Mon, 11 Jan 2010
Thanks to Joey Hess for the request to set up tor bridges. I wholeheartedly agree, and recommend the video he points to. I've installed a Tor bridge at home, and recommend others to do so.
For the most part, I'm not politically active at the moment - I'm doing a PhD Part-time, and thats consuming all my "spare" time, other than work and family. Just given a blog site, however, one subject strikes me as very important - free speech. Hence the side links to Amnesty International, etc. In Ireland this campaign has a particular focus at the moment - the Repeal of the Blasphemy Law. This law came into effect in Ireland this January. While the government claims that this law will 'never be used', its bad in several ways. Firstly, it promotes the ideas of censorship as a method of hiding social issues, and secondly it may actually be used, as pointed out in :
Blasphemy is a Victimless Crime from Limerick Blogger on Vimeo.
Basically, with Europe-wide arrest warrants, if two European countries have criminal blasphemy laws, then someone may be extradited to face prosecution in another country. While the Irish government says they will never prosecute, they open the possibility of say, Irish citizens being extradited to Greece to safe prosecution for blasphemy.
On a wider level, I recommend Index on Censorship. It keeps documenting the cost of censorship around the world, and has been instrumental in campaigning for Libel reform in the UK, which is ncreasingly important for open scientific discussion.
Mon, 24 Aug 2009
Up on arxiv.org today is a paper, "Title: The perihelion precession of Saturn, planet X/Nemesis and MOND", by Lorenzo Iorio.
The perihelion is the point of the planets orbit where it is closest to the Sun. Over the millennia, this point moves, or precesses, under the gravitational pull of other objects. This is a tiny effect, spotted because we have accurate measurements for Saturn thanks to measurements with the Cassini probe. (We have no such measurements further out, for Neptune and Uranus; but we have a more famous case: the Pioneer Anomaly, unexplained changes in the path of the Pioneer probes). Iorio comes up with measurements for a potential planet X to explain this; an Earth-sized planet around 80-150 AU out, up to a Jupiter-sized object at 1000 AU. (1000 times the Earth-Sun distance).I've written before about this: such a planet is remotely feasible to detect by ground-based systems (or perhaps Herschel). It would certainly help explain the architecture of the outer solar system. Perhaps we should start seriously looking for such an object ?
The Brown Dwarf possibility is also interesting; Centauri Dreams has an article on the Wide-field Infrared Survey Explorer (WISE) mission, due for November launch, thats expected to be capable of finding many cold brown dwarfs nearby.
read more »
Thu, 20 Aug 2009
In this weeks Astronomy & Astrophysics was a paper by M. Reidemeister et al., A possible architecture of the planetary system HR 8799.
This revisits HR 8799, one of the few planetary systems seen by direct imaging, actually observing the planets.
These are believed to be three Jupiter-sized planets (of about 5, 7 and 7 times the mass of Jupiter: the exact numbers depend on the precise viewing angle from Earth; Reidmeister think this is nearly pole-on). They were discovered last year by Marois et al..Summarizing all available data, they decide that HR 8799 is less that 50 Million years old, practically still forming. Their proposed layout of the system has at least three dust rings, still coalescing and cooling. By comparison, our Solar system at that stage had formed the main planets but the four outer giants were still moving into position, working their way through the remains of a dusty, gassy disk : another 500 million years or so before Jupiter and Saturn settled into their current orbits, and bombarding the inner system as they did so, leading to the cratering we see on the moon and resurfacing Mars, Earth and Venus.
What makes the HR 8799 system so interesting is that its a good test for theories of planetary or stellar formation. Its unclear whether it formed as a 'planetary system', with the planets formed in the debris disk of the star, or as a "multiple star" system; for the latter. Modelling the formation of HR 8799 will be a good test of Alan Boss's 'Gravitational Instability' theory, vs the 'core accretion' model which has been gaining ground in recent years.
In the meantime for non-theorists, its pole-on orientation gives us a good view of planets in formation. Roll-on the clearer images of the James Webb Space Telescope.
Thu, 13 Aug 2009
WASP-17b is the first planet to be discovered in a retrograde orbit: it rotates about its star in the opposite direction to the spin of the star. (See the nice BBC News write-up, or the ArXiv preprint for the more technical details).
We think planetary systems are formed from a disk of debris as the star forms, and the disk and star would rotate the same way, so most planets rotate pro-grade, in the same direction of the star. For retrograde motion, it would have to have been hit early-on by some large object (another planetary embryo, for example, being ejected from the stars 'solar system' in the game of cosmic billiards as they coalesce to form planets).
