We don't really have challenge to laws in court here, except in a few special cases, but if parliament passes a bad law they can be held responsible at the next election.
The research in question is about the exact process on a molecular level. We may know which cells or synapses are affected, but we don't know much if anything about the chemistry of that process. These simulation studies suggest an intriguing possibility
No there really is no absolute present in relativity. We can calculate that this supernova occurred 40 million years ago, simultaneously with some event on Earth, but an alien whose spaceship was flying past Earth 40 million years ago at near light speed and who later sees the light from the supernova would not calculate that those two events were simultaneous. Neither it, nor we, is wrong. Simultaneity depends on how you are moving.
What relativity does, indepdendently of how you are moving, is divide the universe into five parts:
* your past -- events from which you could have received a slower-than-light message by now * your past light cone -- events from which a light-speed signal is just now arriving * your future light cone -- events which might receive a light-speed signal if your send it now * your future -- events which could receive a slower-than-light message from you * the rest
No observer will disagree (except by mistake) about which of these parts any given event is in with respect to you.
The supernova is on our past light cone. In our stationary reference frame it's about 37 million years away, but again, a moving observer would come up with a different number.
Absolutely right I think. A first step is the difference between being in hospital, where the first thing any doctor does is look at the chart at the end of the bed for the history of your temperature, BP, etc. and going into a GP surgery and having a single measurement. We already have wearable 24 hour BP and ECG monitors. Looking ahead 5-10 years, I can imagine anyone who is ill (or pregnant or old) wearing a wristwatch and maybe a few stick-on or swallowed or injected wireless sensors that records their vitals every few minutes. Looking ahead 20-30 years, imagine microscopic sensors in every vital organ, powered by blood sugar and logging and reporting every significant hormone and mineral level, organ by organ to the processors in your personal area network. Going out 50-100 years, you could imagine a monitor nanobot in every cell: tracking hormones, gene expression levels, firing rates if the cell is a neuron, etc., reproducing when the cell reproduces. Start adding control functions, or distributed memory and computing (all vaporized except two teaspoons of the left foot -- not to worry that has a full brain backup in it just a couple of seconds old...) and we're definitely getting post-human.
My understanding is what these guys have is a way to control the electromagnetic environment of the electrons in the surface layer of the copper which is far more flexible than anything that was around before. They can, at least to some extent say "we're interested in the environment of graphene" put the CO molecules on the surface in the right pattern and "bingo" the electrons from the copper act like they were in graphene. Then they can say "we're interested in this environment, which no actual known material achieves" move the CO molecules and study that.
This is a fantastic research tool. At the moment anyway it's not a production method. If they find an interesting electron behaviour they will have to work out a more "conventional" way of getting it for any production device, but it should make the search easier and allow them to refine their theoretical models.
Can we get this tested under more *interesting* conditions than earth?
Can we test plank's constant as we accelerate an object near light speed or subject it to overwhelming gravitational force? How about as we heat or cool it? How about as we take that quanta and accelerate or decelerate it?
Many of these are possible, in a sense, although what you actually test is not Planck's constant but various combinations of it and other constants which eventually give pure dimensionless numbers. The best known of these is alpha which measures the strength of the electromagnetic force.
Limits on values of alpha in extreme conditions (or over long periods of time) can be determined from astronomical observations -- different spectral lines would shift by different amounts if alpha, changed, for instance, so by comparing their relative positions in light from objects in extreme conditions, we learn something. So we observe light from hot gas falling into a black hole, or light from distant galaxies that has been gravitationally lensed by nearer ones, or whatever and see what the spectra look like. It's not easy, but it is possible. These reports are interestingly, about equally sensitive to change over time as measurements on Earth using ultra-stable atomic clocks, where the time periods are much shorter, but the measurements much more accurate.
We also regularly study the properties of particles and atoms moving very close to light-speed indeed in particle accelerators.
So you can never have a government policy that saves a lot of lives (or money) for many people, but unavoidably harms a few? That rules out policing, any form of warfare,....
