I was a postdoc at Steward Observatory and I worked on a fiber-fed echelle spectrograph which was on the 100 inch telescope. I talked with one of the telescope operators who runs the HK monitoring program whilst we were setting up our spectrograph. A fine telescope, great staff and pleasant surroundings on the mountain above the L.A. basin smog!
There has been a suggestion that weather is tied in with long term variability of the Sun, and many astronomers cite the case of the Maunder minimum back in the 1700's where a lack of sunspot activity was linked to a succession of very cold winters in the Northern hemisphere.
The problem is that solar-type stars may vary on timescales of hundreds and thousands of years (in addition to the known sunspot cycle of our Sun of about 11 years), dominating the long term weather patterns here on Earth. It's still a highly debated point, though, mostly because we've only head modern instruments doing accurate solar flux monitoring for the past 50 years or so, and before that we have to rely on indirect methods, such as historical records of large groups of sunspots seen with the unaided eye.
One of the longest running experiments in modern astronomy has been the monitoring of solar-type stars at the Mount Wilson Observatory in Southern California. I was fortunate enough to meet the people who run this experiment - it's not too often you see papers with 40 years of data from the same instrument!
The thousandth sequential copy of a data CD will be identical to the original, assuming you're verifying the copies each time. You keep copying to new media every few years, which is annoying, but the data will be identical to the original.
The same cannot be said for any analog based data system such as film. If the original is damaged, you're left with an imperfect copy. Of course, pay enough money and your analog copy will be a close reproduction of the original, but it won't be identical.
The star in NOT in a red giant phase - it's still on the Main Sequence for dwarf stars, and is very similiar to our Sun.
The point is that you can't form a large gas giant so close to a star, it must have formed a long distance out and then 'migrated' to its present position near the star. How that happened will keep astro theorists in grants for a long time;)
Also, the size of this gas giant has been noted to be much larger than theoretical models predict, suggesting it is being heated up by the proximity of the parent star - this 'boiling off' of the atmosphere confirms this interpretation.
> Note: I'm a UofA Alum, but their screwup on that mirror deserves mention whenever they do something right...
I'm trying to check my history, but wasn't the Hubble mirror made and tested at Perkin Elmer? I don't remember the U of A being involved with Hubble's mirror. It was an error in the test equipment at Elmer that led to the spherical aberration being put into the mirror...
You may be thinking of the NICMOS camera, which the U of A was involved with, and that had a problem with cryogens boiling off too rapidly, but that was corrected a while ago...
> I'm not sure why they think that a deformable secondary is better than AO afterwords.
Two words: warm surfaces.
All other AO systems have ~20 warm reflecting surfaces that add up to a high near-IR background, and this severely limits your view of the IR universe. This system adds no additional surfaces into the telescope, and so its IR background is much lower.
Heh, a/. article that covers something I worked on!
> but it sure looks like they're making claims of being first when they aren't.
This *is* a first because the deformable mirror *is* the secondary mirror, which all modern reflecting telescopes have nowadays.
The Starfire Optical Range (SOR) telescope and all other adaptive optic (AO) systems use about 10 to 20 additional reflections between the sky and the detector to do the AO correction - it may be a 3.5 meter telescope, but it's more like a 1 meter telescope in light-gathering power after 20 bounces for light loss are taken into account. The SOR telescope was also optimised for taking high resolution picutres of fast moving objects in low earth orbit *think spy satellites*
The other bonus is that the new system is *excellent* for taking near infra-red pictures of the night sky, and a lot of recent astronomy is driven by a need for a good AO system in this regime (about 1 to 10 microns).
I'm probably too late, but these are good questions....
Even though we don't know what the dark matter is, we can use its general properties to model the dynamics of galaxies and evolution of the universe to a good accuracy. Dark matter has mass, is non-baryonic, has no charge, and does not interact with matter via the electromagnetic force. This is quite a bit of information, and means that we can run models without worrying about the details of what it is.
A rough analogy can be made with Boyle's gas laws. Back in the day, these scientists observed that gas properties were linked in a simple equation, PV=nRT. Now they didn't need to know electronic structure or nuclear equations of state within the atoms that make up room temperature gases, but the general bulk properties of the gas were enough to form a simple related equation. We're in that situation with dark matter now - we have a general equation that can model its distribution without knowing its specific nature.
