I can't agree with your comment about medical funding. Considering that the NIH has had their budget quadruple in 15 years, I would say they're doing pretty good. There is a lot of hand wringing because in recent years the budget has been increased either just a little, or even flat, but historically their budget was about $7.5B in 1990, $11.3B in 1995, $17.8B in 2000, and $28.5B in 2005. Their budget can be held flat for the next few years, and they'll still have a budget increase that is the envy of pretty much every part of government outside the DoD.
I would also like to see you defend your comment about most of the space research budget has been diverted to militarizing space. That just sounds like a whole lot of bunk.
If you are concerned about space science budgets, then you should be rooting for the death of the moon-mars initiative and over-emphasis on manned space. That, the ISS, and the shuttle are pretty much killing space research. The ESA is fortunate to not have that millstone around their necks. Besides, in 2001 at least, the ESA space science budget was only about 12.5-percent of the science budget of NASA, so I'm not sure how you can defend your statement that the ESA is doing most of the space research.
Unlike the internet, you need specialized equipment in order to even listen to ham radio
I'm curious as to how you get on the internet. Is there any special equipment involved, or do you just plug some wires into your ears? I understand that equipment can be rather pricey as well.
and the definition of a second was changed so that the length of a second remains constant
This isn't my field of study, but I believe the second is defined as a certain number of oscillations between two hyperfine levels of the cesium-133 atom. This was done in the late sixties to get the definition of the second away from earth rotations and tie it to something more reliable and easy to measure.
I am not sure what the medical profession is supposed to be catching up to. You emphatically state cell phones are causing cancer and assume the medical profession has to eventually come around and accept your truth. The only problem is that, to my knowledge, there are not any carefully-controled studies that show any link between the two. There isn't anything in the physics to suggest it either. I guess I fail to see what you do that would convince me there is anything of significance there.
To be convincing, as in the case of the effects of tobacco on the body, there has to be a pretty strong correlation between the cause and effect. With tobacco, this was very easy to see, even in the pre-modern medical age. When it comes to cell phones, whether go into it believing it one way or the other, the data clearly show no strong correlation between cell phone use and anything. You are now down in the are where the signal to noise ratio in the data is one, and it becomes a heck of a lot harder to attribute the effect to the cause, because now how you slice and dice the data makes big differences in your result.
On the other hand, within the medical community, smoking has been known to be bad on many levels going back hundreds of years.
The fundamental difference between the non-ionizing radiation/cancer link and what you are implying in your post is that the majority of the medical community, to date, do not believe there is a causal relationship between the two. It is hard to claim a corporate/government coverup when most researchers in the biophysical research community do not put much weight in the claim in the first place.
I apologize to my excitable friend and to all the practicing quantum mechanics out there where I have indeed taken liberties with the energy-time relationship and have used them in the more colloquial manner in some QM books. It is true one way to derive the relationship is via the time-dependent Schroedinger equation, but it is not the only way.
As I am so strongly directed to get my facts right, and within this spirit, I should point out a few things. Though even Heisenberg put forth energy-time as well as position-momentum in his original description (as well as angle-action), Pauli noted in 1933 that there isn't any operator that is canoncally conjugate to the Hamiltonian, provided the Hamiltonian is bounded from below (which means they are not complementary variables in the strict sense that I have been taken to task). For what it is worth, Bohr considered them all "complementary quantities."
Now my anonymous critic points out that you derive it from the Schroedinger equation, but that is only one way. Forty-five years ago Ahranov and Bohm summarized this issue very nicely and it has been a topic of study even longer. A good, recent, review paper on this topic can be found by Busch.
As for the issue of the time operator, that is an interesting topic of study as well, and not so cut-and-dried as my combatitive friend would have you to believe. As an example with relation to quantum field theories, one can look at Wang et al.. I would not be a quick as my self-confident friend that there is not a time operator to be found.
Actually, the complementary variables are position and momentum, and energy and time. If you want to get really technical, you can throw in the quantum mechanical spins as well.
That is an interesting use of the colon. I would have to disagree with you regarding it being precise language. Colons are, as your link states, commonly used to denote ratios (the model is 1:20 scale; mix the powder to the dry as 2.5:1; etc.), but it is never used (or at least, I should say, I have never seen it used in the physical sciences or engineering fields over the last 25 years, or even in decades-old textbooks or journal papers), in the units label. Units are usually labeled with the slash or raised to a negative power, though sometimes in a more colloquial setting a letter such as "p" is used, as your MPG example shows.