Essentially when they say "clock" what they mean is "stable oscillator" -- they have a source of (in this case) ultraviolet light whose frequency varies hardly at all. Since this is purely theoretical exercise, they are simply calculating how much stray electric and magnetic fields and other problems would be expected to vary the frequency. To check experimentally, I think they'd need two such sources and then see how the relative phase of the light changes over time (after allowing for relativitistic effects of gravity on the light beam, Earth's rotation and a zillion other things).
Most of the applications on big supercomputers are simulations. In the basic case, each node sits there simulating it's cube of atmosphere, or its bit of the airflow around an aircraft or car design or its bit of a nuclear weapon in a simulated warehouse fire. Every time-step it needs to exchange the state of the borders of it's region with its neighbour nodes. In some other applications, all the nodes are working together to invert a huge matrix or do a massive Fourier transform in several dimensions. These need even more communication.
The demand is genuine, and can't be met by wide-area distributed computing using any algorithms we know.
TDM won't cut it. You might lose crucial milliseconds waiting for your slot.
It's rapidly heading for the point where to trade competitively you need to have your serves within a rack or two of the exchange server in the same datacentre. Before much longer it'll be having your process running on the exchange's server.
Hydrazine is described as corrosive and toxic, both of which will make it expensive to handle, require special pipes and tanks and so on. As far as I know, it's not an environmental consideration -- it surely decays to nitrogen and water pretty fast.
I suspect this is about cost saving in the handling.
If we take it as read from observation that there is only finitely much time before the present (there are theories otherwise, but more or less all of them have a special event of some kind about 13.7 billion years ago), why does this require "something that started everything"? Without a working theory of quantum gravity, we have to accept that the universe has a number of time-space singularities where GR breaks down -- one in every black hole and one at the Big Bang. This tells us that we need a decent theory of quantum gravity, but I don't see that it tells us anything else.
Early life on Earth is still poorly understood, owing to the lack of records, but the smart money seems to be on RNA forming in some kind of primordial soup that was able to duplicate itself from the ingredients in the soup. Once you have that you get a lot of copies of that RNA, and rather less rich soup. The copying is also probably pretty inaccurate, so you get some copies that are better at making copies of themselves from less rich soup, perhaps by doing it more indirectly -- making a protein that helps make more RNA which in turn makes more protein for instance, and so you slowly (and remember this took hundreds of millions of years) bootstrap towards something like a very primitive prokaryotic cell. The jump from RNA to DNA as the basic genome, is a big one, but RNA organisms could have made chunks of DNA for other purposes initially, and then gradually moved more and more of the key functions into the DNA.
Doesn't go nearly far enough. Just getting up through the atmosphere is not really the point. Balloons do that pretty well. The trick is to build a tower so high that it reaches geostationary orbit, so the top of the tower is in orbit, not just in space. That's about 36000 km up.
In a sense. There is a widespread view that we will need 1 Exaflop supercomputers by roughly 2019 or 2020 for a whole range of applications including aircraft design, biochemistry to processing data from new instruments like the square kilometer array. On current trends, such a computer will need gigawatts of power (literally), which amongst other things would force it to be located right next to a large power station that wasn't needed for other purposes. This is felt to be a bit of a problem and this DARPA initiative is just one small part of the effort to tackle this and get the Exaflop machine down to 50MW or so, which is the most that can be routinely supplied by standard infrastructure.
1. The external connectivity -- SATA, USB, ethernet, etc. needs too much power to easily move or handle on a chip (and the radio stuff needs radio power). You can do the protocol work on the main chip if you like, but you'll need amplifiers, and possibly sensors off chip.
2. DRAM and CPUs are made in quite different processes, optimised for different purposes. Cache is memory made using CPU processes (so it's expensive and not very dense). These guys are trying to make CPUs using DRAM processes, which are slow.
