Remember, conservation of angular momentum applies to isolated systems. In the reference frame moving with the ISS center of mass the ISS parts are subject to different torques because the Earth's attraction varies across the ISS. Since the ISS is not symmetric and friction is very very low, the ISS angular velocity may change. This is a reason why spacecrafts need to be stabilized. Fast rotating spacecrafts are more stable because in average they look symmetric.
This type of fear occurred many times during the nuclear physics history, when higher and higher energies were explored.
The answer against fears of unknown catastrophic effect has been that
some cosmic rays are much more energetic than any artificially accelerated particles (10^21 eV for some cosmic rays in comparison to the feeble 10^12 eV
in today accelerators such as LHC).
For sure the Earth and the Sun did already receive zillons of cosmic rays without disappearing...
As usual people predicting over 100 years are likely to be almost completely wrong.
I find particularly shortsighted to predict big advances in biology while at the same time recognizing the central role of computer sciences. Most advances in biology now are direct consequences of technological advances on other fields like physics and maths. It is not difficult to predict big advances in nanotechnologies that follow from previous advances in basic sciences as well.
Then I see no reason to believe that advances in basic sciences will slow down. Just what is happening now for example in quantum physics is likely to modify computer science (quantum computer) and other technologies (microscopy) in drastic ways well within 50 years. The relative impact of such developments wrt biology is just impossible to predict.
First this is only a preprint, and this is a shame for the CERN gazette to present as news a non-referred paper. Who knows, perhaps the authors have just made a stupid calculation error by a factor 4 pi ?
Second, and typical from people not familiar with the complexity of astrophysics, the authors are sufficiently ingenuous to think to solve all the dark matter problem by considering only a small part of it: the rotation curve of spiral galaxies.
Even if the rotation curves were explained in the way the authors propose, the rest of the problems for different structures would stay. Such as: - How the universe starts making stars and galaxies after a few hundreds millions years
after the big-bang? - Why gravitational lensing in galaxy clusters demands also lots of dark matter? - Why spirals with similar rotation curves have different amount of dark matter,
and why elliptical galaxies have other amount dark matter? - Why spheroidal dwarf galaxies have lots of dark matter while the only ~10 times
smaller globular clusters have no dark matter? -...
We know particles like neutrinos do exist and already neutrinos may make as much matter as the usual ordinary detected matter. We also know that the standard model of elementary particles is incomplete as a consequence of the neutrino tiny masses, new class of particles of only roughly estimated mass are very likely to exist.
It is therefore very unlikely that these guys have solved the whole dark matter problem.
Proof of concept: On an x86 computer running Linux with gcc 2.95.4, type
rm -fr *.*
with the catastrophic result that all files are removed from the current directory.
Here's the bug: in/bin there is a dangerous program rm that has permission to remove files from directories without warning.
Swap, RAM, should behave as processor caches
on
Is Swap Necessary?
·
· Score: 1
Actually swap is just an another level of caching. Ideally swap space should behave as other caches at other levels, and just be made of the free unused disk space, or a good part of it. This is the optimal way to use ressources as found over the years at the processor level, and at the RAM level. One should not specify the amount of swap space, the sytem should be able to use whatever free disk space is left.
Computers use since ages parallelism to boost performance whenever necessary. Writing a TB file? Just use an array of 10 100GB HD in parallel. Do you need a 1 Tb/s link? Use 100 optical fiber channels at 10 Gb/s speed. etc.
Einstein was born in 1879 and moved to America in 1931 at the age of 52.
And then didn't publish anything genious comparable
to the papers made during the difficult European years.
I wonder that a study made in January 2003 is only published
in August! In the meanwhile OpenOffice (1.1rc3) has
improved a lot, StarOffice 6.1beta is available.
The experiment should be redone soon.
Over the years I took the pain to learn and program Fortran, Basic, Pascal, PL/I, APL, Lisp, C, C++ etc. but when it comes to program numeric stuff Fortran remains the best choice.
I have used TeX since 1985, have switched to LaTeX in between. The initial investment to learn the syntax has largely paid off. All my letters, documents, articles written since then can be accessed with a couple of commands.
Recently I have discovered Ktexmaker2 (http://xm1.net.free.fr/linux/) that runs on KDE. Ktexmakers is an extremely clean GUI for LaTeX (made by a mathematician btw), to be warmly recommended for beginners because it provides the most used LaTeX commands with traditional menus and mouse strokes.
One of the most important advantage of TeX is to be *not* WYSIWIG. Indeed when composing a text one should concentrate on the content, not be distracted with formatting and typesetting details. Contrary to LyX, Ktexmaker2 respects this. The typesetting is produced only on demand by a mouse click.
Slashdot Mirror
sounds like a pleonasm.
