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And of course the GMT is being built as a single scope with one focus, while things like the VLT, Keck and LBT use interferometry to get sharper images.

(And adaptive optics! I want telescopes with frickin' laser beams strapped to their heads!)

I have calculated[1] that in 1000 years a leap second will be required about every two months. It's likely that at that time we would still be using time standards similar to those in use now.

You're off by a bit, and are making some invalid assumptions to start with.

Steve Allen of the Lick Observatory has a great paper explaining the the fundamental clock problem and also exploring effects and impacts on society. It's really quite fascinating, and considerably more complex than most people imagine. I've read papers on the other side, but agree with Allen that nailing the world's time to TI (atomic time) breaks what has never been broken before in all human history, and that letting a bunch of bureaucrats push this through will have serious global consequences.

This is a real problem, and one that will have huge consequences if we let the "science weenies" redefine clock time. As the article points out, the fundamental problem is that "what time is it?" is a qusetion that has two different answers, depending on what you're trying to do. The vast majority of the time, that question means "What time of day is it?" (which is why replacing UT1 with TI/TAI is unwise), but other times (especially to scientists) it means "what interval in invariant time units (seconds, we hope) has passed since I last looked at the clock?" Of course, seconds haven't always been of the same length, or even, for that matter, of fixed length: as recently as 1971, the world's master clocks used "rubber seconds" instead of leap seconds to keep clocks properly in sync with the real world. (This is mostly why Unix/Posix clocks don't know about leap seconds: because leap seconds were only a proposal until a year after teh epoch.)

There is a fundamental incompatibility between time-of-day and time intervals. Keeping clocks aligned is extrraordinarily difficult, and breaking the lock between the clocks and "earth time" has hideously expensive and insidiously far-reaching consequences. (Not least of all to navigation, which is already complex enough, but becomes even more difficult if you let the day slip around the planet. If you don't understand celestial navigation and how determining longitude is *exactly* the same thing as having a clock that is rigorously synchronized to the sun, then spend a while reading Bowditch.)

The main advantage of space for a telescope was avoiding atmospheric distortion. Now it is possible to adjust the mirrors to compensate for atmospheric distortion (adapive optics), enabling large and clear telescopes on the ground (Earth). Here's an explanation of how a guide star is used to "eliminate twinkling". In short, orbital telescopes may be obsolete once these technologies are perfected.

One of the reasons there's not much interest on maintaining Hubble operational is because of the availability of land telescopes with similar precision nowadays.

The reason Hubble is in Space is because of lack of atmosphere distortion, so we have much more precise pictures.
But now we do have land telescopes which computer-controlled visual compensation which gives similar resolution at a fraction of the cost.

Your method is already being used in astronomy, and it's a kind of interfereometry. Adaptive optics, however, is another wholly different trick.

btw, the image we get inside the atmosphere is not wobbling, it is blurred. So it's quite different to your case.

Why Adaptive Optics?

Ground based astronomy isn't as sexy as space based astronomy, but has one big advantage -- light gathering power. We can build 8-meter (SUBARU and GEMINI), 10-meter (KECK), and in the near future 30 to 50-meter telescopes. The JWST, by comparison, is only 6.5 meters, and that's still 7 years away (at least). It's expensive to get telescopes into orbit, first off, and to send a probe up, well, you only get one look at the system with that! Additionally, launching anything drives the cost up by tens of millions of dollars. Ground based telescopes are easier to service, last virtually forever, and only have the disadvantage of having the atmosphere to fight with. Adaptive optics, and camera technology have significantly advanced in recent years, so that ground based telescopes with adaptive optics have huge advantages over those without it. They haven't caught the space telescopes yet, but the gap is closing. I'm a huge advocate of hubble, chandra and other space-based missions, but what can be accomplished on the ground (such as this) should NOT be overlooked!

NO! Read my other post and get your names correct before you start going on about "knowing nothing about astronomy".

The VLA is the Very Large Array, a RADIO telescope run by the american National Radio Astronomy Observatory (or NRAO). It is certainly NOT run by ESO, which is the European Southern Observatory, the organisation that runs the 4 8m Very Large Telescope (VLT) telescopes in chile.