I think you've missed my point in my original post. In Britain we don't get taught American history. Hence, as a foreigner in America, the phrase ToT does not have the resonance and meaning in Britain that it does in America.
> I'd suggest not using that as a title unless you're writing about the forced death of several thousand people.
Thanks for the information. I'm a Brit working in America and my American history is poor to say the least. I'm not sure that the editor who wrote the headline intended this to be an offensive headline, though. I've used "Trail of tears" as a general comment for any hard task in the past.
I saw a copy at the local bookstore, read the first few pages, and then sat down for four hours and read it from cover to cover. As a novel, it is an excellent read and the creeping horror as the father of the family (told in first person) realises something is 'not quite right' is very well delivered. Mr Crichton writes a compelling story that's hard to put down.
However, it does suck on a few points:
1) It's written like a movie script. There's one part where the characters rush into a supply shed past a large case of dynamite, then scenes later where the sprinkler system is mentioned again, and again. Gosh, those props are not going to be used later in the book, are they?
2) The last third is just plain silly. I don't care if other/. ers think I'm one of the anal types, but especially (this is not really a spoiler) the whole scene inside the cave made me frown and go "What the heck?!?" It also looks as if he was given a deadline and he had to bash out the remaining holes in the story in a very rushed epilogue.
3) Crichton has done the whole "Scientists not understanding the powers they meddle with" thing before. Andromeda Strain, Jurassic Park, Timeline... on the other hand, this has made him a very rich man. More power to him. And I'll probably give the movie a look when (not if) it comes out.
Go read it for the human elements, and don't look at the nanotechnology too closely.
Dr Fish
Do NOT stand in front of one, though....
on
Potato Bazookas
·
· Score: 5, Interesting
My friends and I built a potato canon and regularly fired it over the skies over Tucson. It was fun to a potato hang in the air for up to 10 seconds at a time, and a bit of basic math estimated it to travel over 1/3 a mile. Beware though that the potato emerges at about 100 miles per hour (but slows down alomost immediately due to air resistance).
We stopped fiting it after we stuck a 1/4 inch thick board of plywood about 3 feet in front of the canon and fired away.
Damned if that potato didn't punch a perfect 4 inch hole through that board. As the potato emerged on the far side though, it almost completely stripped off the last ply layer from the board.
We gained a new respect for tuber-based weaponry that day....
What I was saying in my first comment was that the majority of physicists believe gravity has a finite propagation speed, whilst the/. tagline suggested that few physicists do. The experiment itself is being questioned by physicists thinking they're measuring the speed of light, not gravity. Apart from the Newton quote, none of the modern physicists thought that gravity propagated 'infinitely' fast - it's another usual/. not-quite-right headline.
> After all, GR certainly doesn't agree with quantum mechanics
Not sure if I agree with you there - I don't recall that QT is inconsistent with GR. The problem is that it is very, very hard to test a QT of gravity because the hypothesized quanta of gravity are 10^41 times smaller than those of electromagnetism and nuclear forces.
Anyway, they came up with a speed of gravity (if that is what they measured) of plus or minus 20 percent of the speed of light, so if they were measuring gravity, it is consistent with GR.
All general relativists (and for that matter, all physicists) I know think that gravity propagates at the speed of light. In the linked articles, the criticism is that they've measured the speed of light by virtue of the radio photons, not the speed of gravity, which they're claiming.
There's nothing about 'infinitely' fast gravity in the article that I can see, and of the two physicists claiming to disagree with the results, the one who says it is 'nonsense' then refuses to comment any further.
Dr Fish
Re:Ummmm -- has anybody considered the posibilitie
on
Visiting the Big Bang
·
· Score: 4, Informative
"The "inflationary" model was sort of a hack to make the theory agree with the observations. No actual reason for what starts it has been proposed AFAIK."
Yes, you are right about the hack part, but inflationary theory explains why our universe has an omega so close to 1 and why apparently disconnected parts of the cosmic microwave background have similiar temperatures. As for the reason it starts, well, there are plenty of ideas, but none of them easily testable (and I can't remember what they were, but they were all very high energy fields breaking indegeneracy...anyone care to comment?).
