My understanding, based on talking to clock people who were brought to CERN after publication, is that there was no clock person on the original paper. They had access to some clock people at CERN, who helped set up the GPS measurements, but no clock person invested in the results.
If so, then CERN / OPERA does deserve the bad press they are getting. They should have brought in some experts prior to publication.
Absolute clock synchronization at the nanosecond level is notoriously tricky. (I have professional experience here.) It seems like mere bookkeeping, but there is typically (as in this case) no direct way to check whether or not you have gotten it right. It is also confused with clock syntonization (finding the rate difference between clocks), which is easier and is what most "clock sync" is actually used for. (Clock syntonization is easier as you can calculate the expected clock rate differences as a check, and also as many clock sync errors don't have significant long-term rates.)
I really don't see why this is surprising. Hasn't there been a long history of failed attempts to mechanize the reduction of lots of data into hypotheses ? Don't these generally run into a combinatorial explosion of possible hypotheses, which seems like a requirement for a NP hard problem ? As the Wikipedia article says the most notable characteristic of NP-complete problems is that no fast solution to them is known, which seems to apply here,
Both Astrolabe and (especially) their counsel were incompetent here. Counsel never even served Eggert and Olson after filing a complaint September 30th. IANAL, but I think that they had to do that by January, and I assume that that had something to do with the EFFs statement January 12th :
"Today, we’re taking the battle to Astrolabe, and starting the process for seeking sanctions under Rule 11 of the Federal Rules of Civil Procedure.Rule 11 requires litigants to conduct a reasonable inquiry into the facts and law before filing any paper with the court. Obviously, that didn’t happen here. Astrolabe now has 21 days to withdraw its Complaint. If it doesn’t do so, the Rule 11 “safe harbor” expires and we’re free to ask the court for sanctions.
Jan 12 + 21 days is Thursday, February 2nd. I imagine that Astrolabe and their counsel dropped the suit to avoid these sanctions.
60 nanoseconds is a huge cable error, equivalent to about 10 meters of cable. It is possible that there was some internal reflection in the loose cable which caused such a big error, but I suspect that the real problem was the system latched onto the trailing edge of the 1 pps timing signal - this is more likely to happen when something (like a bad cable) is screwing up the timing pulse, and it can cause a considerable excess delay (order 100 nanoseconds or more). In many systems the width of the 1 pps pulse is not controlled, and so it will vary. This leads to the common symptom of this problem - the timing becomes erratic at the nanosecond level.
If something like this was the cause of their error then they deserve the bad PR they will get, as they really should have included a timing professional as part of the experiment (as opposed to a consultant role). I have had several discussions with timing professionals about this, and each time the trailing edge issue has come up.
it's a strength to weight ratio issue isn't it? What's stronger...
Steel... again with only it's own weight to support probably wouldn't go more then a mile. Lets say optimistically that this special nano molecular cable can reach 20 miles before snapping under it's own weight...
Those numbers are more like 30 km (for steel) and 5000 km (projected for Carbon Nanotubes)
The atmosphere isn't a magic burn up place. At the speeds they will be falling, there won't be any signigicant 'burn up'. Meterao are travelling thousands of miles an hour. It will be STATIONARY*, unlike satellites, space stations, and space shuuttles that revolve around the earth at a high rate of speed.
Have you ever numerically integrated a space elevator ? I have.
If you drop something from, say, 6000 km altitude, it will impact the Earth ~ 2000 seconds later at over 7 km / sec. That is plenty fast enough to burn up.
Above about 23, 000 km altitude, released material would not hit the Earth at all, but below that, it will and if it is released (or broken off) at more than about 1000 km, it's going to be coming in fast enough to burn up.
This crucially depends on where the break occurs. A break 1 km from the surface, yes, things just fall down and not much else happens. But...
1.) The cable is not stationary - and neither are you. The Earth is rotating, and so would be any cable (that's what keeps it taut). As it falls, it will stretch out in longitude as it orbits the earth, and the Earth rotates beneath it.
2.) The cable is under considerable tension. Numerical simulations show that full break mid-way up, which of course interrupts that tension, leads to a whipsawing of the two separated ends of the cable, and likely to further breaks (again, unless there are countermeasures).
It would start at 1 g on the Earth, and rapidly decline. The last 1/2 of the trip or so would be in pretty light gravity (0.01 g or less) declining to zero at geostationary altitude.
The prime insight on this that you need to know is that the European Commission is a bunch of mindless jerks who will be the first against the wall when the revolution comes.
