Next comes the physicist, he looks down, does a short calculation in his head, jumps and is saved.
oh this is so unlikely, i think it should read:
"Next comes the physicist, he looks down, does a short calculation in his head, jumps and misses by one meter. What happened ? He calculated only up to orders of magnitude."
or maybe:
"He got caught by a four-sigma event. (he was a High Energy Phsicist)"
or maybe:
"He assumed periodic boundary conditions. (he was a condensed matter theoretician)"
not necessarily: the number of photons (i.e. the intensity) in the blue beam could be smaller. For energy conservation, you have to consider the whole system: light in/out AND sound wave in/out; there is probably some energy transfer from the sound wave to the light.
I think, the proposed device would work in pulsed mode, however, the article states that it would not need gigawatts/cm2 of light fluence, i.e. you don't need focused femtosecond light pulses like in "conventional" frequency doubling/tripling, white light generation or optical parametric amplification.
Re:See outside the bubble?
on
Mastering Light
·
· Score: 5, Informative
converters IR->visible are widely known: night vision goggles.
converters UV->visible do also exist and are commercially available, they are not as common because they do not have so many applications (one of them is to detect corona discharge in high voltage applications, power lines). They use a stack of a photocathode (UV light->electrons), Micro Channel Plates (amplification) and a Phosphor Screen (electrons->visible light).
another thing is interesting to note: there are a LOT of problems in mathematics in which n=1 is trivial, n=2 is hard but straight forward. n>3 is not too hard and usually falls under one proof, and n=3 is EXTRAORDINARILY difficult. poincare, random walks, you name it.
This is really interesting. Is there any explanation why n=3 is so difficult ?
you seem to be assuming that the audio is somehow connected to "the terminal".
it is natural to assume that the audio equipment is connected to the machine where the user is sitting, i.e. the terminal - not the remote machine (that could be located in a different building).
Steel is a quite general term. There are many sorts of steel with different mechanical (strength) and chemical (corrosion) properties. Is the "construction" steel really the optimum w.r.t. corrsion ? I highly doubt it. It's probably a tradeoff between strength and price, with the price being the more important factor. There are, for example, special steel grades for marine applications, which have to withstand salty water for decades.
Another point: there are other metals besides Iron (steel). One would be Titanium, which is also very strong but does not corrode in the same way as Iron: it's very reactive but it develops a protective oxide layer on the surface and oxidation does not penetrate into the depth as in Iron. Yes, it's very expensive, but if the ultimate solution is required, one should consider other materials as well.
It's also not true in Japan, as we can read in the article. Nevertheless, it is interesting to hear that the people in Hong Kong value the time of somebody calling on the phone more than the time of somebody that they have put some effort to meet personally.
I think the vibrate feature is essential. It's a shame that so many people don't use it. It's even more a shame that so many people don't bother to change the default ring melody and/or have the ringing volume set to the maximum. OTOH, the situation is improving - it was worse one or two years ago.
The idea that when they ring you should interrupt whatever you are doing and answer them just seems impolite.
It _is_ considered impolite _especially_ with mobile phones. The article also mentions that before people make an actual call, they send messages to find out whether the partner can be interrupted. The fact that calling somebody on a mobile phone is such an intrusion makes it necessary to "warn" the partner. Thus, phoning somebody get's more complex...Weird, isn't it?
The point is, people don't need network transparency on a desktop machine. The gamers and multimedia freaks are using desktop machines and want to push the development to a direction where it can suit _their_ needs better. However, there are other groups - mostly in corporate environment - where network transparency is _essential_. Therefore, a decision to drop this network transparency would also be a decision to drop the user base in corporate environment.
This worked as long as it was the only means to get help. The times will come where you will be _expected_ to carry a mobile phone and get your help yourself. When you knock on a door asking for help, people will probably suspect that you are a beggar; "What? You don't have a mobile phone to call help? You are either very strange or a beggar or just lying." Two years ago, when I called the police to report some obstacle on the freeway, the operator asked for my mobile phone number. When I told him that I was calling from home, he said: "Oh, I was _assuming_ you were calling from your mobile phone. In that case, I need your name and address...". And this was not in Japan. It was in a European country and it was two years ago.
