From van Belle, et al., ApJ, 559, 2, p. 1155, 2001:
Altair is the first main-sequence star for which direct observations of an oblate photosphere have been reported and the first star for which vsini has been established from observations of the star's photospheric geometry.
It isn't just the UV that causes problems. It is the blue (and green) light as well (they don't necessarily burn tissue,they mess up the chemistry in the retinal cones).
To quote the aforementioned link:
Until 30 years ago, it was thought that the damage caused by the sun to eyes were the result of infrared (heat) injury to the retina alone. Then research on animals showed that ocular tissue rose in temperature by only a few degrees. We now believe that photochemical damage from visible blue light plays a major role in causing injury, especially when exposures are for more than a few seconds. If exposure is limited, some recovery of the nerve cells in the retina, is possible over a period of months.
Actually the teachers are correct. The sun is more dangerous during an eclipse because the sun is dark enough so as not to initiate our natural blink reflexes or aversion to bright lights; however, there is still significant blue to ultraviolet light being emitted from the corona. It is the exposure to this radiation that causes eye damage. A nice explanation can be found here.
Whether or not you are more likely to want to stare at an eclipse is irrelevant. It is the fact that you can comfortably stare at an eclipse long enough to cause retinal damage whereas you cannot easily do this otherwise with the sun.
I'm sure there are all sorts of data that you'd want from the rover while in flight, and you'd want to operate any heaters if needed, etc, so you'll want connectivity between the rover and the spacecraft. However, the more connections you have to handle this data, the more connections you'd need to undo when you want to release it. If you plugged the rover into a rigid socket for launch, it would have to be very very secure so as not to shake loose on launch, but as you make the docking connection more and more secure, the tougher it would be to undock. The easiest solution is to just run a bundle of cable to the rover and cleanly sever the cable when you are done with it.
You typically don't have one part of a spacecraft talking with another part via RF when you can just communicate over the spacecraft bus.
Things like dust won't affect the guillotine because it would be like dust in a gun barrel keeping the bullet from exiting.
I assume some sort of standard connector was ruled out in this case?
Those devices are very common to sever cables and bolts. They are reliable and effective. Essentially they are pyrotechnic devices that fire an explosive charge that drives a knife edge through whatever you want severed---basically a little cannon that shoots out the knife blade. Judging from the short news blurb, it sounds like a problem with the design of the back-end electronics that were supposed to handle the expected severing.
The idea of nuclear pulsed propulsion goes all the way back to Stanislaw Ulam in the 1950's. An investigation into the idea was called Project Orion and was headed by Freeman Dyson. One brief writeup can be found here.
Kepler stated that the planets move in ellipses. Newton showed (derived) that for a central force the resulting orbits (for the two-body problem) are conic sections, and in particular he showed that for an inverse square force in a two-body system that the resulting orbit is an ellipse.
Basically Kepler made postulates (planets follow elliptical orbits with the Sun at one of the foci; planets sweep out equal areas in equal time; planet orbital period relationship to the orbital radius) that fit the data pretty well. Newton mathematically derived these from first principles and added corrections (e.g., the planets don't orbit the Sun, the Sun and planets orbit each other) that fit observations even better. Newton also starting working on the higher order correction terms to describe planetary motion when other bodies are present, which is the three-body (and higher!) problem (the three-body problem, by nature of not being integrable, has occupied the minds of some of the biggest names in mathematics ever since). I believe that above statement is true, that how satellite/spacecraft orbits are calcuated is essentially the same method that Newton was using when working on planetary orbit corrections.
However, better resolution doesn't have to be for imaging. There are a handful of optical interferometer projects (ground and proposed space) that have amazing resolution and are used for very narrow field of view imaging as well as astrometry. In this case, more resolution == better telescope (at least for its intended application). This is why, for instance, NASA has the JWST as well as SIM. Different scopes for different folks.
I know your comment is tongue-in-cheek, but I'll add anyway that the actuator and thin mirror technologies weren't available in the early 80's, and you wouldn't have been able to put up the processing power (then, or even now I suspect).
These kind of things are in the future plans for NASA from the Jack Webb Space Telescope on out (sorry, I don't have the time to dredge up some links).
I think biology is the exception because congressmen and senators are old and they don't want to die. The NIH budget has ballooned disproportionately over the last five to seven years. Last year just the increase in the NIH budget over the previous year was more than the total NSF and NOAA budgets combined. It has gotten so bad that most of the professional societies have expressed concern that way too much money is going to the life sciences at the expense of all other non-DoD basic R&D.
