No, you don't get annihilation from electrons and protons.
You do get radiation, if things are energetic enough. If the electron becomes bound to the proton, you get emissions at one of the Hydrogen lines.
If, for example, the electron went all the way to the Hydrogen ground state, you would have emissions at the limit of the Lyman Series, up in the hard UV at 91 nanometers.
If things are more energetic, you will get electrons and protons combining to form free neutrons. These will decay (this decay is called beta decay) and release gamma rays at 782 KeV, but since the half life of free neutrons is 10.3 minutes, this will be really spread out in time and hard to see. Free neutrons have been directly detected from lightning strikes, so some of this is presumably going on.
The lightning associated gamma rays can be inferred as due to bremsstrahlung associated with electrons released moments after the return stroke and the likely radiation associated with radioactive decay products in the interactions of protons generated in the lightning with the atmospheric constituents
It’s a surprise to have found the signature of positrons during a lightning storm, Briggs said.
No, it's not.
There is a long history of observations and theorizing about gamma ray flashes from lightning strikes and ball lightning, starting in the early 1970's :
Now, not all of these reports include a positron annihilation signature at 511 KeV. But, 511 KeV emissions were explicitly reported from lightning in the 1970's. And, considering that lightning / thunderstorm related gamma rays are routinely observed with energies up to 10 MeV, there is plenty of energy to create positrons, and so I wouldn't be surprised if all of these reports included the positron annihilation line (or, at least the ones with sensitivity in that energy range).
False positives will kill this. Plus, anything that can be measured can be trained for (see, e.g., "lie" detectors).
But, this will be good for some research grants, and maybe even an expensive pilot project, so if you believe that the best security metric is the amount of money wasted, it's all for the good.
The placebo effect is not at all just about pain - in many cases, it is considerably more powerful than the drugs the Doctor prescribes. A rational medical system would spend considerable resources on studying ways to improve the placebo effect. It is a pretty good bet that exhaustive paper work and hospital green paint is not it.
Because air is lost. The human waste in the air is scrubbed and O2 is generated inside the ISS. This is all engineering driven, and I don't see the slightest reason why the same engineering wouldn't be used on any near-term deep space mission.
3 Progress flights per year carry something like 9 tons of supplies to the ISS (that includes propellant, by the way). I don't see why carrying along 9 tons of supplies along on a deep space mission is any different from a biological point of view.
There isn't in a closed environment like a shuttle to Mars.
I don't think that that is really true or relevant. Even the long duration ISS expeditions typically had only 1 or 2 Progress spacecrafts dock with them during the mission. I would imagine that any deep space missions would have provisions kept in lockers or modules that would be opened in time (i.e., whatever perturbations are caused by a Progress supply mission would be similar to that caused by opening a previously closed supply module). BTW, I have never heard of a cold or other disease being transmitted by an unmanned re-provisioning, and I think that the biological perturbations from them are small. (They do typically bring fresh fruit, but just enough for a treat for a day or two.)
Now, the Progress or other supply spacecraft do carry an air supply that is bled into the ISS (i.e., the air is replaced over time), but this is done as an engineering necessity (air is lost), and would presumably have to be done on a long-duration deep space mission as well. In other words, I would argue that a long duration ISS expedition is just about as closed an environment as a long duration deep space mission.
All of the other items might be without our power, but we do not know how to do this :
a) nuclear propulsion that can accelerate the spacecraft to relativistic needs.
Let's consider two candidates - Project Orion, with an effective exhaust velocity of maybe 30 km / sec (10^-4 c) , and the Project Daedalus design, with an effective exhaust velocity of 10,000 km / sec (0.03 c). Suppose we wanted to travel at 0.1 c - landing at the far end means the total delta v is 0.2 c (60,000 km/sec). (Note that Daedalus assumed a design speed of 0.12 c, and so needed a higher mass ratio). Finally, assume that the actual spaceship payload weight (i.e., the space for the people and life support and any instrumentation) is 1000 tons (the ISS is currently 300 tons). Using the rocket equation, and assuming no weight is needed for propellant tanks,
- the Orion design has a mass ratio (initial over final mass) of 10^434 , and is just wildly impossible.
