Near-Light-Speed Starships May Not Fly

www.space.com...

The above link has Marc Millis, former head of NASA's Breakthrough Propulsion Physics Project, explains how physicists approach the intriguing possibility of faster-than-light travel and alternating spacetime with what we know now and theroize .

"Everything within space is restricted by the speed of light," explained Richard Obousy, president of Icarus Interstellar, a non-profit group of scientists and engineers devoted to pursuing interstellar spaceflight. "But the really cool thing is space-time, the fabric of space, is not limited by the speed of light."

QUOTE:
The only problem is, previous studies estimated the warp drive would require a minimum amount of energy about equal to the mass-energy of the planet Jupiter.

But recently White calculated what would happen if the shape of the ring encircling the spacecraft was adjusted into more of a rounded donut, as opposed to a flat ring. He found in that case, the warp drive could be powered by a mass about the size of a spacecraft like the Voyager 1 probe NASA launched in 1977.

Furthermore, if the intensity of the space warps can be oscillated over time, the energy required is reduced even more, White found. END QUOTE:
space.com...

All of these experiments or theroies leave out the multiverse and the possibility of transverse navagation..... I would not want to leave home without a good multiverse map or the road home might be impossible to find. The good news is there are some truly gifted people working on getting a ship and humans from point "A" to "B" with a method that will not take forever and the arrival of passengers @ point "B" will still look human and not like scrambled eggs.

Originally posted by Tajlakz
So what is it about the vacuum that makes 'c' c? What slows light down to that value in the absence of matter?

See also: Ernst Mach. It's a GREAT question.

Originally posted by Bedlam

Originally posted by Diablos
Unfortunately, no. This is because individual particles don't necessarily have a temperature. Temperature itself is an emergent phenomena that results from the interactions of many particles.

Maxwell and Boltzmann would like a word with you.

Omitting the internal energy of the particle (qm states) which will be dwarfed by the kinetic term at relativistic speeds, yes you can calculate a temperature given an average kinetic energy of incoming particles.

Well, you can always calculate an average kinetic energy of particles if you can measure their energies and divide by 'k' and call that 'T'.

It won't have the meaning of temperature unless you're in a near equilibrium mode of interaction.

Do the radio waves of a monochromatic radio transmitter have a "temperature"? Not really useful in that circumstance. Generally you need large numbers of chaotic microscopic interactions (particle collisions, like atoms against atoms or light against atoms) to drive you to Maxwellian energy distributions because that's the one with the most entropy given energy constraints. Radio waves propagate without mutual self-interaction.

Originally posted by XLR8R
reply to post by Astyanax

 

Well, some suggested that gravitation and magnetism is one of the same.

Why do they suggest that? Magnetism influences motion of charged particles. Gravitation influences space-time and motion of all particles. They seem awfully different to me. Explain a unification which is achievable on an engineerable energy and space scale.

So if we can build a ship that can produce it own artificial gravitating magnetic field we could circumvent pretty much anything. Like cosmic radiation, other magnetic fields like those of planets.

Why is that?

Some would say atmospheres would mean nothing. We would just fly right through with out any excess heat. And since the ship has it's own magnetic/gravitational field we would not feel G-forces. We could stop and go as fast as the field could handle.

Even if you turn off inertia with magic, how does that turn off collisions? Ultrarelativistic particles still have extremely violent disintegrating collisions.

reply to post by mbkennel


I know you didn't reply to bedlam's post about altering the permittivity and permeability of space around a craft, but since you are a physicist, I was wondering if I could get your opinion about his assertions. Do you have any idea how what he is describing would be possible? and how it is related to ernst mach?

reply to post by mbkennel


At relativistic velocities, incoming radio waves will shift into hard gammas, and I bet they'd heat that thing up just fine.

reply to post by AnonyWarp


or build a round ship and move the magnets?

Originally posted by Oannes
Tapping the zero-point would yield unlimited output. It is an inexhaustable sea of energy.

It's not an inexhaustable sea of useful thermodynamic work, because you need something colder to dump to. Zero-point means you're at the bottom already. No matter how you calibrate "zero" anything starts at zero.