There is a lot of research money in the life sciences to start with, and a lot of work in the life sciences is done by MDs, who are a group that never seems to have shortages in people.
Again, I'm not trying to steal this guy's thunder. (I'm probably just jealous of his 10" telescope after all;-).) But astrophotography is rather easy with almost any camera once you have a nice big telescope to sit it on.
Not quite. You need to be careful to properly match your pixel sizes to your optics. If the pixels are too big for the performance of the telescope, then you end up with grainy images even if you are using one of the best telescope in the world. And you need to take into account whether you are obtaining color or monochrome pictures with your camera because that determines what your effective pixel size is.
There is also the issue of picture exposure (especially if the imager doesn't have the capability for a variable shutter speed) and how it relates to the performance of the telescope as well as the seeing conditions under which the pictures are taken.
The calculations are fairly easy, and if anyone really wants to see them I can follow up with an example. I would even be bold enough to say that if you have a good handle on what your telescope can do, you can probably select an inexpensive camera that will give you respectable results for even modestly priced telescopes.
Years ago I was at a conference where the session was on results from air shower detectors. During one talk this fella was saying that you shouldn't believe anything less than 4 sigma anyway. The next guy to talk presented his 3 sigma results from a different experiment.
I would also bet that given the length of time and the amount of radiation it has been hammered with, a tape recorder is probably the only storage medium that could stand up to those conditions.
This isn't the sad part. The sad part was just after launch when they realized that the high gain antenna wouldn't deploy properly. That is what prevented us from getting all sorts of data. We've just been fortunate for the people that run the telemetry system who have managed to pack as much information as we've been getting into the low data rate downlink over the last decade.
Certainly there are specific apps that are for Windows and not Linux (and vice versa), but the general argument (or mantra, in some cases) is that Linux is "not ready for the desktop," or cannot compete with Windows in a general sense. My point is that a major distribution (actually, pretty much all distributions) has everything the average desktop user needs: office applications, networking/web capability, multimedia applications, PDA synching, etc., and there is decent cross-application filtering (importing/exporting). And these applications are no more challenging to use (due to their GUI-nature) than Windows apps. Certainly system admin tasks are just as easy as in Windows when you use the GUI tools that Red Hat and Suse (and others) provide.
I don't think most people would argue that there isn't any reason that anyone could not move from Windows to Linux, as your point of a specific application need shows, but I think saying that a general home or business user cannot use Linux because it "isn't ready for the desktop" is a very weak statement.
I think one could argue that the perceived lack of local expert support (i.e., a sysadmin) has cost US businesses billions of dollars due to all the MS Outlook and IIS worms and viruses. If these systems were so easy to administer, then why are there so many unpatched systems? If Joe Blow wants to set up a "it just works" server or Outlook account out of the box and doesn't pay attention to the administrative details, then he shouldn't be surprised when his system goes down and lots of money in time, software, and hardware have to be thrown at it because some l33t scriptkiddie took him down. That is one of the backend costs that others have referred to, and I think that if some of the larger companies that took a big "I Love You" or Code Red hit, that the cost in downtime and repairing/reinstalling their systems was much more than hiring and keeping the aforementioned pricy Unix admins on staff for years.
I think your support argument doesn't hold up because at least Red Hat provides very reasonably priced support. I can't answer for Sun, though my experience with them is that everything they provide is expensive.
I've also never understood the "long way to go" for the desktop argument. Why is Linux so far away from the desktop? What can't you do in Linux that you can do with Windows? I run RH with Gnome and StarOffice. There is nothing I have run into that prevents me from using this as my everyday computer. The only argument against it is that it can't view proprietary MS media formats, that it lags behind deciphering quirky formatting in the latest Office documents. If your standard of argument for equaling MS on the desktop rests on those points, then you'll be disappointed as Linux can never reach that standard unless you think OpenOffice developers can anticipate the next round of formatting commands before the Redmond developers do. And don't even mention the "Joe Blow can't set up Linux" because you apparently never have had to set up a Windows business machine for a neophyte secretary (as well as having them completely relearn the OS when moving from 98 to NT). The "not ready for the desktop" argument has always sounded to me like a catch-all excuse for Linux not having much marketshare and not based on any technical or otherwise decent argument.