Alan Guth wrote a book called "The Inflationary Universe" (admittedly he came up with the idea) which gives a very clear explanation why inflation theory seems more suited than many other alternate theories.
"Who is to say that we might not accidentally create a sort of "mini-inflation" at one of these accelerators, thereby destroying the Earth, the Solar System, or even more. Nobody knows what triggered inflation. What if we do it accidentaly?"
A good question, and it was considered seriously by Martin Rees, a famous astrophysicist now at Cambridge. He did calculations showing that cosmic rays many thousands of times more energetic than the best we can do with earthly accelerators routinely hit our upper atmosphere. Given that billions of years of cosmic ray bombardment have not triggred a new universe type of scenario, it is probably safe to say that our experiments won't trigger one off.
Speaking as a physicist (well, astronomer) the past decade or so has seen the rise of biology in the public's eyes, and the flow of money to the life sciences. If your science is purely defined by public popularity, though, you'd better hope that the public stays interested in biology.
We haven't had the equivalent of a public relations disaster for biology yet, which would cause public opinion to turn against it. All you need is a biological Chernobyl and you'll be tarred with the same brush that physicists have had applied to them. Not that I'd want anything like that, God forbid.
Also, is the authour of the article a bit bitter? Yes, but he does not speak for all physicists.
Don't get me wrong, I'd like a larger grant for some of my research, but we can't always get what we want, and if I *needed* the money, then I should bloody well write a better grant the next time around. Shame on me, not shame on the biologists. My personal moan aside, I think that money in science is well spent, whatever field it is in. If the research is exciting and interesting, by and large it does get funded.
I think there's the relatively modern issue of corporate interests and how they affect the flow of ideas in a given subject, and it just so happens that biology is the science that is facing this at the moment.
You're right about balancing the gravitational binding energy of a pile of neutrons with the nuclear binding energy of the same pile of neutrons. As you add more neutrons, you get to a point where the mass of the neutrons makes the gravitational binding energy pass that of the nuclear binding energy. Of course, this number of neutrons is astronomically large (pun intended).
I did this as an undergrad problem in Nuclear physics - take a ball of N neutrons, assume nuclear type densities, and calculate the neutron ball's radius and mass (and thus it's gravitational binding energy = G * M(neutron) * N/Radius).
When you balance this with the typical binding energy per neutron (erm, cant remember the numbers we used, sorry), you get two simple equations and you solve for N the number of neutrons.
AFAI remembber, you get a radius of 10km and about 2 solar masses - pretty damn good for a back of the envelope calculation!
If I can dig out the old problem sheet, I can post the number later....
Me, I'm waiting for the cheap unit that's sensitive enough to measure the 24 hour rotation of the Earth.
Go find a tall building with a decent staircase, hang a bucket of sand on some piano wire, bring it to one side of the stairwell and release.
Heavy bucket, small surface area, pendulum takes about an hour to swing to a stop. In that time, Earth's rotation will have moved it by (360/15) * cos (latitude). Classic demonstration of the Earth's rotation.
I did it in high school, it gave me my latitude +- 10 degrees. Not bad for an hour's work!
1. It's an electronic clock based on well-known electronic processes and principles
2. A quiet introvert who enjoys people having an accurate sense of time placed a clock on a wall and hid himself behind it, and keeps himself supplied with food from an unknown source whilst twiddling the hands using another time reference.
Now it's the first explanation that's the simplest.
I don't like Occam's razor for this reason - I think you can phrase the choices according to your own biased viewpoint. It is only effective when there is a bare minimum of testable information present - lifting the clock off the wall is a simple experiment, whilst OBE's are all about human-percieved experiences, very hard to dispassionately test.
Slashdot Mirror
Mmmmmm, oily astrophysicist.... /Homer
Dr Fish
Sorry, I'm not Gordon from Caltech :)
I was a postdoc at Steward Observatory and I worked on a fiber-fed echelle spectrograph which was on the 100 inch telescope. I talked with one of the telescope operators who runs the HK monitoring program whilst we were setting up our spectrograph. A fine telescope, great staff and pleasant surroundings on the mountain above the L.A. basin smog!