There is no other complete solution to avoid atmospheric turbulence (i.e. seeing and scintillation) other than going to space. A *partial* solution is to use deformable mirrors in an adaptive optics to attempt to correct the problem.

Even with multiple-conjugate adaptive optics (which use multiple laser guide stars to improve performance), you will NOT get diffraction-limited images on an 8m telescope.

Crisper images taken from space will only be better if the diffraction limit of hte telescope is better than what can be obtained by a ground-based system using AO or MCAO. Although nobody has a working MCAO system yet.

sorry, sounds a bit much like a rant, but might add some helpful info into the discussion...

If you ever visit the Lick Observatory, they have pictures that show how the tiny town of San Jose that existed when the Observatory was built has grown so large. Of course, this causes problems with light pollution. Part of their solution was an agreement with the city in 1980 to use low-pressure sodium lights that the observatory can more easily filter out.

http://mthamilton.ucolick.org/public/lighting/Coop eration2.html

Everyone who visits me notices that the lights in San Jose are "different" and "weird;" it took visiting the Observatory to find out why.

By the way, if you want to visit the Lick and look through the telescopes, they have summer tours that I recommend. Not only do you get to look through the telescopes and learn a lot about astronomy and the history of the Observatory, there are amazing (and even romantic) night-time views of the Bay Area. (They normally discourage night-time visits because the car headlights interfere with the telescopes.) There's a lottery for it because it is so popular:

http://www.ucolick.org/public/sumvispro.html

Joey

If you ever visit the Lick Observatory, they have pictures that show how the tiny town of San Jose that existed when the Observatory was built has grown so large. Of course, this causes problems with light pollution. Part of their solution was an agreement with the city in 1980 to use low-pressure sodium lights that the observatory can more easily filter out.

http://mthamilton.ucolick.org/public/lighting/Coop eration2.html

Everyone who visits me notices that the lights in San Jose are "different" and "weird;" it took visiting the Observatory to find out why.

By the way, if you want to visit the Lick and look through the telescopes, they have summer tours that I recommend. Not only do you get to look through the telescopes and learn a lot about astronomy and the history of the Observatory, there are amazing (and even romantic) night-time views of the Bay Area. (They normally discourage night-time visits because the car headlights interfere with the telescopes.) There's a lottery for it because it is so popular:

http://www.ucolick.org/public/sumvispro.html

Joey

The second statement in quote from parent is false: there are significant pertubations in the orbits of Uranus and Neptune, and also in Pluto's orbit.

No, there aren't.

1) SM4 was canceled due to cost, we believe SM4 can extend the useful life of Hubble 4 or 5 years. Not True! SM4 was canceled primarily due to safety reasons. Please remember this, SM4 was Not Canceled due to Cost!!

2) Hubble is in 100% working order. Not true! The gyros which point the telescope are slowly failing.

3) Adaptive Optics/Clever Image Processing/Ground based telescope are better than or equal to Hubble. Not completly true! AO can image single objects to better than hubble. But AO has poor field of view! For reference, the UDF images have a field of view of 180 arcseconds square. AO fails above, 30, and degrades quickly above a few. Worst, AO needs a bright star to work. There simply are not enough of these stars! I can't reference this, but experts in the field think that it will take 30 years to get to Hubble's level of performance with AO.

4) Finally, AO will never work in at UV or near/mid IR wavelengths.

I am an astronomer, and I feel it is my duty to inform the public about the benefits of Hubble. HST serves a unique roll to the community. We should all understand exactly what the risk will be to fly SM4 before we lose 4 years of Hubble!

1) SM4 was canceled due to cost, we believe SM4 can extend the useful life of Hubble 4 or 5 years. Not True! SM4 was canceled primarily due to safety reasons. Please remember this, SM4 was Not Canceled due to Cost!!

2) Hubble is in 100% working order. Not true! The gyros which point the telescope are slowly failing.

3) Adaptive Optics/Clever Image Processing/Ground based telescope are better than or equal to Hubble. Not completly true! AO can image single objects to better than hubble. But AO has poor field of view! For reference, the UDF images have a field of view of 180 arcseconds square. AO fails above, 30, and degrades quickly above a few. Worst, AO needs a bright star to work. There simply are not enough of these stars! I can't reference this, but experts in the field think that it will take 30 years to get to Hubble's level of performance with AO.

