I have a commercial wet-dry vac, certified for wood dust (from Festool). It requires less than 1kW but is significantly more efficient than my 2.3kW Siemens vacuum due to its better design (e.g., the Siemens has very hot exhaust, the Festool doesn't).
The problem with frequentist statistics as used in the article is that its "recipe" character often results in people using statistics that do not understand its limitations (a good example is assuming a normal distribution when there is none). The bayesian approach does not suffer from this problem, also because it forces you to think a little bit more about the problem you are trying to solve compared to the frequentist approach.
But that's also the problem with the cited article. Just remaining in the framework and going towards more discriminating thresholds is not really a solution of the problem that people do not understand their data analysis (a p-value based on the wrong distribution remains meaningless, even if you change your threshold...). Because it is more logical in its setup, the danger of making such mistakes is smaller in bayesian statistics.
The telescoper over at http://telescoper.wordpress.com/2013/11/12/the-curse-of-p-values/ has a good discussion of these issues.
the current naming system for stars is a.ready unique. The case that you are mentioning (alpha Lyrae etc.) is the so-called Bayer designation, that is a historic naming scheme for the around 1500 brightest stars. Official star names are NOT the Bayer names, but usually done according to their catalogue numbers. For example, my slashdot name, HDE 226868, is the donor star of the black hole Cygnus X-1, which happens to be number 226868 in the Henry Draper Extension catalogue. These names are unique.
The IAU has since then gone to naming schemes that essentially are what you want already, i.e., for new astronomical objects the "names" really are the position of the object in the sky. So, for example, Swift J 164449.3+573451, a black hole candidate. This object was discovered by the Swift satellite and is at the location RA: 16h 44m 49.3s, declination 57d34m51s. (the J means that the coordinate is for the epoch and equinox 2000.0, i.e., it takes the precession of the Earth's axis into account) If the distance of this object were known, its position relative to us would be known. In a few years, when the Gaia mission is done, we will have such coordinates for all objects in the milky way.
Note that your designation using "medium shifts" (similar to names used in some SciFi books and movies) is far less accurate than what astronomers can already do for those stars where distances are known, namely give spatial coordinates (x,y,z coordinates relative to Earth; you can calculate these easily based on the right ascension, declination, and distance). After the Gaia satellite, the Galactic coordinate system will be well enough known such that we can give absolute positions in a Galactic coordinate system instead of Earth centric.
As the IAU notes, there is a clear precedent on how planets are named (essentially alphabetically in order of their discovery). What companies that try to "sell" naming rights are trying to do is to sham people into believing that this system does not exist. That some of that money is being used to fund science does not matter - fact is, not even the discoverers have final naming rights.
And, yes, I am an astronomer.
This is a place to bring my favorite joke by Virginia Trimble: "It is Siding Spring Observatory, not Siding Springs, this being Australia, after all".
I hope that the damage is small. This is the most beautiful observatory site I have been observing at. and it would be a shame to see the telescopes damaged. Not only the AAT, but also the smaller telescopes on that site have been very productive.
I don't think your argument that the American system is more convenient to live in holds. If you talk to people who grew up outside of the US (like me, for example) you will find that they can think as easily in Centigrades and cm as an USAian can think in inches and Fahrenheit. For example, you wouldn't talk about a 2/3m door, but a 70cm door, and people tend to think of room temperature as 20C or 22C. I travel back and forth between Europe and the US quite often and I do not find any practical difference between both systems.
I think you're spot on with your argument why metric hasn't taken over yet. It's one of the idiosyncracies of the US system that are very difficult to understand for people from the outside (others are, e.g., the electoral system, discussions on gun control, etc.)...
The problem with the petition is that the lines are run by the different airport authorities and not by TSA. So the petition is addressing the wrong institution.
I have yet to see an air based heating system in Europe. In Germany, virtually all heating systems are water based.