The issue is that Western manufacturers need to find a way to be as flexible as the Chinese competition while providing an acceptable lifestyle for their staff. Automation might be a way. If this change had required just one employee to be roused from sleep (or possibly just phoned in his/her office in New Zealand where it's daytime) to reprogram the machines in the factory start fitting glass screens into beveled frames, that would work. More realistically, it would still work if it needed 10 employees or maybe 50. They can be paid enough to compensate for the out-of-hours callout (or telecommute from somewhere where it's in hours).
Of course there are several challenges in this approach: you need the capital investment to build the automated factory; you need the education levels to train your population for a world where half the jobs are sophisticated technical problem-solving jobs; you need a LOT of factories like this to keep your whole population employed; and, for now, you need to compete with countries still developing who have workers willing to work for a few bowls of rice per hour. This last problem will go away in due course.
So you either move the power or move the demand. Moving the power might mean supertankers of liquid hydrogen, or long possibly superconducting cables. Moving the demand is basically a matter of pricing, so that it's more economic to spread energy-intensive activities out rather than concentrate them in cities.
1. Use solar power to make chemical fuel. For instance you could electrolyze water to make hydrogen, and either use the hydrogen directly, or react it with CO2 to make something like methanol.
2. Use satellite mounted lasers to heat a target mounted on the top of the 747, then use that heat to heat air in the engines (this only works for the cruise phase of the journey, you still need some other heat source for takeoff and landing.
Ramscoops, as described in the literature have basically two problems:
1. Getting protons (as opposed to deuterium or something heavier) to fuse at a decent rate requires conditions substantially hotter and denser than found in the cores of even quite large stars. Something more like the conditions met in shockwaves in exploding supernovae. Without this your ramscoop isn't much use.
2. The interstellar medium is very unevenly distributed. The sun is deep inside the bubble created by an ancient supernova, so there's not much to collect.
Something like monopole catalyzed proton decay might work to solve problem 1, if it happens, and if we can find or make some monopoles.
Basic physics tells you that total delta-V for any kind of rocket comes down to just two things: how much of the ship you can throw away to get thrust (mass ratio) and how fast you can throw it (exhaust velocity). For mass ratios of less than say 1000 (ie ship at launch no more than 99.9% reaction mass at launch), and non-relativistic exhaust velocities, total delta-V is no more than 8-10 times the exhaust velocity. Exhaust velocity of chemical rockets tops out at about 3-5 km/s, nuclear thermal rockets get up to perhaps 10 km/s, ion and similar rockets at the moment do perhaps 40-50 km/s, although they could get much higher at huge cost in engine size and power and very low thrusts-- not so much a rocket as a particle accelerator!
Basically to get anywhere within spitting distance of relativistic speeds with a rocket you have to get MUCH, MUCH higher exhaust velocities which means some kind of direct nuclear propulsion (where the reaction mass is actually produced and heated in a nuclear explosion). Orion might manage one or two percent of lightspeed in principle, or better if you could replace the fission bombs with some kind of laser ignited fusion or matter-antimatter bombs.
Longer platforms is being done anyway. I suspect the double decker trains would involve so much reworking of tunnels bridges and stations that it would not be cheaper than building a new line.
This is totally offtopic, but the thing about water is that it moves in and out of the atmosphere quickly. Water level in the atmosphere is pretty much determined by temperature and perhaps the distribution of exposed ocean area. The result is a massive positive feedback. If something else warms the atmosphere and oceans, the water vapour level rises, adding to the warming, and vice versa. Modern models take full account of this. Historically, water surface temperatures can be determined from the oxygen isotope ratios in snow.
The amount of lensing measures the mass, since mass is what determines gravity. We don't know how many dark matter particles there are per kilogram, or anything like that, so we only know the amount in one sense, mass, but that we do get from the lensing.
Slashdot Mirror
We don't really have challenge to laws in court here, except in a few special cases, but if parliament passes a bad law they can be held responsible at the next election.