4) Finally, AO will never work in at UV or near/mid IR wavelengths.

I am an astronomer, and I feel it is my duty to inform the public about the benefits of Hubble. HST serves a unique roll to the community. We should all understand exactly what the risk will be to fly SM4 before we lose 4 years of Hubble!

Tough to call "working right now" technology "inferior" to something that doesn't exist yet. By the way, I don't buy for a second that ground-based telescopes will ever have better imaging than Hubble. Sorry.

Tough to call "working right now" technology "inferior" to something that doesn't exist yet. By the way, I don't buy for a second that ground-based telescopes will ever have better imaging than Hubble. Sorry.

The article is incorrect; Jerry's still at UCSC, where in fact he's the director of the Center for Adaptive Optics and project scientist for the Thirty Meter Telescope. He's working pretty much full time on extremely large telescope design and adaptive optics these days.

As for the telescope array, I haven't heard anything about a radio telescope array under development by Santa Cruz. The original poster is more likely thinking of the Allen Telescope Array under construction by UC Berkeley (where I am an astronomer) and the SETI Institute. The ATA will consist of some 350 3 meter dishes located in northern California, and will be used both for the search for extraterrestrial intelligence and for more "traditional" radio astronomy observations.

The article is incorrect; Jerry's still at UCSC, where in fact he's the director of the Center for Adaptive Optics and project scientist for the Thirty Meter Telescope. He's working pretty much full time on extremely large telescope design and adaptive optics these days.

As for the telescope array, I haven't heard anything about a radio telescope array under development by Santa Cruz. The original poster is more likely thinking of the Allen Telescope Array under construction by UC Berkeley (where I am an astronomer) and the SETI Institute. The ATA will consist of some 350 3 meter dishes located in northern California, and will be used both for the search for extraterrestrial intelligence and for more "traditional" radio astronomy observations.

Don't forget, we have ways of mitigating the crappy atmosphere. Without adaptive optics, there would be no point in making these gigantic telescopes. With AO, they will most definitely rock.

It's a shame Hubble is our only orbiting telescope

Agreed, but the bigger shame is that NASA is so unwilling to continue supporting even this one. HST has been its biggest public success since Apollo, and they just can't wait to see it splash into the Pacific. Mind boggling.

UC Santa Cruz is also building a state-of-the-art adaptive optics lab, which is being built in partnership with the National Science Foundation and Lick Observatory.

Yes, UCSC is a very cool school, and not just because of the weed.

It means that the POSIX era counted by 32-bit time_t will end sooner as counted by elapsed SI seconds, but there will be no change in the date read by the clock so long as UTC retains its current definition.

The World of Astronomy site at Wolfram.com is a bit out of date and does not include the most recent changes in time scales. I recommend this page which describes the history of various time scales.

No, and physicists physicists do admit that they are not perfect. They also have a plan to use pulsars to see just how imperfect the atomic clocks are.

Sorry but technological changes don't cause instant DNA updates. I guess if you ever got in a car accident, based on your own ethics, it would be "adapt or die" for you also.

I shouldn't reply to AC's but i will.

If I die in a car accident, it's my own damn fault for getting behind the wheel of a car, no matter who's *fault* it is. Risky behavior by any creature of any intellect can result in death.

Most fish don't swim around dam outlets for a damn good reason. They've learned that they *DIE* there if they get sucked up into the dam pipe.

Birds are more capable than a fish. A bird *should* know better than to swoop down on squirrels around windmills. After 20 years i'm sure the only ones flying into them now are the really stupid ones. The smarter ones have since left for safer feeding ground.

Considering pigeons, which are even dumber than Kestrals, can learn to not only adapt, but *use* cars to their advantage is astounding.

Just because i'm smarter than another person, does that mean I have to go out of my way *protect* that person? Just because a few birds are too stupid, or stubborn to move onto safer feeding ground, does that mean I have to go out of my way to protect them? I don't think so.

Altimont pass is surround by many other places for these birds to feed.
Sure there should be help for handicapped or injured birds, but if a dumb/stubborn one flies into a blender, better off the species I say.