There are particles all around us. Outerspace would serve as the perfect reaction chamber. The amount of zero-point energy in the area of a tea cup, could boil all of the Earth's oceans. This is a simple, yet awesome power source. And yes, this technology has been suppressed. Look up Henry T. Moray. He was shot at on the street for discovering this secret.

To be technical: GMAFB.

If your theory suggests something that is on its face totally unreasonable and inconsistent with physical behavior then it means your mathematics and interpretation of the theory is wrong. Of course quantum field theory is right because there's lots of experimental evidence. Naive interpretation of the 'zero point energy' as being something useful and physically real isn't one of the highlights of QFT.

Originally posted by Tajlakz
reply to post by mbkennel

 

I know you didn't reply to bedlam's post about altering the permittivity and permeability of space around a craft, but since you are a physicist, I was wondering if I could get your opinion about his assertions. Do you have any idea how what he is describing would be possible?

In vacuum, no idea.

Space itself doesn't have permittivity and permeability, in proper theoretical units they are "1". and B=H and E=D.

Permittivity and permeability are properties of bulk matter interacting electromagnetically with EM fields with wavelengths substantially longer than atomic space scales. Free space EM fields come in, interact with the charged atoms, which respond statically and (at high enough frequencies) dynamically, creating their own electromagnetic fields. The combination of the two can be represented as effective parameters in classical E&M changing magnetic and electric propagation. The "force" and "response" in essence.

Example. In just plain glass you have a non-trivial electric permittivity so that the effective speed of light is < c for optical wavelengths. An optical wavelength is thousands of interatomic-distances long and so you get an index of refraction which is a function of the permittivity ratio.

If you shot a gamma photon, which can collide with an electron, did it encounter any effective permittivity on the way? No, it has wavelength as small as an atom or smaller. It came in at c and interacted with the electron. If you figure out the compton effect you put in the energy as E=hc/lambda, and 'c' is vacuum c, not the speed of light you'd measure in the medium at optical frequencies.

and how it is related to ernst mach?

en.wikipedia.org...'s_principle

Roughly, the idea is that inertia is related to relative motion to the enormous mass of the distant universe. There is no single "Mach's principle", just a vague idea of a concept, that local laws and effects may be related somehow by large scale integration over "shell of everything else". Generally not really local realistic field theories.

Quote from WP:

Einstein—before completing his development of the general theory of relativity—found an effect which he interpreted as being evidence of Mach's principle. We assume a fixed background for conceptual simplicity, construct a large spherical shell of mass, and set it spinning in that background. The reference frame in the interior of this shell will precess with respect to the fixed background. This effect is known as the Lense–Thirring effect. Einstein was so satisfied with this manifestation of Mach's principle that he wrote a letter to Mach expressing this:
it... turns out that inertia originates in a kind of interaction between bodies, quite in the sense of your considerations on Newton's pail experiment... If one rotates [a heavy shell of matter] relative to the fixed stars about an axis going through its center, a Coriolis force arises in the interior of the shell; that is, the plane of a Foucault pendulum is dragged around (with a practically unmeasurably small angular velocity).
—[5]
The Lense–Thirring effect certainly satisfies the very basic and broad notion that "matter there influences inertia here"[7] The plane of the pendulum would not be dragged around if the shell of matter were not present, or if it were not spinning. As for the statement that "inertia originates in a kind of interaction between bodies", this too could be interpreted as true in the context of the effect.

The Lense-Thirring effect is really really really tiny. I think it took a heroic experiment by Gravity Probe B satellite (an experiment which took almost 50 years to push through to success) to sniff any expermental evidence of frame dragging from the rotation of the Earth.

I don't see any engineerable mechanism there in standard GR.

Somehow I guess the vague principle is that if you can alter the interaction between "out there" to "in here" then you change properties of 'in here'. How that works with inertia I have even less idea.



There's an alternate formulation of gravitation, 'teleparallelism', originally worked on by Einstein himself which regarded effects as 'torsion' of space instead of the classic curvature. According the the review here

arxiv.org...

they seem to give the same results classically but perhaps this direction may be more amenable to integration with QM. Potentially there could be experimental consequences distinguishing the views.

The physical problem I see is that there are astrophysical observations of phenomena with energy scales so far beyond anything we might dream of working with, and yet there has never been any observed conflict with classical general relativity. If there were some immediately accessible new physics why haven't we seen it yet?