I guess I do not understand your statement that implies that units are ratios and distinct from "divided by." Units are what they are; if you divide the number of meters you traveled by the number of seconds it took you, you get an average velocity with units m/s. If you find it useful to know the product of those two numbers, you get a number with units of m-s. This, at least in the physical sciences and engineering fields, is very precise and unambiguous language.
As usual, your mileage may vary. I've upgraded windows machines (from NT to 2k, and others up to XP) and I have had my share of headaches: drivers that don't work, so I have to hunt them down and install them; the system losing one of the two CD/DVD drives; things like that. So my "out of the box" experience is different than yours.
What appears to have happened to you doesn't surprise me at all. If you put in a new motherboard (that isn't the same make, model, version as the old one), it should be no surprise you need different drivers to operate it. Microsoft either has all the drivers you need pre-installed (which is why the OS footprint can be huge), or they've worked it out with the major hardware makers to know where to go to get updated drivers (the whole Microsoft Certified driver thing). Ubuntu isn't necessarily going to know you now have a completely different graphics hardware setup unless you tell it so, which means telling it to use different drivers.
That Microsoft will detect and attempt to take care of an issue like this automatically for you seems to be your yardstick for quality (as I mentioned, my experience is that I have had to do a lot of that leg work manually, just like I would if I was running Ubuntu); to write it off with a pithy comment about "the vaunted linux stability" is, I think, being very disingenuous of you.
These are some of the reasons I'm glad I went into physics.:)
I do have an appreciation for these kinds of studies in terms of how hard it is to collect and analyze data. But I also do get tired of seeing 1-sigma or less results from exploratory studies blown way out of proportion in the media (I'm not referring specifically to this cell phone study). Remember oat bran? Some preliminary studies came out suggesting its cholesterol reducing properties, then suddenly EVERYTHING on the supermarket shelf had oat bran. Eventually, at least in the case of oat bran, follow up studies either don't show the intial correlation, or show it as a small effect, and the health fad dies a quiet death.
On a related note, it is impossible for a cube to be the sum of two cubes, a fourth power to be the sum of two fourth powers, or in general for any number that is a power greater than the second to be the sum of two like powers. I have discovered a truly marvelous demonstration of this proposition that this Slashdot comment box is too narrow to contain.
I just read TFA and their statement is perfectly reasonable. The statement basically states that the recent, highly publicized, study was based on combining two previously published studies (published in 2002 and 2005), which itself should raise some eyebrows. Other than making an adjustment based on the time of diagnosis, there were no other adjustments made for anything else (make/female, young/old, lifestyle, etc.). That should raise the level of suspicion in the strength of the conclusions greatly.
By my reading, it sounds like they sent mailings to people that have diagnosed brain tumors in those previous two studies and asked them how much they used the cell phone over the last 10 years. They then compared that to a general population sample. Deriving exposure levels from questionnaires is, in my opinion, almost worthless. How many minutes have you used the cell phone in the last 24 hours? Week? Month? Can you come up with a number you believe accurate to within a factor of 2? 10? 100?
This reminds me of a study released in the early 90's that suggested that 60 Hz EMF fields caused cancer. The "researchers" went through death records and picked out people who were listed as having "electrical related" occupations such as electricians and such, then seeing how many of them died of cancer. This study got lots of press, of course. However, a follow-up study was done that looked at 30,000+ workers at an electric generating plant where they actually measured real exposure levels and no correlation was found.
The FDA statement itself says basically that because of all these loose or non-existent controls, it this study cannot really be compared to the other better controled studies that were done. That is a perfectly reasonable and well-explained statement, so I am not sure what the knee-jerk posts about corporate control and suppressing the truth posts are based on. Personally I think that if the study in question was run in the manner described, it is essentially worthless and should not have received any press coverage in the first place.
One joke I recall was that to properly place blame you need to criticise the Jefferson administration because the last time such an alignment was possible was on his watch, and his science advisors didn't advocating launching anything.
If we are still on the topic of traveling at relavistic speeds, that harmless heat radiation you mention gets blue-shifted up to not-so-friendly other radiation such as gamma and x-ray.