I thought I'd introduce some more facts into the discussion. There were, until recently, two major independent efforts to develop a 30 m optical/IR telescope:

• The California Extremely Large Telescope project, brought to you by the same folks responsible for the Keck telescopes - that is, the University of California and Caltech.
• The Giant Segmented Mirror Telescope project, by the National Observatories, headquartered in Arizona.

As part of this, both groups applied for about $35M of funding for the next stage of the development, which will involve doing more detailed design studies, simulations, and construction of subsystem mockups to test performance. The plan is after about three years of this to have a completed design and then be able to break ground around 2008 or so, and become operational around a decade from now.

Incidentally, NOAO asked for their $35M from the National Science Foundation, while the UC/Caltech team approached the Moore Foundation, Gordon Moore's philanthropic organization. So a tiny fraction of every dollar you spend on an Intel chip may someday help to make this telescope a reality!

In the same class is the ITU who have a similar model of charging. Among their standards is ITU-R TF.460 which defines coordinated Universal time (UTC). If you've ever wondered why leap seconds are so poorly implemented by your computer, this proprietary standard is part of the reason. It is evident that the original authors of the POSIX standard had not read it before they declared that a Unix time_t should indicate time in UTC.

As some astronomer pointed out at the time, the repair mission for the Hubble cost more than all the proposed ground-based observatories put together, like the Very Large Telescope and the California Extremely Large Telescope.

NASA - The government version of Hollywood.

Why don't hey ues the Hubble for satelite surveilance of the earth?

I don't believe Hubble could, because it lacks Adaptive Optics that ground-based (and probably orbital surveillance) telescopes have. Without them, the atmosphere makes everything much to blurry. From the ground this makes stars appear to twinkle, and from Hubbles point of view it would make everything appear to wobble - so pictures would end up a blurry mess.

Of course, you might be able to simulate Adaptive Optics in software ... ?

Disclamer: IANAHSTE

There are a lot of nerdy attactions in the San Francisco Bay Area, so you may want to go there.

Possibly the attraction of the greatest interest to the astronomically inclined in the SF Bay Area is the Lick Observatory, and in the summer months they allow the public to look through their 36" refracting and 40" reflecting telescopes.

Details here.

Because Widening Roads Worsens Traffic Congestion.

Seriously.

Read here and here and here

and see some primary sources here and here and these:

Phil Goodwin, "Empirical Evidence on Induced Traffic," Transportation, Vol. 23, No. 1, Feb. 1996, pp. 35-54. This is in a special issue of the journal Transportation devoted to induced travel. It has several very good articles.

Robert Noland, Relationships Between Highway Capacity and Induced Vehicle Travel, Transportation Research Board Annual Meeting Paper 991069 (www.epa.gov/tp/trb-rn.pdf), January 1999.

Harry Cohen, "Review of Empirical Studies of Induced Traffic," Expanding Metropolitan Highways: Implications for Air Quality and Energy Use, Transportation Research Board, Special Report #345, National Academy Press (Washington DC), 1995, Appendix B, pp. 295-309.

Cairns, Hass-Klau and Goodwin, Traffic Impacts of Highway Capacity Reductions: Assessment of the Evidence, London Transport Planning (London; www.ucl.ac.uk/transport-studies/sc1.htm), 1998.

Our scientific users are highly dependant on specific software packages for their research and data reduction. This means, once you follow the multiple "have you tried this?" arguments, is that we need to use RedHat for about half of our 150 scientific workstations (the other half are Solaris).

Due to RedHat's rearrangement of their product lines, our current "approved" version of RedHat Linux is 7.3. We will not migrate to 8.0, as it was the first release in a major version change, and we will not migrate to 9, as it is now the sandbox for potentially unstable features.

We are currently investigating the RedHat Enterprise Linux WS distribution; thanks to being an education institution, we can get volume licenses for a whole lot less than the list price. If it weren't for the price break, we'd already be looking for an alternate distribution to use. If the Enterprise WS distribution doesn't work out, we'll be looking anyway.

Why does this matter? Hardware support. The x86 hardware market will not let us buy 3-4 years behind the times. As it is, we already buy our hardware well behind the bleeding edge, and there's still the occasional compatability issue. We already custom-build most of our software from source, but the hardware support is a real sticker. Custom compiling current kernels for a highly diverse workstation clientele is not a time-effective option.