The research in question is about the exact process on a molecular level. We may know which cells
or synapses are affected, but we don't know much if anything about the chemistry of that process. These
simulation studies suggest an intriguing possibility
No there really is no absolute present in relativity. We can calculate that this supernova occurred 40 million years ago, simultaneously with some event on Earth, but an alien whose spaceship was flying past Earth 40 million years ago at near light speed and who later sees the light from the supernova would not calculate that those two events were simultaneous. Neither it, nor we, is wrong. Simultaneity depends on how you are moving.
What relativity does, indepdendently of how you are moving, is divide the universe into five parts:
* your past -- events from which you could have received a slower-than-light message by now
* your past light cone -- events from which a light-speed signal is just now arriving
* your future light cone -- events which might receive a light-speed signal if your send it now
* your future -- events which could receive a slower-than-light message from you
* the rest
No observer will disagree (except by mistake) about which of these parts any given event is in with respect to you.
The supernova is on our past light cone. In our stationary reference frame it's about 37 million years away, but again, a moving observer would come up with a different number.
Absolutely right I think. A first step is the difference between being in hospital, where the first thing any doctor does is look at the chart at the end of the bed for the history of your temperature, BP, etc. and going into a GP surgery and having a single measurement. We already have wearable 24 hour BP and ECG monitors. Looking ahead 5-10 years, I can imagine anyone who is ill (or pregnant or old) wearing a wristwatch and maybe a few stick-on or swallowed or injected wireless sensors that records their vitals every few minutes. Looking ahead 20-30 years, imagine microscopic sensors in every vital organ, powered by blood sugar and logging and reporting every significant hormone and mineral level, organ by organ to the processors in your personal area network. Going out 50-100 years, you could imagine a monitor nanobot in every cell: tracking hormones, gene expression levels, firing rates if the cell is a neuron, etc., reproducing when the cell reproduces. Start adding control functions, or distributed memory and computing (all vaporized except two teaspoons of the left foot -- not to worry that has a full brain backup in it just a couple of seconds old...) and we're definitely getting post-human.
Thanks for some light.
My understanding is what these guys have is a way to control the electromagnetic environment of the electrons in the surface layer of the copper which is
far more flexible than anything that was around before. They can, at least to some extent say "we're interested in the environment of graphene" put the CO molecules on the surface in the right pattern and "bingo" the electrons from the copper act like they were in graphene. Then they can say "we're interested in this environment, which no actual known material achieves" move the CO molecules and study that.
This is a fantastic research tool. At the moment anyway it's not a production method. If they find an interesting electron behaviour they will have to work out a more "conventional" way of getting it for any production device, but it should make the search easier and allow them to refine their theoretical models.
Can we get this tested under more *interesting* conditions than earth?
Can we test plank's constant as we accelerate an object near light speed or subject it to overwhelming gravitational force? How about as we heat or cool it? How about as we take that quanta and accelerate or decelerate it?
Many of these are possible, in a sense, although what you actually test is not Planck's constant but various combinations of it and other constants which eventually give pure dimensionless numbers. The best known of these is alpha which measures the strength of the electromagnetic force.
Limits on values of alpha in extreme conditions (or over long periods of time) can be determined from astronomical observations -- different spectral lines would shift by different amounts if alpha, changed, for instance, so by comparing their relative positions in light from objects in extreme conditions, we learn something. So we observe light from hot gas falling into a black hole, or light from distant galaxies that has been gravitationally lensed by nearer ones, or whatever and see what the spectra look like. It's not easy, but it is possible. These reports are interestingly, about equally sensitive to change over time as measurements on Earth using ultra-stable atomic clocks, where the time periods are much shorter, but the measurements much more accurate.
We also regularly study the properties of particles and atoms moving very close to light-speed indeed in particle accelerators.
So you can never have a government policy that saves a lot of lives (or money) for many people, but unavoidably harms a few?
That rules out policing, any form of warfare,....
