Discover Magazine | Subatomic Particles

Big Idea: Physicists Carve a Niche in Time

Mon, 07 May 2012 10:30:00 -0400

Physicists routinely baffle reporters, but for once things went the other way. Alexander Gaeta was sitting in his Cornell University office in the fall of 2010 when a reporter called to ask his opinion of a strange new paper in the Journal of Optics: What did he think about the claim that it might be possible to create a time cloak, a device that would render events undetectable?

Gaeta was caught off guard. He was still grappling with the invisibility cloak, a wild idea that turned into reality in 2006, when physicists demonstrated that a class of synthetic materials could bend light completely around an object. (Think of water in a stream flowing around a rock.) Without light bouncing off the object, it would essentially disappear.

But creating a time cloak–something that could hide not just an object but an event–is even more ambitious. Rather than just rerouting the rays of light striking an object, a time cloak would have to deflect all the light beams influenced by the object as it moves through space. The time cloak would, in essence, create an interval during which all information about what an object is doing disappears.

Although Gaeta had not heard of the time-cloak study until that phone call, he dove into it as soon as the reporter sent it over. The author, theoretical physicist Martin McCall of Imperial College London, proposed splitting a light beam into two segments moving at different speeds. As one fragment built a lead on the other, a gap of complete darkness would open up between them. Anything happening within that gap, McCall reasoned, would be impossible to detect, since there would be no light to scatter. Then, to complete the trick, McCall proposed bringing those two segments back together so that by the time the beam of light reached an observer, there would be no way to detect that the gap ever existed...

Is Einstein's Greatest Work All Wrong—Because He Didn't Go Far Enough?

Tue, 01 May 2012 12:35:00 -0400

Julian Barbour cuts an unlikely figure for a radical. We sip afternoon tea at his farmhouse in the sleepy English village of South Newington, and he playfully quotes Faust: That I may understand whatever binds the world’s innermost core together, see all its workings, and its seeds. His love of Goethe’s classic poem, about a scholar who sells his soul to the devil in exchange for unlimited knowledge, is apropos. Forty years ago, Barbour’s desire to uncover the innermost workings of the universe led him to make a seemingly reckless gamble. He sacrificed a secure and potentially prestigious career as an academic to strike out on independent research of his own. His starry-eyed quest: upending Albert Einstein’s theory of relativity, and with it our understanding of gravity, space, and time.

It was less than a century ago that Einstein was the most radical physics thinker around. With his general theory of relativity, he discarded the traditional notion of space and time as fixed and redefined them as flexible dimensions woven together to create a four-dimensional fabric that pervades the universe. In Einstein’s vision, this stretchy version of space-time is the source of gravity. The fabric bends and warps severely around massive objects such as the sun, drawing smaller objects such as planets toward them. The force that we perceive as gravity is the result.

Yet Einstein’s fabric left a few loose threads that cosmologists have struggled to tie up ever since. For one, general relativity alone cannot explain the observed motions of galaxies or the way the universe seems to expand. If Einstein’s model of gravity is correct, around 96 percent of the cosmos appears to be missing. To make up the difference, cosmologists have posited two mysterious, invisible, and as yet unidentified ingredients: dark matter and dark energy, a double budget deficit that makes many scientists uncomfortable. Einstein also failed to deliver an all-encompassing theory of “quantum gravity”—one that reconciled the laws of gravity observed on the scale of stars and galaxies with the laws of quantum mechanics, the branch of physics that explains the behavior of particles in the subatomic realm.

While other scientists tread softly around the edges of Einstein’s theory, hoping to tweak it into compliance, Barbour and a growing cadre of collaborators see a need for a bold march forward. They aim to demolish the space-time fabric that stands as Einstein’s legacy and remap the universe without it. This new cosmic code could eliminate the need to invoke dark matter and dark energy. Even more exciting, it could also open the door to the theory of quantum gravity that Einstein was never able to derive. If Barbour is right, some of the most fundamental things cosmologists think they know about the origin and evolution of the universe would have to be revised...