- the Daedalus design has a mass ratio of 786, thus an initial mass of almost a megaton - but this assumes carrying 1 megaton of fuel with no fuel tanks, which is completely unrealistic. The REPRO version of Daedalus (which allowed for the deceleration of a 443 ton payload) had a design weight in Earth orbit of 10 million tons.
So, Daedalus is an engineering possibility, maybe, for flights to the stars in a human lifetime. Note that this requires megatons of Helium-3, all of which has got to be mined outside the Earth (as our Helium is all Helium-4), and there are various other engineering difficulties, but I could see a major global effort, say of the scale of World War II, producing Daedalus ships.
If you want to get to close to 1 c, say 0.9 c, and then decelerate at the far end, the Daedalus design would require a mass ratio of 10^26, which is not feasible. The only way we know of to do that is with anti-matter. Given that we neither know how to product and store significant quantities of anti-matter, nor how to turn it into a working rocket, I have to conclude that we have no feasible means of creating a relativistic spaceship at present. Generation ships, yes, if we wanted to. But not relativistic ships.
There have been ISS Expeditions that have lasted times comparable to at least one way to Mars - Expeditions 4, 6, 8 and 13 at least. There is no microbiological difference between orbiting the Earth and going to Mars, so I would conclude that people should be able to get to Mars just fine.
I still think that truly deep space exploration will require artificial gravity (i.e., spinning spacecraft), but this sounds like FUD to justify research funds to me.
Here is a basic level answer - in quantum mechanics forces result from the interchange of particles in a flat background space time. In general relativity, forces result from the curvature of space-time, and matter (and all mass energy) cause that curvature, and thus cause their own motion. These are rather different ways of looking at the universe, but in both theories you calculate things using differential equations (i.e., you assume that spacetime is smooth at a small enough scale, so you can deal with differential quantities). In Quantum Mechanics there is a inherent uncertainty - you cannot measure position and velocity perfectly well at the same time. General Relativity does not have this, but it does have black holes - a concept with doesn't map well into Quantum Mechanics when the size of the black hole becomes comparable to the size of the particle. Worse, attempts to model gravity as a force caused by the interchange of gravitons (the way that other forces are done in Quantum Mechanics) have not worked - the infinities are too bad to actually do any calculations.
None of this matters on most scales - in the LHC quantum particles don't care that the spacetime is gently curved, and in the solar system or galaxy the spacetime doesn't care that there is quantum uncertainty at some very small microscopic level. But when the virtual particles get heavy enough that they affect the curvature of spacetime enough to create black holes, then things get nasty - there is not reason to expect that the "spacetime foam" on these small scales has a flat background spacetime , and so both theories are incomplete and break down.
That's not the right question - the real question is, at what mass ratio ?
The mass ratio is final weight / total weight, and it comes into the
delta v = v log(mass ratio)
where delta v is the velocity difference you want, and v is the effective exhaust velocity of the rocket. Rocket efficiency is generally measured in terms of specific impulse, or I_sp, which is in seconds, with v being = I_sp * g, where g is the acceleration due to gravity at the surface of the Earth.
The Shuttle main engines, in vacuum, have I_sp of about 453 seconds, or an effective exhaust velocity of 4,440 m/s. So, to get to orbit (9000 m/s), you need, with the Shuttle main engine, a mass ratio of about e^2, or 7.4.
NERVA had a specific impulse of about 850 seconds (or v = 8,300 m/s), so the mass ratio is more like a factor of 3. Single stage to orbit, which is so tough with chemical rockets, would be a breeze with a thermal nuclear rocket
Now, I agree that the radioactive material shed by a nuclear thermal rocket means you probably don't want to use it for ground lift-off, but if you want to send heavy payloads to the solar system, the factor of 2 in specific impulse means that the mass ratio will be much less for a nuclear thermal rocket. Assuming the technology can be mastered, it would substantially reduce the cost of any manned exploration of the solar system.
