"Prior to the big bang" is almost exactly as meaningful as "North of the North pole". The 3+1 dimensional coordinate system (3 space, 1 time) that can be neatly spplied to events in most regions of the universe fails in the presence of too much energy, as in a black hole, or at the big bang.
I believe that there are tables of special and general relatavistic corrections applied in GPS calculations. Otherwise you get errors in position on the order of 100-200 metres.
So move house or change job. If you take both where you live and where you work as givens then indeed, you have a problem, but both of these things are potentially flexible.
The problem is that to be acceptable, such a shift mustn't change the actual value of the kilogram by more than the current uncertainty in it (about 1 part in 100 million). Hence several efforts underway to try and determine a suitable value for x,xxx,xxx,xxx, in other words to determine Avogadro's number to one part in 100 million.
They want to change the definition of the kilogram from "the platinum-iridium" standard to "a specified number of atoms of a specified isotope".
They want to do it without changing the actual value of the kilogram by more than 1 part in 10^8 (the accuracy to which the current standard is consistent).
To do that, they need to determine the mass of an object and the number of atoms in it to a combined accuracy of better than 1 in 10^8. In principle, once they have done this, they can throw away the object.
One way of viewing this is that they are trying to determine the relation between the dalton (unit of atomic mass) and the kilogram (unit of macroscopic mass).
The original nature article, from which the New Scientist article is drawn makes no mention of life on Europa at all. It reports that the Io and Europa toruses appear to be roughly equally dense, I think, and remarks that either Europa is losing much more mass TO its torus that expected, or Io is losting much more FROM its torus.
See http://lisa.jpl.nasa.gov/. They are planning one -- 5 million kilometer arms, sensitivity to 10^-23 and at much lower
frequencies than LIGO. The instrumentation requiremts for this are pretty scary:
The distance between proof masses on spacecraft separated by five million kilometers will be measured with an accuracy of better than ten picometers to sense the passage of gravitational waves.
Extra bits can improve data movement and a variety of integer operations like xoring one area of memory with another, but (a) this is probably mainly done on the video card and (b) it is usually limited by memory bandwidth, not CPU.
The main point of 64 it CPUs is to address more than 4GB of RAM per process. A few applications will also benefit from 64 bit integer arithmetic.
However, this is a new chip architecture, so how well it performs is interesting independently of the word length
I wonder how exactly they are doing this - what kind of technology can be used to hold two things 4km away at precisely (give or take a few thousandths of the width of a proton) the same relative position all the time.
They don't. They damp out a certain amount of vibration via clever mountings, etc. Then they make sure that all the rest happens at very specific frequencies. You can think of a guitar string. When you jolt a guitar, the string will "sing" at its tuned note. I think the LIGO mirror supports are incredibly precisely tuned.
Now they only look for gravity waves at other frequencies, mainly ones away from where seismic noise mostly is.
Finally, they compare respoonses from two remote detectors and look for "matching" events separated by the speed of light, instead of the speed of seismic waves.
The elevator will not be pure carbon nantubes stretching all the way to orbit. Instead it will be a composite material. Nanotubes embedded in a softer matrix (maybe steel or some kind of resin). The nanotubes basically carry the load, the matrix sticks them together and transfers the load between adjacent nanotubes. Composite materials are pretty well understood. The problem, apparently is to get carbon nanotubes to lie still and point in the same direction while you form the matrix.
Assuming that Castle aren't lying then this goes straight to the hard question of the GPL (and of Copyright law enforcement in general) -- what is a derived work?
They admit that they have a GPL component and offer source. Fine. Then the question: is the product as a whole, a derived work of this component, or are they separate works, distributed together? If the former then Castle are in breach and would need to offer their entire OS under the GPL, the latter they are fine.
This question comes up in other places. For instance is Linux kernel + binary only module a derived work, or are they separate works? This ha snever been tested, but Linus has expressed some opinions.
It seems agreed that Linux kernel + proprietary user mode software (eg a Linux PDA with some proprietary app on it) are separate works, but in the embedded software world, even this becomes murky.
There is a real question here which can only ever be finally resolved by precedent.
a 10Wh battery is a really small capacity. An extra 20 minutes out of that scales up to an extra 100 or so minutes out of a typical medium notebook battery. This is noticeable.
