### Author Topic: Theoretical FTL  (Read 52232 times)

#### Suzy

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##### Re: Theoretical FTL
« Reply #20 on: 07/08/2008 08:42 pm »
Suzy, you could just use a fusion rocket, without messing with a HEAVY black hole.

And antimatter rocket would be better anyway.

But black holes are cooler

#### josh_simonson

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##### Re: Theoretical FTL
« Reply #21 on: 07/08/2008 11:22 pm »
For conservation of energy to maintained, a wormhole or similar conveyance would require a minimum energy input of the difference in potential and kinetic energy between one and and the other in order to work, or perhaps it'd only be possible to fold space to a point of equal energy.

Traveling at the speed of light is instantaneous to the traveler, so I suspect that c is effectively infinite speed, and it's just simply a matter of the ways we perceive and measure time and space don't work well at such extremes.  Looking out across the universe, a star 1 light year away is seen as it was one year ago - so the x,y and z coordinates can be viewed as distances in time.  Then c is 1s/s, or just 1 without units and you can't travel faster than 1.  There, now that sounds better than you can't travel faster than ~3e8m/s.

#### gospacex

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##### Re: Theoretical FTL
« Reply #22 on: 07/09/2008 08:09 am »
For conservation of energy to maintained, a wormhole or similar conveyance would require a minimum energy input of the difference in potential and kinetic energy between one and and the other in order to work

Global conservation of energy is not enforced by General Relativity, only local. It is possible to construct a setup where energy is not only not conserved, but where it is impossible to define a notion of "energy" globally.

Quote
Traveling at the speed of light is instantaneous to the traveler, so I suspect that c is effectively infinite speed, and it's just simply a matter of the ways we perceive and measure time and space don't work well at such extremes.  Looking out across the universe, a star 1 light year away is seen as it was one year ago - so the x,y and z coordinates can be viewed as distances in time.  Then c is 1s/s, or just 1 without units and you can't travel faster than 1.  There, now that sounds better than you can't travel faster than ~3e8m/s.

It sounds not better, but bizarre. Reading more on subject of Special Relativity might help you to get a firmer grasp on what's going on. Wikipedia article is not a bad start.

Can't agree on "c is instantaneous", why radar bounces off planets come back with delay?

Time and space are definitely different dimensions, since they enter into equations with opposite signs, like in ds^2 = dt^2 - dx^2 - dy^2 - dz^2.

#### Eerie

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##### Re: Theoretical FTL
« Reply #23 on: 07/09/2008 01:59 pm »
Can't agree on "c is instantaneous", why radar bounces off planets come back with delay?

C is instantaneous from POV of the traveller. But you will have to be massless.

#### Suzy

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##### Re: Theoretical FTL
« Reply #24 on: 07/29/2008 05:39 am »
Discovery.com article, 28/7: "Warp Drive Engine Would Travel Faster Than Light".

#### TyMoore

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##### Re: Theoretical FTL
« Reply #25 on: 07/29/2008 03:48 pm »
With regards to using blackholes as power sources. A 1000 metric ton black hole will evaporate by Hawking Radiation in less than a microsecond. You'd get a very big bang, but little propulsion!

If you go smaller, much smaller: milligram mass blackholes, and you make them dozens of times a second, then the emissions should be predominantly gamma-rays, and electron/positron pairs, which will annhilate to gamma-rays. Use the gamma-rays to impinge on something dense, like tungsten balls in a pressure vessel and nozzle: you have something akin to a nuclear thermal rocket. Or you could use a closed Brayton cycle and use the electricity to power conventional ion thrusters.

Or if you really want to go wild, why not use the intense gamma-rays to heat something else: like lunar regolith and use that as your working fluid! Who cares if its inefficient from Isp point of view: with enough gamma-rays the plasma will be at tens of millions of degrees anyway. And the drive flare should be visible all the way across the solar system. Cool!
« Last Edit: 07/29/2008 03:50 pm by TyMoore »

#### ChevalierGuard

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##### Re: Theoretical FTL
« Reply #26 on: 07/29/2008 11:05 pm »
Kaluza Klein Theory...

CG

#### khallow

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##### Re: Theoretical FTL
« Reply #27 on: 07/29/2008 11:43 pm »
Kaluza Klein Theory...

What about Kaluza Klein theory? As far as I know, it's the idea that you can start with a higher dimension massless/pure geometry model and reduce by the extra dimensions to get a model with our observed spacetime and physical properties like mass/energy (including curvature and possibly a cosmological constant or "dark energy") or electric current flows.
« Last Edit: 07/29/2008 11:46 pm by khallow »
Karl Hallowell

#### ChevalierGuard

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##### Re: Theoretical FTL
« Reply #28 on: 07/30/2008 10:23 pm »
Kaluza klein theory...