This was proposed by G. Amelino-Camelia et al. back in 1998; here is a review from 2004. Even though the wavelengths of even the most energetic gamma rays are much, much, longer than the Planck length, roughness in space time at the Planck length adds up over cosmological distances, and could be in principle detectable. (The Planck length can be thought of heuristically as the length at which the gravitational effects of virtual particles should be strong enough to create virtual black holes; general relativity cannot be ignored in quantum mechanics at that scale, and vice versa.) What this current test is ruling out is a particular violation of Lorentz invariance - a variation of photon speed with energy. There were similarly negative results using radiation from the Crab nebula in 2003.
It should be noted that this does not rule out quantum gravity - it seems pretty clear that General Relativity and Quantum Mechanics cannot both apply at the Planck scale. What this work is doing is beginning to constrain models of quantum gravity (there is as yet no general theory that makes precise predictions). What would be really cool is to detect some effects, which would maybe help nudge the theorists along.
Thank you for this - it was very informative. However, I will object to one piece
Designs and plans that persist for 50 years are rare in space exploration.
Not so much in Russia, which is one of their strengths. For example, the Soyuz spacecraft was first launched in 1967 (42 years), the Soyuz booster today is derived from the Vostok booster, which was based on the R-7a, which was used to launch Sputnik, 52 years ago. There is a reason why it is so reliable.
Wouldn't work, at least if they do it right, and the text is long enough. This is a form of steganography, and what you are proposing is actually hard to do. Imagine Amazon makes, say, 1024 changes in a text. Each change can be regarded as a binary bit (being either present or absent), so each text copy has a unique 128 byte number hidden in it. If Amazon gives out 4 million copies, that means they only need about 24 bits to uniquely identify any individual. If I get my hands on 5 copies, and can correct each error where the text differs (which I frankly doubt could be always done) then I am doing an AND on all of my 1024 bit numbers, leaving 32 bits intact, and Amazon could determine where all 5 copies came from.
If Amazon has information about who is likely to collude, they can make this even tougher by assigning codes based on this information. (For example, the first bit could be one for all Slashdot users, and zero otherwise, so no matter how many of us collude, Amazon could still say if the pirates came from Slashdot.)
Let's hope that tomorrow's theologians actually know how to read Greek, Aramaic and Hebrew, and so are not dependent on translations, authorized or otherwise.
Mapmakers have been adding fictitious towns for many years (as many have commented).
People who sell lists have been doing this for many years. (Who's Who, for example, adds a few fictitious people for this purpose, and I believe so do the Yellow Pages.)
People trying to catch spies have been doing this for many years. (I first heard about this during the Thatcher years in the UK, and it wasn't new then.)
NASA designed one, called NERVA, it was built and tested, out in Idaho IIRC, and was canceled by the Nixon administration. The photo in the article looks very much like a nuclear thermal engine, and nothing like a pulse system.
Slashdot Mirror
No, you don't get annihilation from electrons and protons.
You do get radiation, if things are energetic enough. If the electron becomes bound to the proton, you get emissions at one of the Hydrogen lines.
If, for example, the electron went all the way to the Hydrogen ground state, you would have emissions at the limit of the Lyman Series, up in the hard UV at 91 nanometers.
If things are more energetic, you will get electrons and protons combining to form free neutrons. These will decay (this decay is called beta decay) and release gamma rays at 782 KeV, but since the half life of free neutrons is 10.3 minutes, this will be really spread out in time and hard to see. Free neutrons have been directly detected from lightning strikes, so some of this is presumably going on.
Why not indeed ?