Seriously damaging a space elevator is very difficult. Firstly whatever it's made of has to be pretty damn tough to do the job. It also has to be a redundant multi-strand affair for most of its length to withstand meteorite impacts. I'd expect most explosions, even big ones, to damage the ancillary structures a bit, smoke blacken the elevator cable itself, maybe weaken it a bit, or cut a strand, but not cut the cable. I imagine that would need a number of shaped charges firmly attached to the cable strands . Secondly, the bottom end is under very little tension. To a first approximation, if you cut it at the bottom, it just hangs there. In reality, probably not, but it will not do anything very spectacular. To get a catastrophic Red Mars style collapse, you need to cut it close to geostationary orbit. Crashing a jet into it 40000 ft up, even if it managed to cut the cable would drop 40000 ft of cable onto the base station and leave the remainder of the cable, intact, to very slosly drift away until it was recovered and fixed. This is a significant disaster for the base station, but not a world-shattering catastrophe.
It's not an idea that appeals to me intuitively, but maybe the thing to do is back off from manned flight for a decade or so. This frees up a huge amount of money for unmanned projects, in orbit, on the moon, on Mars and beyond. Those projects will need launchers, and it would not be hard to nudge things a little so that some of the projects needed largish launchers and some needed reentry vehicles for relatively fragile and large cargo.
With a much bigger market and modest encouragement, new launchers will be developed that are cheaper, more reliable, easier to manage and so on. They might be wholly or partly reusable, they might not. They might use exciting new technologies, they might just refine existing ones.
Once this has happened we can pick the most reliable, proven heavy-lift and reentry systems and essentially put a passenger capsule inside them. The vehicle would already have a track record before we put people in it. Then we can go back into space in a saner fashion.
Given this blueprint for the next 20-30 years (and a lot of exciting science and commercial activity from the unmanned space program) a moderate amount of money could also go into a longer-term research program developing new concepts and materials for the 30-100 year timescale.
If you read the article, the Cadmium selenide layer is a grid of 3nm^3 crystals. Even if it were a solid 3nm layer of metallic cadmium, that could still be only a few micrograms per square meter of display. I don't think it's THAT toxic is it?
Boron 10 captures a neutron and immediately fissions giving two energetic, but heay fragments, which dump their energy within a few microns of the capturs (usually in the same cell), typically killing the cell.
I think we can safely assume it will be their own very special system. The article says:
Tailoring Linux to run on these upcoming machines will require substantial research, according to IBM. The company has, for instance, created a technique where only select processors can access the full hardware resources of the machines. IBM is also looking at ways to reduce interference between different tasks.
Hopefully the fruits of this will feed through into the mainline kernel and so to other systems.
> So it might be secure, but you'd end up paying > for it in speed.
Absolutely right. From what we found out, you may need to send thousands of photons for every bit of shared secret you want.
Of course, at a small cost in security, you could use the shared secret as a session key for your favourite stream cipher, and change keys every time you manage to send enough extra bits over the quantum channel. using AES with (say) a 256 bit key and changing keys every millisecond or so should defeat all but really determined attackers.
You can also leave the quantum channel runnign all the time to build up a stock of one-time-pad for when you need it.
I had a student do a project on this. You can live with quite high levels of photon loss.
Essentially, the process runs:
send a large number of (more-or-less) single photon pulses, carrying random data
recipient reports over an open channel, which pulses they got and some more technical information.
From this, sender and recipient can work out the subset of the random data that they take into the next step.
Now they (openly) exchange some checksums and things to determine the rate of bits which appear to have changed in transit, either due to eavesdropping, or noise and to get a common bitstring. From this, they can work out how to combine the bits of the bitstring to get a shorter bitstring which (with high probability) no eavesdropper can guess any part of.
Finally, they use this common secret bitstring as a key for a one-time pad.
Simulations suggest that even 99.9% photon loss is not fatal.
The two points here -- the cold surface temperature and the 100+ miles of ice, kind of counteract one another.
The surface of Pluto is certain ly inhospitable, very cold (air is actually a SOLID at this point) and with little atmosphere in summer and next to none in winter.
On the other hand, under 100+ miles of ice, and heated from below by radioactive decay, there might be a liquid water layer. This MIGHT be relatively hospitable to life, using energy coming up from below in vaguely the way that the life at deep sea vents does on Earth.
Inaccessible, I will give you. First it's a long way away, and second you have to tunnel down through a lot of very cold, very hard ice to get to it.
Does it really work on a small screen? I watched the films many times in the Arts Cinema in Cambridge (UK) and once on TV and I really missed the big screen and surround sound.
There was always something of a reunion atmosphere when they showed these films in Cambridge. They used to show it at 2pm and 11pm on a Tuesday and again the following Thursday about twice a year, and I used to try to get to both the 11pm showings. As far as I could see, so did most of the rest of audience, you always saw the same faces coming out both nights. I think about half of them also went to the 2pm performances, but sadly, I had work to do.
For graphics, the original PC has 80x25x256 characters. This is actually just 2KB graphics RAM and a 2MB card seems a bit feeble. Maybe something capable of displaying recognisable text in 800x250?
