For those who are interested, the scientific journal has a companion article here. It describes the design and sensitivity of the experiment, as well as some of the context. There is also a link to the actual journal article to the right, but you may need institutional access to download it.
The basic technique is called a Magneto-Optical Trap, or MOT for short, although they probably use a few extra steps to create a Bose-Einstein condensate. As an atomic physicist, I have a couple of MOTs in my lab, and the whole thing will easily fit in a 1-meter long box. These things are actually being miniaturized quite effectively, and sensor packages using cold atoms are being built that fit in your hand. I bet a government-sponsored project could get them a bit smaller still. For example, here's a story about a DARPA project that's working to make a cold-atom based inertial guidance package for missiles that will be 20 cm^3.
we know that simply observing an experiment can change the outcome. We don't know why that is either, AFAIK... So it seems that consciousness and attention can have effects in the physical world, the mechanism of which we cannot explain.
We most certainly *do* know why observation affects an experiment. It's the Heisenberg uncertainty principle in action - if you make a measurement of the state of a system, that variable is known to some degree of precision. Its conjugate variable is thus made uncertain to a degree prescribed by the uncertainty principle. This has nothing to do with consciousness or a living observer.
A simple double-slit experiment works because of the uncertainty in the position of the particle. The wavefunction interferes with itself as it comes out of both slits and affects the possible positions it can be observed at on the detector. If you measure whether the particle passes through one of the slits, it's position is no longer uncertain, the wavefunction changes, and the experiment reflects that. This is well-understood quantum mechanics, although the popular press likes to pretend we don't know anything about it. And yes, IAAP (I am a physicist).
And that's exactly what the CPI does. Read the FAQ. It does include food, fuel, and housing, and weights the prices. There are a lot of smart, dedicated researchers working on these data series - there's no conspiracy. Trust me, the left is far too disorganized for there to be one.
You're very wrong. The CPI is exactly what you suggest we do - they check prices of common consumer goods in real stores. If the government bogeyman scares you, look at MIT's billion price index. It's an online survey of many prices, updated in real time. And it matches the CPI very accurately.
I can second the recommendation for Hartle (the title is Gravity: an Introduction to Einstein's General Relativity). It's a great introduction that I used as an undergrad, but be warned - it's still pretty complicated, even as an introduction. The nice part about it is that it develops the concepts of curved spacetime as you need them to investigate interesting physical systems, like the geometrized version of Special Relativity (which gets you time dilation and the Twin Paradox) or Schwarzschild black holes. My favorite section is where it discusses the metric of the entire universe, which describe the expansion of space and what happens to spacetime in the distant future.
As to Misner, Thorne, and Wheeler - avoid it until you've gone through some more introductory texts. It's really easy to get in over your head and get discouraged in that text, as they dive in head-first with hard-core math.
If you think that a "fat slob" paying more for his insurance means that you'll pay less, you have a very naive view of insurance companies. Or companies in general. Also, how diligent do you think they'll be to check that you're not a fat slob? Remember that banks have been foreclosing on houses that weren't even in default!
I'm a physicist; I work in a laser lab. I never capitalize 'laser', and I've never seen it capitalized in any contemporary publication. Frankly, explicitly capitalizing acronyms gets really annoying once they enter common usage. It just gets in the way of effective communication.
Actually, the waste is vastly *more* radioactive, but this is still a Good Thing. There is more radioactivity, but this causes a significantly shorter half-life, so you don't have to worry about waste that is hot for 30,000 years - only decades or centuries.
I don't think "draconian copy protection" was the reason either SACD or DVD-A didn't catch on. I think the reason they didn't catch on is that they're more expensive than CDs, they can't be played in a regular CD player (or, in the case of SACD, can only be played as an ordinary CD in such a drive), and the improvement in audio is undetectable to most people. I am certainly happy with CD-quality and have no burning desire to switch. Why would you pay more when you don't see any discernible benefit?
Similarly, most people are quite happy with the quality and resolution of DVD. To get the benefit of BD you also need a large HDTV, which not everyone has yet. Of course, considering how often people watch 4:3 content stretched to fill their 16:9 screen, it wouldn't surprise me if most wouldn't notice the resolution improvement even if they have HDTV.
