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Comment Re:If it works (Score 1) 238

The paper is at http://journals.aps.org.secure...

I suspect the article/summary is oversimplifying

You're probably right - it's a safe bet.

Temperature is a measure of the vibration rate of particles - it's not found in vacuums.

I'm not sure that works, r is relevant. There is no such thing as a vacuum - you can remove every particle and all photons from a volume of space ... and as you're doing it the space will remain populated with virtual particles springing out from the void in accord with Heisenberg's Uncertainty Principle. Those particles will have a spectrum of velocities and therefore a temperature in the sense you're denying the existence of.

So you would need 42 thousand trillion trillion joules of energy to raise just one gram of water that high. Just about any other substance - the number goes up.

Water has an unusually high specific heat capacity. In the units you use, yes, it's 4.2 ; for most materials it's 1.0 or lower. Not that that changes your point by much.

Comment Re:Why not? (Score 1) 130

Get over yourself. Uber isn't going to steal $5 from you.

Agreed. They're not going to steal a cent from me if they require a credit card before service delivery. They're not going to get my business.

Actually, where in my country do they have employees? Oh, just the capital and the largest city ; nowhere important. I'll look at the question in another year. Or the next time I use a taxi, whichever comes sooner.

Comment Re: Valid (Score 1) 585

That will depress prices for baby dealers.

You need to throttle the supply to boost prices and increase the value of existing stocks. Though Trump might experience constitutional issues due to his conflicts of interest in this business. He has several investments in this market. Oblig Swift reference.

Comment Re: Valid (Score 1) 585

Too bad the vast majority of eligible/potential voters (over 100 million) chose not to even bother voting, instead they sat back and just watched it happen.

Eh? What? Hang on.

The population of the US is what - 300-odd million. Something like 50 million under 18s. Is it 1 or 2 million in jail? So that's an electorate of 248 million or so.

How do you exclude something over 2/3 of the electorate from voting? Is that the 66% apathy rate that is the price of non-compulsory voting? Or is it because they're black, Hispanic or Cuban?

Comment More other news on "Tabby's Star" this morning. (Score 1) 2

A paper published this morning on Arxiv considers whole families of possible solutions to the puzzle of "Tabby's Star". However it does not in the least address this morning's other paper. As one would expect. However it does address the question of why astronomers continue to find this object fascinating.

Jason Wright and Steinn Sigurdsson have considered "FAMILIES OF PLAUSIBLE SOLUTIONS TO THE PUZZLE OF BOYAJIANâ(TM)S STAR" (that's "Tabby's Star" to the Internet audience) in a paper accepted by Astrophysical Journal Letters (PDF here, abstract here). They consider " a range of plausibilities, including: a cloud in the outer solar system, structure in the ISM [Inter-Stellar Medium], natural and artificial material orbiting Boyajianâ(TM)s Star, an intervening object with a large disk, and variations in Boyajianâ(TM)s Star itself." The paper makes interesting reading for anyone following this topic.

Comment Other news on Tabby's Star today on Arxiv (Score 1) 2

This morning another group published a historical analysis of light changes in "Tabby's Star", from archive photographic plates taken at the Sonneberg Observatory, Germany. (PDF here ; abstract here)

In January this year (Schaefer), an analysis of archive plates from the Harvard Observatory suggested that "Tabby's Star" (formally, "Boyajian's Star") had faded rather consistently at 0.164+-0.013 magnitudes per century. However, this analysis was acknowledged to have problems, not least a period of reduced observation frequency in the 1960s, the so-called "Menzel gap", when organizational changes reduced the observatory activities. (With images taken over a century of development in both telescope technology and photographic emulsion technology, any long archive series is going to have problems. This is no criticism of the Harvard programme. However, it does show why the single-instrument approach of Kepler was taken and has been so productive.)

The obvious thing to do is to re-run the analysis using a different original dataset. This has been done using a library of 275000 plates taken at Sonneburg. After a processing pipeline described in detail (details matter in photometry!), two datasets were acquired, in "red" light ("pv" waveband) and "blue" light ("pg" waveband). Further analysis rejected correlations between brightness in different terrestrial seasons (does the observatory's atmosphere change between seasons, or temperature affect the emulsions? You don't know, so you do check.). Which camera (14 are part of the Sonneburg survey programme) was used for each plate also produced no correlation with the magnitude.

"This result is consistent with no dimming of the star between 1934 and 1995."