Essentially when they say "clock" what they mean is "stable oscillator" -- they have a source of (in this case) ultraviolet light whose frequency varies hardly at all. Since this is purely theoretical exercise, they are simply calculating how much stray electric and magnetic fields and other problems would be expected to vary the frequency. To check experimentally, I think they'd need two such sources and then see how the relative phase of the light changes over time (after allowing for relativitistic effects of gravity on the light beam, Earth's rotation and a zillion other things).
Simulating the airflow over a new car, plane or rocket design.
Weather forecasting
Simulating biochemical networks
etc.
See http://www.nccs.gov/wp-content/media/nccs_reports/Science%20Case%20_012808%20v3__final.pdf
Most of the applications on big supercomputers are simulations. In the basic case, each node sits there simulating it's cube of atmosphere, or its bit of the airflow around an aircraft or car design or its bit of a nuclear weapon in a simulated warehouse fire. Every time-step it needs to exchange the state of the borders of it's region with its neighbour nodes. In some other applications, all the nodes are working together to invert a huge matrix or do a massive Fourier transform in several dimensions. These need even more communication.
The demand is genuine, and can't be met by wide-area distributed computing using any algorithms we know.
TDM won't cut it. You might lose crucial milliseconds waiting for your slot.
It's rapidly heading for the point where to trade competitively you need to have your serves within a rack or two of the exchange server in the same datacentre. Before much longer it'll be having your process running on the exchange's server.
Hydrazine is described as corrosive and toxic, both of which will make it expensive to handle, require special pipes and tanks and so on. As far as I know, it's not
an environmental consideration -- it surely decays to nitrogen and water pretty fast.
I suspect this is about cost saving in the handling.
I can't resist.
If we take it as read from observation that there is only finitely much time before the present (there are theories otherwise, but more or less all of them have a special event of some kind about 13.7 billion years ago), why does this require "something that started everything"? Without a working theory of quantum gravity, we have to accept that the universe has a number of time-space singularities where GR breaks down -- one in every black hole and one at the Big Bang. This tells us that we need a decent theory of quantum gravity, but I don't see that it tells us anything else.
Early life on Earth is still poorly understood, owing to the lack of records, but the smart money seems to be on RNA forming in some kind of primordial soup that was able to duplicate itself from the ingredients in the soup. Once you have that you get a lot of copies of that RNA, and rather less rich soup. The copying is also probably pretty inaccurate, so you get some copies that are better at making copies of themselves from less rich soup, perhaps by doing it more indirectly -- making a protein that helps make more RNA which in turn makes more protein for instance, and so you slowly (and remember this took hundreds of millions of years) bootstrap towards something like a very primitive prokaryotic cell. The jump from RNA to DNA as the basic genome, is a big one, but RNA organisms could have made chunks of DNA for other purposes initially, and then gradually moved more and more of the key functions into the DNA.
Doesn't go nearly far enough. Just getting up through the atmosphere is not really the point. Balloons do that pretty well. The trick is to build a tower so high that
it reaches geostationary orbit, so the top of the tower is in orbit, not just in space. That's about 36000 km up.
In a sense. There is a widespread view that we will need 1 Exaflop supercomputers by roughly 2019 or 2020 for a whole range of applications including aircraft design, biochemistry to processing data from new instruments like the square kilometer array. On current trends, such a computer will need gigawatts of power (literally), which amongst other things would force it to be located right next to a large power station that wasn't needed for other purposes. This is felt to be a bit of a problem and this DARPA initiative is just one small part of the effort to tackle this and get the Exaflop machine down to 50MW or so, which is the most that can be routinely supplied by standard infrastructure.
There are basically two problems:
1. The external connectivity -- SATA, USB, ethernet, etc. needs too much power to easily move or handle on a chip (and the radio stuff needs radio power). You can do the protocol work on the main chip if you like, but you'll need amplifiers, and possibly sensors off chip.
2. DRAM and CPUs are made in quite different processes, optimised for different purposes. Cache is memory made using CPU processes (so it's expensive and not very dense). These guys are trying to make CPUs using DRAM processes, which are slow.