I believe they're referring to Adaptive Optics. You can find out more about AO here: What Is Adaptive Optics?

The technology used by this telescope to counter the effects of the atmosphere in measurements is called adaptive optics. This is the first application I know of for adaptive optics on a solar telescope.

This technology has been around for awhile, and was first seriously developed by the military at the Starfire Optical Range .

Recently it has been used in such telescope projects as the WM Keck Observatory and Gemini Project . I know AO is also used for measurement of eye aberrations, with projects being conducted at several Universities. For more information about Adaptive Optics, I suggest the Center for Adaptive Optics

My personal experience with AO was as an intern for Gemini this past summer. I helped write parallel code for a program that simulates current and future adaptive optics systems planned for the next generation of extremely large telescopes.

What would you consider to be examples of American `organizations' acting in a `totalitarian and domineering' manner overseas? What are your sources for these examples?

Here's a speech on the topic. A newspaper article is here originally published in the Boston Globe. There's a good essay on the subject here, although I am sure you'll pooh-pooh this one as you do anything associated with the UN, the author is extremely credible. I leave the rest of the trivial google searching you can use to do your own research to you.

Or to turn the whole thing on its head, since it is plain to even the metaphorical "Blind Freddy" that large companies get away with whatever they are not specifically prohibited from doing, and act in a totalitarian and domineering manner (click to look 'em up if you have trouble) whenever they possibly can (hence the extremely large amount of legislation existing to regulate corporate behaviour especially monopolistic behaviour) what point, exactly, are you attempting to make?

Adaptive/Active optics can work in two ways. One way is to use a bright (and it has to be damn bright) star near the target that one's hoping to look at. Then, by seeing how the atmosphere distorts this (supposedly point-source) star, we can adjust the mirror to compensate. There are different ways to do this that involve just moving the image around or re-shaping the mirror altogether, but I won't go into that here. The trouble with this plan is that it's hard to find a star bright enough in the part of the sky that you happen to be observing. It has to be damn bright, since you have to read out the CCD several times a second in order to compensate for the atmosphere fast enough. The second method uses a sodium-type laser that excites a layer in the atmosphere very high up (i.e. above most of the clouds/water vapor/crap). This behaves as a sort of artificial bright star that one can have anywhere in the sky.

The Center for Adaptive Optics (at UCSC) has a decent simple explanation here.

All of this aside, this will probably NOT render HST obsolete any time soon, since this is rediculously hard to do and has yet to really be done convincingly in any large-scale way, as people at my institution are finding out.

Post Hoc Ergo Proptor Hoc, anyone?

...from the people that are co-ordinating AO research across the country:

http://cfao.ucolick.org/

I don't have any sources, but this is not a new theory in any way... astronomers and astrophysicists have a rather good understanding of angular momentum and its application, and have maintained for some time that the Earth would not be completely enveloped by the outer layers of our sun as it goes into a red-giant phase.

As others have pointed out, the natural life-cycle of the sun will sear all life from the surface of the Earth long before any potential engulfing happens (as if it was the engulfing that mattered; the outer layers of a red giant are extremely thin, much more tenuous than our atmosphere). We'll experience some kind of runaway greenhouse effect something like a billion years before the sun enters the red giant phase... and our galaxy will collide with Andromeda before the sun goes belly-up.

One of our hopes for preposterously-long-term survival, as researched (with a smile on his face and a glint in his eye) by Greg Laughlin (et al.), is for the Earth to be caught by a wandering type-M star and pulled out of the solar system.

But really now... we're talking billions of years, here. It's fun to think about, but calling it "news" (especially "breaking news") is a pretty harsh misnomer.

A very readable article, but I was surprised to see no other information on the referenced large telescopes. To save others from searching as I did, take a look at:

• VLT (Very Large Telescope)
  
• OWL (OverWhelmingly Large telescope)
  
• CELT (California Extremely Large Telescope)
  
• GSMT (Giant Segmented Mirror Telescope)
  

Keck's been capable of "beating" Hubble for a good long while now. Adaptive Optics is wild and crazy stuff.

Please don't believe that we'll be able to do away with space-based observing because of this innovation. Our atmosphere absorbs an awful lot of interesting wavelengths.