This sounds reasonable to me :
The lightning associated gamma rays can be inferred as due to bremsstrahlung associated with electrons released moments after the return stroke and the likely radiation associated with radioactive decay products in the interactions of protons generated in the lightning with the atmospheric constituents
(from Jayanthi et al., 2006).
Although the previous reports of lightning induced fusion from Slashdot are intriguing.
I am in Japan, and jet-lagged - I mean to say
Now, not all of these abstracts report include a positron annihilation signature at 511 KeV.
I have read these papers (and others) and IIRC 511 KeV reports are fairly common, but I don't have them in front of me to be sure.
It’s a surprise to have found the signature of positrons during a lightning storm, Briggs said.
No, it's not.
There is a long history of observations and theorizing about gamma ray flashes from lightning strikes and ball lightning, starting in the early 1970's :
Is Ball Lightning caused by Antimatter Meteorites?
D. E. T. F. ASHBY, C. WHITEHEAD, Nature 230, 180-182 (19 March 1971).
This has also been observed in connection with "sprites".
And from thunderclouds without lightning.
Oh, and it's also been observed from space before :
RHESSI Observations of Terrestrial Gamma-Ray Flashes
Now, not all of these reports include a positron annihilation signature at 511 KeV. But, 511 KeV emissions were explicitly reported from lightning in the 1970's. And, considering that lightning / thunderstorm related gamma rays are routinely observed with energies up to 10 MeV, there is plenty of energy to create positrons, and so I wouldn't be surprised if all of these reports included the positron annihilation line (or, at least the ones with sensitivity in that energy range).
False positives will kill this. Plus, anything that can be measured can be trained for (see, e.g., "lie" detectors).
But, this will be good for some research grants, and maybe even an expensive pilot project, so if you believe that the best security metric is the amount of money wasted, it's all for the good.
The placebo effect is not at all just about pain - in many cases, it is considerably more powerful than the drugs the Doctor prescribes. A rational medical system would spend considerable resources on studying ways to improve the placebo effect. It is a pretty good bet that exhaustive paper work and hospital green paint is not it.
I think not.
If she said the Sun was shining outside, I would grab my umbrella and raincoat and worry about flash floods.
Because air is lost. The human waste in the air is scrubbed and O2 is generated inside the ISS. This is all engineering driven, and I don't see the slightest reason why the same engineering wouldn't be used on any near-term deep space mission.
3 Progress flights per year carry something like 9 tons of supplies to the ISS (that includes propellant, by the way). I don't see why carrying along 9 tons of supplies along on a deep space mission is any different from a biological point of view.
There isn't in a closed environment like a shuttle to Mars.
I don't think that that is really true or relevant. Even the long duration ISS expeditions typically had only 1 or 2 Progress spacecrafts dock with them during the mission. I would imagine that any deep space missions would have provisions kept in lockers or modules that would be opened in time (i.e., whatever perturbations are caused by a Progress supply mission would be similar to that caused by opening a previously closed supply module). BTW, I have never heard of a cold or other disease being transmitted by an unmanned re-provisioning, and I think that the biological perturbations from them are small. (They do typically bring fresh fruit, but just enough for a treat for a day or two.)
Now, the Progress or other supply spacecraft do carry an air supply that is bled into the ISS (i.e., the air is replaced over time), but this is done as an engineering necessity (air is lost), and would presumably have to be done on a long-duration deep space mission as well. In other words, I would argue that a long duration ISS expedition is just about as closed an environment as a long duration deep space mission.
All of the other items might be without our power, but we do not know how to do this :
a) nuclear propulsion that can accelerate the spacecraft to relativistic needs.
Let's consider two candidates - Project Orion, with an effective exhaust velocity of maybe 30 km / sec (10^-4 c) , and the Project Daedalus design, with an effective exhaust velocity of 10,000 km / sec (0.03 c). Suppose we wanted to travel at 0.1 c - landing at the far end means the total delta v is 0.2 c (60,000 km/sec). (Note that Daedalus assumed a design speed of 0.12 c, and so needed a higher mass ratio). Finally, assume that the actual spaceship payload weight (i.e., the space for the people and life support and any instrumentation) is 1000 tons (the ISS is currently 300 tons). Using the rocket equation, and assuming no weight is needed for propellant tanks,
- the Orion design has a mass ratio (initial over final mass) of 10^434 , and is just wildly impossible.
