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

## Wednesday 15 May 2013

### Cosmic acceleration: no need for dark energy.

The Canadian astronaut Chris Hadfield recently made a brilliant musical video of David Bowie's Space Oddity on the International Space Station. The imagine of his guitar drifting lazily down the central spine of the station gave a nice demonstration of Newton's first law: the one that says that objects travel at constant velocity unless something pushes them. As I've discussed in a previous blog, MiHsC has a slightly different prediction, that nicely does away with the need for dark energy.

Imagine that one of Chris' fellow astronauts launches his guitar into deep space. According to MiHsC, as he launches it, its high acceleration relative to nearby matter means that the guitar sees Unruh radiation with a short wavelength, but as it moves into deep space, away from the gravity of the Sun, it's acceleration becomes tiny and the Unruh waves it sees become longer. Eventually, out beyond Pluto they lengthen to the Hubble scale (Theta), and when they exceed this scale they can never be observed. So following Mach (who said that what you cannot see in principle does not exist) the Unruh waves dissapear in a puff of logic (or an exchange between information and energy). This is also a bit like the notes on a guitar: there is a lowest note with a wavelength that is twice the length of the strings. So MiHsC predicts that in deep space the guitar's inertial mass fails. This makes it easier for the guitar to be accelerated again even by the gravity of the distant Sun, so it accelerates, the Unruh waves shorten, the guitar gets its inertia back, so its acceleration slows, it looses inertia .. and so on.

There is a competition here between the inertial failure caused by MiHsC's Hubble-scale Casimir effect and the inertia regained after the lower inertia causes renewed acceleration. MiHsC predicts that a balance exists between these two effects (and balances are the things that last) at a tiny acceleration of 2c^2/Theta = 6.7x10^-10 m/s^2. This acceleration is so small it would produce a speed change from zero to 60 miles per hour in 8500 years, or from zero to the speed of light in 13 billion years (the supposed age of the universe).. The point is that this minimum cosmic acceleration predicted by MiHsC is close to the recently observed cosmic acceleration, the one that is usually attributed ad hoc to dark energy. MiHsC predicts it far more elegantly from a simple philosophy (see the paper below for more details).

McCulloch, M.E., 2010. Minimum accelerations from quantised inertia. EPL, 90, 29001. Preprint: http://arxiv.org/abs/1004.3303