http://discovermagazine.com Science, Technology, and The Future http://discovermagazine.com/2010/mar/02-the-real-rules-for-time-travelers http://discovermagazine.com/2010/mar/02-the-real-rules-for-time-travelers <p>People all have their own ideas of what a time machine would look like. If you are a fan of the 1960 movie version of H. G. Wells’s classic novel, it would be a steampunk sled with a red velvet chair, flashing lights, and a giant spinning wheel on the back. For those whose notions of time travel were formed in the 1980s, it would be a souped-up stainless steel sports car. Details of operation vary from model to model, but they all have one thing in common: When someone actually travels through time, the machine ostentatiously dematerializes, only to reappear many years in the past or future. And most people could tell you that such a time machine would never work, even if it looked like a DeLorean.</p> <p>They would be half right: That is not how time travel might work, but time travel in some other form is not necessarily off the table. Since time is kind of like space (the four dimensions go hand in hand), a working time machine would zoom off like a rocket rather than disappearing in a puff of smoke. Einstein described our universe in four dimensions: the three dimensions of space and one of time. So traveling back in time is nothing more or less than the fourth-dimensional version of walking in a circle. All you would have to do is use an extremely strong gravitational field, like that of a black hole, to bend space-time. From this point of view, time travel seems quite difficult but not obviously impossible.</p> <p>These days, most people feel comfortable with the notion of curved space-time. What they trip up on is actually a more difficult conceptual problem, the time travel paradox. This is the worry that someone could go back in time and change the course of history. What would happen if you traveled into the past, to a time before you were born, and murdered your parents? Put more broadly, how do we avoid changing the past as we think we have already experienced it? At the moment, scientists don’t know enough about the laws of physics to say whether these laws would permit the time equivalent of walking in a circle—or, in the parlance of time travelers, a “closed timelike curve.” If they don’t permit it, there is obviously no need to worry about paradoxes. If physics is not an obstacle, however, the problem could still be constrained by logic. Do closed timelike curves necessarily lead to paradoxes?</p> Sean Carroll http://discovermagazine.com/2010/mar/02-the-real-rules-for-time-travelers/key_image Tue, 02 Feb 2010 15:30:00 -0600 Tue, 02 Feb 2010 15:30:00 -0600 Print Article http://discovermagazine.com/2009/dec/11-quantum-computing-gets-real http://discovermagazine.com/2009/dec/11-quantum-computing-gets-real Adam Hadhazy http://discovermagazine.com/2009/dec/11-quantum-computing-gets-real/key_image Sun, 31 Jan 2010 21:05:00 -0600 Sun, 31 Jan 2010 21:05:00 -0600 Print Article http://discovermagazine.com/2010/jan-feb/39 http://discovermagazine.com/2010/jan-feb/39 Traffic jams are mathematically like explosions. Drivers armed with info can defuse the bomb. Stephen Ornes http://discovermagazine.com/2010/jan-feb/39/key_image Tue, 26 Jan 2010 09:30:00 -0600 Tue, 26 Jan 2010 09:30:00 -0600 Print Article http://discovermagazine.com/2010/jan-feb/40 http://discovermagazine.com/2010/jan-feb/40 Four ions can become quantum entangled. Why not a human? Elizabeth Svoboda http://discovermagazine.com/2010/jan-feb/40/key_image Tue, 26 Jan 2010 09:30:00 -0600 Tue, 26 Jan 2010 09:30:00 -0600 Print Article http://discovermagazine.com/2010/jan-feb/15 http://discovermagazine.com/2010/jan-feb/15 How do different-sized spheres fit into a large container? Stephen Ornes http://discovermagazine.com/2010/jan-feb/15/key_image Mon, 25 Jan 2010 22:45:00 -0600 Mon, 25 Jan 2010 22:45:00 -0600 Print Article http://discovermagazine.com/2010/jan-feb/23 http://discovermagazine.com/2010/jan-feb/23 Data-heavy phenomena like gene regulation may be too complicated for human scientists to pin down. Douglas Fox http://discovermagazine.com/2010/jan-feb/23/key_image Mon, 25 Jan 2010 21:45:00 -0600 Mon, 25 Jan 2010 21:45:00 -0600 Print Article http://discovermagazine.com/2009/dec/06-visual-science-the-ultimate-x-ray-generator http://discovermagazine.com/2009/dec/06-visual-science-the-ultimate-x-ray-generator <img