What is the basis for these new announcements? What do we know now that we didn't several days ago?
I can see an advance from "it looks very much like a 777 flaperon" to "we've inspected it closely and it absolutely is a 777 flaperon". Is that all that there is?
I'd expect such a significant piece to have a serial number and/or quality inspection stamps that could be traced back to a specific part installed into a known plane - but I've not heard anything about such a trace back.
You can use high powered lasers in short pulses to compress and heat a fuel pellet to achieve fusion. A particular approach called fast ignition requires a petawatt pulse. Given that the laser is named LFEX for "Laser for Fast Ignition Experiments", it is a good bet this is what it is for.
(My expertise in this is limited to having had an inkling which Wikipedia article to look in for the answer. Further input from real experts is welcome.)
If you've ever played with a normal monochrome laser in a dark room, you'll have seen how laser illumination makes things look speckly. Illuminating with this "white" laser will make superimposed speckly in three colours, with the locations of the speckles not coinciding, so it would be iridescent speckly.
Ohm's law: V=IR => I = V/R Power dissipated in a resister: P=VI Substituting for I from Ohm's law: P=V^2/R So for a fixed voltage, you dissipate more energy with a low resistance. This would be what you're remembering from electronics. For example if you attempt to short high tension power lines with a dry kite string, the effect will be unimpressive. On the other hand if you short them with a solid copper bar, expect to be rained with molten copper.
However it is not the case that you're going to take a circuit and replace a Si device with a GaN device and leave everything else (including the voltage) unchanged. You design your circuit to provide voltages appropriate to the components it contains. If you need a certain current to make a device work, and can adjust the voltage to provide that current, then instead you get P=I^2R, and lowering R lowers the power dissipation.
What really keeps police busy is high school chemistry lessons. You know the one where you dissolve crystals in water, put in some electrodes and run a current through? That will get you charged with assault and battery.
It will take a demonstration satellite accelerating through space before the physics community goes into party mode. Until you're in free fall and vacuum, there is too much scope for systematic errors to accept a result of this level of importance.
When LHC were looking for the Higgs boson - a particle entirely expected by modern physics - they required a five sigma signal before they were satisfied that they had really found something.
This is a result not only entirely unexpected, but contradictory to almost all known physics. A two sigma (NASA) and three sigma (Germany) signal is not remotely enough to be convincing. At best it is convincing enough for someone to spend the money to further and better test it.
People are so sceptical of this one because if true the implications are universe-shaking. It would completely overturn not just modern physics but all of physics since Newton. The claim is that the device violates conservation of momentum. Then via Noether's theorem this implies that the laws of physics are not independent of location in space. (Alternatively, the device is creating a beam of hard to detect particles via some completely unknown but low energy mechanism.)
Also, the device was first designed using a provably incorrect analysis - an analysis using standard physics determined that the device would produce thrust without reaction mass, violating conservation of momentum. As all the standard physics used in the analysis conserves momentum, the analysis must be incorrect. If someone adds up many even numbers and comes up with an odd total, we know they have made a mistake, even without examining their calculations to find out where. This case is exactly analogous. So if this device really does violate momentum conservation, it is a complete and utter fluke, and not by design.
So visitors to his website: * Must have been sequenced by 23andMe * And be so interested in his website that they are willing to give him access to their genetic data * And meet whatever genetic filter he has imposed.
At this point, what he is running is less of a 'website', more of a 'diary', as it will have only one reader.
Water on the moon is a non-renewable resource. The rest of the world is likely to say "Hey, that belongs to all of us, not just to the nation who first has the technology to extract it."
The article says "Although NASA paid for the $100,000 report it is unlikely to immediately embrace its conclusions." $100,000 is perhaps half an engineer-year of analysis. It may be a good start, but I'd want to be a whole lot more thorough before deciding how to spend tens of billions of dollars.