Image: Galaxy cluster Abell 1689 seems to be held together by swaths of unseen dark matter; blue shows its theoretically inferred location. But could dark matter be an illusion? Courtesy of NASA

20 Things You Didn't Know About... Math

Fri, 23 Mar 2012 11:20:00 -0400

5 Sometimes the oddest bits of math often turn out to be useful. Quaternions, which can describe the rotation of 3-D objects, were discovered in 1843. They were considered beautiful but useless until 1985, when computer scientists applied them to rendering digital animation.

8 Kurt Gödel, the renowned Austrian logician, made math a lot more confusing in 1931 with his first incompleteness theorem, which said that any sufficiently powerful math system must contain statements that are true but unprovable. Gödel starved himself to death in 1978.

19 Graduate student George Dantzig arrived late to statistics class at Berkeley one day in 1939 and copied two problems off the blackboard. He handed in the answers a few days later, apologizing that they were harder than usual.

20 The “homework” was actually two well-known unproven theorems. Dantzig’s story became famous and inspired a scene from Good Will Hunting...

How to Survive the End of the Universe

Tue, 28 Feb 2012 10:25:00 -0500

Next year will be a doozy for doomsayers. depending on the prophecy, the world is predestined to expire by means of a solar storm, asteroid strike, rogue-planet collision, plague, falling stars, earthquake, debt crisis, or some combination thereof. Of course, nobody seems to be preparing for any of these impending 2012 apocalypses, with the exception of a porn studio reportedly building a clothing-optional underground bunker.

And why should we? Scientifically speaking, the prophecies are strictly ballyhoo. Physicists can do a lot better. When it comes to end-times scenarios, cosmological data-crunchers have at their disposal far more meaningful prognostication tools that can tell us how it’s really going to end—not just Earth, but the whole universe. Best of all, they can tell us how to survive it.

Science, oddly, is a lot better at predicting things like the death of stars than next week’s weather. The same laws of physics that enable scientists to study the Big Bang that occurred 13.7 billion years ago also allow them to gaze into the future with great precision. And few people have peered farther than University of California, Santa Cruz, astronomer Greg Laughlin, science’s leading soothsayer. As a graduate student in 1992, he was plugging away at a simple computer simulation of star formation when he broke for lunch and accidentally left the simulation running. When he returned an hour later, the simulation had advanced 100 million billion years, much further into the future than most scientists ever think (or dare) to explore.

The program itself didn’t reveal anything terribly startling—the simulated star had long since gone cold and died—but Laughlin was intrigued by the concept of using physical simulations to traverse enormous gulfs of time. “It opened my eyes to the fact that things are going to evolve and are still going to be there in timescales that dwarf the current age of the universe,” he says.

Four years later, still fascinated, Laughlin teamed up with Fred Adams, a physics professor at the University of Michigan, to investigate the future of the universe more rigorously. Working in their spare time, the two researchers coauthored a 57-page paper in the journal Reviews of Modern Physics that detailed a succession of future apocalypses: the death of the sun, the end of the stars, and multiple scenarios for the fate of the universe as a whole...

How to See the Invisible: 3 Approaches to Finding Dark Matter

Wed, 22 Feb 2012 10:30:00 -0500

Spiral galaxy M74 holds 100 billion stars. Oddly, stars at its outer edges rotate with the same velocity as those closer in, suggesting the influence of a substantial mass of unseen dark matter.

Credit: NASA

Although we live in a renaissance era of cosmology, in which theories and observations have advanced to the stage where ideas can be precisely tested, we also live in the dark ages. About 23 percent of the universe consists of dark matter, mysterious stuff that exerts gravitational forces but doesn’t interact with light. Ordinary matter makes up just 4 percent. (Another 73 percent is dark energy, an even more mysterious component that permeates the universe.)