src="http://72.32.204.61/2009/dec/06-visual-science-the-ultimate-x-ray-generator/xrayopener.jpg"/> <p><b>Pictured</b>: A generator at the European Synchrotron Radiation Facility (ESRF) in France powers what are known as “kicker magnets,” which help direct beams of high-energy electrons that whiz around the facility at high speeds. Other magnets wiggle the circulating particle beams, causing them to emit intense X-rays. ESRF’s accelerator is the most powerful synchrotron light source in Europe. Researchers at the facility use this energetic radiation to probe the structures of diverse targets that include superstrong glass, fossils trapped in amber, and proteins produced by malaria parasites.</p> http://discovermagazine.com/2009/dec/06-visual-science-the-ultimate-x-ray-generator/key_image Wed, 06 Jan 2010 11:05:00 -0600 Wed, 06 Jan 2010 11:05:00 -0600 Print Article http://discovermagazine.com/2010/jan-feb/054 http://discovermagazine.com/2010/jan-feb/054 By analyzing how waves change speed and direction, researchers were able to locate the boundary between rigid tectonic plates and the hot, pliable asthenosphere. Jennifer Barone http://discovermagazine.com/2010/jan-feb/054/key_image Wed, 30 Dec 2009 13:45:00 -0600 Wed, 30 Dec 2009 13:45:00 -0600 Print Article http://discovermagazine.com/2010/jan-feb/078 http://discovermagazine.com/2010/jan-feb/078 The National Ignition Facility starts warming up for its main act: nuclear fusion research. Amy Barth http://discovermagazine.com/2010/jan-feb/078/key_image Tue, 22 Dec 2009 13:15:00 -0600 Tue, 22 Dec 2009 13:15:00 -0600 Print Article http://discovermagazine.com/2010/jan-feb/079 http://discovermagazine.com/2010/jan-feb/079 No atoms could escape the void within the cloud: “It’s like trying to swim upstream in a river whose current is faster than you.” Marcia Bartusiak http://discovermagazine.com/2010/jan-feb/079/key_image Tue, 22 Dec 2009 11:55:00 -0600 Tue, 22 Dec 2009 11:55:00 -0600 Print Article http://discovermagazine.com/2010/jan-feb/083 http://discovermagazine.com/2010/jan-feb/083 The attraction and repulsion effects make up what is known as the “optical force,” a newly observed phenomenon that works on microscopic scales. Stephen Ornes http://discovermagazine.com/2010/jan-feb/083/key_image Mon, 21 Dec 2009 11:35:00 -0600 Mon, 21 Dec 2009 11:35:00 -0600 Print Article http://discovermagazine.com/2010/jan-feb/086 http://discovermagazine.com/2010/jan-feb/086 The CERN theoretical physicist looks ahead to what will happen when the LHC gets cranked up to full power. Fred Guterl; photography by Robert Huber http://discovermagazine.com/2010/jan-feb/086/key_image Sat, 19 Dec 2009 22:10:00 -0600 Sat, 19 Dec 2009 22:10:00 -0600 Print Article http://discovermagazine.com/2010/jan-feb/093 http://discovermagazine.com/2010/jan-feb/093 The quirks in Einstein's thinging parts may have reflected his “preference for thinking in sensory impressions, including visual images rather than words.” Jane Bosveld http://discovermagazine.com/2010/jan-feb/093/key_image Thu, 17 Dec 2009 17:15:00 -0600 Thu, 17 Dec 2009 17:15:00 -0600 Print Article http://discovermagazine.com/2009/dec/18-what-is-this-hi-tech-pin-cushion http://discovermagazine.com/2009/dec/18-what-is-this-hi-tech-pin-cushion Hint: There are a lot fewer of them now than there were a few years ago. Andrew Grant http://discovermagazine.com/2009/dec/18-what-is-this-hi-tech-pin-cushion/key_image Wed, 18 Nov 2009 12:25:00 -0600 Wed, 18 Nov 2009 12:25:00 -0600 Print Article http://discovermagazine.com/2009/nov/17-the-brain-humanity.s-other-basic-instinct-math http://discovermagazine.com/2009/nov/17-the-brain-humanity.s-other-basic-instinct-math New research suggests that math has evolved its way right into our neurons—and monkeys', too. Carl Zimmer http://discovermagazine.com/2009/nov/17-the-brain-humanity.s-other-basic-instinct-math/key_image Tue, 17 Nov 2009 09:35:00 -0600 Tue, 17 Nov 2009 09:35:00 -0600 Print Article http://discovermagazine.com/2009/oct/12-inside-view-hiccups-at-lhc http://discovermagazine.com/2009/oct/12-inside-view-hiccups-at-lhc Physicist Lisa Randall describes the turbulent first year after the collider's premature celebration. Lisa Randall http://discovermagazine.com/2009/oct/12-inside-view-hiccups-at-lhc/key_image Thu, 12 Nov 2009 10:35:00 -0600 Thu, 12 Nov 2009 10:35:00 -0600 Print Article http://discovermagazine.com/2009/nov/02-visual-science-polishing-a-cosmic-spyglass http://discovermagazine.com/2009/nov/02-visual-science-polishing-a-cosmic-spyglass A tune-up for one of the most sophisticated imaging devices ever made http://discovermagazine.com/2009/nov/02-visual-science-polishing-a-cosmic-spyglass/key_image Mon, 02 Nov 2009 18:00:00 -0600 Mon, 02 Nov 2009 18:00:00 -0600 Print Article http://discovermagazine.com/2009/nov/21-what-is-this-bioluminescent-mushroom http://discovermagazine.com/2009/nov/21-what-is-this-bioluminescent-mushroom <div> <p class="imgcapright"><img src="http://discovermagazine.com/2009/nov/21-what-is-this-bioluminescent-mushroom/stellar.jpg"></p> <p>What is This? A Bioluminescent Mushroom?