A launch site at latitude L can launch into an orbit of inclination L *or higher*. You can launch into a polar orbit from anywhere on the planet. You can only launch into an equatorial orbit from the equator. Equatorial sites have the advantage, not high latitude sites. (Also, the hemisphere doesn't matter. Something launched into low Earth orbit from 45 degrees south will be at 45 degrees north in about 45 minutes time.)
Some technicalities: Yes, you can launch into one orbit then change plane to a lower inclination later - but doing so in LEO is very expensive. (I think the cheapest way to do it is to put yourself into a high eccentricity orbit, do the plane change at max distance from Earth, then recircularize your orbit into LEO.) ('expense' = delta-v.) Launching from latitude L also can't launch into retrograde orbits closer than L to 180 degrees. E.g. from latitude +/- 30 degrees, you can launch directly into orbits with inclination between 30 and 150 degrees. If you specifically want a 45 degree inclination orbit, I don't know whether launching due east from a 45 degree latitude is cheaper or more expensive than launching either NE or SE from an equatorial site. I suspect there is no difference.
Now he says "There was an overpressure event in the upper stage liquid oxygen tank. Data suggests counterintuitive cause." "That's all we can say with confidence right now. Will have more to say following a thorough fault tree analysis." https://twitter.com/elonmusk
OK, on reviewing, the possibly-dragon I saw detached was not the first sign of trouble (which was how I saw it at the time) but actually happened several seconds into the event. I hadn't realized those clouds of vapour were Not Good.
Several minutes into flight, something that looked possibly like the Dragon capsule detached from the rocket and fell behind it. A few seconds later, the rocket disintegrated into fragments. The commentator on the SpaceX stream wasn't very informative (although their coverage was great up to that point, better than NASA's.)
NASA commentary has just confirmed that the vehicle has failed. (SpaceX have stopped streaming.)
As I recall, the first run of LHC was scheduled to run only 6 months out of 12, due to seasonal electricity price differences (although I think they abandoned that to get back on schedule after the catastrophic magnet failure.) Does anyone know if they're really running non-stop for three years, or is there significant down-time that the science reporter didn't know about or glossed over?
The Superconducting Super Collider would, if not cancelled, have had 40TeV collisions about 15-20 years ago. The LHC is using computing resources that are very challenging to supply in 2015, exceeding what would have been achievable for SSC by a factor of perhaps 1000 (15-20 years of Moore's Law.)
Had SSC been completed, would the computing and detector technology have been able to make effective use of the collisions? Was it in fact a correct decision to abandon it at that time? Would the much higher collision energy have reduced the detection/computational load in some way? (E.g. higher signal to noise, leading to needing many fewer collisions.)
The allusion in 451 Bradbury St is obvious to me, so now I'm wondering whether there is some significance to #941A? Have I just had my geek card revoked for not knowing it?
(Most/. readers will be aware that the allusion is to the novel "Farenheit 451" by Ray Bradbury.)
So I'm looking at the lithium price and I see that for $64M I can make a plant/mine which will give me $8M/year profit, and ROI of 12.5%. This looks pretty good. Then I consider than some bright spark might come up with an aluminium based battery technology which would make lithium ion batteries obsolete and could be in production 4 years from now. If this were to happen, in four years I've made back just $32M and now have a worthless mine. Therefore I decide not to invest in lithium production until I can get ROI of 20% because of the risk.
It seems to me that lithium is bound to be either overproduced (if new technology comes along) or underproduced (if new technology does not, but investors are wary of building facilities for fear it might.)
Slashdot Mirror
What is the basis for these new announcements? What do we know now that we didn't several days ago?
I can see an advance from "it looks very much like a 777 flaperon" to "we've inspected it closely and it absolutely is a 777 flaperon". Is that all that there is?
I'd expect such a significant piece to have a serial number and/or quality inspection stamps that could be traced back to a specific part installed into a known plane - but I've not heard anything about such a trace back.
You can use high powered lasers in short pulses to compress and heat a fuel pellet to achieve fusion. A particular approach called fast ignition requires a petawatt pulse. Given that the laser is named LFEX for "Laser for Fast Ignition Experiments", it is a good bet this is what it is for.