If my memory serves me, I believe the first fast food marketing was with Burger King. I still might have a drinking glass or two around somewhere.
Get rid of the lazy typing posture
on
Preventing RSI?
·
· Score: 2, Insightful
Get your forearms and wrists off of the table and sit in a proper manner. This is certainly something that history can teach us. I don't think it is any accident that RSI is a relatively new thing.
A hundred years of typing pools, and several hundred years of piano playing tell you how to sit and work, and it is no accident that proper typing posture is the same as proper piano posture.
You described the Stephan-Boltzmann Law, which only applies to blackbody radiation, which I don't believe is the case here. For non-continuous spectra, you need another method, such as what this post points out.
That makes sense to me if there are 2048x1280 laser sources, i.e., one for each pixel. If that is the case here, which would presumably be done via a fiber bundle, how do you get around the diffraction problem where the light from one pixel gets spread out over the other pixels? Even a nice, collimated laser beam gives you a narrow waist only in a certain region, then spreads out from there.
Now I am entirely confused. I cannot make the connection between depth-of-focus and coherent light; especially this always being in focus. Coherent light usually causes problems because of diffraction; again, if this is just a collimator, then I can understand it (and why you'd need a lens down the line to form an image).
Can anybody give me the 5-dollar summary of the physics behind this?
You hit my peeve right on the head. That annoys the crap out of me and I wish Taco would edit that out with the other fluff (Taco: if you do, I thank you, but please get the other editors on board).
Come on fellow Slashdotters, you must have an opinion on this. What do you think?
Slashdot Mirror
I would also like to see you defend your comment about most of the space research budget has been diverted to militarizing space. That just sounds like a whole lot of bunk.
If you are concerned about space science budgets, then you should be rooting for the death of the moon-mars initiative and over-emphasis on manned space. That, the ISS, and the shuttle are pretty much killing space research. The ESA is fortunate to not have that millstone around their necks. Besides, in 2001 at least, the ESA space science budget was only about 12.5-percent of the science budget of NASA, so I'm not sure how you can defend your statement that the ESA is doing most of the space research.
To be convincing, as in the case of the effects of tobacco on the body, there has to be a pretty strong correlation between the cause and effect. With tobacco, this was very easy to see, even in the pre-modern medical age. When it comes to cell phones, whether go into it believing it one way or the other, the data clearly show no strong correlation between cell phone use and anything. You are now down in the are where the signal to noise ratio in the data is one, and it becomes a heck of a lot harder to attribute the effect to the cause, because now how you slice and dice the data makes big differences in your result.
On the other hand, within the medical community, smoking has been known to be bad on many levels going back hundreds of years.
The fundamental difference between the non-ionizing radiation/cancer link and what you are implying in your post is that the majority of the medical community, to date, do not believe there is a causal relationship between the two. It is hard to claim a corporate/government coverup when most researchers in the biophysical research community do not put much weight in the claim in the first place.
As I am so strongly directed to get my facts right, and within this spirit, I should point out a few things. Though even Heisenberg put forth energy-time as well as position-momentum in his original description (as well as angle-action), Pauli noted in 1933 that there isn't any operator that is canoncally conjugate to the Hamiltonian, provided the Hamiltonian is bounded from below (which means they are not complementary variables in the strict sense that I have been taken to task). For what it is worth, Bohr considered them all "complementary quantities."
Now my anonymous critic points out that you derive it from the Schroedinger equation, but that is only one way. Forty-five years ago Ahranov and Bohm summarized this issue very nicely and it has been a topic of study even longer. A good, recent, review paper on this topic can be found by Busch.
As for the issue of the time operator, that is an interesting topic of study as well, and not so cut-and-dried as my combatitive friend would have you to believe. As an example with relation to quantum field theories, one can look at Wang et al.. I would not be a quick as my self-confident friend that there is not a time operator to be found.
Actually, the complementary variables are position and momentum, and energy and time. If you want to get really technical, you can throw in the quantum mechanical spins as well.
I guess I do not understand your statement that implies that units are ratios and distinct from "divided by." Units are what they are; if you divide the number of meters you traveled by the number of seconds it took you, you get an average velocity with units m/s. If you find it useful to know the product of those two numbers, you get a number with units of m-s. This, at least in the physical sciences and engineering fields, is very precise and unambiguous language.