Not exactly...as far as I know the equations don't show dark energy or matter..

However, there is a compactification.. but primarily it links gravity equations to EM... and vice versa..
I speaking of the 5D case of course.. the other stuff really is nonsense.
speaking of the 11 dimensions..

Not to bore with equations, here is a simple definition from wikpedia..

In physics, Kaluza–Klein theory (or KK theory, for short) is a model that seeks to unify the two fundamental forces of gravitation and electromagnetism. The theory was first published in 1921 and was discovered by the mathematician Theodor Kaluza who extended general relativity to a five-dimensional spacetime. The resulting equations can be separated out into further sets of equations, one of which is equivalent to Einstein field equations, another set equivalent to Maxwell's equations for the electromagnetic field and the final part an extra scalar field now termed the "radion".

This is part of the solution...

Nice chatting with you...

Wish NASA would give pic EM and Beamline and Klystron codes freely.  You could do alot with a small Linux cluster..

Nice chatting..

CG

#### colbourne

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##### Re: Theoretical FTL
« Reply #29 on: 08/01/2008 07:28 am »
This weeks New Scientist (1 August 2008) has an article about how antimatter particles sometimes bounce off normal matter.
This possibly supports my previous assumption about the possible anti-gravity that might occur with anti-matter.

http://www.newscientist.com/channel/fundamentals/mg19926674.600-antimatter-plus-matter-doesnt-always-equal-bang.html

The "Colbourne" drive still might work. I expect we will know soon.

#### gospacex

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##### Re: Theoretical FTL
« Reply #30 on: 08/01/2008 10:35 am »
This weeks New Scientist (1 August 2008) has an article about how antimatter particles sometimes bounce off normal matter.

I think proton/antiproton collision was never thought to 100% reliably result in annihilation, they may just scatter on each other.

Quote
This possibly supports my previous assumption about the possible anti-gravity that might occur with anti-matter.

Magnitude of gravitational interaction in proton-antiproton (or proton-proton) pair is on the order of 10^37 times weaker than electromagnetic. Likely not detectable.

#### khallow

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##### Re: Theoretical FTL
« Reply #31 on: 08/01/2008 05:47 pm »
Kaluza klein theory...

Not exactly...as far as I know the equations don't show dark energy or matter..

However, there is a compactification.. but primarily it links gravity equations to EM... and vice versa..
I speaking of the 5D case of course.. the other stuff really is nonsense.
speaking of the 11 dimensions..

If you instead contract (collapse the direction in question) a 5 dimensional space (4 spatial/1 time dimensions) along a radial direction rather than along a single spatial dimention, you can get de Siter and anti-de Siter spaces. The idea is to treat each ray coming from the origin as a point in a 4 dimensional space. If this were a regular 5 dimensional Euclidean space, the result is a sphere centered at the origin (each ray passes once through this sphere). With one timelike dimension, you end up with a hyperboloid sheet instead (again each ray passing once through the sheet). The cosmological constant shows up as the inverse of a "radius" of this sheet.

Also, given that we observe a strong and weak force, this encourages the consideration of higher dimensional models. They may have limited physical relevance, but it is a good way to generate potential models for the interaction of the four forces and the math might be applicable to a better model. That is, it might turn out that a "good" model has a 10, 11, 26, etc dimensional extension that simplifies the math of the original model. You just need to know how to go from the manipulations of the higher dimension space to the real world space.
Karl Hallowell

#### Capt. Nemo

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##### Re: Theoretical FTL
« Reply #32 on: 08/02/2008 07:35 am »

Miguel Alcubierre took the idea to the extreme by positing large masses: neutronium density or more. Further he used a nifty little gravitational trick: the gravity field inside a spherically symmetric shell of mass is zero--in general relativity terms, the spacetime inside a spherical shell is approximately flat. So putting the two ideas together you get a spherical shell with the forward end composed of positive energy matter, the aft half is composed of negative energy matter, and the 'vessel' or transport is at the center of the shell in the flat spacetime 'island' in the middle. Increase the density of the shell until it comes close to the density of neutronium, and voila you have massive acceleration that the occupants inside won't feel (they're in free fall.)

I wonder if this 'shell' would also act as a 'deflector shield' and/or a 'cloaking device'.  seems to me that something as dense as 'nuetronium' would be damned tough to see thru, if it let any EM radiation thru at all.
"You can't declare yourself the boss of a chicken farm when you've only got one egg."  - Chinese saying

#### khallow

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##### Re: Theoretical FTL
« Reply #33 on: 08/02/2008 06:00 pm »
OTOH, everyone who detects the neutronium would suspect you were hiding something. An analogy is a 50 pound lead brick. There are all sorts of tricks for hiding a brick and usually it's not that hard. It's not particularly big and very few people really care about where you go with a lead brick. But don't try to pass one through an airport X ray security system.

