OK, I just did the experiment. I'm a middle-aged white male, with a large backpack in O'Hare airport. I just made a cell call to a friend discussing the Air-tran incident, and using the words "terrorist", "bomb" and explosion. I said that no sensible terrorist is going to talk about blowing up a plane they are actually about to destroy. I made this call in front of 4 flight-attendants on my flight. So far no one has bothered me.
I have 2 computers, cross-backup every few days. Then every couple of weeks copy everything (copy, not update) to an external HD. The external HD is normally kept off site (at my work). If I accidentally trash a file, I can recover from the other computer. If I somehow wipe out everything on both computers, or if my house burns down, I can recover an at most 2 week old backup from off site. If storage technology changes, I will change the backup media I use. At the moment I use conventional hard disks. I can go to flash, or hyperspace quantum drives or whatever as technology changes. I need 3X the disk space required for a single copy of my data, but disks are cheap. Since my media are regularly used, I know if things are going bad.
As the size of the linear equation problem increases, does the quantum state become more "fragile" (I'm sorry, I don't know the correct terminology). Would a hypothetical quantum computer need to operate at lower temperature, and does this create a limit on the size of problems that could be solved with this technique?
Depends on what you mean by "tubes". For high power pulsed microwave systems (like radar) specialized vacuum tubes are often the most cost effective and most efficient source. At SLAC we use 250, 75 megawatt pulsed klystrons (tubes). There is no practical solid state replacement. Many TV stations use a type of radio-frequency called an IOTs. Microwave ovens use "tubes" (magetron). Low power / low noise is different: I don't know of modern applications for signal-level tubes, but there may still be some.
Making positrons isn't all that hard. At SLAC we use about 20GeV to produce (and capture) 1 positron (efficiency is 1/40,000). Plans for a next generation accelerator did about 10X better. Making anti-protons (like fermilab) is MUCH MUCH harder. The problem is that a proton has 3 quarks and you need to make them all together - very unlikely. The fundamental process is something like 100,000X less efficient that making positrons. The LLNL experiment is still very interesting science, but it doesn't lead in any obvious way to efficient production of antimatter.
Your calculation is about right - if space-time has 4 dimensions. There are some physics theories that suggest there are more very small dimensions. Think of a thin soda-straw: over large distances it has 1 dimension, but if you look closely there are 2. If these extra dimensions exist gravity will behave differently on small scales. It would be possible to make small black holes with much less mass than you would expect from the normal 4-dimensional calculation. This would let the LHC with only 7TeV make tiny black holes. (normally you would need about 1000 TRILLION TEV). These black holes would NOT behave like normal black holes and consume normal matter. They would have very little interaction (they have little mass, so little gravity), and would either fly off into space, or decay. Extra-dimensions are one of several competing theories, one of the jobs of the LHC is to figure out if they exist.
She may not know if she likes science if she hasn't tried. There are lots of places to do summer internships (most of the US national labs have these programs).
Doing science in the real world is nothing like science in movies, or the science taught in school. She might like it or hate it, but it is worth a summer to find out.
I work at a national lab, and have had summer interns who discovered they loved doing science. I've also had interns who decided they hated it when they found out that no matter how smart you are experiments don't always give you the results you expected.
Scientists aren't all nerds either. Some do spend their time reading slashdot, but I know one person who competes in international level in-line speed-skating, and another who goes ice-climbing in the mountains.
Would it be possible for a TSA agent to add something to the luggage, rather than remove it? If not, what protections are in place to prevent smuggling drugs - or adding explosives.
FWIW, I travel in and out of the US 10-20 times a year, carrying a laptop every time. So far I have never had a problem.
If you want to make a legal point, encrypting the data on the laptop is a good start. If you just don't want to be bothered, don't encrypt it, TSA isn't interested in your private pictures - unless they are illegal.
If you have illegal data - well you can't complain if they stop you.
Politically I have strong objections to TSA or customs snooping. As practical matter, so far it isn't very intrusive.
Tharg say fire BAD. Burn things, maybe burn everything. Best not use fire.
All new science and technolgy brings risk, but we are the descendants of the creatures who decided to take the risks. We keep the risk adverse creatures in zoos.
In this particular case though, the risk is tiny. There just isn't much energy stored in the LHC magnetic field, or in the liquid helium.
As viewed by a clock at rest relative to the earth and Alpha Centuri, at least 4.3 years needs to pass. As viewed by a clock on the rocket, it could take much less time.
But, if the rocket carries its own fuel, the required mass ration becomes unreasonable (grows exponentially) if the rocket needs to get very close to C.
If the rocket is powered externally (say by a laser), the required power becomes unreasonable as the rocket gets close to C.