Which is in direct contradiction to the earlier results from the Harvard plates. However it does remove one aspect of the peculiarity of "Tabby's Star," replacing it with questions about one or other of the sets of archive plates. However, the uniformity of the data set from Kepler remains, leaving "Tabby's Star" as a very peculiar object.

Submission + - A physical model for (some of) Tabby's Star's light dips. 2

RockDoctor writes: A fresh paper on Arxiv describes a model proposed to explain at least some of the light dips in "Tabby's Star" (Kepler Input Catalogue KIC 8462852). When the irregular light received from this star was recognised in 2015, nobody could come up with a credible explanation for the irregularity of the star's light dips, or their depth. Further studies suggest sustained dimming over the photographic observation epoch, further deepening the puzzle. This new paper proposes a model of a jet of material which leaves the star's surface, then casts off a plume described as "smoke plume" which is swept around in the stars orbit. The opaque jet and the less-opaque "smoke plume" then intersect with the light travelling towards us to generate an asymmetric dip in the star's light curve, as observed in the past.

Which is an interesting model. The big peculiarity is that the "smoke plume" orientation with respect to the material jet implies that the outer parts of this star's envelope is rotating faster than the inner part where the jet originates. Which would raise almost as many questions as the original discovery.

Definitely, this is a very peculiar system.

(PDF here ; NB, the paper does not appear to have been submitted to a journal, or peer-reviewed.)

Comment Re:Also.. (Score 1) 40

Those box-numbered adverts were paid for by the person posting the advert(*). If that was done by cheque, then there is a traceable route there. If it were done in cash at the newspaper's office (or by postal order), then there were people who would potentially recognise (or at least be able to give a description of) the poster.

It didn't stop frauds and assaults, but it did discourage them.

(*) Remember - every column inch of "content" in a public newspaper or magazine exists solely for the purpose of selling that advertising space. The situation is different for a "house" journal - for example the "Weekly Slashdot News" recounting the drunken antics of the Editors on Saturday nights - where at least some of the production costs are carried as a loss by the home organisation, but even they tend to try to defray their running cots by selling advertising. The advertising sales and accounting staff of newspapers and magazines normally considerably outnumber the journalism department.

Comment Re:What about diatoms? (Score 1) 87

The tendency of silica tetrahedra is strongly to polymerise with themselves and form minerals which have melting temperatures in the high hundreds of centigrade, are insulators, and which don't participate in reactions with more typical "organic" molecules (e.g. biopolymers, water, biological acids and alkalis). In short, their chemistry is very different to and incompatible with interactions with the large majority of "organic" materials. If people got that (not entirely unreasonable) inference from the original article, or that the reactions might lead to "biosilicon" computers, then that should be corrected.

From the other end of the telescope, carbon dioxide can readily interact with other organic molecules - the whole of the organic produce of the Earth has done that already through the good offices of RUBISCO, and those interactions produce compounds with low melting points and relatively high reactivity - look at any text book in organic chemistry for details. Silicon dioxide OTOH, mostly doesn't interact with organic compounds, or other silicate compounds until you're at temperatures in the high hundreds, and then it mostly interacts with metal oxides for form what is better known as glass.

Arguably, the closest you get to close similarity between organic chemistry and silicate chemistry is in the zeolite minerals, and while they're a fascinating, useful and complex group, they're still anonymous crystalline white powders, most of which decompose before reaching their melting point.

Comment Re:What the? (Score 1) 110

So they didn't correlate the IMU data with ranging radar or even barometric altitude information so as to avoid this?

How do you know the barometric pressure profile before you enter the atmosphere? Mars has a trickily variable atmosphere.

There was a large dust storm developing at the time, which is a (potentially) global event. How much does that affect barometric pressure? (On Mars, not necessarily on Earth.)

Comment Re:Kalman filter (Score 1) 110

Presumably the IMU is expected to tell you the probe has run into the planet (i.e. landed) and it's time to get rid of the 'chute before it lands on your probe and also time to shut down the thrusters

Wrong landing sequence. This spacecraft was intended to parachute down to some hundreds of metres, then fire up retro-rockets and jettison the parachutes, then descend to a few metres on the retro-rockets, then drop to the ground. So, the signal from the IMU would vary between free-fall and various substantial decelerations several times during the planned descent.

Well, they achieved the desired state of not having the parachute land on top of the lander.

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