tobychev @tobychev@qoto.org

Slovakia brings its grievances to Brussels after Ukraine’s gas transit ‘sabotage’: Prime Minister Robert Fico said in a video message that his Smer party would consider cutting electricity supplies to Ukraine, adding that a Slovak delegation would discuss the situation in Brussels next Tuesday.

The post Slovakia brings its grievances to Brussels after Ukraine’s gas transit ‘sabotage’ appeared first on Euractiv. https://www.euractiv.com/section/eet/news/slovakia-brings-its-grievances-to-brussels-after-ukraines-gas-transit-sabotage/?utm_source=mastodon&utm_medium=dlvr.it

Poland takes over EU presidency with focus on security: Analysts say the Polish presidency is a key moment for Europe above all due to Trump’s arrival and the situation in Ukraine but also issues related to the broader economy.

The post Poland takes over EU presidency with focus on security appeared first on Euractiv. https://www.euractiv.com/section/politics/news/poland-takes-over-eu-presidency-with-focus-on-security/?utm_source=mastodon&utm_medium=dlvr.it

4/n

"Furthermore, housing finance products available to companies and organizations are not appropriate for developing rental and cooperative housing solutions, because they are calibrated to for-profit real estate developers building apartments for sale."

This is 100% our experience with #cohousing. In Belgium only one bank, @triodos, will even touch cohousing, and its offer is not very well developed. In their defense, the market is small. Chicken and egg problem.

President Biden's statement and order "do not present any credible evidence of a national security issue, making clear that this was a political decision. ...we are left with no choice but to take all appropriate action to protect our legal rights." https://investors.ussteel.com/news-events/news-releases/detail/708/nippon-steel-corporation-and-u-s-steel-condemn-u-s

Compared to the same period in 2023, solar output in California is up 31%, wind power is up 8%, and batteries are up a staggering 105%. Batteries supplied up to 12% of nighttime demand by storing and redistributing excess solar energy.

We really need far better international rules regulating what happens to stuff in low orbit.

As well as rules to stop letting corporations unilaterally make a mess of the sky.

"Space debris weighing over 1,000 pounds reportedly crashes into village in Kenya"

https://www.cbsnews.com/amp/news/space-debris-reportedly-crashes-village-kenya/

Timescape versus Dark Energy?

Just before the Christmas break I noticed a considerable amount of press coverage claiming that Dark Energy doesn’t exist. Much of the media discussion is closely based on a press release produced by the Royal Astronomical Society. Despite the excessive hype, and consequent initial scepticism, I think the paper has some merit and raises some interesting issues.

The main focus of the discussion is a paper (available on arXiv here) by Seifert et al. with the title Supernovae evidence for foundational change to cosmological models. This paper is accompanied by a longer article called Cosmological foundations revisited with Pantheon+ (also available on arXiv) by a permutation of the same authors, which goes into more detail about the analysis of supernova observations. If you want some background, the “standard” Pantheon+ supernova analysis is described in this paper. The reanalysis presented in the recent papers is motivated an idea called the Timescape model, which is not new. It was discussed by David Wiltshire (one of the authors of the recent papers) in 2007 here and in a number of subsequent papers; there’s also a long review article by Wiltshire here (dated 2013).

So what’s all the fuss about?

Simulation of the Cosmic Web

In the standard cosmological model we assume that, when sufficiently coarse-grained, the Universe obeys the Cosmological Principle, i.e. that it is homogeneous and isotropic. This implies that the space-time is described by a Friedmann–Lemaître–Robertson–Walker metric (FLRW) metric. Of course we know that the Universe is not exactly smooth. There is a complex cosmic web of galaxies, filaments, clusters, and giant voids which comprise the large-scale structure of the Universe. In the standard cosmological model these fluctuations are treated as small perturbations on a smooth background which evolve linearly on large scales and don’t have a significant effect on the global evolution of the Universe.

This standard model is very successful in accounting for many things but only at the expense of introducing dark energy whose origin is uncertain but which accounts for about 70% of the energy density of the Universe. Among other things, this accounts for the apparent acceleration of the Universe inferred from supernovae measurements.

The standard cosmology’s energy budget

The approach taken in the Timescape model is to dispense with the FLRW metric, and the idea of separating the global evolution from the inhomogeneities. The idea instead is that the cosmic structure is essentially non-linear so there is no “background metric”. In this model, cosmological observations can not be analysed within the standard framework which relies on the FLRW assumption. Hence the need to reanalyse the supernova data. The name Timescape refers to the presence of significant gravitational time-dilation effects in this model as distinct from the standard model.

I wrote before in the context of a different paper:

….the supernovae measurements do not directly measure cosmic acceleration. If one tries to account for them with a model based on Einstein’s general relativity and the assumption that the Universe is on large-scales is homogeneous and isotropic and with certain kinds of matter and energy then the observations do imply a universe that accelerates. Any or all of those assumptions may be violated (though some possibilities are quite heavily constrained). In short we could, at least in principle, simply be interpreting these measurements within the wrong framework…

So what to make of the latest papers? I have to admit that I didn’t follow all the steps of the supernova reanalysis. I hope an expert can comment on this! I will therefore restrict myself to some general comments.

