink' from Austria

Oct 02, 2005 01:00 AM

Peter Calamai
WATERLOO—Albert Einstein burst figuratively to life here yesterday at the kick-off for an mind-stretching celebration of the science, times, personality and legacy of the world's most recognizable scientist.

Hundreds attended the opening lectures, demonstrations and exhibits of EinsteinFest, an extravaganza that continues daily until Oct. 23. More than 8,000 free tickets have been issued electronically by the organizers at the Perimeter Institute for Theoretical Physics, which sometimes calls itself a "factory" for producing future Einsteins.

The EinsteinFest offerings go well beyond talking about physics, or even science, to feature bistro jazz and classical concerts, silent films, hands-on experiments for children and exhibits that include a can of Einstein "brain" drink from Austria.

There are even four performances of a play by comedian Steve Martin in which Einstein meets Elvis and Picasso at a Paris bar in 1904.

"Science is not some dry and desiccated affair," said Perimeter executive director Howard Burton in opening EinsteinFest.

"Being creative scientifically is no different than being creative musically or artistically," he said.

The festival is Canada's most ambitious contribution to world-wide celebrations marking the centenary of 1905, called Einstein's "miraculous year." In a little over six months the 26-year-old patent clerk in Switzerland poured out a series of scientific papers that revolutionized humanity's concepts of light, matter and energy, including the world's most famous formula, E=mc2.

"His fame is rooted in what he did, but not many people have much knowledge about what he did," American physicist and author John Rigden said.

As Rigden spoke inside the Institute's futuristic building, Jon Hackett was outside in a tent nursing fingers bruised in demonstrating one application of Einstein's most famous formula, the vast energy released by converting just a little mass in a nuclear chain reaction.

Hackett and fellow University of Waterloo physics student Robbie Henderson were trying to set 66 mouse traps, placing ping pong balls where the cheese normally goes, all inside a large acrylic box.

But the slightest jar would spring a trap, bruising fingers and, worse, prematurely loosing the ping pong balls.

Finally all the traps were set. One of the youngsters in the Physica Phantastica tent got to drop a ping pong ball into the box.

In a second 66 balls flew everywhere in the ensuing chain reaction, and Einstein burst to life here yet another time.
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Skepticism is good, but when you reach a certain level where
you're grasping at straws and making little sense... it's not
called skepticism.  It's called ignorance.
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