The last time something was called “dark” in physics was in the mid-1800s, when Urbain-Jean-Joseph Leverrier of France proposed an unseen dark planet, which he named Vulcan. Leverrier’s goal was to explain the peculiar trajectory of the planet Mercury. Leverrier, along with John C. Adams of England, had previously deduced the existence of Neptune based on its effects on the planet Uranus. Yet he was wrong about Mercury. It turned out that the reason for Mercury’s strange orbit was much more dramatic than the existence of another planet. The explanation could be found only with Einstein’s theory of relativity. The first confirmation that the theory of general relativity was correct came when Einstein proved it could be used it to accurately predict Mercury’s orbit.

It could turn out that dark matter presages a similar paradigm change. Even so, I’d say that it is very likely to have a more conventional explanation, consistent with the type of physical laws we now know. After all, even if novel matter acts in accordance with force laws similar to those we know, why should all matter behave exactly like familiar matter? To put it more succinctly, why should all matter interact with light? If the history of science has taught us anything, it should be the shortsightedness of believing that what we see is all there is...

How I Dismantled the World’s Deadliest Weapon

Mon, 20 Feb 2012 07:05:00 -0500

In October Sandia National Laboratories engineer Phil Hoover dismantled the U.S. arsenal’s last B53, a 9-megaton bomb 600 times as powerful as the one dropped on Hiroshima. Hoover talked to DISCOVER about taking apart America’s most powerful weapon.

The B53 was big and heavy, about the size of a minivan and 10,000 pounds. We needed 130 engineers and scientists from across the nuclear weapons enterprise to take it apart. Even though the B53 was designed to be rather easily disassembled, it still took us about two weeks per bomb.

All of the nuclear explosive disassembly was done in one well-lit, clean, and orderly room large enough to hold a Volkswagen van. We wore coveralls, safety glasses, gloves, safety shoes, and dosimeters to track radiation exposure. Typically three or four people at a time actually did the work. There wasn’t much small talk—the operation required focus...

20 Things You Didn't Know About... Clouds

Mon, 30 Jan 2012 12:35:00 -0500

4 So much for People Power. After reviewing 40 years of cloud-seeding efforts in an area north of Israel, researchers at Tel Aviv University have concluded that seeding doesn’t actually produce additional precipitation (pdf).

12 Highest of them all: 50 miles up, noctilucent, or “night shining,” clouds glow an eerie bluish white. They are invisible by day, but after sunset they catch solar rays shining from far below the horizon.

13 Noctilucent clouds seemed to first appear after the 1883 eruption of Krakatoa and are now a common sight.

18 In 1959 Lt. Col. William Rankin was flying his F-8 fighter jet over a cumulonimbus when the engine failed. He parachuted out and spent the next 30 minutes bounced around inside the storm. Amazingly, he survived.

19 In 2007 German paragliding champion Ewa Wisnierska experienced “cloud suck.” While gliding under a cumulonimbus, she was pulled upward to 32,000 feet. She blacked out due to lack of oxygen but regained consciousness at roughly 23,000 feet.

Image: A lenticular cloud over the Tararua Mountains in the North Island of New Zealand. Courtesy: NASA

Selling Cheap: Abandoned, Half-Finished, Would-Be Collider Facility

Fri, 02 Dec 2011 12:50:00 -0500

Image: Wikimedia Commons

$6.5 million: The initial asking price for the 135-acre property in Texas that two decades ago was supposed to be the site of the world’s most powerful particle accelerator, the Superconducting Super Collider. Congress canceled the project in 1993 after spending $2 billion (300 times the site’s current price) to construct eight buildings and 14 miles of underground tunnels. At press time the property was under contract. Bryan Loewen, a real estate agent at Newmark Knight Frank who is handling the sale, says potential buyers expressed interest in using the tunnels  for alternative energy generation, secure storage, and mushroom farming. Nobody has accessed the tunnels since the government closed them off in the mid-90s...

20 Things You Didn't Know About... The Periodic Table

Wed, 30 Nov 2011 12:40:00 -0500

1 You may remember the Periodic Table of the Elements as a dreary chart on your classroom wall. If so, you never guessed its real purpose: It’s a giant cheat sheet.

4 To determine atomic weights, scientists had passed currents through various solutions to break them up into their constituent atoms. Responding to a battery’s polarity, the atoms of one element would go thisaway, the atoms of another thataway. The atoms were collected in separate containers and then weighed.