It's not who is first against the wall. It's not even who is last against the wall. It's the bits in between I worry about.
No, it's considerably messier than that (assuming no countermeasures). Parts would fall to the ground (or, more likely, burn up in the atmosphere), some would go into Earth orbit, and a good chunk would be thrown out into interplanetary space.
Of course, considering all of that makes it clear that there would be countermeasures.
Could this be it for ACTA? Or is this just intended to defuse protests? Any EU slashdotters have any insight on this ? I could see it going either way.
My personal feeling is that the Internet needs to be treated much like the NRA treats gun control - mess with it, and you are in political trouble.
An important parameter for a space elevator is the "free breaking length" - the length of constant width cable that can support its own weight under 1 g (remember, for any real elevator, the actual force of (gravity + rotation) declines rapidly as you ascend).
A terrestrial space elevator needs a material with a free breaking length of 4,960 kilometers. The free breaking length of steel is about 30 km, nanotubes are expected to have breaking lengths of ~ 5000 km.
Any real elevator cable will be tapered (i.e., the width will increase with altitude), but (very roughly) the amount of the taper (in area) is e^(4960/free breaking length). So, for steel, you need a taper of ~ e^160, so a steel space elevator would have to be thicker than the entire galaxy by the time it reaches geostationary altitude, which is of course ridiculous. To have a chance to make a real elevator, you need a free breaking length of at least 1000 km, which no one has exhibited so far, but which nanotubes can probably provide.
A planet like this is highly likely to be like Venus, with more or less the same temperature everywhere on the surface. Thick atmospheres will do that for you, and this is likely to have almost as high a surface pressure as Venus.
Cool picture, but true water worlds are unlikely to have any true land (i.e., rocks at the surface). What they may have are mats of carbon materials too light to sink. On water worlds with biology, creatures may evolve to form such mats in symbiosis with air breathing animals (i.e., giving them a place to live, in return for goodies like nitrogen fixation from the atmosphere in their excretions), in much the same way as corals (the creatures that build coral reefs) get up to 90% of their nutrients from their symbionts.
Now, that would be a water world Kevin Costner could be proud of.
The climber has to have food, toilets, sleeping facilities if you are going to take a week to get to GSO, so it's going to have to be more like a mini-hotel (or at least a mini-space station) than an elevator car. As it happens, the Japanese have some experience with mini-hotels.
Current Carbon nanotube technology is still far from what's needed for a space elevator and (IMO) the field would benefit from a dramatic infusion of cash. It's not clear from this article whether they are planning to support such research, but (again, IMO) if they are not, then this is just idle day-dreaming.
There would be at least an order of magnitude increase in fiber length, and many orders of magnitude increases in fiber production rates, before a carbon nanotube space elevator would become a viable prospect. This is for a terrestrial elevator, a Lunar elevator could be built with existing fiber technology.
With a density of 2 gm/cc, this is likely to be a true water world - a world where a rocky interior is surrounded by thousands of miles of ice (not "our" ice, but Ice XI, X, VII), probably a few 100 km of hot liquid (kept from boiling by pressure), and then a steam bath. Look at this phase diagram, and remember that you are starting at 500 K or so, and the pressure increases greatly at depth, so going down into the planet means you are probably following a nearly vertical (but tilted to the right) line on the phase diagram.
Oh, and I can't resist commenting that the fully functional Apollo seismological network was shut off to save $ 200,000 per year, and that Senator Proxmire was proud to be responsible for this saving of government waste.
The Moon has shallow (non-tidal) Moonquakes. No one knows much about their causes.
No other solar system body (except, of course, for the Earth) has had any seismological data at all. (One of the Viking landers had a working seismometer; it was totally swamped by wind vibrations; at most it may have detected the grand total of one Marsquake, but that's not clear.)
Geologically, "live" means active and "dead," or "extinct" means inactive (as in a dead or extinct volcano). This terminology has been used for a long time (decades, if not centuries) and is reasonably expressive.
By the way, electrical engineering has live wires, using the same analogy. Best not to touch them.
Slashdot Mirror
My understanding, based on talking to clock people who were brought to CERN after publication, is that there was no clock person on the original paper. They had access to some clock people at CERN, who helped set up the GPS measurements, but no clock person invested in the results.
If so, then CERN / OPERA does deserve the bad press they are getting. They should have brought in some experts prior to publication.