Dr Fish
The problem is that solar-type stars may vary on timescales of hundreds and thousands of years (in addition to the known sunspot cycle of our Sun of about 11 years), dominating the long term weather patterns here on Earth. It's still a highly debated point, though, mostly because we've only head modern instruments doing accurate solar flux monitoring for the past 50 years or so, and before that we have to rely on indirect methods, such as historical records of large groups of sunspots seen with the unaided eye.
One of the longest running experiments in modern astronomy has been the monitoring of solar-type stars at the Mount Wilson Observatory in Southern California. I was fortunate enough to meet the people who run this experiment - it's not too often you see papers with 40 years of data from the same instrument!
Dr Fish
The thousandth sequential copy of a data CD will be identical to the original, assuming you're verifying the copies each time. You keep copying to new media every few years, which is annoying, but the data will be identical to the original.
The same cannot be said for any analog based data system such as film. If the original is damaged, you're left with an imperfect copy. Of course, pay enough money and your analog copy will be a close reproduction of the original, but it won't be identical.
Dr Fish
The star in NOT in a red giant phase - it's still on the Main Sequence for dwarf stars, and is very similiar to our Sun.
;)
The point is that you can't form a large gas giant so close to a star, it must have formed a long distance out and then 'migrated' to its present position near the star. How that happened will keep astro theorists in grants for a long time
Also, the size of this gas giant has been noted to be much larger than theoretical models predict, suggesting it is being heated up by the proximity of the parent star - this 'boiling off' of the atmosphere confirms this interpretation.
Dr Fish
Maybe your university should put more $$ into it's English department =)
Or even into your English department =P
> on its 640-mm (2.1-foot) 3.5 Meter deformable mirror
You're comparing the wrong things together.
It's not clear in the article, but the Starfire telescope has a PRIMARY mirror diameter of 3.5m, but the Steward telescope has a diameter of 6.5m.
The flexible secondary mirror of the Steward is the 640mm number you've compared with the primary mirror of the starfire telescope.
Hope that clears it up for you!
Dr Fish
> Note: I'm a UofA Alum, but their screwup on that mirror deserves mention whenever they do something right...
I'm trying to check my history, but wasn't the Hubble mirror made and tested at Perkin Elmer? I don't remember the U of A being involved with Hubble's mirror. It was an error in the test equipment at Elmer that led to the spherical aberration being put into the mirror...
You may be thinking of the NICMOS camera, which the U of A was involved with, and that had a problem with cryogens boiling off too rapidly, but that was corrected a while ago...
Dr Fish
> I'm not sure why they think that a deformable secondary is better than AO afterwords.
Two words: warm surfaces.
All other AO systems have ~20 warm reflecting surfaces that add up to a high near-IR background, and this severely limits your view of the IR universe. This system adds no additional surfaces into the telescope, and so its IR background is much lower.
Dr Fish
Heh, a /. article that covers something I worked on!
> but it sure looks like they're making claims of being first when they aren't.
This *is* a first because the deformable mirror *is* the secondary mirror, which all modern reflecting telescopes have nowadays.
The Starfire Optical Range (SOR) telescope and all other adaptive optic (AO) systems use about 10 to 20 additional reflections between the sky and the detector to do the AO correction - it may be a 3.5 meter telescope, but it's more like a 1 meter telescope in light-gathering power after 20 bounces for light loss are taken into account. The SOR telescope was also optimised for taking high resolution picutres of fast moving objects in low earth orbit *think spy satellites*
The other bonus is that the new system is *excellent* for taking near infra-red pictures of the night sky, and a lot of recent astronomy is driven by a need for a good AO system in this regime (about 1 to 10 microns).
Dr Fish
I'm probably too late, but these are good questions....
Even though we don't know what the dark matter is, we can use its general properties to model the dynamics of galaxies and evolution of the universe to a good accuracy. Dark matter has mass, is non-baryonic, has no charge, and does not interact with matter via the electromagnetic force. This is quite a bit of information, and means that we can run models without worrying about the details of what it is.
