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Rhys Taylor
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www.rhysy.net
www.rhysy.net

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Ya done fucked up, Google

For me, Google+ is the internet. But it's clear that the security concern is a mere pretext for cancellation, so I don't have much hope of a revival.
https://www.blog.google/technology/safety-security/project-strobe/

As a just-in-case move that will take about five seconds of your time and cost you nothing, consider signing the petition :
https://www.change.org/p/google-inc-don-t-shut-down-google-plus-54f15bea-1d8c-4be9-a53f-e2ceee1302f4

My plan is to continue using G+ more or less as normal until the bitter end. I don't currently use any other social media but at some point - not anytime soon - I'll switch to something else, possibly multiple services. I haven't decided anything yet. There's a community dedicated to this here :
https://plus.google.com/communities/112164273001338979772

Feel free to note where you're going (or other ways I can reach you) in the comments on this thread, which I'll pin. Of course, I'll also be manually checking as many people as possible to see where y'all going. I can always be reached via my :
- Website : www.rhysy.net
- Blog : https://astrorhysy.blogspot.com/
- Email : feedback@rhysy.net

On the positive side this is an opportunity to start anew and form new bonds in new communities. On the negative side, G+ already had a fantastic community of people I never would have interacted with elsewhere. It was a great service, poorly understood and maintained by its own developers, kept alive by its wonderful users. Yes, even - especially - the crazy ones. Because while many of you antisocial media users have some views which are frankly worrying, not a single damn one of you didn't have at least something useful to say that I wouldn't have heard otherwise. Whatever's next, it won't be the same.
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Well there we are then.

The government is defeated on its proposed Brexit deal by a majority of 230. The result of the vote is 202 in favour and 432 against. It means the prime minister has three sitting days before returning to Parliament to set out her response.
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Fifteen years well spent.
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Seeds taken up to the Moon by China's Chang'e-4 mission have sprouted, says China National Space Administration. It marks the first time any biological matter has grown on the Moon, and is being seen as a significant step towards long-term space exploration.

Plants have been grown on the International Space Station before but never on the Moon. The Chinese Moon lander was carrying among its cargo soil containing cotton and potato seeds, yeast and fruit fly eggs. The plants are in a sealed container on board the lander. The crops will try to form a mini biosphere - an artificial, self-sustaining environment.

The lunar mini biosphere experiment on the Chang'e-4 lander is designed to test photosynthesis and respiration - processes in living organisms that result in the production of energy. The whole experiment is contained within an 18cm tall, 3kg canister that was designed by 28 Chinese universities.
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Missing Matter Still Even More Missing, Study Finds

Last year a galaxy that seemed to have no dark matter was doing the rounds because that's freakin' weird. Virtually all galaxies appear to be heavily mass dominated by dark matter : it's arguably the best way to define a galaxy as opposed to a giant star cluster. The whole mainstream basis of galaxy formation and evolutionary theory depends on dark matter as an integral feature. While there are some cases of dwarf galaxies formed by tidal encounters that don't have much (or any) dark matter, these tend to be still embedded in the debris associated with their formation. As far as I know there are no good cases of a dark matter free galaxy just sitting there minding its own business.

If such an object were to be found, it would raise awkward questions for the standard theories of galaxy evolution but make life even more difficult for the main alternative : modified gravity. Tidal encounters between galaxies can strip away dark matter, so it's at least possible to reduce the dark matter content in standard theories (but remove it completely ? I doubt it). For modified gravity, on the other hand, any two star systems of the same size and shape ought to have the same dynamics : gravity should work the same everywhere, more or less. A nice control test where one can compare similar objects is not so easy to find as you might think, but such systems have been found - and the results don't look good for modified gravity :
https://plus.google.com/u/0/+RhysTaylorRhysy/posts/DCV3csgBMAQ

Then there is this galaxy, NGC1052-DF2. This is an ultra-diffuse galaxy, meaning it's very large but with few stars per unit area. That makes it difficult to measure how fast its stars are moving, which is what you need to work out its total mass. So previously astronomers used its globular clusters, which are much brighter and easier to measure (though there are only a few of them). They found a velocity dispersion of 8-10 km/s - so low that it's consistent with the galaxy having no dark matter at all.

This made a lot of people very upset. Claims were made that the distance measurements were wrong and that would mean the galaxy was perfectly normal, but then an independent team came along and said nope, the distance measurements are correct, this galaxy really is weird.

Still, having only 10 globular clusters has always raised concerns that the estimate of the velocity resolution is reliant on small number statistics. Other teams have questioned the rigour of the claim for such a low dispersion, though in my opinion the original van Dokkum claim always looked stronger. Now, two teams have used extremely powerful instruments to measure the velocity dispersion of the stars directly. Note that both papers are still under review.

The first paper was by an independent group and came out just before Christmas :
http://adsabs.harvard.edu/abs/2018arXiv181207345E

I read this, but didn't bother writing about it because I found it rather badly-worded : I could not easily extract the main point about just how massive the galaxy is supposed to be. Fortunately the new paper (by the original team) is much more clearly written and comments on the Emsellem work.

The bottom line is that this galaxy does indeed seem to have very little or possibly no dark matter whatsoever. This is in conflict with the Emsellem claim in two ways : first, Emsellem claimed that the velocity dispersion could be much higher (13-27 km/s), whereas this paper says it's 8 km/s (just as the original globular cluster measurements indicated); second, Emsellem claimed the galaxy is rotating (albeit slowly) whereas this paper finds no evidence of that. The authors comment directly on the disagreement , noting that they aren't able to explain it. The only hint is that this latest study has a much greater velocity resolution than the Emesllem paper so it should be more accurate. And their fitted velocity dispersion profiles do seem to match the data extremely well.

As for how well this galaxy does or doesn't fit with modified gravity, as usual there's the complication of the external field effect. In modified dynamics, the presence of nearby galaxy can change the velocity dispersion in a very different way to conventional theories. Based on this, the earlier prediction was that the dispersion should be 13 km/s. This is not consistent with the new results, and only just about consistent with the Emsellem range which is actually more favourable to the galaxy having some dark matter than the modified gravity prediction.

I would expect a great deal of back-and-forth on this issue. My money's on the original van Dokkum team. Though a very strange result, it does seem to stand up to scrutiny so far. Watch this space.
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Binary stars are very common throughout the galaxy, but HD 98000 has a little something extra that made astronomers take special note. As observed by the Atacama Large Millimeter/sub-millimeter Array (ALMA), its protoplanetary disk doesn’t occupy the same plane as the binary orbit; it’s been flipped by 90 degrees over the orbital plane of the binary pair. Although such systems have been long believed to be theoretically possible, this is the first example that has been found.

Should there be a planetary body orbiting the stars on the inner edge of the disk, an observer would be met with a dramatic pillar of gas and dust towering into space with the two stars either side of it in the distance. As they orbit one another, the planetary observer would see them switch positions to either side of the pillar. It goes without saying that any planet orbiting two stars would have very different seasons than Earth. It will even have two different shadows cast across the surface.
The binary system observed by ALMA isn’t wonky, it’s the first example of a polar protoplanetary disk Some star systems simply don’t like conforming to cosmic norms. Take HD 98000, for example: It’s a binary system consisting of two sun-like stars and it…
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Gamers are about the become the fittest group of people on the planet.
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No doubt things will get ugly later, so here's something cute.
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Philosophy Job Interview
Philosophy Job Interview
existentialcomics.com
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