- the Daedalus design has a mass ratio of 786, thus an initial mass of almost a megaton - but this assumes carrying 1 megaton of fuel with no fuel tanks, which is completely unrealistic. The REPRO version of Daedalus (which allowed for the deceleration of a 443 ton payload) had a design weight in Earth orbit of 10 million tons.
So, Daedalus is an engineering possibility, maybe, for flights to the stars in a human lifetime. Note that this requires megatons of Helium-3, all of which has got to be mined outside the Earth (as our Helium is all Helium-4), and there are various other engineering difficulties, but I could see a major global effort, say of the scale of World War II, producing Daedalus ships.
If you want to get to close to 1 c, say 0.9 c, and then decelerate at the far end, the Daedalus design would require a mass ratio of 10^26, which is not feasible. The only way we know of to do that is with anti-matter. Given that we neither know how to product and store significant quantities of anti-matter, nor how to turn it into a working rocket, I have to conclude that we have no feasible means of creating a relativistic spaceship at present. Generation ships, yes, if we wanted to. But not relativistic ships.
There have been ISS Expeditions that have lasted times comparable to at least one way to Mars - Expeditions 4, 6, 8 and 13 at least. There is no microbiological difference between orbiting the Earth and going to Mars, so I would conclude that people should be able to get to Mars just fine.
I still think that truly deep space exploration will require artificial gravity (i.e., spinning spacecraft), but this sounds like FUD to justify research funds to me.
The photon timing for GLAST is supposed to be good to 10 microseconds.
Is it because the frequencies involved are so high?
Yes. That's true even for visible light, much less gamma rays.
A very good summary - thanks.
Here is a basic level answer - in quantum mechanics forces result from the interchange of particles in a flat background space time. In general relativity, forces result from the curvature of space-time, and matter (and all mass energy) cause that curvature, and thus cause their own motion. These are rather different ways of looking at the universe, but in both theories you calculate things using differential equations (i.e., you assume that spacetime is smooth at a small enough scale, so you can deal with differential quantities). In Quantum Mechanics there is a inherent uncertainty - you cannot measure position and velocity perfectly well at the same time. General Relativity does not have this, but it does have black holes - a concept with doesn't map well into Quantum Mechanics when the size of the black hole becomes comparable to the size of the particle. Worse, attempts to model gravity as a force caused by the interchange of gravitons (the way that other forces are done in Quantum Mechanics) have not worked - the infinities are too bad to actually do any calculations.
None of this matters on most scales - in the LHC quantum particles don't care that the spacetime is gently curved, and in the solar system or galaxy the spacetime doesn't care that there is quantum uncertainty at some very small microscopic level. But when the virtual particles get heavy enough that they affect the curvature of spacetime enough to create black holes, then things get nasty - there is not reason to expect that the "spacetime foam" on these small scales has a flat background spacetime , and so both theories are incomplete and break down.
This Judge should be impeached and removed from office for this. Start a campaign fund; I'll donate.
I am tired of these lovers of tyranny who pretend that Constitution's protections only apply to technologies in existence in 1789.
That's not the right question - the real question is, at what mass ratio ?
The mass ratio is final weight / total weight, and it comes into the
delta v = v log(mass ratio)
where delta v is the velocity difference you want, and v is the effective exhaust velocity of the rocket. Rocket efficiency is generally measured in terms of specific impulse, or I_sp, which is in seconds, with v being = I_sp * g, where g is the acceleration due to gravity at the surface of the Earth.
