June 11, 2015
While thermodynamics has a quantity called "free energy," free in this case just means available. We all know that nothing good can be obtained at no cost. That idea is summarized by the expression, "There's no such thing as a free lunch. The economist, Milton Friedman, actually used this expression as the title of a book.
The No Free Lunch idea describes the fundamental economic principle of opportunity cost. Opportunity cost is the money you would have made by selling your graphite and wood, rather than transforming them into pencils for sale.
Over the centuries, ambitious inventors have struggled for a free lunch in the form of a perpetual motion machine. I wrote about such machines in two previous articles (Second Law of Thermodynamics, February 7, 2011, and Perpetual Motion, May 17, 2013).
Physicists don't waste their energy (pun intended) on perpetual motion, since it's disallowed by the first and second law of thermodynamics. The first law of thermodynamics is the conservation of energy law, while the second law states that thermal systems will equilibrate after sufficient time, and natural processes are irreversible.
Thermodynamics has been proven valid for hundreds of years, so physicists are not timid in their belief that perpetual motion is impossible. In 2003, the American Physical Society issued the following statement:
"The American Physical Society deplores attempts to mislead and defraud the public based on claims of perpetual motion machines or sources of unlimited useful energy, unsubstantiated by experimentally tested established physical principles."
The US Patent and Trademark Office does not grant patents for perpetual motion machines, as explained in its Manual of Patent Examining Procedure (MPEP).
"A rejection on the ground of lack of utility is appropriate when (1) it is not apparent why the invention is “useful” because applicant has failed to identify any specific and substantial utility and there is no well established utility, or (2) an assertion of specific and substantial utility for the invention is not credible. Such a rejection can include the more specific grounds of inoperativeness, such as inventions involving perpetual motion."(Section 706.03a)
Perpetual motion might lurk outside the realm of thermodynamics. One fictional example is the Zero Point Module (ZPM) of the various Stargate television series. The Zero Point Modules apparently harvest the zero-point energy of the vacuum.
Zero-point energy is the ground state energy of the vacuum. The uncertainty principle requires every quantum mechanical system to have a ground state energy that's greater than zero. One manifestation of this is that there's motion even at absolute zero. For this reason, every place in the universe seems to sit atop a baseline energy reservoir, although the term, "reservoir," is a misnomer, since it doesn't appear possible to tap into this energy.
There's an effect involving the vacuum zero-point energy that encourages speculation that this energy can fuel some interesting devices. This is the Casimir effect, predicted in 1948 by Dutch physicist, Hendrik Casimir.
Casimir predicted that very closely-spaced conductors will attract each other in a perfect vacuum. That's because the region between the conductors form an electromagnetic resonator that only supports a subset of the frequency modes of the vacuum state, so the vacuum outside this region, which supports all modes, will exert a pressure on the conductors.
Ten years after his prediction, Casimir's effect was roughly demonstrated by one of Casimir's colleagues at the Philips Research Laboratories. An experiment in 1997 demonstrated the Casimir Effect to 95% accuracy. Atomic force microscopy experiments, for which separations can be very small, has brought the agreement to 99%.
It's easy to believe that lurking in the Casimir effect is the means to extract energy from the vacuum. Square centimeter parallel plate conductors separated by ten nanometers have an attractive force of 10 newtons, or one kilogram of force! The problem, however, is that the same force is needed to separate the plates, so any cycle involving movement of the plates will yield no useful work.
The zero-point state of the vacuum was the first thing that came to my mind when I read reports about a seemingly impossible propulsion drive being investigated by scientists at NASA. It appears that forces defying conservation of momentum are exhibited by closed, asymmetric, microwave cavities. This concept originated with the UK company, Satellite Propulsion Research Ltd., in 2001. Since the device violates a fundamental law of mechanics, it might be lumped together with perpetual motion machines, and no one was interested in further experiments until recently.
About a year ago, a team of NASA scientists led by Harold White at the Johnson Space Center presented positive results in follow-up experiments at the 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Cleveland, Ohio, July 28-30, 2014. Evidence was presented for a direct conversion of electrical energy to thrust without propellant. The NASA work followed work by Chinese scientists in which 0.720 newtons of thrust was obtained with 2.5 kilowatts of electrical power.[3,5]
When so much electrical power is involved, there's always the problem that heating of the object might cause convective forces in the surrounding Air that cause the propulsion. That's why the Chinese instrumented their experiment with temperature sensors. In the most recent experiments, the NASA research team tested their device in a vacuum chamber, which nullified the hypothesis that the thrust came from thermal convection.
As I discussed in a previous article (The Pioneer Anomaly, December 19, 2012), photons emitted by an object will impart momentum, but the observed propulsive thrust is several thousands times greater than such an effect. The NASA team believes that virtual particle pairs from the quantum vacuum are acting as propellant ions, and the device is a type of magnetohydrodynamic drive. The problem with this interpretation is that it's supposedly impossible to ionize the quantum vacuum; and, even if you do, you can't really "push" against it.
Whatever the cause of the propulsion, the NASA team was able to calculate the efficiency of their device, about one newton per kilowatt. The efficiency appears to increase as the power increases. An input power of 100 kilowatts is calculated to give about 1300 newtons of thrust. As if a drive operating via the quantum vacuum wasn't speculative enough, the NASA research team is performing experiments with an interferometer to see whether time-varying electromagnetic fields could distort spacetime.
- Milton Friedman, "There's No Such Thing as a Free Lunch," Open Court Publishing Company, 1975, ISBN 087548297X (via Amazon).
- S. K. Lamoreaux, "Demonstration of the Casimir Force in the 0.6 to 6 μm Range," Phys. Rev. Lett. vol. 78, no. 1 (January 6, 1997), pp. 5-8.
- José Rodal, Jeremiah Mullikin and Noel Munson, "Evaluating NASA's Futuristic EM Drive," NASA Press Release, April 29, 2015.
- Web Site of the 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Cleveland, Ohio, July 28-30, 2014.
- EM Drive Page on Wikipedia.
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