Don't we all realize how - with the increasing ability to always get in contact with our friends - the people directly around us get less and less important? They _have_ to get less important, because we can and do now spend more time to communicate with our friends (the people we already know). Consequently, we cannot spend that time with people around us that we do not know yet. For example, if you get bored on subway you call a friend or send him/her messages, while in previous times the only option was to talk to the the stranger on the next seat (thus possibly making a new acquaintance). Not that talking to strangers in a subway was something we did regularly. In that context, isn't it remarkable that the more people are around us (city vs. small village), the less common is it to talk to people you don't know ? I find it more and more difficult to make new acquaintances because the reasons to talk to people I don't already know are vanishing...You are not expected to do it - next step is: you are expected to not do it.
Of course, all this has consequences: If your friends are spread out throughout the country (and this is only a matter of time), transport will become more important...not _less_ important as some have predicted for the age of connected world. But this a different story...
Yes it does, but this depends of the level of support for a particular video card. You can look up the details in the Xfree documentation. This is not the problem, however. The problem is, that X Windows is more complex than strictly necessary for a desktop machine. X Windows was designed for network computers, where people run programs one one machine and the display and user input is a seperate machine (the X terminal) both connected through the TCP/IP network. This unnecessary overhead of having to run a network protocol and duplicate some resources (esp. RAM) on the client and server machine (which are identical on for desktop machine) is what is criticised by people. Now it would be nice If we could run the X Server code on a seperate hardware, the gfx card. Unfortunately the X Server is too complicated to run on today's gfx cards. But the trend in gfx cards is clearly towards more independent computing power on the cards. Therefore it would be unwise to remove a layer of abstraction that we probably could use in forseeable future.
We have VNC, why does X need to go through TCP/IP to draw a window?
Because going through a network is an abstraction. It detaches the job of computing and displaying so that they can be easily implemented on different hardware. Removing this abstraction is a step backwards, esp. if you keep in mind that hardware is getting faster all the time. The logical step would be rather to implement the X Server on seperate hardware, i.e. the graphics card.
word! AmigaOS had preemptive multitasking when most people were still using DOS on their PCs. Now that you say it, I also realize that no Windows machine that I have been using has ever been as responsive as the old Amiga. Of course this is also a hardware issue: the Amiga had pretty strict timing for all I/O operations and memory access. The different subsystems had their own time slots in DMA, which was based on the video refresh timing. To a certain amount other subsystems, like the "Blitter", could steal DMA cycles from the CPU. There was even a chip, the "Copper", that could perform certain actions based on the position of the electron beam of the monitor. In my opinion, this chip was the key to most of the impressive effects that could be produced by the Amiga. OTOH, such a design is pretty hard to scale w.r.t. speed. In the end, the Amiga declined because Commodore neglected hardware development for too long.
Actually I would be interested in a program that can simulate an electron gun (steady state, no dynamics required but space charge effects are an issue). Is there any free software that can do this ? It would be nice if we could optimize our e-beam heating, however I can not spend money on this, because it's not a central part of our experiment and it already kind of works.
These chips will not be based on cut diamond wafers in the way today chips are based on cut silicon wafers because it's pretty much impossible to cut diamond. Rather they would be based on evaporated diamond films (like the SOI - Silicon On Insulator - technique). The fact that diamond is more suitable at higher temperatures is due to it's large band-gap: 5.5 eV (Si has 1.1 eV). So even at high temperature diamond is an (very good) isolator (very pure Si is also an good isolator at room temperature but it gets a lot more conductive at higher temperatures due to its small band gap). This large band-gap is also the reason why diamond would be a candidate for UV LEDs or lasers (UV starts at about 3eV). OTOH, Silicon with 1.1eV is in the infrared. BTW, the 235nm radiation they mention in the article corresponds to ~5.2 eV.
Rocket propulsion has the fundamental disadvantage over all other means of propulsion in that it "throws away" mass - which requires a large starting mass if you want long operation times (you are limited by the rocket equation). Jet propulsion on the other hand just accelerates the surrounding air - you don't have to carry all the air with you, whereas you have to carry all rocket fuel with you (and in the beginning you have to lift all the rocket fuel that will be used at later time of the flight).