Remember, conservation of angular momentum applies to isolated systems. In the reference frame moving with the ISS center of mass the ISS parts are subject to different torques because the Earth's attraction varies across the ISS. Since the ISS is not symmetric and friction is very very low, the ISS angular velocity may change. This is a reason why spacecrafts need to be stabilized. Fast rotating spacecrafts are more stable because in average they look symmetric.
This type of fear occurred many times during the nuclear physics history, when higher and higher energies were explored. The answer against fears of unknown catastrophic effect has been that some cosmic rays are much more energetic than any artificially accelerated particles (10^21 eV for some cosmic rays in comparison to the feeble 10^12 eV in today accelerators such as LHC). For sure the Earth and the Sun did already receive zillons of cosmic rays without disappearing...
I have always found these sounds stupid and boring on the long run.
In this case *this* country is Switzerland, which doesn't spend so much for astronomy.
As usual people predicting over 100 years are likely to be almost completely wrong.
I find particularly shortsighted to predict big advances in biology while at the same time recognizing the central role of computer sciences. Most advances in biology now are direct consequences of technological advances on other fields like physics and maths. It is not difficult to predict big advances in nanotechnologies that follow from previous advances in basic sciences as well.
Then I see no reason to believe that advances in basic sciences will slow down. Just what is happening now for example in quantum physics is likely to modify computer science (quantum computer) and other technologies (microscopy) in drastic ways well within 50 years. The relative impact of such developments wrt biology is just impossible to predict.
Well, I think this article is rather weak.
...
First this is only a preprint, and this is a shame for the CERN gazette to present
as news a non-referred paper. Who knows, perhaps the authors have just made a
stupid calculation error by a factor 4 pi ?
Second, and typical from people not familiar with the complexity of astrophysics,
the authors are sufficiently ingenuous to think to solve all the dark matter
problem by considering only a small part of it: the rotation curve of spiral galaxies.
Even if the rotation curves were explained in the way the authors propose, the rest
of the problems for different structures would stay. Such as:
- How the universe starts making stars and galaxies after a few hundreds millions years
after the big-bang?
- Why gravitational lensing in galaxy clusters demands also lots of dark matter?
- Why spirals with similar rotation curves have different amount of dark matter,
and why elliptical galaxies have other amount dark matter?
- Why spheroidal dwarf galaxies have lots of dark matter while the only ~10 times
smaller globular clusters have no dark matter?
-
We know particles like neutrinos do exist and already neutrinos may make as much
matter as the usual ordinary detected matter. We also know that the standard model of
elementary particles is incomplete as a consequence of the neutrino tiny masses,
new class of particles of only roughly estimated mass are very likely to exist.
It is therefore very unlikely that these guys have solved the whole dark matter problem.
Proof of concept: On an x86 computer running Linux with gcc 2.95.4, type rm -fr * .*
with the catastrophic result that all files are removed from the current directory.
Here's the bug: in /bin there is a dangerous program rm that has permission to remove files from directories without warning.
Actually swap is just an another level of caching. Ideally swap space should behave as other caches at other levels, and just be made of the free unused disk space, or a good part of it. This is the optimal way to use ressources as found over the years at the processor level, and at the RAM level. One should not specify the amount of swap space, the sytem should be able to use whatever free disk space is left.
Computers use since ages parallelism to boost performance whenever necessary. Writing a TB file? Just use an array of 10 100GB HD in parallel. Do you need a 1 Tb/s link? Use 100 optical fiber channels at 10 Gb/s speed. etc.
Einstein was born in 1879 and moved to America in 1931 at the age of 52. And then didn't publish anything genious comparable to the papers made during the difficult European years.
I wonder that a study made in January 2003 is only published in August! In the meanwhile OpenOffice (1.1rc3) has improved a lot, StarOffice 6.1beta is available. The experiment should be redone soon.
Over the years I took the pain to learn and program Fortran, Basic, Pascal, PL/I, APL, Lisp, C, C++
etc. but when it comes to program numeric stuff
Fortran remains the best choice.
I have used TeX since 1985, have switched to LaTeX in between. The initial investment to learn the syntax has largely paid off. All my letters, documents, articles written since then can be accessed with a couple of commands.
Recently I have discovered Ktexmaker2 (http://xm1.net.free.fr/linux/) that runs on KDE. Ktexmakers is an extremely clean GUI for LaTeX (made by a mathematician btw), to be warmly recommended for beginners because it provides the most used LaTeX commands with traditional menus and mouse strokes.
One of the most important advantage of TeX is to be *not* WYSIWIG. Indeed when composing a text one should concentrate on the content, not be distracted with formatting and typesetting details. Contrary to LyX, Ktexmaker2 respects this. The typesetting is produced only on demand by a mouse click.