Absolute clock synchronization at the nanosecond level is notoriously tricky. (I have professional experience here.) It seems like mere bookkeeping, but there is typically (as in this case) no direct way to check whether or not you have gotten it right. It is also confused with clock syntonization (finding the rate difference between clocks), which is easier and is what most "clock sync" is actually used for. (Clock syntonization is easier as you can calculate the expected clock rate differences as a check, and also as many clock sync errors don't have significant long-term rates.)
So science is impossible? duh, at least we have a theorem that says it.
Only if you believe our brains are congruent with Turing machines, which (adjusting flame resistant sunglasses) I do not.
I really don't see why this is surprising. Hasn't there been a long history of failed attempts to mechanize the reduction of lots of data into hypotheses ? Don't these generally run into a combinatorial explosion of possible hypotheses, which seems like a requirement for a NP hard problem ? As the Wikipedia article says the most notable characteristic of NP-complete problems is that no fast solution to them is known, which seems to apply here,
Both Astrolabe and (especially) their counsel were incompetent here. Counsel never even served Eggert and Olson after filing a complaint September 30th. IANAL, but I think that they had to do that by January, and I assume that that had something to do with the EFFs statement January 12th :
"Today, we’re taking the battle to Astrolabe, and starting the process for seeking sanctions under Rule 11 of the Federal Rules of Civil Procedure.Rule 11 requires litigants to conduct a reasonable inquiry into the facts and law before filing any paper with the court. Obviously, that didn’t happen here. Astrolabe now has 21 days to withdraw its Complaint. If it doesn’t do so, the Rule 11 “safe harbor” expires and we’re free to ask the court for sanctions.
Jan 12 + 21 days is Thursday, February 2nd. I imagine that Astrolabe and their counsel dropped the suit to avoid these sanctions.
60 nanoseconds is a huge cable error, equivalent to about 10 meters of cable. It is possible that there was some internal reflection in the loose cable which caused such a big error, but I suspect that the real problem was the system latched onto the trailing edge of the 1 pps timing signal - this is more likely to happen when something (like a bad cable) is screwing up the timing pulse, and it can cause a considerable excess delay (order 100 nanoseconds or more). In many systems the width of the 1 pps pulse is not controlled, and so it will vary. This leads to the common symptom of this problem - the timing becomes erratic at the nanosecond level.
If something like this was the cause of their error then they deserve the bad PR they will get, as they really should have included a timing professional as part of the experiment (as opposed to a consultant role). I have had several discussions with timing professionals about this, and each time the trailing edge issue has come up.
it's a strength to weight ratio issue isn't it? What's stronger...
Steel... again with only it's own weight to support probably wouldn't go more then a mile. Lets say optimistically that this special nano molecular cable can reach 20 miles before snapping under it's own weight...
Those numbers are more like 30 km (for steel) and 5000 km (projected for Carbon Nanotubes)
The atmosphere isn't a magic burn up place. At the speeds they will be falling, there won't be any signigicant 'burn up'. Meterao are travelling thousands of miles an hour. It will be STATIONARY*, unlike satellites, space stations, and space shuuttles that revolve around the earth at a high rate of speed.
Have you ever numerically integrated a space elevator ? I have.
If you drop something from, say, 6000 km altitude, it will impact the Earth ~ 2000 seconds later at over 7 km / sec. That is plenty fast enough to burn up.
Above about 23, 000 km altitude, released material would not hit the Earth at all, but below that, it will and if it is released (or broken off) at more than about 1000 km, it's going to be coming in fast enough to burn up.
This crucially depends on where the break occurs. A break 1 km from the surface, yes, things just fall down and not much else happens. But...
1.) The cable is not stationary - and neither are you. The Earth is rotating, and so would be any cable (that's what keeps it taut). As it falls, it will stretch out in longitude as it orbits the earth, and the Earth rotates beneath it.
2.) The cable is under considerable tension. Numerical simulations show that full break mid-way up, which of course interrupts that tension, leads to a whipsawing of the two separated ends of the cable, and likely to further breaks (again, unless there are countermeasures).
No no wants to spend a week in an elevator even if it means you get to go into orbit.
Cargo doesn't care. One of the main attractions of a space elevator is that you can lift very heavy loads into space very cheaply and at little risk.
If you are migrating to Mars, with 6 months in route, what's a week to get to your spaceship ?
I have taken the trans-Siberian, and you do get to get off at stations, at least for a few minutes. But, all in all, it's probably a good analogy.
It would start at 1 g on the Earth, and rapidly decline. The last 1/2 of the trip or so would be in pretty light gravity (0.01 g or less) declining to zero at geostationary altitude.
