I've suggested (& published in 15 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

Thursday, 11 May 2017

Emdrives and dielectrics

I am giving a seminar tomorrow to the Plymouth Astronomical Society, so here is a summary of the talk which is humbly titled: "How to predict the impossible". The impossible in this case is of course the emdrive, a truncated cone-shaped microwave oven that seems to move very, very slightly towards its narrow end as the microwaves resonate within it. This is causing a lot of incredulity in physics, since humanity has never before encountered a system that is able to move itself in one direction without apparently expelling reaction mass in the other direction. The usual rule is called the conservation of momentum and is a very well tested. The emdrive anomaly was first discovered by Roger Shawyer and has recently been reproduced by others, including NASA's Eagleworks Lab.

For many years I have been proposing a theory called quantised inertia, that states that the property of inertia (that which makes it hard to stop walking into lamp-posts) is caused by relativistic horizons damping the quantum vacuum. When you accelerate in one direction two things happen 1) the waves of the quantum vacuum that you see get shorter (Unruh radiation) and 2) a horizon (like a black hole horizon) appears in the opposite direction that damps those waves. Quantised inertia states that the resulting asymmetry in the quantum vacuum pulls you back against the initial acceleration and so it predicts inertia for the first time, but also predicts a new loss of inertia when accelerations are so low that the Unruh waves get damped symmetrically by the cosmic horizon, so it also predicts galaxy rotation, and its change with time, perfectly without dark matter.

How about the impossible emdrive then? Well, it is an asymmetrical cavity, so the idea is that in the narrow end the microwave photons lose some inertia because the Unruh waves don't fit so well (just like galactic edge stars lose inertia because the Unruh waves they see don't fit well inside the cosmic horizon, and so feel less centrifugal force). As a result the emdrive photons gain inertia every time they shuttle towards the wide end, and to conserve momentum the cavity has to move towards its narrow end. Quantised inertia predicts the emdrive thrust data quite well, as I showed in a previous paper. Further, quantised inertia predicts that if you happen to put a dielectric in the wide end, this will shorten the Unruh waves, so more will fit and the gain of inertia from the narrow to the wide end will be enhanced and the cavity will accelerate more. Considering the dielectrics too, quantised inertia predicts the emdrive thrusts extremely well. The Figure below shows the observed thrust on the y axis and the thrusts predicted by quantised inertia on the x-axis, both without considering the dielectrics (white squares) and considering the dielectrics (black diamonds).

The diagonal line marks perfect theory-data agreement. The effect of the dielectrics can be seen most clearly for the tests marked 'NASA2016' (the four white squares, lower centre) where quantised inertia over-predicted the thrusts (the values ideally should be on the diagonal line) until I noticed that NASA put dielectrics in the narrow end of the cavity, thus inadvertently reducing the thrust. When this is considered in quantised inertia, the white squares shift left to become the black diamonds, close to the diagonal line. It can also be seen for Shawyer1, who put a dielectric in the wide end, thus boosting the thrust (top right). This dielectric dependence is a good confirmation of quantised inertia.

Applications of this are to be found in any form of terrestrial of space transport, and one advantage of the explanation from quantised inertia is that it suggests that dielectrics can be used to enhance the effect, which has been too small to be useful as yet. My latest paper on this is just about to appear in EPL (see the reference below).

To change the subject for a bit, it would be fascinating to go to another star in a human lifetime, but for that you need to travel close to the speed of light so that relativistic time dilation gives you an Einsteinian version of suspended animation. For example, if you accelerate at 9.8 m/s^2 for one year, travel at 90% the speed of light (c) for 10 years and then decelerate for one year at 9.8 m/s^2 you could make the 25 light-year trip to Gliese 667 in 12 years (the duration for those on the ship). Unfortunately, although theoretically possible, engineering gets in the way. To get a habitable normal spaceship to 90% of c you would need more energy than can be produced by our civilisation, or as much fuel as a small planet. The emdrive, though, as quantised inertia suggests, uses 'nothing' as its fuel and nothing is readily available everywhere in space (of course, a power source would need to be included).


McCulloch, M.E., 2017. Testing quantised inertia on emdrives with dielectrics. EPL.. Preprint