The renewable energy used to make power in Germany is not only solar but also wind based. Plus there are backup sources (e.g., water based power plants). And, adding to that an infrastructure that actually works.
I live in Germany, my significant other in the US. In the past seven years I had a few seconds of power outage TOTAL. My significant other had more than one week this year alone.
Ok, I stand corrected. I mainly work with people who started their careers during Berlusconi, so they might have seen the earlier governments in a more positive light, just because they did not experience them...
But the point is, the occurrence of an earthquake was very improbable. This fact is not changed even by the occurrence of an earthquake shortly after.
What the scientists were asked to do is effectively the same as predicting who would win the lottery. This is just not possible - even if somebody still wins it every few weeks...
I work with people from INAF (the national astronomy institute), ASI (the space agency), INFN (the nuclear physics institute), and several universities (Milan, Catania, Roma, Palermo, and others). For none of them your statements are correct, most of them (in their 40s) have around 100-150 refereed publications.
I am not going to name names on slashdot, but I really think that discussions should be based on facts and not on unfunded allegations as the ones you are bringing up here. It is not the people that are the problem, it is the system in Italy - as also evidenced by this very, very unfortunate court decision today.
I work quite a lot with scientists from Italy in my area (astrophysics). They are among the most dedicated scientists I know and are doing world leading science. They are also among the least well paid - which shows their dedication to science.
The former Italian government (under Berlusconi) tried for years to marginalize science and research in Italy and this is yet another blow to the scientific system in Italy. The result will be disastrous and lead to an even larger brain drain of highly qualified people from Italy than what Italy has already experienced in the past 10-20 years. Everybody can imagine what this means for the long-term future of Italy as a place of innovation and science, which has already been damaged badly.
This is correct. originally the AU was defined as the average distance between the Earth and the Sun. The problem then was to convert this distance to meters. The way to do this conversion in the end involves the product of the mass of the Sun and the Gravitational constant G. Both quantities are not well known (e.g., G is known to 4 or 5 digits only). But their product can be determined from modeling the motions in the Solar system to much higher precision. So by that time the AU was then redefined by defining the product GM (often called k^2, where k is called the "Gaussian gravitational constant"). It is my understanding that this has now been simplified. The difference between both is only a few meters.
No, this has nothing to do with JWST being over budget.
The review concerns the astronomy funding through the National Science Foundation, whose budget is independent of NASA's funding.
NASA funds all of space based astronomy (including data analysis), while NSF funds ground based astronomy. NSF mainly funds the national optical astronomy observatory on Kitt Peak in Arizona and the National Radio Astronomy Observatory in Charlottesville, VA, with facilities in West Virginia and in New Mexico (plus some other states). In addition, NSF funds data analysis/theory grants. Overall, NSF's budget is much smaller than NASA's, but then, ground based hardware is much cheaper than space based. To put things in perspective: for about 50% of all university astronomers, NSF facilities are the only way to get optical observing time (the remainder of astronomers have access via privately funded telescopes, such as the Keck).
The closures of the instruments proposed in the report to NSF essentially mean the US giving up its current leadership in large areas of radio astronomy, and significantly reducing access to medium sized facilities for optical astronomers, if the (realistic) flat budget for the astronomy program is realized.
I would assume that it is something similar to what NASA did with the ESA L-class missions last year, where they also pulled out and then held scientific workshops. NASA's problem is that it has no money to participate in ExoMars or the L-class missions, and that's why they pulled out of ExoMars. However, legally speaking NASA is required to follow the decadal reports, and the planetary one recommend Mars research. This then led to the schizophrenic situation that they have held workshops for ideas on how to do gravitational wave research (LISA), X-ray astronomy (IXO), and now apparently Mars, where they previously pulled out of all joint ventures with ESA and JAXA.