Slashdot Mirror
I believe that there are tables of special and general relatavistic corrections applied in GPS calculations. Otherwise you get errors in position on the order of 100-200 metres.
So move house or change job. If you take both where you live and where you work as givens then indeed, you have a problem, but both of these things are potentially flexible.
The problem is that to be acceptable, such a shift mustn't change the actual value of the kilogram by more than the current uncertainty in it (about 1 part in 100 million). Hence several efforts underway to try and determine a suitable value for x,xxx,xxx,xxx, in other words to determine Avogadro's number to one part in 100 million.
They want to change the definition of the kilogram from "the platinum-iridium" standard to "a specified number of atoms of a specified isotope".
They want to do it without changing the actual value of the kilogram by more
than 1 part in 10^8 (the accuracy to which the current standard is consistent).
To do that, they need to determine the mass of an object and the number of atoms in it to a combined accuracy of better than 1 in 10^8. In principle, once they have done this, they can throw away the object.
One way of viewing this is that they are trying to determine the relation between the dalton (unit of atomic mass) and the kilogram (unit of macroscopic mass).
The original nature article, from which the New Scientist article is drawn makes no mention of life on Europa at all. It reports that the Io and Europa toruses appear to be roughly equally dense, I think, and remarks that either Europa is losing much more mass TO its torus that expected, or Io is losting much more FROM its torus.
That's all. The rest is journalistic hype.
See http://lisa.jpl.nasa.gov/. They are planning one -- 5 million kilometer arms, sensitivity to 10^-23 and at much lower frequencies than LIGO. The instrumentation requiremts for this are pretty scary: The distance between proof masses on spacecraft separated by five million kilometers will be measured with an accuracy of better than ten picometers to sense the passage of gravitational waves.
Not a great deal is the quick answer.
Extra bits can improve data movement and a variety of integer operations like xoring one area of memory with another, but (a) this is probably mainly done on the video card and (b) it is usually limited by memory bandwidth, not CPU.
The main point of 64 it CPUs is to address more than 4GB of RAM per process. A few applications will also benefit from 64 bit integer arithmetic.
However, this is a new chip architecture, so how well it performs is interesting independently of the word length
They don't. They damp out a certain amount of vibration via clever mountings, etc.
Then they make sure that all the rest happens at very specific frequencies. You can think of a guitar string. When you jolt a guitar, the string will "sing" at its tuned note. I think the LIGO mirror supports are incredibly precisely tuned.
Now they only look for gravity waves at other frequencies, mainly ones away from where seismic noise mostly is.
Finally, they compare respoonses from two remote detectors and look for "matching" events separated by the speed of light, instead of the speed of seismic waves.
The elevator will not be pure carbon nantubes stretching all the way to orbit. Instead it will be a composite material. Nanotubes embedded in a softer matrix (maybe steel or some kind of resin). The nanotubes basically carry the load, the matrix sticks them together and transfers the load between adjacent nanotubes. Composite materials are pretty well understood. The problem, apparently is to get carbon nanotubes to lie still and point in the same direction while you form the matrix.
What you say seems sensible enough, but I'm not sure it's the law.
Assuming that Castle aren't lying then this goes straight to the hard question of the GPL (and of Copyright law enforcement in general) -- what is a derived work?
They admit that they have a GPL component and offer source. Fine. Then the question: is the product as a whole, a derived work of this component, or are they separate works, distributed together? If the former then Castle are in breach and would need to offer their entire OS under the GPL, the latter they are fine.
This question comes up in other places. For instance is Linux kernel + binary only module a derived work, or are they separate works? This ha snever been tested, but Linus has expressed some opinions.
It seems agreed that Linux kernel + proprietary user mode software (eg a Linux PDA with some proprietary app on it) are separate works, but in the embedded software world, even this becomes murky.
There is a real question here which can only ever be finally resolved by precedent.
a 10Wh battery is a really small capacity. An extra 20 minutes out of that scales up to an extra 100 or so minutes out of a typical medium notebook battery. This is noticeable.
Seriously damaging a space elevator is very difficult. Firstly whatever it's made of has to be pretty damn tough to do the job. It also has to be a redundant multi-strand affair for most of its length to withstand meteorite impacts. I'd expect most explosions, even big ones, to damage the ancillary structures a bit, smoke blacken the elevator cable itself, maybe weaken it a bit, or cut a strand, but not cut the cable. I imagine that would need a number of shaped charges firmly attached to the cable strands
.