Within our solar system we see retrograde motion in Venus as it spins (on its own axis) in the opposite direction of other planets, but this is the first time we've seen a planet orbit in retrograde. Similarly, Uranus' spin axis is tilted at 89 degrees, but it orbits in a pro-grade manner; its thought that Uranus was hit by a giant object causing its tilt. As we find more exoplanets, the statistics of how many are pro-grade or retrograde will help us learn about the formation of planetary systems.
WASP-17b is a "Hot Jupiter", discovered by the Wide Area Search for Planets (WASP) consortium of UK Universities by Radial velocity methods.
Sun, 21 Jun 2009
Unfortunately I won't be able to make it to DebConf9, so as an aid to those who are going, here's a summary of current work:
I've just uploaded terralib 3.3.1 to Debian, and its sitting in the NEW queue, as the older version was removed from the archive due to lack of maintenance (it had an RC bug in both including its own copy of libtiff and failing to link against it - now it links against an external copy of libgeotiff and libtiff).
In the NEW queue it joins g2clib, hdf-eos4, hdf-eos5 and udunits. These are there as dependencies of other Meteorology-related packages I'm working on: magics++ needs terralib and gshhs; zygrib needs gshhs (it has a copy built-in). NCL (NCAR Command Language) has a rake of dependencies including udunits, hdf-eos, g2clib and vis5d+ (ITP'd) . I'm also packaging VISIT for visualization.
Then there is the GSHHS issue: I think I'll end up packaging 'gmt-coastline-high', but the format of the coastline maps needs to be decided (netCDF or its own binary format) and updating the sundry packages to read the latest version needs tackling.
I'm packaging these as they are used at ICHEC and i've experience building them. One of the main aims I had in setting up Debian Meteorology (beyond adding the software to Debian) was to help integrate all the Free and Open Source code in the Earth-sciences field, and sort out dependency and build issues. I hadn't expected to encounter quite so many so quickly, though. I don't expect to get more done before vacation-time, but I'll be happy if I get these done this summer.
Thu, 18 Jun 2009
As mentioned before, I've started working on Debian Meteorology, adding "standard" meteorology-related packages to Debian. Part of the aim of this is to jump-start an effort of integrating the FLOSS in the field: all the usual libraries that people working in the field use and expect to be on the supercomputers and workstations they use.
So, two packages I've been working on are Magics++ and zyGrib, which are plotting and visualisaton tools. respectively. So they both contain coastline maps of the world. Digging deeper shows they use the same files : a binary database called 'GSHHS', or Global Self-consistent Hierarchical High-resolution Shorelines. Some scope for integration here.
So, I start investigating GSHHS in order to create a 'coastline data' package to be shared. It turns out that building GSHHS depends on GMT, the Generic Mapping Tools, already present in Debian, and this coastline issue has been explored before, and a package gmt-coast-low created.
"gmt-coast-low" is 5.5 MB in size, and as its name suggests, there was once a "gmt-coast-high", but this has since been dropped for taking up too much space in the Debian archive (in its place, a script which will download this data for you has been created. But the files in gmt-coastline-low are in netCDF rather than GSHHS's own binary format; what to do? Posting a mail for help and it turns out that another package is being considered, Basemap, an add-on for Mathplotlib, that also includes the GSHHS data.
I've summarized the files, sizes and versions here in the Debian Wiki. Offhand it appears that there is scope for re-adding a gmt-coastline-high package (with perhaps additional small datafiles on states boundaries, etc. seen in Basemap), though some questions remain:
Fri, 08 May 2009
Adrian von Bidder raises an interesting discussion on why public health care is difficult. Basically, it comes back to the challenge:
The problem is, the majority of health costs are in the last few years of a persons life: when the body is breaking down. If viewed from the problem of health-care funding vs. eg. education, you have an ethical dilemma: is it worth it ? Here there are no easy answers.
Nick Bostrom wrote a very interesting and persuasive essay a while back, The fable of the Dragon Tyrant. In short, we are getting somewhere with regenerative medicine While cures are hard to come by at this stage, there is a growing realization in medicine that senesence, what we used to call "old age", is curable. But we have a lot of psychological defensive mechanisms to help us cope with the carnage of old age that make us deny the problem: if we look afresh at "old age" knowing it to be curable, any delay in doing so is abhorrent.
