I've suggested (& published in 21 journal papers) a new theory called quantised inertia (or MiHsC) that assumes that inertia is caused by relativistic horizons damping quantum fields. It predicts galaxy rotation, cosmic acceleration & the emdrive without any dark stuff or adjustment. My Plymouth University webpage is here, I've written a book called Physics from the Edge and I'm on twitter as @memcculloch

Tuesday, 2 July 2019

Evidence for Unruh Radiation?

Last week I went for a very pleasant walk at lunchtime, into town and to a tea shoppe. I was trying to understand the recent paper by Hu et al. (reference 2) where they claimed to see 'simulated' Unruh radiation by exciting a Bose-Einstein condensate with a high frequency magnetic field. During the walk I realised that this is very similar to a paper I read way back in 2011 by Wilson et al. in Nature (reference 1) where they observed what they called a dynamic Casimir effect. Several people at the Interstellar workshop I've just attended also mentioned the DCE to me, including Heidi Fearn. This 2011 paper is closer to showing real Unruh radiation, & is simpler to understand as well.

In 1948 Casimir himself noted that mirrors produce a 'boundary condition' on electromagnetic waves (I understand this to be a horizon) since at the mirror the electric field must be zero at the surface. The implication is that if you move a mirror in the quantum vacuum, then it has to zero the vacuum fields as it goes through it. However, moving mirrors fast enough has always been the problem with testing this.

Enter the SQUID. Wilson et al first set up a transmission line with a SQUID (Superconducting Quantum Interference Device) on one end. A SQUID is a loop allowing current to go both ways around, with a Josephson junction along each path. The Josephson junctions and therefore the SQUID responds to changes in the applied magnetic field and the change in the SQUID changes the boundary condition of the transmission line so that it is as if it was getting longer or shorter. Its electrical length changes. This means you can make what is effectively a moving mirror (in my view, a moving horizon) since, as Wilson et al say "In the same way as for the mirror, the boundary condition is enforced by currents that flow thru the SQUID". This is much easier than physically varying the length, since nothing solid is moving and you can get much higher accelerations that way (great for seeing QI).

Wilson et al applied a magnetic field varying with a frequency of about 10GHz to move the boundary condition (aka horizon) back and forth, and they stated that the speed of movement of the apparent end of the line (horizon) was 10% of the speed of light. In the paper they go through a complex analysis to show that what they are getting are paired photons emitted from the end of the line due to its speed through the quantum vacuum.

When I first read this paper back in 2011, I immediately tried a back of the envelope calculation and found it can also be understood as Unruh radiation. Since the frequency of the oscillation (f) they applied was 10GHz and the speed of the boundary was 10% the speed of light, then the acceleration of the horizon is 2 x 0.1 x c/t = 0.2cf = 6x10^17 m/s^2. The predicted wavelength of Unruh radiation is then 8c^2/a = 1.2 m. The radiation Wilson et al detected in their experiment ran a range from 0.4 m to 1 m in wavelength, so it seems plausible that what they saw can also be thought of as Unruh radiation. Also, this is a different way to look at horizons. Usually, in quantised inetia, we consider the horizon made by an accelerating object. Here we are looking at an accelerating horizon!

If this really is Unruh radiation then it is a well documented example (in Nature after all). Two symmetric Unruh photons are being emitted in opposite directions, and if we can just add some asymmetry, then we would have thrust. Is this then a direct mainstream way through to a QI thruster?


Wilson C.M., G. Johansson, A. Pourkabirian, M. Simoen, J. R. Johansson, T. Duty, F. Nori & P. Delsing, 2011. Observation of the dynamical Casimir effect in a superconducting circuit.
Nature, 479, 376–379. Journal: https://www.nature.com/articles/nature10561 arxiv: https://arxiv.org/abs/1105.4714

Hu, J., L. Feng, Z. Zhang, C. Chin, 2019. Quantum Simulation of Coherent Hawking-Unruh Radiation. https://arxiv.org/abs/1807.07504


Gaaark said...

I was hoping for an update, and I got one!

Initially I thought you were going into a Michelson-Morley experiment type description.

Will have to look at this closer: trying to get a better/fuller understanding.

Thanks for your work and your blog!

Simon Derricutt said...