6 Fond of card games, Mendeleyev wrote the weight for each element on a separate index card and sorted them as in solitaire. Elements with similar properties formed a “suit” that he placed in columns ordered by ascending atomic weight.

9 Ehen argon was discovered in 1894, it didn’t fit into any of Mendeleyev’s columns, so he denied its existence—as he did for helium, neon, krypton, xenon, and radon...

Image: Lawrence Berkeley National Lab

Out There: Are There Mysterious Forces Lurking in Our Atoms and Galaxies?

Fri, 04 Nov 2011 14:40:00 -0400

Caption: Far more delicate than the tug on a spider's web: If a fifth force is out there, its impact on our world must be nearly imperceptible.

iStockphoto

At the turn of the 20th century, finding a new form of radiation could put a physicist’s career on the fast track. Wilhelm Röntgen changed the world by discovering X-rays in 1895. Soon thereafter, Ernest Rutherford and Paul Villard identified three different kinds of radiation, dubbed alpha, beta, and gamma rays, emitted by radioactive compounds. In 1903 French scientist René Blondlot added to the frenzy with his announcement of N-rays, a strangely democratic form of radiation emitted by wood, iron, living organisms—just about anything at all.

Some 300 scientific papers were written about N-rays. There was just one problem: They weren’t real. A skeptical physicist named Robert Wood visited Blondlot’s lab and secretly removed a key part of his apparatus; this had no effect on Blondlot’s perception of N-rays, showing that they were purely a product of the imagination.

Blondlot’s reversal of fortune served as a reminder that the world isn’t really full of countless kinds of radiation waiting patiently to be discovered. Nature is more parsimonious than that. Even as forms of radiation seemed to proliferate, theory was driving physics the other way, toward consolidation. X-rays and gamma rays were soon recognized as different forms of electromagnetic radiation, like radio waves and visible light but more energetic. Beta rays are simply fast-moving electrons, and alpha rays are fast-moving helium nuclei. Beneath the dazzling array of new phenomena lurked just a few simple ingredients...

Out There: Welcome to the Multiverse

Tue, 18 Oct 2011 12:35:00 -0400

Theoretical cosmologist isn’t one of the more hazardous occupations of the modern world. The big risks include jet lag, caffeine overdose, and possibly carpal tunnel syndrome. It wasn’t always so. On February 17, 1600, Giordano Bruno, a mathematician and Dominican friar, was stripped naked and driven through the streets of Rome. Then he was tied to a stake in the Campo de’ Fiori and burned to death. The records of Bruno’s long prosecution by the Inquisition have been lost, but one of his major heresies was cosmological. He advocated that other stars were like our sun, and that they could each support planets teeming with life. Orthodox thought of the time preferred to think that Earth and humanity were unique.

These days, cosmologists like me may be safer, but our ideas have grown only more radical. One of the most controversial but widely discussed concepts in the field resembles a hugely amplified version of Bruno’s cosmology: the idea that the thing we call “the universe” is just one of an infinite number of regions in a much larger universe of universes, or multiverse. A big focus of my own research asks whether a multiverse can help explain the arrow of time...

Twisting Radio Waves Could Give Us 100x More Wireless Bandwidth

Mon, 10 Oct 2011 14:25:00 -0400

As more people stream video to their mobile devices, wireless bandwidth is becoming an increasingly precious commodity. Data traffic increased 8,000 percent in the past four years on AT&T’s network alone. In trying to avoid what the Federal Communications Commission calls a “looming spectrum crisis,” telecommunications companies are lobbying the government to assign them more spectrum space in the 300- to 3,000-megahertz range, the sweet spot for wireless communication. But Italian astrophysicist Fabrizio Tamburini says a solution may lie in making better use of the frequencies already in use. In a recent paper, he demonstrated a potential way to squeeze 100 times more bandwidth out of existing frequencies.