I mostly watch video on my laptop, and only occasionally watch HD content online. I do notice the improvement over regular DVD, but it's still not something I think about if I'm watching something that I enjoy in standard definition. I certainly don't see why I should pay significantly inflated prices for BD discs when I just don't care about the improvement very much.
It all depends on your reference frame. You can write the Schwarzschild metric (the mathematical description of a non-rotating, non-electrically charged black hole) in such a way that nothing at all unusual happens at the event horizon and matter falls all the way into the center. Looking at it from the outside, with our conventional way of measuring time, it does actually look like infalling matter stops at the event horizon (though the light coming from it gets infinitely redshifted, too). The world outside the event horizon behaves the same way no matter where the mass is located, in any case.
I suggest "Why don't you just cross off the professor from the first time around and put the name of the new professor there, you already got 95% and it was your own work".
At the school where I did my undergraduate work, we had an academic honor code that explicitly forbade reusing your own work without proper citation. It was considered plagiarism. We never got recycled homeworks like your example, so it really was quite reasonable. An honor code that is strongly respected and enforced can actually create an environment of great freedom, because you know the boundaries and the professors trust you. As an example, exams were never proctored; you could have 50 students working on the same test in a room with no professor, and nobody would even think of cheating. It's really nice to be treated as an adult.
When it comes to concerns of academic misconduct, I've found that the best policy is to talk to the professor about it beforehand. Having an open channel of communication will help to build trust on both sides, not to mention keeping you out of trouble for misunderstandings like that.
Even if they still vote the same way (and they, or I should say we, could vote for a further-left and more representative Democrat in the primaries), the reduction in donations, voter-turnout efforts, and other benefits of MoveOn's support would be significant.
Most Democrats are trying to distance themselves from the likes of Code Pink, ANSWER, MoveOn.org,
I don't know how true this is, but the Democrats should stop and think before they distance themselves from MoveOn. MoveOn is an organization with over 3 million active, politically interested members, all of whom are rooting for the Democrats right now. It has amply demonstrated its ability to organize people effectively, not to mention being able to raise boatloads of cash. It's not any group that can raise $1 million in a few days whenever they have a need, but MoveOn does this regularly. This is a popular, broad-based group that is very much representative of a large minority of America, if not a majority on some issues.
Given the rates of political involvement, the numbers this group has are huge. Even the summary in its Wikipedia article says that it may have tipped the 2006 election. Politicians ignore MoveOn at their own peril.
this guy had half a kilo of potassium nitrate, 250g of calcium chloride, videos of beheadings and he had recently visited Pakistan,
You do realize that this means he had a pound of fertilizer, half a pound of ice-melter, and some gross but widely-distributed web videos? Oh, and he visited a country that is supposedly our closest ally in the "War On Terror."
I've looked at the web site you linked to, and the ideas presented there are, unfortunately, childish nonsense. I really hope you don't believe any of that garbage. I don't want to be insulting, but the writer clearly didn't understand his intro physics classes, since he badly misunderstands very basic concepts. If you're interested, any introductory physics textbook can help you clear up his bad explanations and show you where he's going wrong. There is a wikibook on physics, but it's incomplete, so I won't link to it from here.
Although I'm not an astrophysicist, I have studied astrophysics as an undergraduate and know some things about dark matter theories and cosmology. You are absolutely correct in saying that dark matter must be non-baryonic under current models. Baryonic dark matter is excluded because big-bang nucleosynthesis models (which take observed primordial elemental abundances as input) show that only ~4% of the mass of the universe can be baryonic matter.
You are, however, incorrect in stating that dark matter shares no properties with ordinary matter besides gravity. All energy, including electromagnetic radiation and dark energy, affect the curvature of spacetime. Dark matter also has the property that it behaves in the same way as matter when the universe expands, i.e. that its density decreases as the cube of the scale factor (which determines the rate of expansion). Ordinary radiation and dark energy each behave differently in this regard, so dark matter is indeed uniquely matter-like in a very important way. Aside from galactic rotation curves, very good data from the WMAP project that studies the cosmic microwave background has determined that ~30% of the universe must be matter-like. Combined with the BBN studies, this means that 26% of the universe, by mass, is dark matter, which thus outnumbers ordinary matter by more than a factor of 6.