However, the good thing is that with the recommendation from the decadal reports and the results from such workshops the scientists at NASA headquarters have an argument that spending some money for R&D in these areas is necessary, because they can prove need. As a result this important research does not die. There is money for general R&D in the budget, so while some larger programs have been explicitly canceled by either OMB or congress, the Mars/X-ray/gravitational wave research can at least be partially funded this way.
I'd not blame NASA for this but rather congress, which tends to try to exert strong control over NASA, which in many areas really amounts to micro-managing projects, without Congress really understanding what it is doing...
JWST's funding crisis does not only impact astronomy missions, but all of science funding. This includes planetary missions and also the manned space program. The space review (http://www.thespacereview.com/article/1926/1) has a good summary.
This comment is probably a good explanation why journalism in the US, and therefore also the newspapers in the US, are in such big trouble - that most people think it is the opinion page of a newspaper that matters, rather than the information provided by a newspaper.
What I want in journalists is to select the information that is relevant for me. The NYT does this rather well, as do other newspapers such as the Economist and the Guardian in the UK, Spiegel, FAZ and the Sueddeutsche in Germany, or Le Monde in France. In my opinion, this unbiased selection of information is the main job of journalists - people still can do such a selection much better than automated searches. For that reason, I couldn't care less about the opinion or comments pages, although it is usually these pages that people mainly talk about. I mean, shouldn't educated users be able to form their own opinions based on the available information? If that's the case, and I believe it is, shouldn't one read the newspaper that provides the best selection of such information available, regardless of the (unimportant) opinion section?
Die Zeit definitively has news and probably has one of the best teams of journalists worldwide.
But as a weekly newspaper they serve a different audience than the daily newspapers we're mainly discussing here.
Sorry, while I agree with your programming statement, please be aware that with antilock brakes in most situations the stopping distance is decreased, not increased as you claim (see, e.g., http://www.abs-education.org/faqs/faqindex.htm). The reason is that usually you have better traction when your wheels are rolling, not when they're blocked. It is only in very rare situations that you'd be better off without ABS. So you want ABS even for good drivers since as a human you just aren't fast enough to modify the braking force on the wheels to keep them from blocking.
I am an astrophysicist, so let me try and explain in a little bit more detail why this result is so interesting.
First of all: No, the discovery of these black holes has nothing to do with questions concerning the dark energy or missing mass. Note that one has to distinguish between dark energy or missing mass. What is meant by missing mass is the fact that in order to explain the rotation of many galaxies we need to invoke about 10 times more mass than what is found from observing the galaxies. What we do here is that we look at the rotation of the galaxies from which it is possible to infer their mass using simple dynamics arguments. In order to infer the mass present in a galaxy independently of the dynamics, you can simply make a picture of it. Since we know that typical stars have about the luminosity of the Sun it is then possible to calculate from the observed light how much radiating matter is present in the galaxy. It turns out that to explain the observed motions, about ten times more mass is required. Similar arguments also apply to galaxy clusters. This is what's called the missing mass.
Dark energy, on the other hand, is a term proposed in the Einstein field equations, and therefore also in the Friedmann-Equations, which describe the expansion of the universe. With a so-called cosmological constant, these equations predict an accelerated expansion of the universe. It turns out that this is what's observed. About 85 percent of what is causing the curvature of the universe (the so-called Omega-parameter) is due to this cosmological constant, and many astronomers call the cosmological constant "dark energy".
There is a nice plot by Mike Turner summarizing the different terms that need to be added to explain by the observed matter density of the universe.
To turn to the question as to why we astronomers were looking for black holes enshrouded in gas: there is a long standing question about the number density of black holes in the universe. We know that in the local universe most galaxies, including our milky way, harbor a supermassive black hole in their center. These black holes are difficult to find since most are just sitting there, doing nothing. The mass of such a black hole is on the order of one million to one billion solar masses. This sounds a lot, but is really not very much: the typical radiating mass of a galaxy is 100 times more, and if you add the missing mass, then the supermassive black hole only contributes less than 0.1 per cent to the mass of the galaxy. So, on cosmological terms, the mass contained in these black holes is really negligable.