A rough analogy can be made with Boyle's gas laws. Back in the day, these scientists observed that gas properties were linked in a simple equation, PV=nRT. Now they didn't need to know electronic structure or nuclear equations of state within the atoms that make up room temperature gases, but the general bulk properties of the gas were enough to form a simple related equation. We're in that situation with dark matter now - we have a general equation that can model its distribution without knowing its specific nature.
Hope this helps,
Dr Fish
I think you've missed my point in my original post. In Britain we don't get taught American history. Hence, as a foreigner in America, the phrase ToT does not have the resonance and meaning in Britain that it does in America.
> I'd suggest not using that as a title unless you're writing about the forced death of several thousand people.
Indeed. I'll consider that from now on.
Dr Fish
Thanks for the information. I'm a Brit working in America and my American history is poor to say the least. I'm not sure that the editor who wrote the headline intended this to be an offensive headline, though. I've used "Trail of tears" as a general comment for any hard task in the past.
Dr Fish
Yes, I bought the book.
Dr Fish
I saw a copy at the local bookstore, read the first few pages, and then sat down for four hours and read it from cover to cover. As a novel, it is an excellent read and the creeping horror as the father of the family (told in first person) realises something is 'not quite right' is very well delivered. Mr Crichton writes a compelling story that's hard to put down.
/. ers think I'm one of the anal types, but especially (this is not really a spoiler) the whole scene inside the cave made me frown and go "What the heck?!?" It also looks as if he was given a deadline and he had to bash out the remaining holes in the story in a very rushed epilogue.
However, it does suck on a few points:
1) It's written like a movie script. There's one part where the characters rush into a supply shed past a large case of dynamite, then scenes later where the sprinkler system is mentioned again, and again. Gosh, those props are not going to be used later in the book, are they?
2) The last third is just plain silly. I don't care if other
3) Crichton has done the whole "Scientists not understanding the powers they meddle with" thing before. Andromeda Strain, Jurassic Park, Timeline... on the other hand, this has made him a very rich man. More power to him. And I'll probably give the movie a look when (not if) it comes out.
Go read it for the human elements, and don't look at the nanotechnology too closely.
Dr Fish
My friends and I built a potato canon and regularly fired it over the skies over Tucson. It was fun to a potato hang in the air for up to 10 seconds at a time, and a bit of basic math estimated it to travel over 1/3 a mile. Beware though that the potato emerges at about 100 miles per hour (but slows down alomost immediately due to air resistance).
We stopped fiting it after we stuck a 1/4 inch thick board of plywood about 3 feet in front of the canon and fired away.
Damned if that potato didn't punch a perfect 4 inch hole through that board. As the potato emerged on the far side though, it almost completely stripped off the last ply layer from the board.
We gained a new respect for tuber-based weaponry that day....
Dr Fish
> quantum mechanics isn't relativistically invarient.
Ah, my bad. It's been too long since my QM undergrad course. Thanks for the correction!
Dr Fish
What I was saying in my first comment was that the majority of physicists believe gravity has a finite propagation speed, whilst the /. tagline suggested that few physicists do. The experiment itself is being questioned by physicists thinking they're measuring the speed of light, not gravity. Apart from the Newton quote, none of the modern physicists thought that gravity propagated 'infinitely' fast - it's another usual /. not-quite-right headline.
> After all, GR certainly doesn't agree with quantum mechanics
Not sure if I agree with you there - I don't recall that QT is inconsistent with GR. The problem is that it is very, very hard to test a QT of gravity because the hypothesized quanta of gravity are 10^41 times smaller than those of electromagnetism and nuclear forces.
Anyway, they came up with a speed of gravity (if that is what they measured) of plus or minus 20 percent of the speed of light, so if they were measuring gravity, it is consistent with GR.
Dr Fish
All general relativists (and for that matter, all physicists) I know think that gravity propagates at the speed of light. In the linked articles, the criticism is that they've measured the speed of light by virtue of the radio photons, not the speed of gravity, which they're claiming.
There's nothing about 'infinitely' fast gravity in the article that I can see, and of the two physicists claiming to disagree with the results, the one who says it is 'nonsense' then refuses to comment any further.
Dr Fish
"The "inflationary" model was sort of a hack to make the theory agree with the observations. No actual reason for what starts it has been proposed AFAIK."