I think the fact that the 5000K or 50000K plasma doesn't affect the temperature of Pioneer much is not the presence or absence of vacuum but the fact that the density of that plasma is very low. The thermal effect of electromagnetic radiation from the sun is much higher because there is a lot more of it.
Genetic algorithms are great to search a large parameter space for a solution if you have plenty of time and resources. Remember, for a genetic algoritm to work you need lots of organisms that have to compete and mate and you need to do it for a number of generations to have it converge to a solution. (And then, as Chris Burke pointed out, you still need a criterion to judge the "fitness" of the organisms with respect to flying). It may be possible, if you do this all in a computer simulation, but if you want a real result you will have to test it sooner or later in a real sample.
Regardless of what smack you smoke, it comes down to going out and voting. 1 person. 1 vote. 1 count towards the overall total. If you are an idiot and vote because of a campaign ad or heavy influence from, campaign finance reform is not going to change that--that's a fundamental nature of the system.
Your reasoning has a crucial error, which is the reason why up to now voting did not eliminate this problem: When people vote they usually do not vote on the basis of one issue (i.e. party fincancing OR economic considerations OR foreign affairs etc.) but they try to set priorities and find a balance between advantages and disadvantages of their voting options. When you vote, you vote the whole package; you can't vote person X for his views on party fincancing and and at the same time vote person Y for his views on economy. Now, obviously party fincancing is not top priority list of people which is the reason why the politicians' views on this topic do not affect the votes very much. Generally, for topics not on the top priority list of the masses voting only produces a random outcome (in statistics speech, the votes and views of the voted politicians on that topic are not correlated). This is the reason why for minor topics you have to use other mechanims than voting to achieve an effect (e.g. lobbying, founding a new party or joining an established one).
Of course this would lead to full employment. In the stone age we had full employment, too. (Unconditional) full employment is not good per se. We have only partial employment because our economy is so efficient that we do not NEED full employment to sustain the extremely high living standard. The Green now want to reduce efficiency to old levels to reach full employment again. I think this is the wrong way. The correct way is to look either for mechanisms to distribute the work more equally over the population (i.e. encourage part-time work or opening up new fields of economy with need for manpower) or to assist the few people that have no work (i.e. welfare). I think the first option is the better one, because welfare has some drawbacks: it's expensive above a certain unemployment level and to have no work at all has also severe psychological consequences for the affected people and their families. That does not mean that welfare should be eliminated completely - it should just be a last hope for difficult cases.
Increasing the rate of pulses (repetition rate) with the energy per pulse staying the same would indeed increase the thermal (destructive) load on the surrounding material. However, the question is, whether this increase would be significant. This really depends on where you start from (pulse energy) and what material you are looking at, i.e. on the actual numbers.
However, increasing the repetition rate without reducing pulse energy is not easy. In fact, to get the pulse energy to levels where you can evaporate material you have to reduce the repetition rate. Usually fs-Lasers are built in the way that there is an "oscillator" that delivers short but weak pulses at a very high repetition rate (around 100 MHz). To get more intense pulses you have to amplify them, which usually results in a lower repetition rate, because for an amplification to take effect you have to apply it for a certain time (sum up several round trips of the pulse in the amplifier). For example in the laser I'm working with the oscillator delivers 20fs long pulses at 80MHz with each pulse having an energy of 5nJ. These pulses are fed into an "Regenerative Amplifier" that delivers 50fs pulses at 200kHz with each pulse having 5uJ of energy (a factor of 1000 more). The amplifier does this by letting a "seed" pulse from the oscillator run several times through an amplifier medium (a laser crystal) until a maximum pulse energy is reached and the amplified pulse is released to the output. You cannot however amplify every of the 80MHz pulses this way, because the amplifier medium has to regenerate ("charge up") before it can amplify again - that's where the name "regenerative amplifier" comes from.
In some systems you can trade repetition rate for pulse energy, i.e. get more intense pulses by lowering the repetition rate (giving the amlifying medium more time to regenerate and therby reaching higher "charge" levels), but only in a limited range.
