Thursday, March 24, 2005 ... Deutsch/Español/Related posts from blogosphere

Susskind: wormholes can't work

Lenny Susskind has a new paper:

He argues that the time travellers will have to find a different technology than the traversable wormholes (TW).

The large wormholes are impossible classically because they would violate the positive energy theorem. Quantum mechanically, there could be loopholes that make them possible. However, Lenny Susskind argues that
  • the energy must be conserved locally, and therefore the energy eaten by the throat is exactly zero
  • because we know the energy exactly, we can't know the moment in which the object jumped into the wormhole - by the energy-time uncertainty relation
  • consequently, you should have the same probability to reappear from the second throat at any moment, which does not seem like if you reappear at a particular moment of the history of the Universe

Add to Digg this Add to reddit

snail feedback (3) :

reader PlatoHagel said...

Many times I have heard the time traveller scenario. Even, Ronald Mallet's research.

But one thing that I have learnt from the gravitonic production idealization, is that if such a cyclical nature was to be realized, the primirodial information that is in the bulk, would have allowed us to look at the past, but not change it.

Is this not what we are doing afterall, when we look at cosmological events, from looking backwards to today?

We are trying very hard with the Window on the Universe to get very close to this source?

Yet, we know full well the basis of this exploration is evidenced in what we would measure by LIGO.

So the past is inhernetly with us every moment, and it continues past the earth, in it's expression? If one does recognize this dimensional attribute it will not make much sense to them.

So the problem is finding the means as you have shown Lubos, by introducy Lenny's paper.

I will look at this deeper for consideration as I do not understand it fully.

I introduced quantum jittery to show the other side of what might have motived such string valuations, as a negative feature of this motivation and support, in regards to momentum and tension.

This I do not understand well either, but I am working too.

We use glast Calorimeter to understand this exchange of early information, yet spintronics can orientate expressive features of design? Use it as a analogy of a deeper implication of design manipulation?

reader PlatoHagel said...

A time machine based on an immense cylinder spinning at near-light speed. The physicist W. J. van Stokum realized in 1937 that such an object would effectively stir spacetime as if it were treacle, dragging it along as the cylinder turned. What van Stokum didn't realize is that circumnavigating such a cylinder can lead to closed time-like paths. Anyone orbiting the cylinder in the direction of the spin would be caught in the current and, from the perspective of a distant observer, exceed the speed of light and thus travel back in time. Circling the cylinder in the other direction with just the right trajectory would project the subject into the future. The van Stokum time machine is based on the Lense-Thiring effect and uses ordinary matter but of enormous density - many orders of magnitude greater than that of nuclear matter.

The first Time Machine?

reader Quantoken said...

Lubos said:
"the energy must be conserved locally, and therefore the energy eaten by the throat is exactly zero"

Why do you fail to see that the Susskind arguments is total rubbish, regardless whether the conclusion can be correct or not through a different argument.

The energy conservation is a classical law. The freedom to extend the energy conservation law ends at the nose of quantum mechanics, where uncertainty principle kicks in.

Any student should understand that energy conservation law only works to the uncertainty allowable by the uncertainty principle. i.e., the energy is conserved, but within a range of plus or minus a small amount allowed by the uncertainty principle.

Otherwise you could have always calculated the EXACT energy, with zero error, using energy conservation law, and claim you have broken the uncertainty principle. The fact is you can't. You can not apply a classical law to beyond the "nose" where QM kicks in.

All QM stuff, vacuum energy, intermediate bosons and things like that all "break" the energy conservation law, but OK for a very brief time allowable by the uncertainty principle. Textbook stuff. I guess Suskind is getting too old to remember it.


(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o), m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m) })(window,document,'script','//','ga'); ga('create', 'UA-1828728-1', 'auto'); ga('send', 'pageview');