What appears to have happened to you doesn't surprise me at all. If you put in a new motherboard (that isn't the same make, model, version as the old one), it should be no surprise you need different drivers to operate it. Microsoft either has all the drivers you need pre-installed (which is why the OS footprint can be huge), or they've worked it out with the major hardware makers to know where to go to get updated drivers (the whole Microsoft Certified driver thing). Ubuntu isn't necessarily going to know you now have a completely different graphics hardware setup unless you tell it so, which means telling it to use different drivers.
That Microsoft will detect and attempt to take care of an issue like this automatically for you seems to be your yardstick for quality (as I mentioned, my experience is that I have had to do a lot of that leg work manually, just like I would if I was running Ubuntu); to write it off with a pithy comment about "the vaunted linux stability" is, I think, being very disingenuous of you.
It would cost a heck of a lot more to design, develop, build, test, launch, and staff a fleet of rovers than it would to do this mission.
I do have an appreciation for these kinds of studies in terms of how hard it is to collect and analyze data. But I also do get tired of seeing 1-sigma or less results from exploratory studies blown way out of proportion in the media (I'm not referring specifically to this cell phone study). Remember oat bran? Some preliminary studies came out suggesting its cholesterol reducing properties, then suddenly EVERYTHING on the supermarket shelf had oat bran. Eventually, at least in the case of oat bran, follow up studies either don't show the intial correlation, or show it as a small effect, and the health fad dies a quiet death.
On a related note, it is impossible for a cube to be the sum of two cubes, a fourth power to be the sum of two fourth powers, or in general for any number that is a power greater than the second to be the sum of two like powers. I have discovered a truly marvelous demonstration of this proposition that this Slashdot comment box is too narrow to contain.
By my reading, it sounds like they sent mailings to people that have diagnosed brain tumors in those previous two studies and asked them how much they used the cell phone over the last 10 years. They then compared that to a general population sample. Deriving exposure levels from questionnaires is, in my opinion, almost worthless. How many minutes have you used the cell phone in the last 24 hours? Week? Month? Can you come up with a number you believe accurate to within a factor of 2? 10? 100?
This reminds me of a study released in the early 90's that suggested that 60 Hz EMF fields caused cancer. The "researchers" went through death records and picked out people who were listed as having "electrical related" occupations such as electricians and such, then seeing how many of them died of cancer. This study got lots of press, of course. However, a follow-up study was done that looked at 30,000+ workers at an electric generating plant where they actually measured real exposure levels and no correlation was found.
The FDA statement itself says basically that because of all these loose or non-existent controls, it this study cannot really be compared to the other better controled studies that were done. That is a perfectly reasonable and well-explained statement, so I am not sure what the knee-jerk posts about corporate control and suppressing the truth posts are based on. Personally I think that if the study in question was run in the manner described, it is essentially worthless and should not have received any press coverage in the first place.
One joke I recall was that to properly place blame you need to criticise the Jefferson administration because the last time such an alignment was possible was on his watch, and his science advisors didn't advocating launching anything.
Yes, but as the saying goes, it is the man with two clocks that never knows what the time is.
If we are still on the topic of traveling at relavistic speeds, that harmless heat radiation you mention gets blue-shifted up to not-so-friendly other radiation such as gamma and x-ray.
If my memory serves me, I believe the first fast food marketing was with Burger King. I still might have a drinking glass or two around somewhere.
A hundred years of typing pools, and several hundred years of piano playing tell you how to sit and work, and it is no accident that proper typing posture is the same as proper piano posture.
I just Googled up an interesting site that discusses both issues.
You described the Stephan-Boltzmann Law, which only applies to blackbody radiation, which I don't believe is the case here. For non-continuous spectra, you need another method, such as what this post points out.
That makes sense to me if there are 2048x1280 laser sources, i.e., one for each pixel. If that is the case here, which would presumably be done via a fiber bundle, how do you get around the diffraction problem where the light from one pixel gets spread out over the other pixels? Even a nice, collimated laser beam gives you a narrow waist only in a certain region, then spreads out from there.
Can anybody give me the 5-dollar summary of the physics behind this?
Infinite focus to me sounds like a collimator. Does this mean that you need another lens somewhere to form the image?
I don't know about this one, but the next Falcon payload will.
Come on fellow Slashdotters, you must have an opinion on this. What do you think?