What matters, however, is that models for the evolution of black holes predict that there should be a large number of black holes that are enshrouded in rather dense material in many galaxies. It has been difficult to detect these objects so far, since the dense material absorbs most radiation from the accreting black hole. With infrared observations with Spitzer that are summarized in the press release the Slashdot posting points to it has finally been possible to confirm the long-standing assumption that these black holes exist. What is the nice thing in all of this is that these observations confirm the predicted space density of black holes inferred from previous observations, which is a very nice and important result.
The black holes seen by Spitzer are supermassive black holes (i.e., black holes with a few million solar masses). These black holes will not evaporate for a long time.
What is generally taken to be the reason that the density of Active Galaxies is less high currently than at
higher redshifts in the earlier universe is that the matter required to fuel the Active Galaxies is exhausted.
This does not mean that these black holes do not exist anymore, just that it is virtually impossible to detect them. But the general assumption of most astrophysicists is that they are still around and in the centers of most, if not all, galaxies. For example, our own Milky Way has a supermassive black hole at its center. Its
brightness is very low, so were this black hole not so close, relatively speaking, we would not be able to
detect it at all.
It is a trilogy, not a duology, and the first volume (The Dreaming Void) came out in the UK in August in hardcover. I just finished reading it (bought it in Stansted airport on Wednesday) and it is well worth reading.
The orbital radius increases because the earth's rotation velocity is greater than the moon's angular velocity. If the moon orbited the earth quickly (say.. at LEO speeds assuming that were possible...) the transfer of angular momentum would go the other way.
yes, point taken. To finish this discussion, I have finally found the relevant paper in my files. Piet Hut showed in 1980 that one does reach a stable configuration when more than 3/4 of the total angular momentum of a system is in orbital angular momentum. In your case (moon in LEO) the angular momentum of the system would be dominated by the rotational angular momentum of the Earth and the system would indeed be unstable.
Also, a jovian IS significant compared to its star. especially as evidenced by the detectable wobble.
Again, you are right (the mass ratio of Jupiter to the galilean planets is 1:20000, while Jupiter is about 0.01 solar masses).
However, for all practical purposes you will still find that the observed system is stable, which was the original question of this thread. While hot jupiters often violate the Hut criterion and are thus formally in the unstable regime, numerical calculations show that Jovians next to main sequence stars are stable on timescales longer than the typical lifetime of a star. See, for example, Rasio et al. (1996, http://adsabs.harvard.edu/cgi-bin/bib_query?1996Ap J...470.1187R, click on arXiv preprint if you do not have a subscription to ApJ). These authors find that Jovians next to main sequence stars are stable on timescales longer than the typical age of a lower main sequence star down to orbital periods of 10 hours (their Fig. 1 is a nice summary). And this is also what is corroborated from the large number of hot Jupiters found - we just wouldn't see them if their orbits were not stable.
In most extrasolar planetary systems we have detected so far, the systems are dominated by a small number (1 to a few) of jovians. For all practical purposes these systems can be considered stable on long timescales. For our solar system, which is dominated by a few jovians in the outer solar system, while there are resonance effects between these orbits, which can significantly change the orbital parameters of the inner planets (see, e.g., Laskar, http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bi bcode=1997A%26A...317L..75L) the system itself is quite stable (Ito and Tanikawa, http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bi bcode=2002MNRAS.336..483I).
With the Earth-Moon system, you are citing the most extreme non-stellar case known, with two bodies close to each other which are of similar size. This system will in the end lock into a system where both bodies have a bound rotation, but the timescale of this is long (by observation more than 4.5 billion years). Note that in this case, different from what you imply, the semi-major axis of the system increases and that generally for two-body systems with a tidal exchange one tends to see a circularization of the orbit (see, e.g., Hilditch, An Introduction to Close Binary Systems, CUP, 2001). Again, such effects would stop the planet from falling into its star.
