The Timescape Illusion That Changes Everything! David Wiltshire

It sounds like dark energy/matter is essentially the manifestation of the rounding error you get when you assume the universe has a uniform density.

David Wiltshire actually makes a better case for his position than standard cosmology. He is addressing many of the questions that seemed to point to defects in conventional theory.

Hello Brian, I see that you changed the title from "The TIMESCAPE Illusion that Changes Everything!" to "Earth TRAPPED In Giant Space Void?". That can easily mislead. Among cosmologists, a *giant* void means a hypothetical 1 Gpc void or larger, whereas I address the abundant directly observed *small* voids of radius 15/h Mpc, or diameter 30/h Mpc; i.e, at least 25 times smaller. I completely agree with any astrophysicist (including Ethan Siegel) who says that large void models are unphysical! Not only are large voids completely at odds with accepted physical models of the Cosmic Microwave Background but they are not falsifiable by the Clarkson-Bassett-Lu test. At 58:07 I show a slide which in addition to the timescape and tardis curves, and standard model projected data points for the Euclid mission, also shows a broken curve labelled LTB. LTB stands for a Lemaître-Tolman-Bondi void model. The 1.4 Gpc large void toy model shown in the plot at 58:07 is typical of models which has been much investigated by researchers studying possible alternative explanations for the apparent acceleration of cosmic expansion. The LTB and Szekeres models are analytic solutions of Einstein's equations and so are much studied as they are relatively simple. In my view, if we add a cosmological constant then Λ-Szekeres models give a good effective description of non-kinematic differential expansion on *small* cosmological scales < 100/h Mpc. The timescape expansion history is close to ΛCDM - so to isolate particular effects, such as non-kinematic differential expansion dipoles, Λ-Szekeres models can be useful. That is not something we discussed in the interview. But just to be clear, the timescape effect is about a *calibration of canonical clocks* - through an averaged conformal frame ambiguity admitted by general relativity - which is simply never addressed in the standard FLRW cosmology, nor in giant void models. Unlike the LTB model shown in the slide, timescape is falsifiable and the verdict will be known this decade, now that sufficient precision of astronomical probes has finally been achieved. Best wishes, David

listening to that is fascinating and hurts my brain at the same time. Like balancing between madness and brilliant discovery. Awesome stuff, huge respect to people dedicated to exploring these strange new horizons. And props to you Dr Keating for allowing us to dive deeper into our love/hobby/passion. What a time to be alive!

When I was in school, I was told that General Relativity did not bear out Mach's principle, even though it was one the motivating thoughts behind GR. And now, 100 years after the theory was formulated, we still don't understand it deep enough to see that Mach's principle really IS contained within GR. Mind blown.

One of the greatest physicists alive. Being right while almost everybody else is wrong is a rare situation. We are witnessing it.

Thankyou Brian for giving David the exposure his ideas deserve. Prof Wiltshire has stuck to his guns over the years - looks like it is paying off 😊

How lucky am i to get to start my day listening to these good people talking❤

What a brilliant and pursuasive theory. Cant wait for experimental results

I think there is tremendous potential for this theory and would not be surprised if continued observation bears it out more and more.