With respect to gamma/X-ray shielding who depend on electron number, I don't think that large improvements in total weight of shielding can be made. The reason is of course that for charge neutrality reasons each electron has to be balanced by one proton in a core plus some amount of neutrons. It is only the amount of additional neutrons that can be varied by chosing different materials and as it happens to be the percentage of neutrons in nuclei increases with Z, with the extreme being the hydrogen 1H atom that has no proton at all. From this reasoning it would be best to use materials with high hydrogen amount (polymers for example) to reduce weight. But then volume is a concern too, esp. with polymers who have a low density (compared to high Z metals).
Neutrinos, however, (almost) do not interact, so they leave the star at c
Latest results indicate that neutrinos have mass and therefore they have to move below c. As the SN are lightyears away even a small deviation from c could be important. So the question remains: is this effect negligible compared to the time differences you mentioned ?
Slashdot Mirror
Next comes the physicist, he looks down, does a short calculation in his head, jumps and is saved.
oh this is so unlikely, i think it should read:
"Next comes the physicist, he looks down, does a short calculation in his head, jumps and misses by one meter. What happened ? He calculated only up to orders of magnitude."
or maybe:
"He got caught by a four-sigma event. (he was a High Energy Phsicist)"
or maybe:
"He assumed periodic boundary conditions. (he was a condensed matter theoretician)"
or maybe:
"He neglected all factors of 2 Pi."
or maybe:
"He had set hbar=c=1."
not necessarily: the number of photons (i.e. the intensity) in the blue beam could be smaller. For energy conservation, you have to consider the whole system: light in/out AND sound wave in/out; there is probably some energy transfer from the sound wave to the light.
I think, the proposed device would work in pulsed mode, however, the article states that it would not need gigawatts/cm2 of light fluence, i.e. you don't need focused femtosecond light pulses like in "conventional" frequency doubling/tripling, white light generation or optical parametric amplification.
converters IR->visible are widely known: night vision goggles.
converters UV->visible do also exist and are commercially available, they are not as common because they do not have so many applications (one of them is to detect corona discharge in high voltage applications, power lines). They use a stack of a photocathode (UV light->electrons), Micro Channel Plates (amplification) and a Phosphor Screen (electrons->visible light).
another thing is interesting to note: there are a LOT of problems in mathematics in which n=1 is trivial, n=2 is hard but straight forward. n>3 is not too hard and usually falls under one proof, and n=3 is EXTRAORDINARILY difficult. poincare, random walks, you name it.
This is really interesting. Is there any explanation why n=3 is so difficult ?
you seem to be assuming that the audio is somehow connected to "the terminal".
it is natural to assume that the audio equipment is connected to the machine where the user is sitting, i.e. the terminal - not the remote machine (that could be located in a different building).
Steel is a quite general term. There are many sorts of steel with different mechanical (strength) and chemical (corrosion) properties. Is the "construction" steel really the optimum w.r.t. corrsion ? I highly doubt it. It's probably a tradeoff between strength and price, with the price being the more important factor. There are, for example, special steel grades for marine applications, which have to withstand salty water for decades.
Another point: there are other metals besides Iron (steel). One would be Titanium, which is also very strong but does not corrode in the same way as Iron: it's very reactive but it develops a protective oxide layer on the surface and oxidation does not penetrate into the depth as in Iron. Yes, it's very expensive, but if the ultimate solution is required, one should consider other materials as well.
It's also not true in Japan, as we can read in the article. Nevertheless, it is interesting to hear that the people in Hong Kong value the time of somebody calling on the phone more than the time of somebody that they have put some effort to meet personally.
I think the vibrate feature is essential. It's a shame that so many people don't use it. It's even more a shame that so many people don't bother to change the default ring melody and/or have the ringing volume set to the maximum. OTOH, the situation is improving - it was worse one or two years ago.
The idea that when they ring you should interrupt whatever you are doing and answer them just seems impolite.
It _is_ considered impolite _especially_ with mobile phones. The article also mentions that before people make an actual call, they send messages to find out whether the partner can be interrupted. The fact that calling somebody on a mobile phone is such an intrusion makes it necessary to "warn" the partner. Thus, phoning somebody get's more complex...Weird, isn't it?
The point is, people don't need network transparency on a desktop machine. The gamers and multimedia freaks are using desktop machines and want to push the development to a direction where it can suit _their_ needs better. However, there are other groups - mostly in corporate environment - where network transparency is _essential_. Therefore, a decision to drop this network transparency would also be a decision to drop the user base in corporate environment.
