Miércoles 29 de Junio de 2005, Ip nº 115

Even a Time Lord Couldn't Change History
IT'S a giant step for physicists but a disaster for Dr Who scientists have found that even if we could travel back to the past, it would be impossible to change the future.

The breakthrough contradicts the basic premise of hit movies such as Back To The Future and The Time Machine.

For centuries man has fantasised about going back in time to save a tragically doomed romance or alter the course of history by ridding the world of tyrants such as Hitler.

But a new approach to the subject, using quantum mechanics theory, has shown that the past is fixed. A time traveller would not be able to deviate from events that have already happened in his or her present; the only option available would be to follow the path already taken.

Professor Daniel Greenberger, based at City University of New York, and Professor Karl Svozil, of the Technical University of Vienna, spent hours poring over the equations. They found that when they modelled a journey going backwards in time, the paths followed only reinforced the route already taken killing off all other options.

Professor Svozil, 48, explained: 'According to our model, if you travel to the past, you would only see those alternatives consistent with the world you left behind.

'It would appear that things were happening which you could not control, which just do not allow you to alter the past in a way that would be inconsistent with the future you came from.' Professor Greenberger added: 'Once something has happened, the effect is that it kills the other possibilities because there is this feedback into the past. The past is determined. The future is still undetermined, which is consistent with our ideas of free will. It is a nice philosophical solution.' Their findings solve the conundrum which has puzzled scientists for years: if a time traveller can change the past, could he jeopardise his own survival?

It was this that nearly spelt the end for Michael J. Fox's character Marty McFly in Back To The Future when his mother fell in love with him instead of with his father. As Marty's own existence was threatened he gradually began to fade from view.

Professor Svozil accepts that generations of fans of time-travel films and books will be disappointed. But he says: 'In our model this would not happen.

'It is a fantasy we all have sometimes. You have a romance with a girl and you say I would have done things differently, or, I should have spoken to that girl on the train. Unfortunately, that would not be possible.' While there have never been practical demonstrations of time travel, it is not ruled out by the known laws of physics.

Heidelberg-based physicist Professor Heinz-Dieter Zeh agreed with Greenberger and Svozil's conclusion, but said their method was unrealistic.

He added: 'Changing the past is incompatible with nature's irreversibility, which is based on thermodynamics as well as quantum measurements.' And physicist Avshalom Elitzur, of the Weizmann Institute in Israel, said: 'This is a very nice idea. Time is very mysterious.' Quantum theory was developed in the early 20th Century by scientists including Nobel prizewinner Einstein.

It is described as the physics of tiny particles but, bizarrely for the lay person, gives only probabilities instead of definite measurements to properties such as their location at a point in time.

Science fiction fans can take some comfort in the knowledge that teleportation, at least, is possible. Last summer, physicists in Austria transferred the properties of light particles over a distance of nearly 2,000ft with no physical link, demonstrating what Einstein described as 'spooky action at a distance'.

But in the near future it is more likely to find a use in super- fast computers than to beam humans across the galaxy.

Who's the best - official THE revamped Dr Who ended its first series in triumph last night after exterminating the opposition on rival channels and being voted the most popular cult TV show ever knocking Star Trek from the No1 spot.

Ten million viewers watched the first episode on BBC1 and audiences stayed at 7 million to 8 million for the entire 13-week series hailed by critics as the best Dr Who ever relegating ITV1's muchhyped-Celebrity Wrestling to the graveyard Sunday morning spot after ratings slumped.

The BBC suffered a blow when star Christopher Eccleston quit, but he is being replaced in a new incarnation by Casanova star David Tennant for the next series.

And after reports that she was also quitting, Billie Piper was persuaded to stay on as his assistant Rose when fans protested she was irreplaceable.

  21/06/2005. RedNova News.