You are also incorrect in assuming that we haven't found dark matter. There is actually a very excellent photo of colliding galaxies that shows convincing evidence of dark matter. The caption does a decent job at giving an explanation of the photo's significance. If you want a more thorough explanation, both of the photo and why the result is significant, I recommend this blog maintained by several well-known cosmologists.
As a physics TA (for non-physics majors), I can say that the Chinese question would send my students running for the hills, whereas the British one wouldn't bother them too much. Also, the British question requires only very simple geometric and trigonometric principles, while the Chinese one requires a reasonable knowledge of vectors (at least that's the only way I could think of solving the last part). Too, at each step it involved good spatial reasoning and required you to think about the principles behind the question, not just say "Oh, a right triangle, use SOH-CAH-TOA!" If you actually have to understand what a dot product means physically, isn't that better than memorizing the definition of the tangent?
You can define an (acute) angle between the two lines by the dot product of their vectors. If you write the position vectors for the points A, D, B, and C1 you can construct vectors AD and BC1. Find the dot product as |AD||BC1|Cos[theta], and again by using the column vector forms. Set these two scalars equal and solve for the angle. I got an angle of ArcCos[Sqrt[3/5]], which is approximately equal to 39.23 degrees. That's the best method I could come up with, but there was quite a bit of prep work to get there. Fortunately, I enjoyed solving the problem thoroughly, and used vectors for the first part, so I had the information I needed when I got to that part. Does anyone know a simpler method?
By the way, if you didn't see it, there's a competition on the RSC's site where correct solutions are entered into a drawing for a 500 Pound prize if you submit it by 12:00 UTC. I don't think I'll have time to Tex up my solutions before then, though, so I'm probably not entering.
Slashdot Mirror
For those who are interested, the scientific journal has a companion article here. It describes the design and sensitivity of the experiment, as well as some of the context. There is also a link to the actual journal article to the right, but you may need institutional access to download it.
The basic technique is called a Magneto-Optical Trap, or MOT for short, although they probably use a few extra steps to create a Bose-Einstein condensate. As an atomic physicist, I have a couple of MOTs in my lab, and the whole thing will easily fit in a 1-meter long box. These things are actually being miniaturized quite effectively, and sensor packages using cold atoms are being built that fit in your hand. I bet a government-sponsored project could get them a bit smaller still. For example, here's a story about a DARPA project that's working to make a cold-atom based inertial guidance package for missiles that will be 20 cm^3.
we know that simply observing an experiment can change the outcome. We don't know why that is either, AFAIK ... So it seems that consciousness and attention can have effects in the physical world, the mechanism of which we cannot explain.
We most certainly *do* know why observation affects an experiment. It's the Heisenberg uncertainty principle in action - if you make a measurement of the state of a system, that variable is known to some degree of precision. Its conjugate variable is thus made uncertain to a degree prescribed by the uncertainty principle. This has nothing to do with consciousness or a living observer.
A simple double-slit experiment works because of the uncertainty in the position of the particle. The wavefunction interferes with itself as it comes out of both slits and affects the possible positions it can be observed at on the detector. If you measure whether the particle passes through one of the slits, it's position is no longer uncertain, the wavefunction changes, and the experiment reflects that. This is well-understood quantum mechanics, although the popular press likes to pretend we don't know anything about it. And yes, IAAP (I am a physicist).
And that's exactly what the CPI does. Read the FAQ. It does include food, fuel, and housing, and weights the prices. There are a lot of smart, dedicated researchers working on these data series - there's no conspiracy. Trust me, the left is far too disorganized for there to be one.
You're very wrong. The CPI is exactly what you suggest we do - they check prices of common consumer goods in real stores. If the government bogeyman scares you, look at MIT's billion price index. It's an online survey of many prices, updated in real time. And it matches the CPI very accurately.