The idea is to twist radio waves like corkscrews and create multiple subfrequencies, distinguished by their degree of twistedness. Each subchannel carries discrete data sets. “You can tune the wave with a given frequency as you normally do, but there is also a fingerprint left by the twist,” Tamburini says...

Image: Warped radio waves may satisfy the ballooning demand for spectrum space. Source: iStockphoto

Discover Magazine | Subatomic Particles

Big Idea: Physicists Carve a Niche in Time

Is Einstein's Greatest Work All Wrong—Because He Didn't Go Far Enough?

20 Things You Didn't Know About... Math

How to Survive the End of the Universe

How to See the Invisible: 3 Approaches to Finding Dark Matter

How I Dismantled the World’s Deadliest Weapon

20 Things You Didn't Know About... Clouds

Top 100 Stories of 2011: #1: Faster than the Speed of Light

Top 100 Stories of 2011: #14: Astronomers Watch Black Hole Devour Star

Top 100 Stories of 2011: #17: Quantum Weirdness Enters the Larger World

Top 100 Stories of 2011: #20: Helium’s Antimatter Twin Created

Top 100 Stories of 2011: #26: The New Physics of Bicycles

Top 100 Stories of 2011: #32: Where’s the Higgs?

Top 100 Stories of 2011: #62: Star Birth Seen in Action

Top 100 Stories of 2011: #65: America’s Atom Smasher, 1983–2011

Top 100 Stories of 2011: #82: Could Random Airplane Boarding Speed Your Trip?

Top 100 Stories of 2011: #83: Gravity Probe B Gives Einstein an A

Top 100 Stories of 2011: #93: Super- Rocket Tested

Top 100 Stories of 2011: #95: Computer Builds  A Perfect Galaxy

Top 100 Stories of 2011: #11: Scientist of the  Arab Spring

Selling Cheap: Abandoned, Half-Finished, Would-Be Collider Facility

20 Things You Didn't Know About... The Periodic Table

Out There: Are There Mysterious Forces Lurking in Our Atoms and Galaxies?

Out There: Welcome to the Multiverse

Twisting Radio Waves Could Give Us 100x More Wireless Bandwidth

Discover Magazine | Subatomic Particles

Big Idea: Physicists Carve a Niche in Time

Is Einstein's Greatest Work All Wrong—Because He Didn't Go Far Enough?

20 Things You Didn't Know About... Math

How to Survive the End of the Universe

How to See the Invisible: 3 Approaches to Finding Dark Matter

How I Dismantled the World’s Deadliest Weapon

20 Things You Didn't Know About... Clouds

Top 100 Stories of 2011: #1: Faster than the Speed of Light

Top 100 Stories of 2011: #14: Astronomers Watch Black Hole Devour Star

Top 100 Stories of 2011: #17: Quantum Weirdness Enters the Larger World

Top 100 Stories of 2011: #20: Helium’s Antimatter Twin Created

Top 100 Stories of 2011: #26: The New Physics of Bicycles

Top 100 Stories of 2011: #32: Where’s the Higgs?

Top 100 Stories of 2011: #62: Star Birth Seen in Action

Top 100 Stories of 2011: #65: America’s Atom Smasher, 1983–2011

Top 100 Stories of 2011: #82: Could Random Airplane Boarding Speed Your Trip?

Top 100 Stories of 2011: #83: Gravity Probe B Gives Einstein an A

Top 100 Stories of 2011: #93: Super- Rocket Tested

Top 100 Stories of 2011: #95: Computer Builds A Perfect Galaxy

Top 100 Stories of 2011: #11: Scientist of the Arab Spring

Selling Cheap: Abandoned, Half-Finished, Would-Be Collider Facility

20 Things You Didn't Know About... The Periodic Table

Out There: Are There Mysterious Forces Lurking in Our Atoms and Galaxies?

Out There: Welcome to the Multiverse

Twisting Radio Waves Could Give Us 100x More Wireless Bandwidth

Top 100 Stories of 2011: #93: Super- Rocket Tested

Top 100 Stories of 2011: #95: Computer Builds  A Perfect Galaxy

Top 100 Stories of 2011: #11: Scientist of the  Arab Spring