None of your 'facts' is a direct proof that a controlled demolition took place. These reports could easily be explained by the much simpler scenario: 1) The fire is indeed making the building unstable. 2) Firefighters hear the building making sounds and don't trust it. 3) They evacuate everyone with the warning that the building might collapse soon. 4) Two reporters (out of several thousand), based on hearsay, make a wrong statement on a hectic day and misreport an imminent collapse as a imminent demolition.
1 is made plausible by hard core science, see the NIST report. 2 and 3 are in the public record. 4 is not proven, but some erroneous reporting on a day like that seems entirely possible to me. Do me a favor and list the steps and their probabilities needed in your scenario. I would be glad to discuss Occam's razor with you after that.
If you start trolling here, at least get your math, your numbers and your units right. First of all, both the report and wikipedia state the height of the building as 610 feet. Second, the gravitational acceleration g (not 'gravity') is given in feet per second *squared*. Last, the formula to calculate the time it takes a distance under constant acceleration is t = sqrt(2*x/a) and not whatever you are using. And real man use SI units.
According to statements issued by Silverstein Properties, "In the afternoon of Sept. 11, Mr Silverstein spoke to the Fire Department Commander on the site at WTC7. The commander told Silverstein that there were several firefighters in the building working to contain the fires. Silverstein expressed his view that the most important thing was to protect the safety of those firefighters, including, if necessary, to have them withdraw from the building." "With respect to Silverstein's statement, when recounting these events for a television documentary, that 'I said, you know, we've had such terrible loss of life. Maybe the smartest thing to do is to pull it.' (a Silverstein Properties spokesman) has said that by 'it,' Silverstein meant the contingent of firefighters remaining in the building.
No need to resort to conspiracies to explain that comment...
more whitewashing, make sure you never watch the actual footage of that building coming down either, looks pretty symmetrical to me
Sorry to feed the troll, but just for the record: the claim about asymmetry refers to the layout of the floor beams, which is asymmetric around some beams due to the trapeziodal shape of the building.
Crackpot theories can be discussed elsewhere; please limit the discussion to the science here.
What site is this, and what has it done with Slashdot
Well, for sure Digg is one of the places where this is happening, some idiots over there get +100 for the most ridiculous comments. What this has done to Slashdot? I hope they drew away some of the trolls from here...
True, but only if you know were you are pointing (they do this with satellites). If ET does not know where we are, and just randomly points his laser in the sky, the detection chance drops enormously, I guess the two effects cancel each other in the detection probability. Also note that any light you sent will might be lost in the background radiation of the star or the planet (I don't know if this is better or worse with radio).
The type of data analysis they perform on these radio signals looks pretty similar to what they do with the data from gravitational wave detectors such as LIGO, which also look at both periodic sources and short glitches. In that community, they do an estimation of detection rates based on hard science: number and distribution of stars and expected rates of supernovae etc. Detection rate for last years' science run is on the order of 1 per 10 to 100 years, which should increase to hopefully tens per year with the advanced detectors that should come online in several years. Nothing has been detected yet, but this is more or less understood. If the advanced detectors detect nothing, the taxpayer owes an explanation.
I wonder if similar detection rates have been calculated for SETI (e.g., assume ET having a transmitter of 1 MW, at what distance would you still detect anything? And how many life supporting planets are in that range? ) This will depend a lot on the parameters in your Drake's equations, but they should at least give some order of magnitudes. I remember reading some skeptic article several years ago, which claimed that even with optimistic estimates, the chance of detecting anything would be absolutely zero.
Until that time, I rather waste my computer cycles on the LIGO data (Einstein at home) or one of the various medical applications (e.g. Folding at home), which produce scientific results today.
Consider someone connecting a stolen laptop to a corporate network. Just because your laptop was stolen doesn't mean you have a right to examining the internal topography of that corporate network, and sending the information to a third party. I'm amazed that the authors of this software are stupid enough to do so!
So according to your logic, if I have a machine at my office that (for some good reason) sends a scan of the local network to HQ, reboots random local machines and sends goatse pictures to the local printer, then if someone steals this machine and plugs it into his network, they have the right to complain??