From a public, societal perspective, we spend a fortune every year on health. But we do so in a very disjointed way: we pay colossal amounts for health care, but also for basic health science: in the US, for example, the budget for the National Institutes of Health is about 30 billion dollars. Nearly twice that of NASA. Similar figures are spent in Europe, but there is this strange gap in the middle: the drug companies and medical industry. We start the development of new drugs with public money, and we buy the drugs with public money, but the choice of what drugs and treatments are developed are left to private industry, that is, a profit motive. This results in many cases in expensive treatments to treat symptoms rather than necessarily cure the problem. Faced with the huge costs of geriatric medicine and senesence, the response should be co-ordinated: funding a cure will be expensive, but save a fortune (Think, instead of a pensioner slowly dying and 'being a drain on resources', of 'experienced citizen in the prime of their productive, tax-paying years'). Instead of funding the basic science alone, we should be funding the complete drug and treatment development publically, only farming out the actual manufacture to private industry.
It is silly to spend a fortune to keep merely keep someone alive at the age of eighty or so, when we know for a larger investment (bigger than a private company can do), we can cure them properly. The solution to the dilemma, then, is to stop thinking of the elderly being a drain, but actually applying our public efforts in a co-ordinated manner to solving the carnage of old age.
Wed, 22 Apr 2009
At work I've been promoting the use of pkg-config and modules to solve the problems of avoiding hard-coded paths and an environment where we've multiple compilers. In summary, "module load intel-cc" to load the intel compiler, "module load netcdf-intel" to, which among other things appends /ichec/packages/netcdf/4.0-intel/pkgconfig to $PKG_CONFIG_PATH, and then:
in the application code. Replace "intel-cc" and "netcdf-intel" with "gcc" and "netcdf-gcc", and it builds with gcc.This would work better if upstream supplied .pc files, which means the next stage in world domination is to send patches to do just that. But it's not that easy, apparently.
netcdf (for example) supplies two libraries, libnetcdf.so and libnetcff.so, with the second including code only needed for Fortran. So, for gcc I have the following netcdf file:
prefix=/ichec/packages/netcdf/4.0-gcc exec_prefix=${prefix} libdir=${prefix}/lib includedir=${prefix}/include Name: netcdf Description: netCDF libraries, include files and development tools (gcc version) Version: 4.0 Libs: -L${libdir} -Wl,--as-needed -lnetcdf -lnetcdff Cflags: -I${includedir}While for Intel I have:prefix=/ichec/packages/netcdf/4.0-intel # Add fortran libs forlibs=/ichec/packages/intel/fce/11.0.081/lib/intel64 exec_prefix=${prefix} libdir=${prefix}/lib includedir=${prefix}/include Name: netcdf Description: netCDF libraries, include files and development tools Version: 4.0 Libs: -L${libdir} -lnetcdf -L${forlibs} -lnetcdff -lifcore Cflags: -I${includedir}The main problem is that --as-needed is not understood by non GNU-ld linkers, and must be conditionally removed somehow. Any ideas ? (There is a second wrinkle of needing to add additional libraries for Intel Fortran here, but I'm sure I can remove that with the addition of more .pc files.).
A second issue is that --as-needed can break otherwise working pkg-config usages. Thanks to galtgendo at PhP Bugs for this example:
works, but: The problem being that --as-needed removes libraries as unnecessary before the linker sees the test.o code.Tue, 21 Apr 2009
From the exoplanets mailing list:
Gliese 581d is now more solidly inside the habitable zone; it was considered before to be on the outer edge of the habitable zone (this work moves its believed semi-major axis from 0.25 AU to 0.22 AU). Gliese 581d was a maybe for habitability (see this Centauri dreams article for example), depending on cloud cover, etc. Now its definitely in. The new Gl 581e is beyond the classical habitable zone.
These planets are quite close in: Rory Barnes and colleagues at Lunar and Planetary Laboratory in Arizona did some good work on the habitability of Gliese 581 c (paper online) and concluded that it would be tidally heated to such a degree it was probably never habitable. Such tidal heating might make Gl 581e habitable; time to run the model again.
Correction: On reading the ESO Press release and paper (via) it appears that Gl 581e is inside the orbit of Gl 581b, and too close to the star to be habitable. To date, planets have been labelled b, c, d .. as they are discovered, and they've been discovered shortest-period first, so 'b' also meant closest to the star. Now Gl 581e is closest to the star, with a period of 3 days.