(google on relativity rocket equation for the math, or ref. Meisner Thorne, Wheeler, "Gravity").
The maximum magnetic field you can put on a superconductor depends on temperature. You can operate a superconducting magnet with a stronger magnetic field at 2 Kelven instead of 4.5 kelvin. Also, below 2.17 degrees kelvin, helium becomes super-fluid and has better heat conductivity - this is important in some applications.
For alternating fields (like microwaves) superconductors are not perfectly superconducting, they have a bit if residual resistance. This resistance decreases as the temperature goes down.
For an automotive engine efficiency is simple: total energy out of the drive shaft divide by the amount of fuel burned. At a constant speed, vehicle efficiency is simple as well, miles per gallon of fuel.
For an aircraft engine it is much trickier. The engine (jet or prop) causes some mass of air to move backwards. A jet moves a little bit of air at high velocity, a prop a lot at low velocity. Even if the total energy in the moving air is the same, there will be a difference in how effectively they move the airplane.
If you have a high speed plane, you need to move the exhaust at high velocity (jet). If you fly slowly, you can use a low velocity exhaust (prop).
The early jet engines were pure turbojets - produced very high velocity exhaust. This was poorly matched to a sub-sonic airplane, so even though the engine efficiency wasn't too bad, the overall aircraft efficiency was bad.
A modern jet is "high bypass", basically the turbine drives a large fan (almost the same as a prop) that you can see in the front of the engine. This moves a modest amount of air at a speed matched to the slightly sub-sonic speed of a modern airliner.
Small aircraft are typically slower, and so use props which produce a lower velocity exhaust.
Now, independent of that a piston engine is somewhat more efficient than a turbine engine, but weights more. For most large aircraft applications, the lower weight of a turbine results in better efficiency, even though the engine itself is a bit worse.
(sorry for double posting - just opened an account).
frisch
AMEL
I'm a small aircraft pilot, have studied quite a bit about aircraft engines as well.
Small aircraft engines need to operate under different conditions from car engines. In a typical car, you cruise at 10-20% of the maximum engine power. In a light aircraft, you cruise at 60-80% of maximum engine power (no speed limits).
If you made the aircraft engine larger, it would add significantly to the overall weight, and decrease the range or carrying capacity of the plane. In a typical small plane, the engine is already around 1/4 of the total weight. If I put in a large enough engine to run at 20% power rather than 80% it would weigh as much as the rest of the plane.
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OK, I just did the experiment. I'm a middle-aged white male, with a large backpack in O'Hare airport. I just made a cell call to a friend discussing the Air-tran incident, and using the words "terrorist", "bomb" and explosion. I said that no sensible terrorist is going to talk about blowing up a plane they are actually about to destroy. I made this call in front of 4 flight-attendants on my flight. So far no one has bothered me.
I have 2 computers, cross-backup every few days. Then every couple of weeks copy everything (copy, not update) to an external HD. The external HD is normally kept off site (at my work). If I accidentally trash a file, I can recover from the other computer. If I somehow wipe out everything on both computers, or if my house burns down, I can recover an at most 2 week old backup from off site. If storage technology changes, I will change the backup media I use. At the moment I use conventional hard disks. I can go to flash, or hyperspace quantum drives or whatever as technology changes. I need 3X the disk space required for a single copy of my data, but disks are cheap. Since my media are regularly used, I know if things are going bad.
As the size of the linear equation problem increases, does the quantum state become more "fragile" (I'm sorry, I don't know the correct terminology). Would a hypothetical quantum computer need to operate at lower temperature, and does this create a limit on the size of problems that could be solved with this technique?
Depends on what you mean by "tubes". For high power pulsed microwave systems (like radar) specialized vacuum tubes are often the most cost effective and most efficient source. At SLAC we use 250, 75 megawatt pulsed klystrons (tubes). There is no practical solid state replacement. Many TV stations use a type of radio-frequency called an IOTs. Microwave ovens use "tubes" (magetron). Low power / low noise is different: I don't know of modern applications for signal-level tubes, but there may still be some.
Making positrons isn't all that hard. At SLAC we use about 20GeV to produce (and capture) 1 positron (efficiency is 1/40,000). Plans for a next generation accelerator did about 10X better. Making anti-protons (like fermilab) is MUCH MUCH harder. The problem is that a proton has 3 quarks and you need to make them all together - very unlikely. The fundamental process is something like 100,000X less efficient that making positrons. The LLNL experiment is still very interesting science, but it doesn't lead in any obvious way to efficient production of antimatter.