Mike - if the horizon can be accelerated more in one direction than the other, then you'd emit higher frequency (thus higher momentum) waves in one direction than the other and thus get a net thrust. Needs a sawtooth wave generator involved. Still, there seems to be a problem with detecting Unruh waves using normal methods for photons, since Unruh waves should be continuous monochromatic waves and not photons, so I wonder if the waves detected really are Unruh waves. In this case, because you're producing them in pulses, though, they will have a set duration (the time it takes to shift the horizon one way until it stops) and thus have a start and stop time, and that also means that they cannot be a single frequency but must be a superposition of a range of frequencies. That seems to imply that they'll be "normal" photons.

Whether or not they are Unruh waves, though, it remains that you'll be emitting more momentum in one direction than another, and thus should get a net thrust. May need to emit a lot of them to get a measurable thrust, though.

Robert said...

I read one article that claimed you were hoping to get 1N thrust from a 10 Watt light based EmDrive device. Is that true or a misquote? Thanks.

Mike McCulloch said...

Robert: The thrust is often given in terms of Newtons per kiloWatt. The experimental test of QI being done in Spain should extract about 0.01 N/kW of thrust from the vacuum whereas the one in Germany should produce 200 N/kW (2N from 10 Watts, close to what was quoted) but this experiment relies on more assumptions than the one in Spain.

Robert said...

Thanks! Here's wishing the teams success!

mikenyc said...


mikenyc said...

This recently appeared: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.041601

I don't know enough to comment on it, but it seems relevant to your approach.

A. Javier M. M. said...

Mike, there is one only way that momentum conservation can rise in nature.

The observed inertial mass of the objects, must look diferent from diferent observers.

This comes from a work I did in 2003, about some works of James F. Woodward .

Very near to this is your 'horizont' asumption.

But I do not see easy to match, theoretically, this.

In fact, your analogy with ships on the sea, near stones, made me think you do not take in acount the whole system, the stones and our planet, where momentum is conservated.

Only this point Mike:

Momentum conservations is just the expresion of the way universe is. it is derived from the way universe impose, all observers, to see the same energy balance.

In others words, is the way universe tell us that it does not allow any obserber (who can see mases, and speeds), any trap on energy, from any observer.

This comes from equations not to complex.

It is really nice to see this kind of things in the way the universe is.

It seems it is playng with us.

Well Mike, may be your 'horizont' is jus the way.

¿what about the experiments in My Clountry (Spain) and Germany?

A. Javier M. M. said...
This comment has been removed by the author.
A. Javier M. M. said...

Mike, first of all, thanks for allow my comments, still I am not an scientific (59 years old, telecommunication Engineer, Phd, Spain).

Thanks Mike, I know how difficult is your enterprise (For decades, I had similar ones).

Second, I would try to point the dialog, to a point that for years have shocked to me.

The "power/trust" relation.

Let us, Mike, talk like old Physics, those before Feynman died.

If a system, any, make trust, and there is not movement of any load, then, there is not needed any energy, so, the gradient of energy by time (Power), is zero.

Sure, there would be trust (Force, the gradient of energy with 3-D space), but while this trust is not used to move some load, there would be no energy done to the load.

¿Do you follow me Mike?, I am sure yes.

So, Mike, this point is on this land since the first works of James F. Woodward.

Yesterday, I read an old work I have on my PC from years ago:

1.-> Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum
Harold White,∗ Paul March,† James Lawrence,‡ Jerry Vera,§ Andre Sylvester,
David Brady,** and Paul Bailey††
NASA Johnson Space Center, Houston, Texas 77058

It give a Trust / Power measured about 1.2(mN∕kW)

Another (One I love, is very nice to read Thomas fighting with experiments) is older:

2.-> Propellantless Propulsion: Recent Experimental Results
Exploiting Transient Mass Modification
Thomas L. Mahood
Department of Physics, alifornia State University,
Fullerton, PO Box 6828, Fullerton, CA 92834-6850

Similarly, it gets a relation Trust/Power (Theoretically, and experimentally).

The same happens with the famous EM-Drive.

But Mike, !!! ¿Where do this energy go?. ¡¡¡¡

If the Trust (Call it T<0>) is get, measured, and not used to acelerate nothing, or move nothing, then ¿Where do this energy go?.