Yes, you are right about the hack part, but inflationary theory explains why our universe has an omega so close to 1 and why apparently disconnected parts of the cosmic microwave background have similiar temperatures. As for the reason it starts, well, there are plenty of ideas, but none of them easily testable (and I can't remember what they were, but they were all very high energy fields breaking indegeneracy...anyone care to comment?).
Alan Guth wrote a book called "The Inflationary Universe" (admittedly he came up with the idea) which gives a very clear explanation why inflation theory seems more suited than many other alternate theories.
"Who is to say that we might not accidentally create a sort of "mini-inflation" at one of these accelerators, thereby destroying the Earth, the Solar System, or even more. Nobody knows what triggered inflation. What if we do it accidentaly?"
A good question, and it was considered seriously by Martin Rees, a famous astrophysicist now at Cambridge. He did calculations showing that cosmic rays many thousands of times more energetic than the best we can do with earthly accelerators routinely hit our upper atmosphere. Given that billions of years of cosmic ray bombardment have not triggred a new universe type of scenario, it is probably safe to say that our experiments won't trigger one off.
I'm keeping my fingers crossed!
Dr Fish
Speaking as a physicist (well, astronomer) the past decade or so has seen the rise of biology in the public's eyes, and the flow of money to the life sciences. If your science is purely defined by public popularity, though, you'd better hope that the public stays interested in biology.
We haven't had the equivalent of a public relations disaster for biology yet, which would cause public opinion to turn against it. All you need is a biological Chernobyl and you'll be tarred with the same brush that physicists have had applied to them. Not that I'd want anything like that, God forbid.
Also, is the authour of the article a bit bitter? Yes, but he does not speak for all physicists.
Don't get me wrong, I'd like a larger grant for some of my research, but we can't always get what we want, and if I *needed* the money, then I should bloody well write a better grant the next time around. Shame on me, not shame on the biologists. My personal moan aside, I think that money in science is well spent, whatever field it is in. If the research is exciting and interesting, by and large it does get funded.
I think there's the relatively modern issue of corporate interests and how they affect the flow of ideas in a given subject, and it just so happens that biology is the science that is facing this at the moment.
Hurm. Time for coffee!
Dr Fish
You're right about balancing the gravitational binding energy of a pile of neutrons with the nuclear binding energy of the same pile of neutrons. As you add more neutrons, you get to a point where the mass of the neutrons makes the gravitational binding energy pass that of the nuclear binding energy. Of course, this number of neutrons is astronomically large (pun intended).
/Radius).
I did this as an undergrad problem in Nuclear physics - take a ball of N neutrons, assume nuclear type densities, and calculate the neutron ball's radius and mass (and thus it's gravitational binding energy = G * M(neutron) * N
When you balance this with the typical binding energy per neutron (erm, cant remember the numbers we used, sorry), you get two simple equations and you solve for N the number of neutrons.
AFAI remembber, you get a radius of 10km and about 2 solar masses - pretty damn good for a back of the envelope calculation!
If I can dig out the old problem sheet, I can post the number later....
Dr Fish
Go find a tall building with a decent staircase, hang a bucket of sand on some piano wire, bring it to one side of the stairwell and release.
Heavy bucket, small surface area, pendulum takes about an hour to swing to a stop. In that time, Earth's rotation will have moved it by (360/15) * cos (latitude). Classic demonstration of the Earth's rotation.
I did it in high school, it gave me my latitude +- 10 degrees. Not bad for an hour's work!
Dr Fish
You could rephrase the two statements like this:
1. It's an electronic clock based on well-known electronic processes and principles
2. A quiet introvert who enjoys people having an accurate sense of time placed a clock on a wall and hid himself behind it, and keeps himself supplied with food from an unknown source whilst twiddling the hands using another time reference.
Now it's the first explanation that's the simplest.
I don't like Occam's razor for this reason - I think you can phrase the choices according to your own biased viewpoint. It is only effective when there is a bare minimum of testable information present - lifting the clock off the wall is a simple experiment, whilst OBE's are all about human-percieved experiences, very hard to dispassionately test.
Dr Fish
So would they call the new company Snapple?