I can second the recommendation for Hartle (the title is Gravity: an Introduction to Einstein's General Relativity). It's a great introduction that I used as an undergrad, but be warned - it's still pretty complicated, even as an introduction. The nice part about it is that it develops the concepts of curved spacetime as you need them to investigate interesting physical systems, like the geometrized version of Special Relativity (which gets you time dilation and the Twin Paradox) or Schwarzschild black holes. My favorite section is where it discusses the metric of the entire universe, which describe the expansion of space and what happens to spacetime in the distant future.
As to Misner, Thorne, and Wheeler - avoid it until you've gone through some more introductory texts. It's really easy to get in over your head and get discouraged in that text, as they dive in head-first with hard-core math.
If you think that a "fat slob" paying more for his insurance means that you'll pay less, you have a very naive view of insurance companies. Or companies in general. Also, how diligent do you think they'll be to check that you're not a fat slob? Remember that banks have been foreclosing on houses that weren't even in default!
1 = 0! Holy shit!
The irony here is that 0!=1 is a true statement. And yes, I do think factorials are exciting.
I'm a physicist; I work in a laser lab. I never capitalize 'laser', and I've never seen it capitalized in any contemporary publication. Frankly, explicitly capitalizing acronyms gets really annoying once they enter common usage. It just gets in the way of effective communication.
Actually, the waste is vastly *more* radioactive, but this is still a Good Thing. There is more radioactivity, but this causes a significantly shorter half-life, so you don't have to worry about waste that is hot for 30,000 years - only decades or centuries.
I don't think "draconian copy protection" was the reason either SACD or DVD-A didn't catch on. I think the reason they didn't catch on is that they're more expensive than CDs, they can't be played in a regular CD player (or, in the case of SACD, can only be played as an ordinary CD in such a drive), and the improvement in audio is undetectable to most people. I am certainly happy with CD-quality and have no burning desire to switch. Why would you pay more when you don't see any discernible benefit?
Similarly, most people are quite happy with the quality and resolution of DVD. To get the benefit of BD you also need a large HDTV, which not everyone has yet. Of course, considering how often people watch 4:3 content stretched to fill their 16:9 screen, it wouldn't surprise me if most wouldn't notice the resolution improvement even if they have HDTV.
I mostly watch video on my laptop, and only occasionally watch HD content online. I do notice the improvement over regular DVD, but it's still not something I think about if I'm watching something that I enjoy in standard definition. I certainly don't see why I should pay significantly inflated prices for BD discs when I just don't care about the improvement very much.
It all depends on your reference frame. You can write the Schwarzschild metric (the mathematical description of a non-rotating, non-electrically charged black hole) in such a way that nothing at all unusual happens at the event horizon and matter falls all the way into the center. Looking at it from the outside, with our conventional way of measuring time, it does actually look like infalling matter stops at the event horizon (though the light coming from it gets infinitely redshifted, too). The world outside the event horizon behaves the same way no matter where the mass is located, in any case.
Ironically enough, when I first read your post I thought, "What does Douglas Adams have to do with this?"
Stop it now, I mean it!
Anybody got a pea
At the school where I did my undergraduate work, we had an academic honor code that explicitly forbade reusing your own work without proper citation. It was considered plagiarism. We never got recycled homeworks like your example, so it really was quite reasonable. An honor code that is strongly respected and enforced can actually create an environment of great freedom, because you know the boundaries and the professors trust you. As an example, exams were never proctored; you could have 50 students working on the same test in a room with no professor, and nobody would even think of cheating. It's really nice to be treated as an adult.
When it comes to concerns of academic misconduct, I've found that the best policy is to talk to the professor about it beforehand. Having an open channel of communication will help to build trust on both sides, not to mention keeping you out of trouble for misunderstandings like that.
Even if they still vote the same way (and they, or I should say we, could vote for a further-left and more representative Democrat in the primaries), the reduction in donations, voter-turnout efforts, and other benefits of MoveOn's support would be significant.