The issue is that Western manufacturers need to find a way to be as flexible as the Chinese competition while providing an acceptable lifestyle
for their staff. Automation might be a way. If this change had required just one employee to be roused from sleep (or possibly just phoned in his/her office in New Zealand where it's daytime) to reprogram the machines in the factory start fitting glass screens into beveled frames, that would work. More realistically, it would still work if it needed 10 employees or maybe 50. They can be paid enough to compensate for the out-of-hours callout (or telecommute from somewhere where it's in hours).
Of course there are several challenges in this approach: you need the capital investment to build the automated factory; you need the education levels to train your population for a world where half the jobs are sophisticated technical problem-solving jobs; you need a LOT of factories like this to keep your whole population employed; and, for now, you need to compete with countries still developing who have workers willing to work for a few bowls of rice per hour. This last problem will go away in due course.
So you either move the power or move the demand. Moving the power might mean supertankers of liquid hydrogen, or long possibly superconducting cables. Moving the demand is basically a matter of pricing, so that it's more economic to spread energy-intensive activities out rather than concentrate them in cities.
There are at least two approaches:
1. Use solar power to make chemical fuel. For instance you could electrolyze water to make hydrogen, and either use the hydrogen directly, or react it with CO2 to make something like methanol.
2. Use satellite mounted lasers to heat a target mounted on the top of the 747, then use that heat to heat air in the engines (this only works for the cruise phase of the journey, you still need some other heat source for takeoff and landing.
Ramscoops, as described in the literature have basically two problems:
1. Getting protons (as opposed to deuterium or something heavier) to fuse at a decent rate requires conditions substantially hotter and denser than found in the cores of even quite large stars. Something more like the conditions met in shockwaves in exploding supernovae. Without this your ramscoop isn't much use.
2. The interstellar medium is very unevenly distributed. The sun is deep inside the bubble created by an ancient supernova, so there's not much to collect.
Something like monopole catalyzed proton decay might work to solve problem 1, if it happens, and if we can find or make some monopoles.
Basic physics tells you that total delta-V for any kind of rocket comes down to just two things: how much of the ship you can throw away to get thrust (mass ratio) and how fast you can throw it (exhaust velocity). For mass ratios of less than say 1000 (ie ship at launch no more than 99.9% reaction mass at launch), and non-relativistic exhaust velocities, total delta-V is no more than 8-10 times the exhaust velocity. Exhaust velocity of chemical rockets tops out at about 3-5 km/s, nuclear thermal rockets get up to perhaps 10 km/s, ion and similar rockets at the moment do perhaps 40-50 km/s, although they could get much higher at huge cost in engine size and power and very low thrusts-- not so much a rocket as a particle accelerator!
Basically to get anywhere within spitting distance of relativistic speeds with a rocket you have to get MUCH, MUCH higher exhaust velocities which means some kind of direct nuclear propulsion (where the reaction mass is actually produced and heated in a nuclear explosion). Orion might manage one or two percent of lightspeed in principle, or better if you could replace the fission bombs with some kind of laser ignited fusion or matter-antimatter bombs.
Longer platforms is being done anyway. I suspect the double decker trains would involve so much reworking of tunnels bridges and stations that it would not be cheaper than building a new line.
This is totally offtopic, but the thing about water is that it moves in and out of the atmosphere quickly. Water level in the atmosphere is pretty much determined by temperature and perhaps the distribution of exposed ocean area. The result is a massive positive feedback. If something else warms the atmosphere and oceans, the water vapour level rises, adding to the warming, and vice versa. Modern models take full account of this. Historically, water surface temperatures can be determined from the oxygen isotope ratios in snow.
We can probably get an idea of the typical velocity spread of the dark matter from the extent to which it is clumped. That's sort of like temperature.
The amount of lensing measures the mass, since mass is what determines gravity.
We don't know how many dark matter particles there are per kilogram, or anything like that, so we only
know the amount in one sense, mass, but that we do get from the lensing.