My attitude to the standard cosmological model is that it is simply a working hypothesis and we should not elevate it to a status any higher than that. It is based not only on the Cosmological Principle (which could be false), but on the universal applicability of general relativity (which might not be true), and on a number of other assumptions that might not be true either.
It is important to recognize that one of the reasons that the standard cosmology is the front-runner is that it provides a framework that enables relatively straightforward prediction and interpretation of cosmological measurements. That goes not only for supernova measurements but also for the cosmic microwave background, galaxy clustering, gravitational lensing, and so on. This is much harder to do accurately in the Timescape model simply because the equations involved are much more complex; there are few exact solutions of Einstein’s equations that can help. It is important that people work on alternatives such as this.
Second, the idea that inhomogeneities might be much more important than assumed in the standard model has been discussed extensively in the literature over the last twenty years or so under the heading “backreaction”. My interpretation of the current state of play is that there are many unresolved questions, largely because of technical difficulties. See, for example, work by Thomas Buchert (here and, with many other collaborators here) and papers by Green & Wald (here and here). Nick Kasiser also wrote about it here.
The new papers under discussion focus entirely on supernovae measurements. It must be recognized that these provide just one of the pillars supporting the standard cosmology. Over the years, many alternative models have been suggested that claim to “fix” some alleged problem with cosmology only to find that it makes other issues worse. That’s not a reason to ignore departures from the standard framework, but it is an indication that we have a huge amount of data and we’re not allowed to cherry-pick what we want. We have to fit it all. The strongest evidence in favour of the FLRW framework actually comes from the cosmic microwave background (CMB) with the supernovae provide corroboration. I would need to see a detailed prediction of the anisotropy of the CMB before being convinced.
The Timescape model is largely based on the non-linear expansion of cosmic voids. These are undoubtedly important, and there has been considerable observational and theoretical activity in understanding them and their evolution in the standard model. It is not at all obvious to me that the voids invoked to explain the apparent acceleration of the Universe are consistent with what we actually see in our surveys. That is something else to test.
Finally, the standard cosmology includes a prescription for the initial conditions from which the present inhomogeneities grew. Where does the cosmic web come from in the Timescape model?

Anyway, I’m sure there’ll be a lot of discussion of this in the next few weeks as cosmologists return to the Universe from their Christmas holidays!

Comments are welcome through the box below, especially from people who have managed to understand the cos.

#arXiv241215143 #CosmicWeb_ #cosmologicalPrinciple #DarkEnergy #Pantheon #supernovae #Timescape #timescapeModel

A very stylish #Roman woman's shoe with a decorative pattern punched into the leather.
Found in 1907 in a well in the  civilian settlement of the Saalburg fort. The damp environment preserved the shoe in a good condition. Dating 2nd c. AD.

📷 Römerkastell Saalburg

Persistent but weak magnetic field at the Moon’s midstage revealed by Chang’e-5 basalt: https://www.science.org/doi/10.1126/sciadv.adp3333 -> The #Moon goddess’s magnetic midlife: https://www.science.org/doi/10.1126/sciadv.adu7441

Thus, this case, Carroll v. Trump illustrates how a Supreme Court that has abandoned judicial craft undermines the legitimacy of the entire federal court process. If the Supreme Court cannot be trusted to abide by settled law, including the law of civil procedure and evidence, neither lower court judges nor litigants can assume that their proper conduct counts for anything. 3/

What's causing the Great Stagnation? Most branches of physics are thriving. But in so-called "fundamental physics" - briefly, the search for the ultimate laws of nature - we haven't seen a successful new theory since 1980. Why not?

There are many causes. One is that string theory got a stranglehold on the market, crowding out other ideas. Another is that university bureaucrats are pressuring physicists to spend more and more time getting grants, which means following trends. But there's a third reason that is rarely discussed: physics is hard.

Just kidding: we all know physics is hard. But quantum gravity in particular is hard, and people don't spend enough time talking about exactly why it's hard.

First, physicists tend to assume that combining quantum mechanics, relativity and gravity will make us see strange new things when we probe down to a distance we get by combining Planck's constant ℏ, the speed of light 𝑐 and Newton's gravitational constant G. This distance, the 'Planck length', is about 10¹⁵ times smaller than what we can study now with particle accelerators. But a bunch of unexpected new stuff could happen long before we get down to the Planck length! Indeed we usually see surprises when we look at things 1000 times smaller than before.

Second, physicists like theories that can be extrapolated to *arbitrarily small* distances. These are called 'renormalizable' quantum field theories. The quest for such theories led physicists to supersymmetry and strings.

In these theories spacetime is a continuum - that is, it has no 'graininess' at small distances. We don't know this is true. Why don't we simply drop this assumption?

Well....

(1/n)

On Monday, Russia and Ukraine exchanged prisoners of war, trading 150 captured Russian servicemen for 189 captured Ukrainian soldiers — the 11th swap of the year and the 59th of the war, so far. https://buff.ly/3DCbYfP

To be fair, Rosalynn Carter wasn’t a brown baby killed in a nest of barbed wire Abbott installed at the border. And she wasn’t murdered by a right-wing creep Abbott could pardon in a gross celebration of political violence. So it’s not really fair to expect him to have noticed.

Greg Abbott sent condolences t...

We collaborated with the #SabinCenterForClimateChangeLaw to adapt their excellent rebuttals to 33 #RenewableEnergyMyths for easy granular access outside of the original single report, which was published as a PDF.

Commencing Nov. 5 we've been highlighting one of these #FossilFuelPropaganda #Debunkings per week. Here's the last for 2024. Stay tuned for more in 2025!

#EnergyModernization

https://skepticalscience.com/will-solar-development-destroy-jobs.htm?utm-source=mastodon&utm-campaign=socialnetworks&utm-term=sks

When you are posting in a different language on Mastodon and want to increase the reach of your post, you can set the language of the post to the language you are posting in, rather than the default, which is often English. This will allow Mastodon to translate your post into different languages like German, English, French, or another language

#38c3 #ccc