The prime insight on this that you need to know is that the European Commission is a bunch of mindless jerks who will be the first against the wall when the revolution comes.
It's not who is first against the wall. It's not even who is last against the wall. It's the bits in between I worry about.
No, it's considerably messier than that (assuming no countermeasures). Parts would fall to the ground (or, more likely, burn up in the atmosphere), some would go into Earth orbit, and a good chunk would be thrown out into interplanetary space.
Of course, considering all of that makes it clear that there would be countermeasures.
Could this be it for ACTA? Or is this just intended to defuse protests? Any EU slashdotters have any insight on this ? I could see it going either way.
My personal feeling is that the Internet needs to be treated much like the NRA treats gun control - mess with it, and you are in political trouble.
An important parameter for a space elevator is the "free breaking length" - the length of constant width cable that can support its own weight under 1 g (remember, for any real elevator, the actual force of (gravity + rotation) declines rapidly as you ascend).
A terrestrial space elevator needs a material with a free breaking length of 4,960 kilometers. The free breaking length of steel is about 30 km, nanotubes are expected to have breaking lengths of ~ 5000 km.
Any real elevator cable will be tapered (i.e., the width will increase with altitude), but (very roughly) the amount of the taper (in area) is e^(4960/free breaking length). So, for steel, you need a taper of ~ e^160, so a steel space elevator would have to be thicker than the entire galaxy by the time it reaches geostationary altitude, which is of course ridiculous. To have a chance to make a real elevator, you need a free breaking length of at least 1000 km, which no one has exhibited so far, but which nanotubes can probably provide.
Are there any manufacturers who haven't gone down this path ?
Have Bad Cars Gone Extinct?
Nah, they're just hibernating. Once the car industry settles down again to only 2 to 3 major players, they'll be back.
A planet like this is highly likely to be like Venus, with more or less the same temperature everywhere on the surface. Thick atmospheres will do that for you, and this is likely to have almost as high a surface pressure as Venus.
Cool picture, but true water worlds are unlikely to have any true land (i.e., rocks at the surface). What they may have are mats of carbon materials too light to sink. On water worlds with biology, creatures may evolve to form such mats in symbiosis with air breathing animals (i.e., giving them a place to live, in return for goodies like nitrogen fixation from the atmosphere in their excretions), in much the same way as corals (the creatures that build coral reefs) get up to 90% of their nutrients from their symbionts.
Now, that would be a water world Kevin Costner could be proud of.
The climber has to have food, toilets, sleeping facilities if you are going to take a week to get to GSO, so it's going to have to be more like a mini-hotel (or at least a mini-space station) than an elevator car. As it happens, the Japanese have some experience with mini-hotels.
Current Carbon nanotube technology is still far from what's needed for a space elevator and (IMO) the field would benefit from a dramatic infusion of cash. It's not clear from this article whether they are planning to support such research, but (again, IMO) if they are not, then this is just idle day-dreaming.
There would be at least an order of magnitude increase in fiber length, and many orders of magnitude increases in fiber production rates, before a carbon nanotube space elevator would become a viable prospect. This is for a terrestrial elevator, a Lunar elevator could be built with existing fiber technology.
With a density of 2 gm /cc, this is likely to be a true water world - a world where a rocky interior is surrounded by thousands of miles of ice (not "our" ice, but Ice XI, X, VII), probably a few 100 km of hot liquid (kept from boiling by pressure), and then a steam bath. Look at this phase diagram, and remember that you are starting at 500 K or so, and the pressure increases greatly at depth, so going down into the planet means you are probably following a nearly vertical (but tilted to the right) line on the phase diagram.
Oh, and I can't resist commenting that the fully functional Apollo seismological network was shut off to save $ 200,000 per year, and that Senator Proxmire was proud to be responsible for this saving of government waste.
...the moon has none, as long as we've been observing it.
Don't be so sure.
The Moon has shallow (non-tidal) Moonquakes. No one knows much about their causes.
No other solar system body (except, of course, for the Earth) has had any seismological data at all. (One of the Viking landers had a working seismometer; it was totally swamped by wind vibrations; at most it may have detected the grand total of one Marsquake, but that's not clear.)
Geologically, "live" means active and "dead," or "extinct" means inactive (as in a dead or extinct volcano). This terminology has been used for a long time (decades, if not centuries) and is reasonably expressive.
By the way, electrical engineering has live wires, using the same analogy. Best not to touch them.