Due to the density of the lead brick, you can stick anything in the center and it won't be scannable by X ray machines. But what would be the point? Most circumstances where the shielding matters, the brick itself would raise suspicion. The biggest exception is when the hidden item generates a signal somehow (say because it is a kilogram of plutonium 239).
« Last Edit: 08/02/2008 09:54 pm by khallow »
Karl Hallowell

#### ChevalierGuard

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##### Re: Theoretical FTL
« Reply #34 on: 08/03/2008 01:33 am »
Creation of Mini black holes?

and capturing virtual particles?

any thoughts, known papers, etc?

CG

#### khallow

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##### Re: Theoretical FTL
« Reply #35 on: 08/03/2008 04:58 am »
Creation of Mini black holes?

Very small rotating black holes do appear to be promising. I wouldn't recommend doing it on a planet or near a star. But it does look a good way to store energy.

Quote
and capturing virtual particles?

any thoughts, known papers, etc?

My take on virtual particles is that they are artifacts of particular models. For example, quantum electrodynamics (or QED, a quantum field theory used to describe electromagnetism) requires "virtual photons" to adequately describe the interaction between charged particles. Normal photons have two vibration modes (usually called "degrees of freedom") while virtual photons have the full four modes of vibration (sound waves are an example of waves that have four vibration modes). If one uses the QED model and attempts to observe a virtual photon, a strange thing happens. The two modes that we see have the expected positive probability of being observed. But the other two modes have a negative probability of being observed. This leads to the convention that observable states are only the states with positive probability.

Still the talk of black holes and virtual particles does allow for the possibility of gravitational capture of hard to observe particles. For example, any sufficiently dense object (possibly a neutron star just a bit shy of unrestrained collapse) can have a photon sphere. That is, the object through it's deep gravity well can actually trap photons in orbit around the object. Anything moving slower than that will be trapped in higher orbits. One can then attempt to scatter observable stuff off of what is in the photon sphere.
« Last Edit: 08/03/2008 04:59 am by khallow »
Karl Hallowell

#### ChevalierGuard

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##### Re: Theoretical FTL
« Reply #36 on: 08/04/2008 03:02 am »
Karl,

Thanks for the link Photon sphere link...  I knew of virtual particles (QED based stuff) thought you might have additional info..

Has anyone modeled collisions or merges of mini black holes? Cactus simulations?

I haven't modeled anything astronomical in years..  need to get a Linux cluster up and running...
Recently only working on beamline stuff... O and M devices..

I heard that
Physicists are actually trying to probe other spatial dimensions using particle physics experiments?
True? if so, papers?

thx

CG

#### gospacex

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##### Re: Theoretical FTL
« Reply #37 on: 08/04/2008 09:42 am »
any sufficiently dense object (possibly a neutron star just a bit shy of unrestrained collapse) can have a photon sphere. That is, the object through it's deep gravity well can actually trap photons in orbit around the object. Anything moving slower than that will be trapped in higher orbits. One can then attempt to scatter observable stuff off of what is in the photon sphere.

I don't think so. Photon sphere is not a stable orbit, you can't "accumulate" orbiting photons there. IIRC lowest stable orbit around non-rotating black hole has a radius of 3*Rs.

#### khallow

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##### Re: Theoretical FTL
« Reply #38 on: 08/04/2008 10:35 pm »
any sufficiently dense object (possibly a neutron star just a bit shy of unrestrained collapse) can have a photon sphere. That is, the object through it's deep gravity well can actually trap photons in orbit around the object. Anything moving slower than that will be trapped in higher orbits. One can then attempt to scatter observable stuff off of what is in the photon sphere.

I don't think so. Photon sphere is not a stable orbit, you can't "accumulate" orbiting photons there. IIRC lowest stable orbit around non-rotating black hole has a radius of 3*Rs.

I'm not sure I understand what you're saying. This would be an orbit, then you effectively have that photon trapped in this zone. It can still escape either by hitting other things or due to the quantum nature of the photon, tunneling either into the massive object or out of the system.
« Last Edit: 08/04/2008 10:35 pm by khallow »
Karl Hallowell

#### ChevalierGuard

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##### Re: Theoretical FTL
« Reply #39 on: 08/05/2008 02:54 am »
Gentlemen,

Using miniblack holes to capture virtual particles and hence using the miniblackhole as storage device may not be the trick...Remember, Stephen Hawking predicted that black holes eventually evaporate!

Darn that negative energy virtual particle..

CG

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