Your calculation is about right - if space-time has 4 dimensions. There are some physics theories that suggest there are more very small dimensions. Think of a thin soda-straw: over large distances it has 1 dimension, but if you look closely there are 2. If these extra dimensions exist gravity will behave differently on small scales. It would be possible to make small black holes with much less mass than you would expect from the normal 4-dimensional calculation. This would let the LHC with only 7TeV make tiny black holes. (normally you would need about 1000 TRILLION TEV). These black holes would NOT behave like normal black holes and consume normal matter. They would have very little interaction (they have little mass, so little gravity), and would either fly off into space, or decay. Extra-dimensions are one of several competing theories, one of the jobs of the LHC is to figure out if they exist.
She may not know if she likes science if she hasn't tried. There are lots of places to do summer internships (most of the US national labs have these programs). Doing science in the real world is nothing like science in movies, or the science taught in school. She might like it or hate it, but it is worth a summer to find out. I work at a national lab, and have had summer interns who discovered they loved doing science. I've also had interns who decided they hated it when they found out that no matter how smart you are experiments don't always give you the results you expected. Scientists aren't all nerds either. Some do spend their time reading slashdot, but I know one person who competes in international level in-line speed-skating, and another who goes ice-climbing in the mountains.
Would it be possible for a TSA agent to add something to the luggage, rather than remove it? If not, what protections are in place to prevent smuggling drugs - or adding explosives.
FWIW, I travel in and out of the US 10-20 times a year, carrying a laptop every time. So far I have never had a problem. If you want to make a legal point, encrypting the data on the laptop is a good start. If you just don't want to be bothered, don't encrypt it, TSA isn't interested in your private pictures - unless they are illegal. If you have illegal data - well you can't complain if they stop you. Politically I have strong objections to TSA or customs snooping. As practical matter, so far it isn't very intrusive.
Tharg say fire BAD. Burn things, maybe burn everything. Best not use fire. All new science and technolgy brings risk, but we are the descendants of the creatures who decided to take the risks. We keep the risk adverse creatures in zoos. In this particular case though, the risk is tiny. There just isn't much energy stored in the LHC magnetic field, or in the liquid helium.
As viewed by a clock at rest relative to the earth and Alpha Centuri, at least 4.3 years needs to pass. As viewed by a clock on the rocket, it could take much less time. But, if the rocket carries its own fuel, the required mass ration becomes unreasonable (grows exponentially) if the rocket needs to get very close to C. If the rocket is powered externally (say by a laser), the required power becomes unreasonable as the rocket gets close to C. (google on relativity rocket equation for the math, or ref. Meisner Thorne, Wheeler, "Gravity").
The maximum magnetic field you can put on a superconductor depends on temperature. You can operate a superconducting magnet with a stronger magnetic field at 2 Kelven instead of 4.5 kelvin. Also, below 2.17 degrees kelvin, helium becomes super-fluid and has better heat conductivity - this is important in some applications. For alternating fields (like microwaves) superconductors are not perfectly superconducting, they have a bit if residual resistance. This resistance decreases as the temperature goes down.
For an automotive engine efficiency is simple: total energy out of the drive shaft divide by the amount of fuel burned. At a constant speed, vehicle efficiency is simple as well, miles per gallon of fuel. For an aircraft engine it is much trickier. The engine (jet or prop) causes some mass of air to move backwards. A jet moves a little bit of air at high velocity, a prop a lot at low velocity. Even if the total energy in the moving air is the same, there will be a difference in how effectively they move the airplane. If you have a high speed plane, you need to move the exhaust at high velocity (jet). If you fly slowly, you can use a low velocity exhaust (prop). The early jet engines were pure turbojets - produced very high velocity exhaust. This was poorly matched to a sub-sonic airplane, so even though the engine efficiency wasn't too bad, the overall aircraft efficiency was bad. A modern jet is "high bypass", basically the turbine drives a large fan (almost the same as a prop) that you can see in the front of the engine. This moves a modest amount of air at a speed matched to the slightly sub-sonic speed of a modern airliner. Small aircraft are typically slower, and so use props which produce a lower velocity exhaust. Now, independent of that a piston engine is somewhat more efficient than a turbine engine, but weights more. For most large aircraft applications, the lower weight of a turbine results in better efficiency, even though the engine itself is a bit worse. (sorry for double posting - just opened an account). frisch AMEL
I'm a small aircraft pilot, have studied quite a bit about aircraft engines as well. Small aircraft engines need to operate under different conditions from car engines. In a typical car, you cruise at 10-20% of the maximum engine power. In a light aircraft, you cruise at 60-80% of maximum engine power (no speed limits). If you made the aircraft engine larger, it would add significantly to the overall weight, and decrease the range or carrying capacity of the plane. In a typical small plane, the engine is already around 1/4 of the total weight. If I put in a large enough engine to run at 20% power rather than 80% it would weigh as much as the rest of the plane.