The case under discussion here more resembles the Galilean moons (several small bodies next to a large one), which is what is called in the Laplace resonance. While again there is lots of angular momentum exchange between these moons (e.g., responsible for the heating of Io), but again overall that system can be considered stable, at least according to current simulations (see, e.g., the paper by Musotto et al., accessible via http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bi bcode=2002Icar..159..500M). Point in case: observationally we KNOW that the system has existed for 4.5 billion years.
So, to summarize, not much danger here for the planet!
First of all, sunspots are more or less static in location on the surface of the star. For typical late type stars the rotation period is similar to that of our Sun, about a month, so you wouldn't see this type of variations on a timescale of 4d (we can measure the rotation speed of stars spectroscopically using standard techniques). Furthermore, even if the star rotates with a 4d period, since sunspots change in shape, each time you see the sunspot pass the surface of the star you'd see a slightly different lightcurve. Planets don't change in shape and are very symmetric objects, so the lightcurves will look very different. Finally, sunspots don't last for a very long time, so if you see a planet now and you still see it one year later, you've excluded the sunspot theory, even if you couldn't exclude it using my previous arguments.
Slashdot Mirror
I have a commercial wet-dry vac, certified for wood dust (from Festool). It requires less than 1kW but is significantly more efficient than my 2.3kW Siemens vacuum due to its better design (e.g., the Siemens has very hot exhaust, the Festool doesn't).
The problem with frequentist statistics as used in the article is that its "recipe" character often results in people using statistics that do not understand its limitations (a good example is assuming a normal distribution when there is none). The bayesian approach does not suffer from this problem, also because it forces you to think a little bit more about the problem you are trying to solve compared to the frequentist approach. But that's also the problem with the cited article. Just remaining in the framework and going towards more discriminating thresholds is not really a solution of the problem that people do not understand their data analysis (a p-value based on the wrong distribution remains meaningless, even if you change your threshold...). Because it is more logical in its setup, the danger of making such mistakes is smaller in bayesian statistics. The telescoper over at http://telescoper.wordpress.com/2013/11/12/the-curse-of-p-values/ has a good discussion of these issues.
the current naming system for stars is a.ready unique. The case that you are mentioning (alpha Lyrae etc.) is the so-called Bayer designation, that is a historic naming scheme for the around 1500 brightest stars. Official star names are NOT the Bayer names, but usually done according to their catalogue numbers. For example, my slashdot name, HDE 226868, is the donor star of the black hole Cygnus X-1, which happens to be number 226868 in the Henry Draper Extension catalogue. These names are unique. The IAU has since then gone to naming schemes that essentially are what you want already, i.e., for new astronomical objects the "names" really are the position of the object in the sky. So, for example, Swift J 164449.3+573451, a black hole candidate. This object was discovered by the Swift satellite and is at the location RA: 16h 44m 49.3s, declination 57d34m51s. (the J means that the coordinate is for the epoch and equinox 2000.0, i.e., it takes the precession of the Earth's axis into account) If the distance of this object were known, its position relative to us would be known. In a few years, when the Gaia mission is done, we will have such coordinates for all objects in the milky way. Note that your designation using "medium shifts" (similar to names used in some SciFi books and movies) is far less accurate than what astronomers can already do for those stars where distances are known, namely give spatial coordinates (x,y,z coordinates relative to Earth; you can calculate these easily based on the right ascension, declination, and distance). After the Gaia satellite, the Galactic coordinate system will be well enough known such that we can give absolute positions in a Galactic coordinate system instead of Earth centric. As the IAU notes, there is a clear precedent on how planets are named (essentially alphabetically in order of their discovery). What companies that try to "sell" naming rights are trying to do is to sham people into believing that this system does not exist. That some of that money is being used to fund science does not matter - fact is, not even the discoverers have final naming rights. And, yes, I am an astronomer.