As already explained by others, the goal of this research is to make a shiny ball, count its number of atoms using x-ray diffraction and other techniques and then calibrate it as good as possible against the kilo in Paris. This yields the number of silicon atoms in a kilo, but with an uncertainty given by the current kilo. The last step is to pick a random number within the error bars and define this to be the new definition of the kilo.
There was a very nice article in American Scientist, which suggested that instead of defining this number of atoms, you could define the constant of Avogadro instead. Since this is linked to the gram via the weight of a carbon atom, this definition is equivalent. Since you are free to pick any number within the error bars of the current definition, they suggest to pick a nice number instead, just like the speed of light was defined as an integer. Their funny requirement was that it should be a perfect cube, since this would define one mole as a cube with an integer number of atoms on its side. This leaves essentially only one number: define N_A as the third power of 84.446.888!
The rate I heard was once every 30 years. This is the kind of explosion that LIGO and others are waiting for, since this would be a pretty easy target for observing gravitational waves. This one was at 28k lightyear or about 8 kiloparsec. LIGO has been running last year with a 'detection horizon' of about 15 Megaparsec, so this one was really at spitting distance.
This is the reason why the gravitational wave community does an effort to keep at least one interferometer running at all times by scheduling the planned downtime. Even the less sensitive GEO could hear something if it blows up in our galaxy.
They didn't observe anything so far (they estimate a chance of 1/100 to 1/10 per year) but this will get better after the current upgrades: increasing the horizon with a factor 10 will increase the reachable volume (and thus detection rate) by a factor of 1000.
Reminded me of this great commercial from a Dutch campaign that warns children of the dangers of webcams. Guy is camming with some hot girl on the internet and is then called for dinner. Guess who he was camming with... (worksafe)
True, but as your article describes, this is a quadratic effect which only works at high amplitudes. This is usually achieved by focussing the microwaves in mid-air using a phased array. Using two divergent sources as the OP suggested is not going to do the trick.
As your parent says, the combination of two high frequencies only causes amplitude modulation. The beat frequency is observed by your brain. This still requires that both individual frequencies are observed by your ear, which would not work for the old guy. You need a nonlinear element to actually generate the difference frequency (e.g. a diode in an AM-radio receiver).
Well at least one married couple has flown on the space shuttle. If an experiment was ever performed they would be the prime candidates, so go ask them.
I also heard a story of a pair on a shuttle having a relation and getting married shortly after the flight. Apparently NASA wasn't told before and was not happy. (Might have been the same couple.) And of course the rumours that some Russkies sacrificed themselves for science. I can't find a reference for both stories unfortunately.
My bank, used to rely on both a password and a 'TAN'-code, which is a number that is usable only once. They would send you a list of say 20 numbers by certified mail and every time you make a transaction you would use one number. The new system uses SMS to send the code. To make a transaction you log in to your account, fill in all the details of the money transfer and press the send button. You then receive a SMS some 15 seconds later, copy the number in your browser and you're done. The good thing is that you can access your account from anywhere, since you are carrying your mobile anyhow.
If a bad guy would somehow crack my password he could only check my account (bad for my privacy, but not the end of the world). To empty my account he would have to get my password, my mobile and its pin-code.
I have been following the Dutch team for some time since I happen to work at the same university. Based on what I've read in the university newspaper and their website some key factors to the success are:
Best grade solar cells: triple junction cells which are normally only used in satellites, efficiency around 25%. Probably only the top 3 cars can afford this.
High efficiency electronics: maximum power point trackers and brushless motors, both with efficiencies over 95%. Most teams use this.
Low weight (less than 200 kg): judging from the pictures the car is a load bearing carbon frame, which is much lighter than a tube frame with a shell as used by most otherteams. Low weight obviously saves energy when going uphill and it is said to save a lot of flat tires.
Aerodynamics: the design was heavily optimized and tested in a windtunnel. With side-wind, for example, the design works a little bit like a sailing boat. One of their advisors is world famous for his designs of glider wings.
Lot of testing and preparation: they did first aid courses, skid courses, test drives on the local race track (the local formula 1 driver did some laps), they have been in Australia for more than a month before the race to test on the road,....
Good facilities/advisors: TUDelft is a technical university with (among others) faculties of aerospace, electrical and mechanical engineering. One of the advisors was former astronout Wubbo Ockels.
