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Hawking's Explanation of Wormhole destruction via Feedback

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Hon1nbo

Wed Jun 30 2010, 03:24AM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042

hello all,
I recently have been learning a lot about the cosmos from various sources, and the topic that really intrigued me were Wormholes.
Current understanding of wormholes is that they do transverse both time and space and are all around us on a sub-microscopic size, but even if we could enlarge one it would be destroyed by radiation feedback before it could be used.
Before I get to my comments, a little background on Hawking's proposed feedback destruction.
A wormhole would suck in radiation which, after being emitted from the exit, would then return again to the entrance and begin a cycle. This feedback would be similar to a stereo system that is not properly adjusted, and after a certain amount of time (in this case a short amount of time) the wormhole would be destroyed by feedback within a moment.
This destruction would prevent a paradox from forming due to time travel, such as the Grandfather Paradox.

However, there is an inconsistency that I can see with this basic explanation and I cannot find any information on it. A certain set of circumstances that may be a workaround to feedback and the grandfather paradox. I could be missing something, in which case I will gladly accept any explanations or feedback.

First, nothing travels faster than the speed of light, including radiation. So say you wanted to travel through time to one second in the past, if you could "pick and choose" a wormhole of at least 3.00x10^8 meters in length, then you could theoretically have it stay open for long enough to use as the radiation will take time to reach the entrance again. Or, make it a light year in distance, and the wormhole would stay open for a year etc etc.
This would also solve the paradox problem as you can't do things like travel to Earth in the past as short distance of travel would not allow it due to the rapid speed of the radiation causing feedback.

Let's say you wanted to try to make the paradox occur: you would exit the wormhole, and aim a projectile at near light speed back towards yourself entering the wormhole. Assuming the distance is not too short to cause feedback destruction hence the inability to use the wormhole, your projectile would always arrive at best a moment after you entered the wormhole.

Let's open this up to a discussion, as I know I am not an expert in the field of Cosmology or General Relativity, so there is likely something I am missing and would be glad to know about it.

-Jimmy

Bjørn

Wed Jun 30 2010, 04:11AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

First I would like to point out that wormholes are mathematical concepts and are not something that has been observed. The math is also done by very crude approximations so the conclusions are uncertain and possibly completely wrong.

A possible flaw in your thought experiment is that the wormhole must be created with the ends very distant from the start, it might not be possible.

Killa-X

Wed Jun 30 2010, 04:48AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

Discovery had a small series going about some of his ideas. They mention the thing about how nothing is faster than the speed of light, and he gave an example where if we can make a train go around the world faster than the speed of light, we could slow down time. Were 1 week in the train can be 1 year outside the train. The faster you push to the speed of light, the slower things go to prevent you from ever going any faster, was his claim.

He also had his theory on teleporters, how they wouldn't be possible due to feedback. Like a mic and a speaker, it keeps amplifying until the amp possibly explodes...The same way with a teleporter, particles can keep cycling in and out amplifying until it destroys it self.

As said about wormholes, feedback with teleporters would destroy them, making it rather difficult to create...

1-5 i think talks about his teleporter and time travel. They do indeed talk of wormholes in part 1 :)

Video 2, 3:32 starts your talk on paradox,

6:15 is when he says a paradox / wormhole cant exist due to feedback, due to radiation.

radiotech

Wed Jun 30 2010, 08:24AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
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Posts: 1546

Electromagnetic fields travel through space which has an impedance of 377 ohms. Henrys and Farads per meter define that impedance. So speed of light depends on gravity being constant.

Coronafix

Wed Jun 30 2010, 09:54AM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

You are assuming that a wormhole has any length at all, and that nothing travels faster than the speed of light.

If every particle in the universe is interconnected with every other particle in the universe, then why would a wormhole have any length?

Hon1nbo

Wed Jun 30 2010, 02:53PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042

ok, I understand that assuming a wormhole could transverse that much space is a potential problem,

but would this radiation move faster than the speed of light? - how fast would it be then, if not instantaneous such as photon entanglement?

-Jimmy

Bjørn

Wed Jun 30 2010, 03:21PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

If we connect two distant points in space with a wormhole then the distance when going through the wormhole can be 0. So the light will move at infinite speed when viewed from an outside viewpoint. From the wormhole viewpoint it would move at the normal speed.

radiotech

Wed Jun 30 2010, 03:22PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

"but would this radiation move faster than the speed of light?"

How about Cherenkov radiation, how fast does it move with respect to the speed of light?

Hon1nbo

Wed Jun 30 2010, 03:48PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042

BjÃ¸rn wrote ...

If we connect two distant points in space with a wormhole then the distance when going through the wormhole can be 0. So the light will move at infinite speed when viewed from an outside viewpoint. From the wormhole viewpoint it would move at the normal speed.

but for feedback destruction, wouldn't the radiation have to travel back to the entrance via normal travel? - or could it go back to the original entrance via the wormhole again, in which case I wouldn't have used the stereo system example I keep seeing elsewhere, but more of a destructive resonance explanation.

@radiotech: I never knew that about Cherenkov radiation - maybe the radiation Hawking was talking about can do something similar

-Jimmy

UltraMagnus

Tue Jul 06 2010, 09:08AM

Registered Member #2875 Joined: Mon May 24 2010, 08:28AM
Location: England
Posts: 42

As I read it, the radiation goes back and fourth through the wormhole.

which begs the question, couldn't you just chuck a bug hunk of lead into the event horizon to absorb all the radiation?

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