This worked as long as it was the only means to get help. The times will come where you will be _expected_ to carry a mobile phone and get your help yourself. When you knock on a door asking for help, people will probably suspect that you are a beggar; "What? You don't have a mobile phone to call help? You are either very strange or a beggar or just lying."
Two years ago, when I called the police to report some obstacle on the freeway, the operator asked for my mobile phone number. When I told him that I was calling from home, he said: "Oh, I was _assuming_ you were calling from your mobile phone. In that case, I need your name and address...". And this was not in Japan. It was in a European country and it was two years ago.
Don't we all realize how - with the increasing ability to always get in contact with our friends - the people directly around us get less and less important? They _have_ to get less important, because we can and do now spend more time to communicate with our friends (the people we already know). Consequently, we cannot spend that time with people around us that we do not know yet. For example, if you get bored on subway you call a friend or send him/her messages, while in previous times the only option was to talk to the the stranger on the next seat (thus possibly making a new acquaintance). Not that talking to strangers in a subway was something we did regularly. In that context, isn't it remarkable that the more people are around us (city vs. small village), the less common is it to talk to people you don't know ?
I find it more and more difficult to make new acquaintances because the reasons to talk to people I don't already know are vanishing...You are not expected to do it - next step is: you are expected to not do it.
Of course, all this has consequences: If your friends are spread out throughout the country (and this is only a matter of time), transport will become more important...not _less_ important as some have predicted for the age of connected world. But this a different story...
Yes it does, but this depends of the level of support for a particular video card. You can look up the details in the Xfree documentation. This is not the problem, however. The problem is, that X Windows is more complex than strictly necessary for a desktop machine. X Windows was designed for network computers, where people run programs one one machine and the display and user input is a seperate machine (the X terminal) both connected through the TCP/IP network. This unnecessary overhead of having to run a network protocol and duplicate some resources (esp. RAM) on the client and server machine (which are identical on for desktop machine) is what is criticised by people.
Now it would be nice If we could run the X Server code on a seperate hardware, the gfx card. Unfortunately the X Server is too complicated to run on today's gfx cards. But the trend in gfx cards is clearly towards more independent computing power on the cards. Therefore it would be unwise to remove a layer of abstraction that we probably could use in forseeable future.
We have VNC, why does X need to go through TCP/IP to draw a window?
Because going through a network is an abstraction. It detaches the job of computing and displaying so that they can be easily implemented on different hardware. Removing this abstraction is a step backwards, esp. if you keep in mind that hardware is getting faster all the time.
The logical step would be rather to implement the X Server on seperate hardware, i.e. the graphics card.
word! AmigaOS had preemptive multitasking when most people were still using DOS on their PCs.
Now that you say it, I also realize that no Windows machine that I have been using has ever been as responsive as the old Amiga. Of course this is also a hardware issue: the Amiga had pretty strict timing for all I/O operations and memory access. The different subsystems had their own time slots in DMA, which was based on the video refresh timing. To a certain amount other subsystems, like the "Blitter", could steal DMA cycles from the CPU. There was even a chip, the "Copper", that could perform certain actions based on the position of the electron beam of the monitor. In my opinion, this chip was the key to most of the impressive effects that could be produced by the Amiga. OTOH, such a design is pretty hard to scale w.r.t. speed. In the end, the Amiga declined because Commodore neglected hardware development for too long.
Actually I would be interested in a program that can simulate an electron gun (steady state, no dynamics required but space charge effects are an issue). Is there any free software that can do this ? It would be nice if we could optimize our e-beam heating, however I can not spend money on this, because it's not a central part of our experiment and it already kind of works.
I really would like to see the error bars on these FPS numbers. Maybe 2 FPS is not even significant.
These chips will not be based on cut diamond wafers in the way today chips are based on cut silicon wafers because it's pretty much impossible to cut diamond. Rather they would be based on evaporated diamond films (like the SOI - Silicon On Insulator - technique).