A lot of money to pay the things above: they got a huge sponsorship deal with a big local electricity company. Budget per race is probably around 1MEuro. Part of the money comes from the university itself, which has paid back big time in PR value.
Hard work: as I understood the whole team (~11 persons) took a one year brake from their studies.
I agree that 12 hour is too optimistic. Pulling some numbers out of the air (e.g. here) gives not much more than 2 to 6 hours of sun per day effectively, averaged over the whole year and depending on the climate. This probably includes the fact that a fixed panel will only have perpendicular illumination at noon and recieves under an angle the rest of the day. You forgot to multiply with the number of square meters and a normal size garage would easily fit 10 m^2.
Best case is thus 6 hour * 1.2 kW/m^2 * 10 m^2 * 0.15 efficiency = 11 kWh per day. If you would consume this energy in one hour yould thus can run your car with 11kW, or 15 horsepower.
The nice thing about this telescope is that the whole design is aimed at keeping it cheap. To start with it is almost a direct copy of the Hobby-Eberly telescope, so go there if SALT is slashdotted. Reusing a design of course saves a lot and there will not be a lot of redundant science since HET is located at the northern hemisphere and SALT at the southern. The project has a lot of international partners, but obviously the South African astronomy community is the big winner here.
Then the design of the telescope, this is very uncommon to keep costs down: First of all the telescope cannot cover the whole sky, it has a fixed elevation (something like 40 degrees?) and can only rotate around its vertical axis. This saves of course a lot of mechanics and has as an added benefit that the structure will have a constant sagging due to gravity. The cost you pay is of course a limited view of the sky, but there is plenty to see in the part that is visible.
The second innovation is that the shape of the mirror is not parabolic, as in most telescopes, but spherical. This has two benefits: first, all the mirror segments can be produced with the same curvature, which is cheaper than custom segments as for Keck. Secondly, you can change the elevation of your telescope (over a limited range) without moving the main mirror by rotating the rest of the optics from a point in the center of the sphere (this is possible because of spherical symmetry of the mirror). The downside of the spherical optics is that the optical aberations of the system are more severe than for a parabolic mirror, so you need to add some extra optics to compensate. This is no big problem since HET and SALT are not built for making nice pictures, but primarily for spectroscopy, for which a big light collecting area is more important than the best possible imaging system.
Good for cutting back in the number of lincences
on
OpenOffice Goes LGPL
·
· Score: 1
I think cutting back the number of licenses is a good thing to clean up the mess that you see at opensource.org: they list more than 50 licenses, some of which might not be mutually compatible due to some minor details. Why not go for the creative commons approach: have a very limited set of licences, with mightbe some optional clauses that can be used on a case by case basis.
If there are only 4 or 5 licenses it also becomes much easier to assure compatibility (only in the direction from less restricted to more restricted, not the other way around). Something like Public Domain -> Attribute only (MIT style?) -> Link only (LGPL?) -> totally copyleft (GPL).
Not really my idea, heard it some time ago here on/.
I am in optics too, but all the wave mechanics you learn there are equily valid in acoustics. I didn't read the acoustic laser article well enough to see how it operates, but I think it wouldn't be impossible to generate some acoustic oscillator by plain old pneumatics. Not really quantum stuff, but you can amplify.
As for coherence length: this depends a lot on the scale of the wavelength. Roughly speaking the coherence length is the length over which a wave train is coherent with itself. If the oscillator is stable to one part in a million you would have to shift over a million wavelengths before you could see the wave deviating significantly from the nominal case. In optics your laser should be stable to 1 part in 10^9 to reach a coherence length of a meter, since the wavelength is roughly a micrometer. In acoustics however, the wavelength is on the order of a meter, so you would only need a source that is stable to one part in you 10^3 to reach a coherence length of a kilometer! Easy...
What might be the problem is the turbulent air, which probably acts like a scatter plate in optics. What about adaptive acoustics (phased array of loudspeakers with a tuned phase delays for each speaker)??
Slashdot Mirror
None of your 'facts' is a direct proof that a controlled demolition took place. These reports could easily be explained by the much simpler scenario: 1) The fire is indeed making the building unstable. 2) Firefighters hear the building making sounds and don't trust it. 3) They evacuate everyone with the warning that the building might collapse soon. 4) Two reporters (out of several thousand), based on hearsay, make a wrong statement on a hectic day and misreport an imminent collapse as a imminent demolition.