This is a place to bring my favorite joke by Virginia Trimble: "It is Siding Spring Observatory, not Siding Springs, this being Australia, after all". I hope that the damage is small. This is the most beautiful observatory site I have been observing at. and it would be a shame to see the telescopes damaged. Not only the AAT, but also the smaller telescopes on that site have been very productive.
I don't think your argument that the American system is more convenient to live in holds. If you talk to people who grew up outside of the US (like me, for example) you will find that they can think as easily in Centigrades and cm as an USAian can think in inches and Fahrenheit. For example, you wouldn't talk about a 2/3m door, but a 70cm door, and people tend to think of room temperature as 20C or 22C. I travel back and forth between Europe and the US quite often and I do not find any practical difference between both systems. I think you're spot on with your argument why metric hasn't taken over yet. It's one of the idiosyncracies of the US system that are very difficult to understand for people from the outside (others are, e.g., the electoral system, discussions on gun control, etc.)...
The problem with the petition is that the lines are run by the different airport authorities and not by TSA. So the petition is addressing the wrong institution.
I have yet to see an air based heating system in Europe. In Germany, virtually all heating systems are water based. The renewable energy used to make power in Germany is not only solar but also wind based. Plus there are backup sources (e.g., water based power plants). And, adding to that an infrastructure that actually works. I live in Germany, my significant other in the US. In the past seven years I had a few seconds of power outage TOTAL. My significant other had more than one week this year alone.
Ok, I stand corrected. I mainly work with people who started their careers during Berlusconi, so they might have seen the earlier governments in a more positive light, just because they did not experience them...
What the scientists were asked to do is effectively the same as predicting who would win the lottery. This is just not possible - even if somebody still wins it every few weeks...
I am not going to name names on slashdot, but I really think that discussions should be based on facts and not on unfunded allegations as the ones you are bringing up here. It is not the people that are the problem, it is the system in Italy - as also evidenced by this very, very unfortunate court decision today.
I work quite a lot with scientists from Italy in my area (astrophysics). They are among the most dedicated scientists I know and are doing world leading science. They are also among the least well paid - which shows their dedication to science.
The former Italian government (under Berlusconi) tried for years to marginalize science and research in Italy and this is yet another blow to the scientific system in Italy. The result will be disastrous and lead to an even larger brain drain of highly qualified people from Italy than what Italy has already experienced in the past 10-20 years. Everybody can imagine what this means for the long-term future of Italy as a place of innovation and science, which has already been damaged badly.
This is correct. originally the AU was defined as the average distance between the Earth and the Sun. The problem then was to convert this distance to meters. The way to do this conversion in the end involves the product of the mass of the Sun and the Gravitational constant G. Both quantities are not well known (e.g., G is known to 4 or 5 digits only). But their product can be determined from modeling the motions in the Solar system to much higher precision. So by that time the AU was then redefined by defining the product GM (often called k^2, where k is called the "Gaussian gravitational constant"). It is my understanding that this has now been simplified. The difference between both is only a few meters.
No, this has nothing to do with JWST being over budget. The review concerns the astronomy funding through the National Science Foundation, whose budget is independent of NASA's funding. NASA funds all of space based astronomy (including data analysis), while NSF funds ground based astronomy. NSF mainly funds the national optical astronomy observatory on Kitt Peak in Arizona and the National Radio Astronomy Observatory in Charlottesville, VA, with facilities in West Virginia and in New Mexico (plus some other states). In addition, NSF funds data analysis/theory grants. Overall, NSF's budget is much smaller than NASA's, but then, ground based hardware is much cheaper than space based. To put things in perspective: for about 50% of all university astronomers, NSF facilities are the only way to get optical observing time (the remainder of astronomers have access via privately funded telescopes, such as the Keck). The closures of the instruments proposed in the report to NSF essentially mean the US giving up its current leadership in large areas of radio astronomy, and significantly reducing access to medium sized facilities for optical astronomers, if the (realistic) flat budget for the astronomy program is realized.