(My expertise in this is limited to having had an inkling which Wikipedia article to look in for the answer. Further input from real experts is welcome.)
Not just a projected image, but anything it illuminates (so long as there is little other illumination to mess up the effect.)
If you've ever played with a normal monochrome laser in a dark room, you'll have seen how laser illumination makes things look speckly. Illuminating with this "white" laser will make superimposed speckly in three colours, with the locations of the speckles not coinciding, so it would be iridescent speckly.
Ohm's law: V=IR => I = V/R
Power dissipated in a resister: P=VI
Substituting for I from Ohm's law: P=V^2/R
So for a fixed voltage, you dissipate more energy with a low resistance. This would be what you're remembering from electronics. For example if you attempt to short high tension power lines with a dry kite string, the effect will be unimpressive. On the other hand if you short them with a solid copper bar, expect to be rained with molten copper.
However it is not the case that you're going to take a circuit and replace a Si device with a GaN device and leave everything else (including the voltage) unchanged. You design your circuit to provide voltages appropriate to the components it contains. If you need a certain current to make a device work, and can adjust the voltage to provide that current, then instead you get P=I^2R, and lowering R lowers the power dissipation.
What really keeps police busy is high school chemistry lessons. You know the one where you dissolve crystals in water, put in some electrodes and run a current through? That will get you charged with assault and battery.
It will take a demonstration satellite accelerating through space before the physics community goes into party mode. Until you're in free fall and vacuum, there is too much scope for systematic errors to accept a result of this level of importance.
Looking at this another way:
When LHC were looking for the Higgs boson - a particle entirely expected by modern physics - they required a five sigma signal before they were satisfied that they had really found something.
This is a result not only entirely unexpected, but contradictory to almost all known physics. A two sigma (NASA) and three sigma (Germany) signal is not remotely enough to be convincing. At best it is convincing enough for someone to spend the money to further and better test it.
People are so sceptical of this one because if true the implications are universe-shaking. It would completely overturn not just modern physics but all of physics since Newton. The claim is that the device violates conservation of momentum. Then via Noether's theorem this implies that the laws of physics are not independent of location in space. (Alternatively, the device is creating a beam of hard to detect particles via some completely unknown but low energy mechanism.)
Also, the device was first designed using a provably incorrect analysis - an analysis using standard physics determined that the device would produce thrust without reaction mass, violating conservation of momentum. As all the standard physics used in the analysis conserves momentum, the analysis must be incorrect. If someone adds up many even numbers and comes up with an odd total, we know they have made a mistake, even without examining their calculations to find out where. This case is exactly analogous. So if this device really does violate momentum conservation, it is a complete and utter fluke, and not by design.
So visitors to his website:
* Must have been sequenced by 23andMe
* And be so interested in his website that they are willing to give him access to their genetic data
* And meet whatever genetic filter he has imposed.
At this point, what he is running is less of a 'website', more of a 'diary', as it will have only one reader.
Water on the moon is a non-renewable resource. The rest of the world is likely to say "Hey, that belongs to all of us, not just to the nation who first has the technology to extract it."
The article says "Although NASA paid for the $100,000 report it is unlikely to immediately embrace its conclusions." $100,000 is perhaps half an engineer-year of analysis. It may be a good start, but I'd want to be a whole lot more thorough before deciding how to spend tens of billions of dollars.
"a cubic foot of natural gas is about equivalent to four sticks of dynamite."
This seems implausible to me. Using as sources
https://en.wikipedia.org/wiki/...
https://en.wikipedia.org/wiki/...
1 cubic foot of methane -> 28.3 litres -> 18.6g (at 25 C, 1 atmosphere) -> 1.16 mole -> 1.03 MJ combustion energy (at 890 kJ/mol).
4 sticks dynamite -> 0.744 kg -> 3.72MJ (at 5MJ/kg, 186g sticks)
So it is more like a cubic foot of methane = 1 stick of dynamite -- still much more than I expected.
Scanning tunnelling electron microscopes have already solved this problem via piezoelectric crystals.