1 is made plausible by hard core science, see the NIST report. 2 and 3 are in the public record. 4 is not proven, but some erroneous reporting on a day like that seems entirely possible to me. Do me a favor and list the steps and their probabilities needed in your scenario. I would be glad to discuss Occam's razor with you after that.
If you start trolling here, at least get your math, your numbers and your units right. First of all, both the report and wikipedia state the height of the building as 610 feet. Second, the gravitational acceleration g (not 'gravity') is given in feet per second *squared*. Last, the formula to calculate the time it takes a distance under constant acceleration is t = sqrt(2*x/a) and not whatever you are using. And real man use SI units.
According to statements issued by Silverstein Properties, "In the afternoon of Sept. 11, Mr Silverstein spoke to the Fire Department Commander on the site at WTC7. The commander told Silverstein that there were several firefighters in the building working to contain the fires. Silverstein expressed his view that the most important thing was to protect the safety of those firefighters, including, if necessary, to have them withdraw from the building." "With respect to Silverstein's statement, when recounting these events for a television documentary, that 'I said, you know, we've had such terrible loss of life. Maybe the smartest thing to do is to pull it.' (a Silverstein Properties spokesman) has said that by 'it,' Silverstein meant the contingent of firefighters remaining in the building.
No need to resort to conspiracies to explain that comment ...
more whitewashing, make sure you never watch the actual footage of that building coming down either, looks pretty symmetrical to me
Sorry to feed the troll, but just for the record: the claim about asymmetry refers to the layout of the floor beams, which is asymmetric around some beams due to the trapeziodal shape of the building.
Crackpot theories can be discussed elsewhere; please limit the discussion to the science here.
What site is this, and what has it done with Slashdot
Well, for sure Digg is one of the places where this is happening, some idiots over there get +100 for the most ridiculous comments. What this has done to Slashdot? I hope they drew away some of the trolls from here...
Before anyone is going to post the story about Bill Gates and the director of GM about cars crashing 3 times a day: it never happened...
True, but only if you know were you are pointing (they do this with satellites). If ET does not know where we are, and just randomly points his laser in the sky, the detection chance drops enormously, I guess the two effects cancel each other in the detection probability. Also note that any light you sent will might be lost in the background radiation of the star or the planet (I don't know if this is better or worse with radio).
I wonder if similar detection rates have been calculated for SETI (e.g., assume ET having a transmitter of 1 MW, at what distance would you still detect anything? And how many life supporting planets are in that range? ) This will depend a lot on the parameters in your Drake's equations, but they should at least give some order of magnitudes. I remember reading some skeptic article several years ago, which claimed that even with optimistic estimates, the chance of detecting anything would be absolutely zero.
Until that time, I rather waste my computer cycles on the LIGO data (Einstein at home) or one of the various medical applications (e.g. Folding at home), which produce scientific results today.
Apparently, NASA has already issued a statement denying this rumor. I couldn't find a press release on NASA's own website, though.
Consider someone connecting a stolen laptop to a corporate network. Just because your laptop was stolen doesn't mean you have a right to examining the internal topography of that corporate network, and sending the information to a third party. I'm amazed that the authors of this software are stupid enough to do so!
So according to your logic, if I have a machine at my office that (for some good reason) sends a scan of the local network to HQ, reboots random local machines and sends goatse pictures to the local printer, then if someone steals this machine and plugs it into his network, they have the right to complain??
There was a very nice article in American Scientist, which suggested that instead of defining this number of atoms, you could define the constant of Avogadro instead. Since this is linked to the gram via the weight of a carbon atom, this definition is equivalent. Since you are free to pick any number within the error bars of the current definition, they suggest to pick a nice number instead, just like the speed of light was defined as an integer. Their funny requirement was that it should be a perfect cube, since this would define one mole as a cube with an integer number of atoms on its side. This leaves essentially only one number: define N_A as the third power of 84.446.888!
