No Worm Holes For Us Time Travelers

[echostation]

FROM BBC SETHU


Wormhole 'no use' for time travel
By Paul Rincon
BBC News science reporter

Artist's impression of a wormhole Image: SPL
Wormholes contort the fabric of the Universe
For budding time travellers, the future (or should that be the past?) is starting to look bleak.

Hypothetical tunnels called wormholes once looked like the best bet for constructing a real time machine.

These cosmic shortcuts, which link one point in the Universe to another, are favoured by science fiction writers as a means both of explaining time travel and of circumventing the limitations imposed by the speed of light.

The concept of wormholes will be familiar to anyone who has watched the TV programmes Farscape, Stargate SG1 and Star Trek: Deep Space Nine.

The opening sequence of the BBC's new Doctor Who series shows the Tardis hurtling through a tunnel that suspiciously resembles a wormhole - although the Doctor's preferred method of travel is not known.

But the idea of building these so-called traversable wormholes is looking increasingly shaky, according to two new scientific analyses.

Remote connection

A common analogy used to visualise these phenomena involves marking two holes at opposite ends of a sheet of paper, to represent distant points in the Universe. One can then bend the paper over so that the two remote points are positioned on top of each other.


[The wormholes] you would like to build - the predictable ones where you can say Mr Spock will land in New York at 2pm on this day - those look like they will fall apart
Stephen Hsu, University of Oregon
If it were possible to contort space-time in this way, a person might step through a wormhole and emerge at a remote time or distant location.

The person would pass through a region of the wormhole called the throat, which flares out on either side.

According to one idea, a wormhole could be kept open by filling its throat with an ingredient called exotic matter.

This is strange stuff indeed, and explaining it requires scientists to look beyond the laws of classical physics to the world of quantum mechanics.

Exotic matter is repelled, rather than attracted, by gravity and is said to have negative energy - meaning it has even less than empty space.

Law breaker

But according to a new study by Stephen Hsu and Roman Buniy, of the University of Oregon, US, this method of building a traversable wormhole may be fatally flawed. In a paper published on the arXiv pre-print server, the authors looked at a kind of wormhole in which the space-time "tube" shows only weak deviations from the laws of classical physics.

These "semi-classical" wormholes are the most desirable type for time travel because they potentially allow travellers to predict where and when they would emerge.

The Tardis (BBC)
The concept is a favourite of science fiction writers
Wormholes entirely governed by the laws of quantum mechanics, on the other hand, would likely transport their payloads to an undesired time and place.

According to Leonard Susskind, of Stanford University in California, US, a time traveller would emerge "in the infinitely remote future or the infinitely remote past".

Calculations by the Oregon researchers show a wormhole that combines exotic matter with semi-classical space-time would be fundamentally unstable.

This result relies in part on a previous paper in which Hsu and Buniy argued that systems which violate a physical principle known as the null energy condition become unstable.

"We aren't saying you can't build a wormhole. But the ones you would like to build - the predictable ones where you can say Mr Spock will land in New York at 2pm on this day - those look like they will fall apart," Dr Hsu said.

Tight squeeze

A separate study by Chris Fewster, of the University of York, UK, and Thomas Roman, of Central Connecticut State University, US, takes a different approach to tackling the question of wormholes.

Amongst other things, their analysis deals with the proposal that wormhole throats could be kept open using arbitrarily small amounts of exotic matter.

Fewster and Roman calculated that, even if it were possible to build such a wormhole, its throat would probably be too small for time travel.

It might - in theory - be possible to carefully fine-tune the geometry of the wormhole so that the wormhole throat became big enough for a person to fit through, says Fewster.

But building a wormhole with a throat radius big enough to just fit a proton would require fine-tuning to within one part in 10 to the power of 30. A human-sized wormhole would require fine-tuning to within one part in 10 to the power of 60.

"Frankly no engineer is going to be able to do that," said the York researcher.

The authors are currently preparing a manuscript for publication.

Supporting view

However, there is still support for the idea of traversable wormholes in the scientific community. One physicist told BBC News they could see problems with Hsu and Buniy's conclusions.

"Violations of the null energy condition are known to occur in a number of situations. And their argument would prohibit any violation of it," they commented.

"If that's true, then don't worry about Hawking radiation from a black hole, the entire black hole vacuum becomes unstable."

Cambridge astrophysicist Stephen Hawking is amongst those researchers that have pondered the question of wormholes.

In the 1980s, he argued that even if a wormhole could be stabilised by exotic matter, something fundamental in the laws of physics would prevent them being used for time travel. This idea forms the basis of Hawking's Chronology Protection Conjecture.

[Hemingford Gray]

Well, Stephen Hawking thought it is possible, but black holes "eject" matter or radiation. I forgot it. He lost his bet and he had to bought a book about *I don't know*.

[Mentok]

[Lord Valumart]

don't matter, i have the TARDIS and the Delorian.

[M.E.H.Z.E.B]

no matter what those brits say...
wormholes exist, and they can be rigged for time travel

[Captain_Obvious]

what an upset

[TheSumOfGod]

Oh, for f***'s sake! We're a bunch of talking apes driving primitive gas-powered cars on ashphalt roads! What the f*** do WE know about wormholes and time travel? Just a bunch of theories based upon another bunch of theories.

[echostation]

speak for yourself sumofgod. have you ever thought about why some of my posts concern sethu, pashtu, malayali hupti kaanji mafiso shempion talk. I am a traveler... I'm not even human sethu

[Lord Valumart]

only i know, since i'm a timelord.

now wheres that sonic screwdriver

*looks*

[TheSumOfGod]

Originally Posted by echostation

speak for yourself sumofgod. have you ever thought about why some of my posts concern sethu, pashtu, malayali hupti kaanji mafiso shempion talk. I am a traveler... I'm not even human sethu

You weren't breast-fed, were you?

[echostation]

all aliens are breastfed... simple as is, ur judgemental reign of terror has ended upon narry a pompido due to the liege... it cannot be inidinigo of how we shantee upon ilasterine. simple as this, this is why it is powerful.

[Lord Valumart]

Originally Posted by echostation

all aliens are breastfed... simple as is

well i'm an alien(Time Lord) and i wasn't.

[TheSumOfGod]

Originally Posted by echostation

all aliens are breastfed... simple as is, ur judgemental reign of terror has ended upon narry a pompido due to the liege... it cannot be inidinigo of how we shantee upon ilasterine. simple as this, this is why it is powerful.

Aliens can't type either, apparently.

[echostation]

good you have proved my due forth point upon the narry a centre pompidoo that aliens we are as such... i'm a traveler, a shempion traveler and this is the article that upsets because such facets in time warping have existed, physical manifestations of it i can do yes yesshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhh

[echostation]

at the end of the day what does it matter that can really process the narry a pompidoo upon which we can establish our lineage upon due forth processes... THIS IS NOT ABOUT THIS BUT ABOUT SETHU NOT EVEN BEING WITH THE ONE THAT WE CAN

[Immortalfire]

[C.F. Kane]

Dr. Who never made sense anyway.

[Doobie88]

Is it just me, or does the idea of "a time traveller would emerge in the infinitely remote future or the infinitely remote past" sound way more exciting then a pertictable time travel??