Still there may be a regime in which the gear system is useful, and it need not have a ratio as high as 11 million to one.
A launch site at latitude L can launch into an orbit of inclination L *or higher*. You can launch into a polar orbit from anywhere on the planet. You can only launch into an equatorial orbit from the equator. Equatorial sites have the advantage, not high latitude sites. (Also, the hemisphere doesn't matter. Something launched into low Earth orbit from 45 degrees south will be at 45 degrees north in about 45 minutes time.)
Some technicalities:
Yes, you can launch into one orbit then change plane to a lower inclination later - but doing so in LEO is very expensive. (I think the cheapest way to do it is to put yourself into a high eccentricity orbit, do the plane change at max distance from Earth, then recircularize your orbit into LEO.) ('expense' = delta-v.)
Launching from latitude L also can't launch into retrograde orbits closer than L to 180 degrees. E.g. from latitude +/- 30 degrees, you can launch directly into orbits with inclination between 30 and 150 degrees.
If you specifically want a 45 degree inclination orbit, I don't know whether launching due east from a 45 degree latitude is cheaper or more expensive than launching either NE or SE from an equatorial site. I suspect there is no difference.
Now he says "There was an overpressure event in the upper stage liquid oxygen tank. Data suggests counterintuitive cause."
"That's all we can say with confidence right now. Will have more to say following a thorough fault tree analysis."
https://twitter.com/elonmusk
OK, on reviewing, the possibly-dragon I saw detached was not the first sign of trouble (which was how I saw it at the time) but actually happened several seconds into the event. I hadn't realized those clouds of vapour were Not Good.
Thanks for the link.
NASA stream says no information will be forthcoming until a press conference at 12:30 at the earliest.
Elon Musk's twitter says "Falcon 9 experienced a problem shortly before first stage shutdown. Will provide more info as soon as we review the data."
NASA says aircraft will soon be allowed into the area where debris will have fallen.
Several minutes into flight, something that looked possibly like the Dragon capsule detached from the rocket and fell behind it. A few seconds later, the rocket disintegrated into fragments. The commentator on the SpaceX stream wasn't very informative (although their coverage was great up to that point, better than NASA's.)
NASA commentary has just confirmed that the vehicle has failed. (SpaceX have stopped streaming.)
As I recall, the first run of LHC was scheduled to run only 6 months out of 12, due to seasonal electricity price differences (although I think they abandoned that to get back on schedule after the catastrophic magnet failure.) Does anyone know if they're really running non-stop for three years, or is there significant down-time that the science reporter didn't know about or glossed over?
Thank you very much for such a complete response.
The Superconducting Super Collider would, if not cancelled, have had 40TeV collisions about 15-20 years ago. The LHC is using computing resources that are very challenging to supply in 2015, exceeding what would have been achievable for SSC by a factor of perhaps 1000 (15-20 years of Moore's Law.)
Had SSC been completed, would the computing and detector technology have been able to make effective use of the collisions? Was it in fact a correct decision to abandon it at that time? Would the much higher collision energy have reduced the detection/computational load in some way? (E.g. higher signal to noise, leading to needing many fewer collisions.)
(Sorry, somebody had to ask.)
The allusion in 451 Bradbury St is obvious to me, so now I'm wondering whether there is some significance to #941A? Have I just had my geek card revoked for not knowing it?
(Most /. readers will be aware that the allusion is to the novel "Farenheit 451" by Ray Bradbury.)
So I'm looking at the lithium price and I see that for $64M I can make a plant/mine which will give me $8M/year profit, and ROI of 12.5%. This looks pretty good. Then I consider than some bright spark might come up with an aluminium based battery technology which would make lithium ion batteries obsolete and could be in production 4 years from now. If this were to happen, in four years I've made back just $32M and now have a worthless mine. Therefore I decide not to invest in lithium production until I can get ROI of 20% because of the risk.
It seems to me that lithium is bound to be either overproduced (if new technology comes along) or underproduced (if new technology does not, but investors are wary of building facilities for fear it might.)