The rate I heard was once every 30 years. This is the kind of explosion that LIGO and others are waiting for, since this would be a pretty easy target for observing gravitational waves. This one was at 28k lightyear or about 8 kiloparsec. LIGO has been running last year with a 'detection horizon' of about 15 Megaparsec, so this one was really at spitting distance. This is the reason why the gravitational wave community does an effort to keep at least one interferometer running at all times by scheduling the planned downtime. Even the less sensitive GEO could hear something if it blows up in our galaxy. They didn't observe anything so far (they estimate a chance of 1/100 to 1/10 per year) but this will get better after the current upgrades: increasing the horizon with a factor 10 will increase the reachable volume (and thus detection rate) by a factor of 1000.
Reminded me of this great commercial from a Dutch campaign that warns children of the dangers of webcams. Guy is camming with some hot girl on the internet and is then called for dinner. Guess who he was camming with ... (worksafe)
True, but as your article describes, this is a quadratic effect which only works at high amplitudes. This is usually achieved by focussing the microwaves in mid-air using a phased array. Using two divergent sources as the OP suggested is not going to do the trick.
As your parent says, the combination of two high frequencies only causes amplitude modulation. The beat frequency is observed by your brain. This still requires that both individual frequencies are observed by your ear, which would not work for the old guy. You need a nonlinear element to actually generate the difference frequency (e.g. a diode in an AM-radio receiver).
Wife to Einstein:
Imagine that we would have kids together: they might be as smart as you and as pretty as me.
Einstein to wife:
But what if they would be as ugly as me and as stupid as you?
I also heard a story of a pair on a shuttle having a relation and getting married shortly after the flight. Apparently NASA wasn't told before and was not happy. (Might have been the same couple.) And of course the rumours that some Russkies sacrificed themselves for science. I can't find a reference for both stories unfortunately.
If a bad guy would somehow crack my password he could only check my account (bad for my privacy, but not the end of the world). To empty my account he would have to get my password, my mobile and its pin-code.
Best case is thus 6 hour * 1.2 kW/m^2 * 10 m^2 * 0.15 efficiency = 11 kWh per day. If you would consume this energy in one hour yould thus can run your car with 11kW, or 15 horsepower.
Microsoft has stopped working on IE7 and has its PhD's working full-time on writing exploits for known holes...
mister 'ik zou eigenlijk druk moeten zijn met mijn proefschrift' absolute afstandsmetrology mazzel, B
Then the design of the telescope, this is very uncommon to keep costs down: First of all the telescope cannot cover the whole sky, it has a fixed elevation (something like 40 degrees?) and can only rotate around its vertical axis. This saves of course a lot of mechanics and has as an added benefit that the structure will have a constant sagging due to gravity. The cost you pay is of course a limited view of the sky, but there is plenty to see in the part that is visible.
The second innovation is that the shape of the mirror is not parabolic, as in most telescopes, but spherical. This has two benefits: first, all the mirror segments can be produced with the same curvature, which is cheaper than custom segments as for Keck. Secondly, you can change the elevation of your telescope (over a limited range) without moving the main mirror by rotating the rest of the optics from a point in the center of the sphere (this is possible because of spherical symmetry of the mirror). The downside of the spherical optics is that the optical aberations of the system are more severe than for a parabolic mirror, so you need to add some extra optics to compensate. This is no big problem since HET and SALT are not built for making nice pictures, but primarily for spectroscopy, for which a big light collecting area is more important than the best possible imaging system.
If there are only 4 or 5 licenses it also becomes much easier to assure compatibility (only in the direction from less restricted to more restricted, not the other way around). Something like Public Domain -> Attribute only (MIT style?) -> Link only (LGPL?) -> totally copyleft (GPL).
Not really my idea, heard it some time ago here on /.
As for coherence length: this depends a lot on the scale of the wavelength. Roughly speaking the coherence length is the length over which a wave train is coherent with itself. If the oscillator is stable to one part in a million you would have to shift over a million wavelengths before you could see the wave deviating significantly from the nominal case. In optics your laser should be stable to 1 part in 10^9 to reach a coherence length of a meter, since the wavelength is roughly a micrometer. In acoustics however, the wavelength is on the order of a meter, so you would only need a source that is stable to one part in you 10^3 to reach a coherence length of a kilometer! Easy...
What might be the problem is the turbulent air, which probably acts like a scatter plate in optics. What about adaptive acoustics (phased array of loudspeakers with a tuned phase delays for each speaker)??