Originally posted by Bedlam
reply to post by mbkennel

 

At relativistic velocities, incoming radio waves will shift into hard gammas, and I bet they'd heat that thing up just fine.

Sure would.

Originally posted by mbkennel


In vacuum, no idea.

Space itself doesn't have permittivity and permeability, in proper theoretical units they are "1". and B=H and E=D.

epsilon0 and mu0 (can't do the symbols on a phone) would like a word with you

Permittivity and permeability are properties of bulk matter interacting electromagnetically with EM fields with wavelengths substantially longer than atomic space scales. Free space EM fields come in, interact with the charged atoms, which respond statically and (at high enough frequencies) dynamically, creating their own electromagnetic fields. The combination of the two can be represented as effective parameters in classical E&M changing magnetic and electric propagation. The "force" and "response" in essence.

Is vacuum dispersive?

Originally posted by Bedlam

Is vacuum dispersive?

Wouldnt you say there is no such thing as vacuum (or actually how would you define vacuum)? Since the vacuum is really multiple 'fields', that can also be curved in the case of gravity? Wouldnt the 'vacuum' have to be dispersive if it is able to be distorted and curved?

reply to post by ImaFungi


Dispersion relates to characteristics that differ depending on the wavelength of the wave traversing the medium. It relates to a comment mb made. I basically asked him a physics shorthanded question about whether his statement was always correct as to effect being dependent on wave length.

Sorry, it was a geek thing.

reply to post by Bedlam


When would effect not be dependent on wavelength? Would it be when an object perpendicularly crosses the path of differing wavelengths?

reply to post by ImaFungi


In a non-dispersive medium, wavelength doesn't matter. If it's dispersive, different wavelengths will travel at different rates as the shorter ones interact less with plasmons in the material. A prism is a classic example - it separates the colors because it's dispersive. As a radio guy, I see air/rain/fog blur pulses by dispersion.

reply to post by Bedlam


So you are saying space is non-dispersive, so all wavelengths are equal?

Originally posted by ImaFungi
reply to post by Bedlam

 

So you are saying space is non-dispersive, so all wavelengths are equal?

Doesn't appear to be, and Lipschitz will tell you it can't be by GR.

So since there is an absolute non-zero non-unity value for permittivity and permeability, and it's not dispersive, it isn't likely to be plasmon delay.

(not relative u or e, absolute...)

reply to post by ImaFungi

In terms of velocity of propagation, not wavelength.

Originally posted by Bedlam

Originally posted by mbkennel


In vacuum, no idea.

Space itself doesn't have permittivity and permeability, in proper theoretical units they are "1". and B=H and E=D.

epsilon0 and mu0 (can't do the symbols on a phone) would like a word with you

They and their equally dubious multiples-of-pi fellow-travellers have been renamed 1.

en.wikipedia.org...

Stress-energy tensor of EM doesn't have any epsilon0 and mu0 or other crap in it. (Landau + Lif#z Classical theory of Fields

Permittivity and permeability are properties of bulk matter interacting electromagnetically with EM fields with wavelengths substantially longer than atomic space scales. Free space EM fields come in, interact with the charged atoms, which respond statically and (at high enough frequencies) dynamically, creating their own electromagnetic fields. The combination of the two can be represented as effective parameters in classical E&M changing magnetic and electric propagation. The "force" and "response" in essence.

Is vacuum dispersive?


No.

Or really, almost negligibly 'No' until you start to get energies of photons enough so that QFT effects like virtual or real pair production matter. So until hard gammas, No.

Astrophysics would look different, we'd see supernovae turn one color and then another as we watched, and we could use the time between the red and the blue to figure out how far they are away. But they don't look like that. Light pulses close by and far away come as they are.

cds.cern.ch...

At least looking at the abstract of that I will take back my assumption that there could be dispersion for hard gammas; the group looked at MeV and GeV level gammas too and saw no dispersion.

Originally posted by Bedlam
reply to post by ImaFungi

 

In terms of velocity of propagation, not wavelength.

Explain please what you're hinting. (and the modifying the permittivity/permeability of free space business)

Experimentally dispersion means group velocity changes as a function of wavelength. Physical observations show none of that for vacuum.