Harold “Sunny” White and Miguel Alcubierre and Warp Drives
“Sunny” White, a frustrated propulsion designer unhappy with puny ion and plasma drives etc., seems to be trying to stimulate enthusiasm for the field of faster-than-light travel by making scale models of interplanetary or interstellar ships relying on an artifact of the ways of motion in a curved space by posting pictures of a concrete ship design to indicate that the idea is so good that the time is ripe to build a spaceship. It reminds me of some pictures of the block of a V-8 motor with tubes coming out of various ports sent by an ambitious inventor to my CPA brother to provide a concrete reason for him to invest in his company. This V-8 motor was going to initiate fusion reactions and use the heat to drive the car. The last I heard they were not successful.
Sunny is hanging his hat on an idea by Miguel Alcubierre, a theorist who asked the question, “What if there was a negative energy mass E= -mc^2?” Well, it would be possible to generate a closed time like world line which allows you to get somewhere faster than light by going a little way in positive time direction and the rest of the way in the negative time direction allowing you to go between point A and point B in no time at all.
But, the basis of all physics would be undermined, based as it is on the conservation of energy and that energy is the ability to do work. This exotic negative energy matter is not antimatter, it is something that has never been seen, but just like the perpetual motion machine, I’ll believe it when I see it.
Problems with an Alcubierre warp drive.
First, it requires a negative energy density. If E = mc^2, then negative energy means that there is negative or “exotic” mass with the value m which has never been observed. The idea is similar to other more successful reinterpretations of a mathematical physics equations like where the negative of a square root led to a prediction of antimatter. This negative mass is not antimatter. In order to propel the ship of exotic materials (the object is called a time-warp bubble) on a one way trip, matter has to be distributed along the path at faster than light speeds (tachyons). In fact, I think this Alcubierre idea is the tachyon idea regurgitated. A semi-intense search for tachyons by Leon Lederman, Jack Steinberger, and Sam Ting suggested and named by my quantum mechanics teacher at Columbia, Gerald Feinberg, hasn’t done anything but expose the weakness of such an idea. So to make a faster than light machine you need a faster than light machine and in the simplest case, -1064 kg of material. That is many orders of magnitude greater than the mass of the observable universe.
To control the ship, the various parts need to talk to each other, which is impossible if you are traveling faster than the speed of light.
Extremely high temperatures caused by Hawking radiation on the surface of the ship would destroy anything inside the bubble anyway and the particles accumulated on the trip would vaporize the destination of the ship as it decelerates upon arrival.
The exotic matter (10 billion times the universe’s mass), must have a wall thickness of 10-32 m, almost as thin as the Planck length 1.6 x 10-35 m. It’s not easy to machine something that thin. (That’s a joke, it’s impossible.)
These warp bubbles could create closed time like curves which means they could be used for backwards time travel, making a mess of causality and undermining the very equations you are using. As Miguel Alcubierre says, “That doesn’t mean you can’t go faster than the speed of light, it’s just that something bad will happens (to the math) when you do.”
To this incomplete list of problems, I add one last item,. The space-time metric this conjecture is based on, is not a solution to Einstein's equation.
One last hope is an unusual effect suggested by Hendrick Casimir. Two parallel plates out in space provide a resonating geometry sort of like an organ pipe, not for sound but for the virtual electromagnetic fluctuations of the vacuum. Even though there is nothing physical in between the plates there are virtual energy oscillations in there and around it in space due to the uncertainty principle. These oscillations cancel each other out on average. Since some of the oscillations don't fit neatly inside the gap, some energy is missing inside. This reduces the energy inside from zero to negative. That is what you need, negative energy density. To fit inside means that the gap emphasizes wavelengths (essentially all wavelengths are available in the vacuum) which are submultiples of the gap width. Sunny has some tenuous ideas and hopes that an interferometer test which is based on a changing gap can show how to use this force.
However, everyone besides Mr, White who can do these types of calculations are dubious. A significant force requires a gap of less than 10 nm or the width of 100 atoms. The force in such a gap is one atmosphere. That’s a good force, but the total energy is density times volume and the energy between 2 one meter squared plates is 10-4 J. A car going 30 mph has about 200,000 J of energy. A spaceship the size of a car going at 0.9 times the speed of light has an energy of 1.16 x 1010 J. And I don’t know how you cycle this effect, perhaps with a motor which resets the gap after using its energy. Somehow you always need real energy, not negative energy, to get work done. It’s hard for a trained scientist to ignore conservation of energy when you are trying figure how to get something done. Normally space travel ideas wreck on the problem of how you transport enough fuel to travel long distances.
My opinion is that this subject is great for science fiction and is used in a good new book called “Terms of Enlistment” by Marko Kloos which I have just read and enjoyed.
However, for Mr. White to put out a concrete image of a warp drive spaceship and say this isn’t science fiction is misleading in the extreme. Notice he is not claiming it would go faster than light. Is that a warp drive? This reduces some of the above mentioned problems, but not nearly all. The idea is based on things which don’t exist and reminds me of the wormhole approach to traveling superluminally which require millions of solar masses for their realization. Its probability of happening is smaller than the chance of you living forever.
“The Physics of Star Trek” by Lawrence M. Krauss
“Faster than Light: Superluminal Loopholes in Physics” by Nick Herbert, a good book to go with his “Quantum Reality”. He is a brilliant local guy who eschews the academic grind to think and innovate..