Most Democrats are trying to distance themselves from the likes of Code Pink, ANSWER, MoveOn.org,
I don't know how true this is, but the Democrats should stop and think before they distance themselves from MoveOn. MoveOn is an organization with over 3 million active, politically interested members, all of whom are rooting for the Democrats right now. It has amply demonstrated its ability to organize people effectively, not to mention being able to raise boatloads of cash. It's not any group that can raise $1 million in a few days whenever they have a need, but MoveOn does this regularly. This is a popular, broad-based group that is very much representative of a large minority of America, if not a majority on some issues.
Given the rates of political involvement, the numbers this group has are huge. Even the summary in its Wikipedia article says that it may have tipped the 2006 election. Politicians ignore MoveOn at their own peril.
You do realize that this means he had a pound of fertilizer, half a pound of ice-melter, and some gross but widely-distributed web videos? Oh, and he visited a country that is supposedly our closest ally in the "War On Terror."
Nice sensationalism there.
That is positively amazing. Thank you!
What really bothers me is that Bush is the most corrupt, awful president in the history of the nation. This is a perfect example of that corruption.
I've looked at the web site you linked to, and the ideas presented there are, unfortunately, childish nonsense. I really hope you don't believe any of that garbage. I don't want to be insulting, but the writer clearly didn't understand his intro physics classes, since he badly misunderstands very basic concepts. If you're interested, any introductory physics textbook can help you clear up his bad explanations and show you where he's going wrong. There is a wikibook on physics, but it's incomplete, so I won't link to it from here.
Buy from CowboyNeal
Although I'm not an astrophysicist, I have studied astrophysics as an undergraduate and know some things about dark matter theories and cosmology. You are absolutely correct in saying that dark matter must be non-baryonic under current models. Baryonic dark matter is excluded because big-bang nucleosynthesis models (which take observed primordial elemental abundances as input) show that only ~4% of the mass of the universe can be baryonic matter.
You are, however, incorrect in stating that dark matter shares no properties with ordinary matter besides gravity. All energy, including electromagnetic radiation and dark energy, affect the curvature of spacetime. Dark matter also has the property that it behaves in the same way as matter when the universe expands, i.e. that its density decreases as the cube of the scale factor (which determines the rate of expansion). Ordinary radiation and dark energy each behave differently in this regard, so dark matter is indeed uniquely matter-like in a very important way. Aside from galactic rotation curves, very good data from the WMAP project that studies the cosmic microwave background has determined that ~30% of the universe must be matter-like. Combined with the BBN studies, this means that 26% of the universe, by mass, is dark matter, which thus outnumbers ordinary matter by more than a factor of 6.
You are also incorrect in assuming that we haven't found dark matter. There is actually a very excellent photo of colliding galaxies that shows convincing evidence of dark matter. The caption does a decent job at giving an explanation of the photo's significance. If you want a more thorough explanation, both of the photo and why the result is significant, I recommend this blog maintained by several well-known cosmologists.
As a physics TA (for non-physics majors), I can say that the Chinese question would send my students running for the hills, whereas the British one wouldn't bother them too much. Also, the British question requires only very simple geometric and trigonometric principles, while the Chinese one requires a reasonable knowledge of vectors (at least that's the only way I could think of solving the last part). Too, at each step it involved good spatial reasoning and required you to think about the principles behind the question, not just say "Oh, a right triangle, use SOH-CAH-TOA!" If you actually have to understand what a dot product means physically, isn't that better than memorizing the definition of the tangent?
You can define an (acute) angle between the two lines by the dot product of their vectors. If you write the position vectors for the points A, D, B, and C1 you can construct vectors AD and BC1. Find the dot product as |AD||BC1|Cos[theta], and again by using the column vector forms. Set these two scalars equal and solve for the angle. I got an angle of ArcCos[Sqrt[3/5]], which is approximately equal to 39.23 degrees. That's the best method I could come up with, but there was quite a bit of prep work to get there. Fortunately, I enjoyed solving the problem thoroughly, and used vectors for the first part, so I had the information I needed when I got to that part. Does anyone know a simpler method?
By the way, if you didn't see it, there's a competition on the RSC's site where correct solutions are entered into a drawing for a 500 Pound prize if you submit it by 12:00 UTC. I don't think I'll have time to Tex up my solutions before then, though, so I'm probably not entering.