I've suggested (& published in 21 journal papers) a new theory called quantised inertia (or MiHsC) that assumes that inertia is caused by horizons damping quantum fields. It predicts galaxy rotation & lab thrusts without any dark stuff or adjustment. My University webpage is here, I've written a book called Physics from the Edge and I'm on twitter as @memcculloch. Most of my content is at patreon now: here

Tuesday 27 April 2021

Response to Tajmar's New Cavity Results

First of all, there is no criticism of Tajmar's team here. Their work ethic & professionalism have always been impressive and their results are useful, as you will see. The problems that have arisen are my fault, and probably caused by not demanding detailed schematics before the experiments.

I employed the Tajmar group, to test quantised inertia as part of my DARPA project. They manufactured several very attractive copper and silver cavities. All of them had asymmetric distributions of metal to asymmetrically damp Unruh waves and hopefully cause thrust. A laser was fired into each and a sensitive double pendulum balance was used to detect very small (nanoNewton) forces.

Unfortunately, and I did not know this until I read their paper last month (mea culpa). On page 7 they say “every copper [and silver] cavity was encapsulated in an aluminium case, similar to the beam trap mentioned earlier to reduce heat radiation to balance components”. The problem is that the addition of a symmetric metal box will cancel the thrust from quantised inertia. Here is a schematic to explain.

Figure (a) shows an incomplete understanding of quantised inertia. The Unruh waves seen by a highly-accelerated object (photon, black circle) in an asymmetric cavity are more energetic (hotter) at the wide end (red), and cooler at the narrow end (blue), so an internal object is pushed left, but the cavity is not: any forces are only internal. A better picture is (b): the Unruh waves seen by the accelerated object also exist outside the cavity which is partially transparent to them and therefore the cavity ‘falls down’ the Unruh gradient. This is how quantised inertia predicts thrust. In case (c), representing Tajmar’s copper or silver cavity tests, the cavity is inside a metal box so there will be a push (see colours) between the cavity & box but friction stops movement. QI predicts that the combined cavity+box must show no or much less thrust: there’s no background gradient.

Tajmar's thrust results indeed show no thrust. It is important to point out that none of the results I'm going to discuss now are significant since the error bars are about the same size as the values, but please look at this graph which I made to summarise Tajmar's thrust data. The x axis shows the expected photon thrust from the laser (F=P/c). The y axis shows the observed thrust minus the expected photon thrust. So dots above the x axis show the thrust we hope to see.

Firstly, most of the points are above the x axis, so there is slightly more than the photon thrust (but not significantly). This might be expected since all of the cavities, no matter what their geometrical shape had a thicker wall in the positive thrust direction, and quantised inertia predicts more Unruh damping in that direction which predicts a positive thrust. This 'wall thickness' effect should be more robust to the addition of the metal box than the variations in the geometry of the cavities which are thin walled, like the metal box.

Second, the silver cavities (labelled Ag) show more ‘thrust’ then the copper (Cu) ones. This is interesting & makes sense because the Q value for Cu was 9 and for the Ag it was 39 (silver is more reflective) so we would expect 4.3 times the energy to be present in the silver cavities and 4.3 times the thrust from them. The average thrust is shown on the plot as the narrow dashed line for copper at .05 nN and 0.16 nN for silver. The factor is 3.2.

Again, these results are all smaller than the errors, so we cannot say anything solid from them. Yes, I know, excruciatingly frustrating, blame me, but given that the cavities were inside a metal box, it's the best we can hope for from this data and on this blog I will give you the real deal, not just the slam-dunk stuff. The next step will be to do the same tests without a metal box while also trying out the capacitor method of Becker & Bhatt which is perhaps 1000 times more powerful.

The true path never did run smooth!

I thank the Tajmar team because these results are very useful.


Neunzig, O., M. Weikert and M. Tajmar, 2021. Thrust measurements and evaluation of asymmetric infrared laser resonators for space propulsion. SP2020+1, March 2021. Link https://www.researchgate.net/publication/350108417_Thrust_Measurements_and_Evaluation_of_Asymmetric_Infrared_Laser_Resonators_for_Space_Propulsion