MEMS also has a bright future in Adaptive Optics, for both astronomy and vision sciences.

AO for the next generation of extremely large telescopes requires something like 500k to 1,000k actuators, something that is only economically feasible with something like MEMS.

Almost anyone that's not support staff @ UCO/Lick uses Linux or Solaris as their operating system of choice. That comes out to about 150-200 machines total.

That's what happens when people want to do tricky things like "research" with their computers.

The allegory gives a classical view of key management.

Actually, it can also be used by non-child processes as long as they have permission to search for the socket and pid. There's a script at http://www.ucolick.org/~sla/ssh/fsa that does just that (drop the trailing /fsa for more hints). This allows you to launch an agent and provide an identity at boot and make that identity available to cron jobs for scp or other secure remote functions. Very useful.

As for actually imaging things on the moon, you're correct, even the Hubble does not have the resolution to pick out the Apollo landers. Some actual numbers to back this up:

Angular resolution of a telescope goes roughly as wavelength/diameter. For visible light at 5000 Angstroms, this means the 2.4 m HST can resolve down to about 0.04 arcsecond (= 1x10^-5 degrees), and the 10m Keck, largest telescope on Earth, could get down to 0.01 arcsec in theory, but in reality atmospheric effects limit it to about ten times that. At a distance of 384400 km, these resolutions correspond to 80 m and 20m per pixel, which is not *quite* good enough to make out anything man-made on the surface. The proposed 30m California Extremely Large Telescope could maybe barely do it, but that's probably 30 years off.

HST has a 2 micron filter. The filter is used with NICMOS which is currently not working. NICMOS is scheduled to be fixed for the next servicing mission, assuming it ever flies.

Adaptive optics is quite promising for planetary science. Soon we will be getting HST quality images from the ground with these techniques. Just don't ask me how soon soon is....

For propaganda about Adaptive Optics, check out the CfAO homepage

i think even if you spend 1 billion $ for a 100m aperture telescope on earth, that a e.g. 20m telescope in orbit will be better. Also i think that there's too much "competition" in the huge telescope market, we've got the GTC, the LBT, the SALT, the VISTA, the LAMOST, the DMT, the CELT, the XLT, the OWL, the LSST, the GSMT, the MAXAT, the ELT. Why? why not make only one bigger/better on earth, or even in space? the 2.4m HST proved the bettest scope is in space.
--
BeDevId 15453 - Download BeOS R5 Lite free!

"... to be actionable the use must not fall within any of the statutory exemptions. Under the Act, 'fair use' of a mark in comparative advertising, 'non- commercial' use of a mark, and news reporting and commentary are not actionable."

While originally created to notate traditional (i.e. Irish, Scottish, Bretton, etc) music using simple ASCII text, the standard now supports some pretty complex notation. In fact there is a version of Beethoven's Symphony No.7, Movement 2 by Steve Allen.

Most of the ABC interpreters out there are GPL'd (including abc2ps, the ABC to Postscript Converter) and there are apps ou there for just about every platform (including a java based interpreter for embedding in you web pages). There are also a couple converters to or from MIDI, and a few apps that get a little fancier (add harmonies, etc). See the ABC Homepage for a complete list of software and music available.

Anyway I'm done ranting....just wanted to see my favorite notation system get some air time. :}

The Keck telescopes (10 meter main reflecting mirrors) are located in Hawaii, on top of Mauna Kea mountain, at 14,000 feet. When people from our lab went to install equipment, they had to write down what tools they were going into another room for, because the lack of oxygen would cause short term memory loss. It takes a few days to acclimate, which is about the time it takes to do an installation. So they left about the time they were ready to work normally.

Hope that this helps, Louis Wu.


Thinking is one of hardest types of work.

The Keck telescopes (10 meter main reflecting mirrors) are located in Hawaii, on top of Mauna Kea mountain, at 14,000 feet. When people from our lab went to install equipment, they had to write down what tools they were going into another room for, because the lack of oxygen would cause short term memory loss. It takes a few days to acclimate, which is about the time it takes to do an installation. So they left about the time they were ready to work normally.

Hope that this helps, Louis Wu.


Thinking is one of hardest types of work.