I'd not blame NASA for this but rather congress, which tends to try to exert strong control over NASA, which in many areas really amounts to micro-managing projects, without Congress really understanding what it is doing...
JWST's funding crisis does not only impact astronomy missions, but all of science funding. This includes planetary missions and also the manned space program. The space review (http://www.thespacereview.com/article/1926/1) has a good summary.
What's wrong with saying 4 deciliters?
or using what's done in most metric countries, namely use 250ml or 500ml ?
This comment is probably a good explanation why journalism in the US, and therefore also the newspapers in the US, are in such big trouble - that most people think it is the opinion page of a newspaper that matters, rather than the information provided by a newspaper.
What I want in journalists is to select the information that is relevant for me. The NYT does this rather well, as do other newspapers such as the Economist and the Guardian in the UK, Spiegel, FAZ and the Sueddeutsche in Germany, or Le Monde in France. In my opinion, this unbiased selection of information is the main job of journalists - people still can do such a selection much better than automated searches. For that reason, I couldn't care less about the opinion or comments pages, although it is usually these pages that people mainly talk about. I mean, shouldn't educated users be able to form their own opinions based on the available information? If that's the case, and I believe it is, shouldn't one read the newspaper that provides the best selection of such information available, regardless of the (unimportant) opinion section?
Die Zeit definitively has news and probably has one of the best teams of journalists worldwide. But as a weekly newspaper they serve a different audience than the daily newspapers we're mainly discussing here.
Sorry, while I agree with your programming statement, please be aware that with antilock brakes in most situations the stopping distance is decreased, not increased as you claim (see, e.g., http://www.abs-education.org/faqs/faqindex.htm). The reason is that usually you have better traction when your wheels are rolling, not when they're blocked. It is only in very rare situations that you'd be better off without ABS. So you want ABS even for good drivers since as a human you just aren't fast enough to modify the braking force on the wheels to keep them from blocking.
I am an astrophysicist, so let me try and explain in a little bit more detail why this result is so interesting.
First of all: No, the discovery of these black holes has nothing to do with questions concerning the dark energy or missing mass. Note that one has to distinguish between dark energy or missing mass. What is meant by missing mass is the fact that in order to explain the rotation of many galaxies we need to invoke about 10 times more mass than what is found from observing the galaxies. What we do here is that we look at the rotation of the galaxies from which it is possible to infer their mass using simple dynamics arguments. In order to infer the mass present in a galaxy independently of the dynamics, you can simply make a picture of it. Since we know that typical stars have about the luminosity of the Sun it is then possible to calculate from the observed light how much radiating matter is present in the galaxy. It turns out that to explain the observed motions, about ten times more mass is required. Similar arguments also apply to galaxy clusters. This is what's called the missing mass.
Dark energy, on the other hand, is a term proposed in the Einstein field equations, and therefore also in the Friedmann-Equations, which describe the expansion of the universe. With a so-called cosmological constant, these equations predict an accelerated expansion of the universe. It turns out that this is what's observed. About 85 percent of what is causing the curvature of the universe (the so-called Omega-parameter) is due to this cosmological constant, and many astronomers call the cosmological constant "dark energy". There is a nice plot by Mike Turner summarizing the different terms that need to be added to explain by the observed matter density of the universe.
To turn to the question as to why we astronomers were looking for black holes enshrouded in gas: there is a long standing question about the number density of black holes in the universe. We know that in the local universe most galaxies, including our milky way, harbor a supermassive black hole in their center. These black holes are difficult to find since most are just sitting there, doing nothing. The mass of such a black hole is on the order of one million to one billion solar masses. This sounds a lot, but is really not very much: the typical radiating mass of a galaxy is 100 times more, and if you add the missing mass, then the supermassive black hole only contributes less than 0.1 per cent to the mass of the galaxy. So, on cosmological terms, the mass contained in these black holes is really negligable.