The Shuttle main engines, in vacuum, have I_sp of about 453 seconds, or an effective exhaust velocity of 4,440 m/s. So, to get to orbit (9000 m/s), you need, with the Shuttle main engine, a mass ratio of about e^2, or 7.4.
NERVA had a specific impulse of about 850 seconds (or v = 8,300 m/s), so the mass ratio is more like a factor of 3. Single stage to orbit, which is so tough with chemical rockets, would be a breeze with a thermal nuclear rocket
Now, I agree that the radioactive material shed by a nuclear thermal rocket means you probably don't want to use it for ground lift-off, but if you want to send heavy payloads to the solar system, the factor of 2 in specific impulse means that the mass ratio will be much less for a nuclear thermal rocket. Assuming the technology can be mastered, it would substantially reduce the cost of any manned exploration of the solar system.
This was proposed by G. Amelino-Camelia et al. back in 1998; here is a review from 2004. Even though the wavelengths of even the most energetic gamma rays are much, much, longer than the Planck length, roughness in space time at the Planck length adds up over cosmological distances, and could be in principle detectable. (The Planck length can be thought of heuristically as the length at which the gravitational effects of virtual particles should be strong enough to create virtual black holes; general relativity cannot be ignored in quantum mechanics at that scale, and vice versa.) What this current test is ruling out is a particular violation of Lorentz invariance - a variation of photon speed with energy. There were similarly negative results using radiation from the Crab nebula in 2003.
It should be noted that this does not rule out quantum gravity - it seems pretty clear that General Relativity and Quantum Mechanics cannot both apply at the Planck scale. What this work is doing is beginning to constrain models of quantum gravity (there is as yet no general theory that makes precise predictions). What would be really cool is to detect some effects, which would maybe help nudge the theorists along.
Thank you for this - it was very informative. However, I will object to one piece
Designs and plans that persist for 50 years are rare in space exploration.
Not so much in Russia, which is one of their strengths. For example, the Soyuz spacecraft was first launched in 1967 (42 years), the Soyuz booster today is derived from the Vostok booster, which was based on the R-7a, which was used to launch Sputnik, 52 years ago. There is a reason why it is so reliable.
NERVA had a specific impulse about twice that of Oxygen-Hydrogen. A factor of 2 is cool, but you will not get to 1/10th the speed of light with it.
Wouldn't work, at least if they do it right, and the text is long enough. This is a form of steganography, and what you are proposing is actually hard to do. Imagine Amazon makes, say, 1024 changes in a text. Each change can be regarded as a binary bit (being either present or absent), so each text copy has a unique 128 byte number hidden in it. If Amazon gives out 4 million copies, that means they only need about 24 bits to uniquely identify any individual. If I get my hands on 5 copies, and can correct each error where the text differs (which I frankly doubt could be always done) then I am doing an AND on all of my 1024 bit numbers, leaving 32 bits intact, and Amazon could determine where all 5 copies came from.
If Amazon has information about who is likely to collude, they can make this even tougher by assigning codes based on this information. (For example, the first bit could be one for all Slashdot users, and zero otherwise, so no matter how many of us collude, Amazon could still say if the pirates came from Slashdot.)
Let's hope that tomorrow's theologians actually know how to read Greek, Aramaic and Hebrew, and so are not dependent on translations, authorized or otherwise.
Mapmakers have been adding fictitious towns for many years (as many have commented).
People who sell lists have been doing this for many years. (Who's Who, for example, adds a few fictitious people for this purpose, and I believe so do the Yellow Pages.)
People trying to catch spies have been doing this for many years. (I first heard about this during the Thatcher years in the UK, and it wasn't new then.)
So, how, exactly is this new and non-obvious ?
Does anyone have any real information on this ? (NASA Contractor Report 179614, SPI-25-l. (1988) doesn't count.)
NASA designed one, called NERVA, it was built and tested, out in Idaho IIRC, and was canceled by the Nixon administration. The photo in the article looks very much like a nuclear thermal engine, and nothing like a pulse system.