Secondly, the bottom end is under very little tension. To a first approximation, if you cut it at the bottom, it just hangs there. In reality, probably not, but it will not do anything very spectacular. To get a catastrophic Red Mars style collapse, you need to cut it close to geostationary orbit. Crashing a jet into it 40000 ft up, even if it managed to cut the cable would drop 40000 ft of cable onto the base station and leave the remainder of the cable, intact, to very slosly drift away until it was recovered and fixed. This is a significant disaster for the base station, but not a world-shattering catastrophe.
It's not an idea that appeals to me intuitively, but maybe the thing to do is back off from manned flight for a decade or so. This frees up a huge amount of money for unmanned projects, in orbit, on the moon, on Mars and beyond. Those projects will need launchers, and it would not be hard to nudge things a little so that some of the projects needed largish launchers and some needed reentry vehicles for relatively fragile and large cargo.
With a much bigger market and modest encouragement, new launchers will be developed that are cheaper, more reliable, easier to manage and so on. They might be wholly or partly reusable, they might not. They might use exciting new technologies, they might just refine existing ones.
Once this has happened we can pick the most reliable, proven heavy-lift and reentry systems and essentially put a passenger capsule inside them. The vehicle would already have a track record before we put people in it. Then we can go back into space in a saner fashion.
Given this blueprint for the next 20-30 years (and a lot of exciting science and commercial activity from the unmanned space program) a moderate amount of money could also go into a longer-term research program developing new concepts and materials for the 30-100 year timescale.
Steve
If you read the article, the Cadmium selenide layer is a grid of 3nm^3 crystals. Even if it were a solid 3nm layer of metallic cadmium, that could still be only a few micrograms per square meter of display. I don't think it's THAT toxic is it?
10B + n -> 4He + 7Li + gamma
Boron 10 captures a neutron and immediately fissions giving two energetic, but heay fragments, which dump their energy within a few microns of the capturs (usually in the same cell), typically killing the cell.
There's A nice presentation[ibm.com] that describes the system quite well.
Hopefully the fruits of this will feed through into the mainline kernel and so to other systems.
> So it might be secure, but you'd end up paying
> for it in speed.
Absolutely right. From what we found out, you may need to send thousands of photons for every bit of shared secret you want.
Of course, at a small cost in security, you could use the shared secret as a session key for your favourite stream cipher, and change keys every time you manage to send enough extra bits over the quantum channel. using AES with (say) a 256 bit key and changing keys every millisecond or so should defeat all but really determined attackers.
You can also leave the quantum channel runnign all the time to build up a stock of one-time-pad for when you need it.
I had a student do a project on this. You can live with quite high levels of photon loss.
Essentially, the process runs:
send a large number of (more-or-less) single photon pulses, carrying random data
recipient reports over an open channel, which pulses they got and some more technical information.
From this, sender and recipient can work out the subset of the random data that they take into the next step.
Now they (openly) exchange some checksums and things to determine the rate of bits which appear to have changed in transit, either due to eavesdropping, or noise and to get a common bitstring. From this, they can work out how to combine the bits of the bitstring to get a shorter bitstring which (with high probability) no eavesdropper can guess any part of.
Finally, they use this common secret bitstring as a key for a one-time pad.
Simulations suggest that even 99.9% photon loss is not fatal.
The two points here -- the cold surface temperature and the 100+ miles of ice, kind of counteract one another.
The surface of Pluto is certain ly inhospitable, very cold (air is actually a SOLID at this point) and with little atmosphere in summer and next to none in winter.
On the other hand, under 100+ miles of ice, and heated from below by radioactive decay, there might be a liquid water layer. This MIGHT be
relatively hospitable to life, using energy coming up from below in vaguely the way that the life at deep sea vents does on Earth.
Inaccessible, I will give you. First it's a long way away, and second you have to tunnel down through a lot of very cold, very hard ice to get to it.
Does it really work on a small screen? I watched the films many times in the Arts Cinema in Cambridge (UK) and once on TV and I really missed the big screen and surround sound.
There was always something of a reunion atmosphere when they showed these films in Cambridge. They used to show it at 2pm and 11pm on a Tuesday and again the following Thursday about twice a year, and I used to try to get to both the 11pm showings. As far as I could see, so did most of the rest of audience, you always saw the same faces coming out both nights. I think about half of them also went to the 2pm performances, but sadly, I had work to do.
Also one or two 180MB floppy drives (Zip).
For graphics, the original PC has 80x25x256 characters. This is actually just 2KB graphics RAM and a 2MB card seems a bit feeble. Maybe something capable of displaying recognisable text in 800x250?
Read the article:
Gallileo did do experiments rolling cannonballs down inclined planes, which are what is being rated.
Young did get interference fringes by putting a small obstacle in the path of a light-beam.