</p><p>Hint: It's actually not on the ground, nor in the oceans, but up in the sky—way up in the sky.</p></div> Andrew Grant http://discovermagazine.com/2009/nov/21-what-is-this-bioluminescent-mushroom/key_image Wed, 21 Oct 2009 08:50:00 -0500 Wed, 21 Oct 2009 08:50:00 -0500 Print Article http://discovermagazine.com/2009/sep/06-discover-interview-roger-penrose-says-physics-is-wrong-string-theory-quantum-mechanics http://discovermagazine.com/2009/sep/06-discover-interview-roger-penrose-says-physics-is-wrong-string-theory-quantum-mechanics One of the greatest thinkers in physics says the human brain—and the universe itself—must function according to some theory we haven't yet discovered. Susan Kruglinski; photography by Oliver Chanarin http://discovermagazine.com/2009/sep/06-discover-interview-roger-penrose-says-physics-is-wrong-string-theory-quantum-mechanics/key_image Tue, 06 Oct 2009 11:20:00 -0500 Tue, 06 Oct 2009 11:20:00 -0500 Print Article http://discovermagazine.com/2009/jul-aug/11-being-stephen-hawking http://discovermagazine.com/2009/jul-aug/11-being-stephen-hawking Former Nature editor John Maddox on one of the most famous scientists of our age Sir John Maddox http://discovermagazine.com/2009/jul-aug/11-being-stephen-hawking/key_image Tue, 29 Sep 2009 12:10:00 -0500 Tue, 29 Sep 2009 12:10:00 -0500 Print Article http://discovermagazine.com/2009/jul-aug/11-stephen-hawking-is-making-his-comeback http://discovermagazine.com/2009/jul-aug/11-stephen-hawking-is-making-his-comeback Stephen Hawking, the master of time, space, and black holes, steps back into the spotlight to secure his scientific legacy—and to explain the greatest mystery in physics: the origin of the universe. Tim Folger; photography by Mackenzie Stroh http://discovermagazine.com/2009/jul-aug/11-stephen-hawking-is-making-his-comeback/key_image Fri, 11 Sep 2009 12:10:00 -0500 Fri, 11 Sep 2009 12:10:00 -0500 Print Article http://discovermagazine.com/2009/jul-aug/08-ways-scientists-look-dark-matter http://discovermagazine.com/2009/jul-aug/08-ways-scientists-look-dark-matter Scientists hunt for the unseen matter that glues together the cosmos. But some wonder whether it even exists. Stephen Ornes http://discovermagazine.com/2009/jul-aug/08-ways-scientists-look-dark-matter/key_image Mon, 22 Jun 2009 12:45:00 -0500 Mon, 22 Jun 2009 12:45:00 -0500 Print Article http://discovermagazine.com/2009/jun/04-game-theory-meets-darwin http://discovermagazine.com/2009/jun/04-game-theory-meets-darwin A computer simulation correctly predicts that ravens should have evolved a behavior called "gang foraging." How did researchers see this behavior? They tracked ravens by implanting carcasses with different-colored beads that the birds ingested and later coughed up. Andrew Grant http://discovermagazine.com/2009/jun/04-game-theory-meets-darwin/key_image Fri, 22 May 2009 12:40:00 -0500 Fri, 22 May 2009 12:40:00 -0500 Print Article http://discovermagazine.com/2009/may/01-the-biocentric-universe-life-creates-time-space-cosmos http://discovermagazine.com/2009/may/01-the-biocentric-universe-life-creates-time-space-cosmos Stem-cell guru Robert Lanza presents a radical new view of the universe and everything in it. Robert Lanza and Bob Berman http://discovermagazine.com/2009/may/01-the-biocentric-universe-life-creates-time-space-cosmos/key_image Fri, 01 May 2009 20:50:00 -0500 Fri, 01 May 2009 20:50:00 -0500 Print Article http://discovermagazine.com/2009/may/20-things-you-didnt-know-about-tunnels http://discovermagazine.com/2009/may/20-things-you-didnt-know-about-tunnels New York has a forgotten one, Texas has a $2 billion wasted one, and Switzerland's building the longest. Jocelyn Rice http://discovermagazine.com/2009/may/20-things-you-didnt-know-about-tunnels/key_image Wed, 29 Apr 2009 10:15:00 -0500 Wed, 29 Apr 2009 10:15:00 -0500 Print Article