Recent content by timmdeeg

Wikipedia: Messier 83 or M83, also known as the Southern Pinwheel Galaxy and NGC 5236, is a barred spiral galaxy<a href="https://en.wikipedia.org/wiki/Messier_83#cite_note-WISE-7"><span>[</span>7<span>]</span></a> approximately 15 million light-years away in the constellation borders of Hydra...

Thanks, its very hard to see the connection of the strong Equivalence Principle with Timescape though. According to the paper I showed #14 Timescape is physically motivated "by an extension of Einstein’s Strong Equivalence Principle to cosmological averages at small scales"

To me its hard to grasp how Timescape works. It is e.g. argued that clocks in voids tick faster and in gravitational walls around them tick slower compared to "cosmic Time", which I understand but I don't see the connection with Timescale. Thinking that the volume of voids is bigger by far than...

Here is an update of this paper: https://arxiv.org/pdf/2412.15143 They argue that according to the timescape model the cosmological constant can be replaced: .... Instead of a matter density parameter relative to average Friedmann-Lemaître Robertson-Walker model (as in ΛCDM), timescape is...

That's the reason why I mentioned "voids expand faster because of under density" as an example. That seems to refer to the Friedmann equations. But its a local effect, so why if at all is the conclusion in "" still reasonable?

This raises the question to which extent "the FLRW idealized model" is applicable locally? E.g. it is said that voids expand faster because of under density.

Yes, agreed.

The example shows that a far away clock ticks faster compared to a clock close to a black hole.

Compared to the duration of a far away supernova.

And another point, wouldn't this result change the expansion history significantly? The temperature of the plasma at recombination is estimated around 3000 K, which we measure 2.7 K today, which if I see it correctly corresponds to an expansion factor of around 1100 since then. Does this still...

Very interesting! How would this conclusion fit to the (almost) flatness of the universe?

Perhaps this helps: https://www.astro.ucla.edu/~wright/cosmology_faq.html#MX Are galaxies really moving away from us or is space just expanding? This depends on how you measure things, or your choice of coordinates. In one view, the spatial positions of galaxies are changing, and this causes...

Thanks, to me its hard to see though how 1) and 2) result in a dark matter halo without visible matter.

... around the bulge, yes. From here we start. The Bullet Cluster shows that even after collisions of Galaxies dark matter is still around visible matter. So, how can visible matter, e.g. the bulge of a galaxy, get rid off its halo of dark matter?

The main mass of a galaxy is located in its bulge. In this case separation is hard to imagine, isn't it?