I understand (For instance in EM-Drive) loses on the Microwave cavity sould be an acceptable explanation for the door that this energy take to go.

That is, heat.

¿But in your theoretical system, where does it go?.

If I am correct, we must calculate not the relation between Power (Who, theoretically, while nothing is moved, MUST be zero) and trust, but between Maximum Field (Electric for instance in EM-Drive) on some specific point of the cavity, an trust.

Moreover, Power required to make a trust, is needed only because with a specific device (EM-Drive, or Woodward Device, or your Device, Mike), this power (Which end as heat while nothing is moved, this is just energy conservation) generate some fields on some regions of space with the adequate level to made the trust.

For instance, Mike from 2 (Nw/Kwat) to 0.01 (Nw/Kw), the only difference, could be the use of superconductors as surfaces for microwave (I know it is not easy Mike, still the central idea is this, eliminate the lose in the device).

Theoretically (While you give a mechanism where the energy can go whiteout being converted on thermal energy, that is, heat, for instance, radiation to the space out of the devices) we must not talk about (Trust/Power) , but about (Trust/(Fields or Energy internal to Device)).

Mike, this was the old Feynman language.

I loved it.

joesixpack said...

Off-topic Dr Mike, but;

Are there any references in the literature to LENR being catalyzed by the Dirac Sea?

Simon Derricutt said...

Antonio - I suspect you meant "thrust" when you wrote "trust".

You have hit on the reason why this is regarded as fringe physics at best and why the EMDrive and similar devices are regarded as impossible. Since the thrust is produced relative to the EMDrive then no matter what the relationship between power and thrust, at some velocity you will be producing more kinetic energy than you are putting in as electrical power. Such a drive will violate Conservation of Energy. In fact, any such device that violates Conservation of Momentum will also violate Conservation of Energy.

A more fundamental question is thus "why is momentum conserved?". Momentum is only transferred via fields, and if we have two particles colliding then the force multiplied by the time that one acts on the other should be the same as the force multiplied by time of the second particle on the first, with the forces in opposite directions. However, since there is a minimum distance between those particles, the force that particle 1 puts into the field can only propagate at the (local) speed of light, and the same for particle 2 putting its force into the field, and so there is a time delay between particle 1 acting on particle 2 and particle 2 acting on particle 1. The force times time is thus not necessarily the same for both particles (because the speed of light is finite) and momentum is not necessarily absolutely conserved once we get to relativistic speeds.

Another point here is that particle 1 puts the force (and thus momentum) into the field and, a little later, particle 2 receives that force (and thus a change of momentum). The field can thus accept momentum on its own, and we don't actually need particle 2 to be there. At the time that particle 1 puts the force into the field, it cannot know where particle 2 will be to take that force out again because that knowledge is beyond its current horizon. All the particle will know is where particle 2 was at the time the information reaches it and that is delayed by the flight-time of that information.

The fields themselves are thus both a source and sink for momentum, and though in general we see momentum conserved because we look at interactions between particles and masses, there will be situations where it is possible to simply produce a force by interacting with a field and thus momentum may not be conserved. As a simple thought-experiment, consider 2 loop antennae spaced 1/4 wave apart and being driven with a sine-wave with a 90° phase-shift between one loop and the other. Because of the speed of light delay, instead of the force between the loops being equal and opposite they are both in the same direction. For a real experiment, this force is pretty small and of the order of micronewtons per watt at 5.8GHz, but maybe with a bit of resonance and a high-Q cavity it could be improved. However, the reasons for the force are sitting in all the textbooks already and I can see no reason why we should doubt that that force will exist. We don't actually need QI to explain it, either, since it's simply AC magnetic fields acting on each other and the delay caused by the finite speed of light.

If Conservation of Momentum is no longer absolute, then a lot of basic physics will need to be re-considered. That also implies that Conservation of Energy is also not absolute. The two-loop experiment shows that we can violate both fairly simply at a low level anyway, and so we need to accept that both those fundamental laws have limitations and are not universally valid. I figure a lot of people will reject those assertions even if they can't find any problem in the logic, so this will remain heretical until someone produces a large-enough force to be undeniable. That person could well be Mike....

Lord Acesco said...

Hello Mike,

I wonder if this discovery fits with QI predictions:


Best & keep inspiring us!