What matters, however, is that models for the evolution of black holes predict that there should be a large number of black holes that are enshrouded in rather dense material in many galaxies. It has been difficult to detect these objects so far, since the dense material absorbs most radiation from the accreting black hole. With infrared observations with Spitzer that are summarized in the press release the Slashdot posting points to it has finally been possible to confirm the long-standing assumption that these black holes exist. What is the nice thing in all of this is that these observations confirm the predicted space density of black holes inferred from previous observations, which is a very nice and important result.
The black holes seen by Spitzer are supermassive black holes (i.e., black holes with a few million solar masses). These black holes will not evaporate for a long time.
What is generally taken to be the reason that the density of Active Galaxies is less high currently than at higher redshifts in the earlier universe is that the matter required to fuel the Active Galaxies is exhausted. This does not mean that these black holes do not exist anymore, just that it is virtually impossible to detect them. But the general assumption of most astrophysicists is that they are still around and in the centers of most, if not all, galaxies. For example, our own Milky Way has a supermassive black hole at its center. Its brightness is very low, so were this black hole not so close, relatively speaking, we would not be able to detect it at all.
It is a trilogy, not a duology, and the first volume (The Dreaming Void) came out in the UK in August in hardcover. I just finished reading it (bought it in Stansted airport on Wednesday) and it is well worth reading.
Again, you are right (the mass ratio of Jupiter to the galilean planets is 1:20000, while Jupiter is about 0.01 solar masses).
However, for all practical purposes you will still find that the observed system is stable, which was the original question of this thread. While hot jupiters often violate the Hut criterion and are thus formally in the unstable regime, numerical calculations show that Jovians next to main sequence stars are stable on timescales longer than the typical lifetime of a star. See, for example, Rasio et al. (1996, http://adsabs.harvard.edu/cgi-bin/bib_query?1996Ap J...470.1187R, click on arXiv preprint if you do not have a subscription to ApJ). These authors find that Jovians next to main sequence stars are stable on timescales longer than the typical age of a lower main sequence star down to orbital periods of 10 hours (their Fig. 1 is a nice summary). And this is also what is corroborated from the large number of hot Jupiters found - we just wouldn't see them if their orbits were not stable.
With the Earth-Moon system, you are citing the most extreme non-stellar case known, with two bodies close to each other which are of similar size. This system will in the end lock into a system where both bodies have a bound rotation, but the timescale of this is long (by observation more than 4.5 billion years). Note that in this case, different from what you imply, the semi-major axis of the system increases and that generally for two-body systems with a tidal exchange one tends to see a circularization of the orbit (see, e.g., Hilditch, An Introduction to Close Binary Systems, CUP, 2001). Again, such effects would stop the planet from falling into its star.
The case under discussion here more resembles the Galilean moons (several small bodies next to a large one), which is what is called in the Laplace resonance. While again there is lots of angular momentum exchange between these moons (e.g., responsible for the heating of Io), but again overall that system can be considered stable, at least according to current simulations (see, e.g., the paper by Musotto et al., accessible via http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bi bcode=2002Icar..159..500M). Point in case: observationally we KNOW that the system has existed for 4.5 billion years.
So, to summarize, not much danger here for the planet!
First of all, sunspots are more or less static in location on the surface of the star. For typical late type stars the rotation period is similar to that of our Sun, about a month, so you wouldn't see this type of variations on a timescale of 4d (we can measure the rotation speed of stars spectroscopically using standard techniques). Furthermore, even if the star rotates with a 4d period, since sunspots change in shape, each time you see the sunspot pass the surface of the star you'd see a slightly different lightcurve. Planets don't change in shape and are very symmetric objects, so the lightcurves will look very different. Finally, sunspots don't last for a very long time, so if you see a planet now and you still see it one year later, you've excluded the sunspot theory, even if you couldn't exclude it using my previous arguments.