Flares are not "predicted" easily. The physics is not well understood, and the observational resolution (e.g., from magnetographs) is not good enough to predict well where or when a flare will pop up. In any event, geomagnetic storms are not caused by flares but mostly by Coronal Mass Ejections (CMEs) that hit the Earth. Some flares result in CMEs and some do not. The CMEs that affect us are the ones that hit us, but not all CMEs hit us. Spacecraft like SOHO might see a flare eruption, but they cannot reliably tell if the CME is heading towards or away from Earth. The best candidates seem to be what they call "halo events." One of the big problems with CMEs is that they are very hard to detect because the amount of light they give off is millions of times less intense than then background light from the Sun.
We also get hit by CMEs that are caused by "backside events," which are flares or other disturbances that erupt behind the limb of the Sun and we didn't see them occur. STEREO is supposed to help there.
One researcher in the field of solar weather forecasting put the maturity level of space weather forecasting 50 years behind that of terrestrial weather forecasting. That was the state in 2000 and not much has improved since. The biggest difference is that for Earth weather forecasting we have continuous global weather observations on both the ground and from space. There is only a tiny fraction of coverage for space weather, and as I mentioned in my first post it still isn't clear what kinds of instruments are sufficient.
Good information resources on space weather can be found at the Space Environment Center at NOAA's web site. They have a nice education page on space weather. For a look into what the space weather field priorities are, one place to start is the Living With A Star program page.
N.B. Space weather is much less predictable than terrestrial weather, and that is not well at all. Sometimes flare events cause space weather events at earth, sometimes not. Space weather events increase with solar activity, but some of the most intense events happen around the minimum in the solar activity cycle. There are very few monitoring stations (on the ground or in space) that can make the necessary measurements. The physics behind these events is not well known, and it isn't well known what kind of monitoring equipment is best (visible imagers, ultraviolet imagers, magnetographs, etc.).
Aurorae aren't the only things "regular" folk see. Six million people in Quebec lost power because of a solar storm. Commercial and military institutions lose satellites fairly frequently due to solar storms. Most of the people in the US lost pager service for this reason.
These issues are a high priority for NASA, NOAA, and the Air Force. Lots of good data have come from SOHO, WIND, and ACE, but these are either nearing the end of their lives or they are done. STEREO should provide the next round of very good data. Just about any spacecraft that measures the solar wind contributes to understanding space weather, and some missions are designed with that as their primary mission. There are also ground-based programs that make very valuable observations. A good page with some space missions can be found here.
If you want some electronics, you can study for an amateur radio license. The ARRL has a lot of plans for good radio-related equipment you can build from scratch. Plus, you can get in on developing and testing software radios.
As another example that the Supreme Court doesn't necessarily have the last word: in the 1830's the Cherokees successfully challenged the State of Georgia in the Supreme Court regarding the Indian Removal Act. The Supreme Court ruled in favor of the Cherokees, but President Jackson moved them out anyway.
The fameous Jackson quote went something like: "John Marshall [the Chief Justice] has made his
decision; let him enforce it now if he can."
Slashdot Mirror
To quote the aforementioned link:
Whether or not you are more likely to want to stare at an eclipse is irrelevant. It is the fact that you can comfortably stare at an eclipse long enough to cause retinal damage whereas you cannot easily do this otherwise with the sun.
Lots of books (some on some very interesting topics) are found at The Assayer.
You typically don't have one part of a spacecraft talking with another part via RF when you can just communicate over the spacecraft bus.
Things like dust won't affect the guillotine because it would be like dust in a gun barrel keeping the bullet from exiting.
The idea of nuclear pulsed propulsion goes all the way back to Stanislaw Ulam in the 1950's. An investigation into the idea was called Project Orion and was headed by Freeman Dyson. One brief writeup can be found here.
One that I like can be found here.
Basically Kepler made postulates (planets follow elliptical orbits with the Sun at one of the foci; planets sweep out equal areas in equal time; planet orbital period relationship to the orbital radius) that fit the data pretty well. Newton mathematically derived these from first principles and added corrections (e.g., the planets don't orbit the Sun, the Sun and planets orbit each other) that fit observations even better. Newton also starting working on the higher order correction terms to describe planetary motion when other bodies are present, which is the three-body (and higher!) problem (the three-body problem, by nature of not being integrable, has occupied the minds of some of the biggest names in mathematics ever since). I believe that above statement is true, that how satellite/spacecraft orbits are calcuated is essentially the same method that Newton was using when working on planetary orbit corrections.
However, better resolution doesn't have to be for imaging. There are a handful of optical interferometer projects (ground and proposed space) that have amazing resolution and are used for very narrow field of view imaging as well as astrometry. In this case, more resolution == better telescope (at least for its intended application). This is why, for instance, NASA has the JWST as well as SIM. Different scopes for different folks.
These kind of things are in the future plans for NASA from the Jack Webb Space Telescope on out (sorry, I don't have the time to dredge up some links).
"Introduction to Adaptive Optics", ISBN 0-8194-3511-2
"Principles of Adaptive Optics", ISBN 0-12-705902-4
There is a lot of research money in the life sciences to start with, and a lot of work in the life sciences is done by MDs, who are a group that never seems to have shortages in people.
There is also the issue of picture exposure (especially if the imager doesn't have the capability for a variable shutter speed) and how it relates to the performance of the telescope as well as the seeing conditions under which the pictures are taken.
The calculations are fairly easy, and if anyone really wants to see them I can follow up with an example. I would even be bold enough to say that if you have a good handle on what your telescope can do, you can probably select an inexpensive camera that will give you respectable results for even modestly priced telescopes.
A whole bunch of other good, related links can be found here.
Years ago I was at a conference where the session was on results from air shower detectors. During one talk this fella was saying that you shouldn't believe anything less than 4 sigma anyway. The next guy to talk presented his 3 sigma results from a different experiment.
I would also bet that given the length of time and the amount of radiation it has been hammered with, a tape recorder is probably the only storage medium that could stand up to those conditions.
This isn't the sad part. The sad part was just after launch when they realized that the high gain antenna wouldn't deploy properly. That is what prevented us from getting all sorts of data. We've just been fortunate for the people that run the telemetry system who have managed to pack as much information as we've been getting into the low data rate downlink over the last decade.
I don't think most people would argue that there isn't any reason that anyone could not move from Windows to Linux, as your point of a specific application need shows, but I think saying that a general home or business user cannot use Linux because it "isn't ready for the desktop" is a very weak statement.
I think your support argument doesn't hold up because at least Red Hat provides very reasonably priced support. I can't answer for Sun, though my experience with them is that everything they provide is expensive.
I've also never understood the "long way to go" for the desktop argument. Why is Linux so far away from the desktop? What can't you do in Linux that you can do with Windows? I run RH with Gnome and StarOffice. There is nothing I have run into that prevents me from using this as my everyday computer. The only argument against it is that it can't view proprietary MS media formats, that it lags behind deciphering quirky formatting in the latest Office documents. If your standard of argument for equaling MS on the desktop rests on those points, then you'll be disappointed as Linux can never reach that standard unless you think OpenOffice developers can anticipate the next round of formatting commands before the Redmond developers do. And don't even mention the "Joe Blow can't set up Linux" because you apparently never have had to set up a Windows business machine for a neophyte secretary (as well as having them completely relearn the OS when moving from 98 to NT). The "not ready for the desktop" argument has always sounded to me like a catch-all excuse for Linux not having much marketshare and not based on any technical or otherwise decent argument.
We also get hit by CMEs that are caused by "backside events," which are flares or other disturbances that erupt behind the limb of the Sun and we didn't see them occur. STEREO is supposed to help there.
One researcher in the field of solar weather forecasting put the maturity level of space weather forecasting 50 years behind that of terrestrial weather forecasting. That was the state in 2000 and not much has improved since. The biggest difference is that for Earth weather forecasting we have continuous global weather observations on both the ground and from space. There is only a tiny fraction of coverage for space weather, and as I mentioned in my first post it still isn't clear what kinds of instruments are sufficient.
Good information resources on space weather can be found at the Space Environment Center at NOAA's web site. They have a nice education page on space weather. For a look into what the space weather field priorities are, one place to start is the Living With A Star program page.
Aurorae aren't the only things "regular" folk see. Six million people in Quebec lost power because of a solar storm. Commercial and military institutions lose satellites fairly frequently due to solar storms. Most of the people in the US lost pager service for this reason.
These issues are a high priority for NASA, NOAA, and the Air Force. Lots of good data have come from SOHO, WIND, and ACE, but these are either nearing the end of their lives or they are done. STEREO should provide the next round of very good data. Just about any spacecraft that measures the solar wind contributes to understanding space weather, and some missions are designed with that as their primary mission. There are also ground-based programs that make very valuable observations. A good page with some space missions can be found here.
If you want some electronics, you can study for an amateur radio license. The ARRL has a lot of plans for good radio-related equipment you can build from scratch. Plus, you can get in on developing and testing software radios.
For the aspiring metallurgist in you, you can do your own metal pouring and casting.
Summertime is a good time for stargazing. You can build your own telescope.
The fameous Jackson quote went something like: "John Marshall [the Chief Justice] has made his decision; let him enforce it now if he can."
Don't forget the Integrity in Physics guidelines too.