The fact that diamond is more suitable at higher temperatures is due to it's large band-gap: 5.5 eV (Si has 1.1 eV). So even at high temperature diamond is an (very good) isolator (very pure Si is also an good isolator at room temperature but it gets a lot more conductive at higher temperatures due to its small band gap). This large band-gap is also the reason why diamond would be a candidate for UV LEDs or lasers (UV starts at about 3eV). OTOH, Silicon with 1.1eV is in the infrared. BTW, the 235nm radiation they mention in the article corresponds to ~5.2 eV.
Rocket propulsion has the fundamental disadvantage over all other means of propulsion in that it "throws away" mass - which requires a large starting mass if you want long operation times (you are limited by the rocket equation). Jet propulsion on the other hand just accelerates the surrounding air - you don't have to carry all the air with you, whereas you have to carry all rocket fuel with you (and in the beginning you have to lift all the rocket fuel that will be used at later time of the flight).
I think the fact that the 5000K or 50000K plasma doesn't affect the temperature of Pioneer much is not the presence or absence of vacuum but the fact that the density of that plasma is very low. The thermal effect of electromagnetic radiation from the sun is much higher because there is a lot more of it.
Genetic algorithms are great to search a large parameter space for a solution if you have plenty of time and resources. Remember, for a genetic algoritm to work you need lots of organisms that have to compete and mate and you need to do it for a number of generations to have it converge to a solution. (And then, as Chris Burke pointed out, you still need a criterion to judge the "fitness" of the organisms with respect to flying). It may be possible, if you do this all in a computer simulation, but if you want a real result you will have to test it sooner or later in a real sample.
Regardless of what smack you smoke, it comes down to going out and voting. 1 person. 1 vote. 1 count towards the overall total. If you are an idiot and vote because of a campaign ad or heavy influence from, campaign finance reform is not going to change that--that's a fundamental nature of the system.
Your reasoning has a crucial error, which is the reason why up to now voting did not eliminate this problem: When people vote they usually do not vote on the basis of one issue (i.e. party fincancing OR economic considerations OR foreign affairs etc.) but they try to set priorities and find a balance between advantages and disadvantages of their voting options. When you vote, you vote the whole package; you can't vote person X for his views on party fincancing and and at the same time vote person Y for his views on economy. Now, obviously party fincancing is not top priority list of people which is the reason why the politicians' views on this topic do not affect the votes very much.
Generally, for topics not on the top priority list of the masses voting only produces a random outcome (in statistics speech, the votes and views of the voted politicians on that topic are not correlated). This is the reason why for minor topics you have to use other mechanims than voting to achieve an effect (e.g. lobbying, founding a new party or joining an established one).
Of course this would lead to full employment. In the stone age we had full employment, too. (Unconditional) full employment is not good per se. We have only partial employment because our economy is so efficient that we do not NEED full employment to sustain the extremely high living standard. The Green now want to reduce efficiency to old levels to reach full employment again. I think this is the wrong way. The correct way is to look either for mechanisms to distribute the work more equally over the population (i.e. encourage part-time work or opening up new fields of economy with need for manpower) or to assist the few people that have no work (i.e. welfare).
I think the first option is the better one, because welfare has some drawbacks: it's expensive above a certain unemployment level and to have no work at all has also severe psychological consequences for the affected people and their families. That does not mean that welfare should be eliminated completely - it should just be a last hope for difficult cases.
Increasing the rate of pulses (repetition rate) with the energy per pulse staying the same would indeed increase the thermal (destructive) load on the surrounding material. However, the question is, whether
this increase would be significant. This really depends on where you start from (pulse energy) and what material you are looking at, i.e. on the actual numbers.
However, increasing the repetition rate without reducing pulse energy is not easy. In fact, to get the pulse energy to levels where you can evaporate material you have to reduce the repetition rate.
Usually fs-Lasers are built in the way that there is an "oscillator" that delivers short but weak pulses at a very high repetition rate (around 100 MHz). To get more intense pulses you have to amplify them, which usually results in a lower repetition rate, because for an amplification to take effect you have to apply it for a certain time (sum up several round trips of the pulse in the amplifier).
For example in the laser I'm working with the oscillator delivers 20fs long pulses at 80MHz with each pulse having an energy of 5nJ. These pulses are fed into an "Regenerative Amplifier" that delivers 50fs pulses at 200kHz with each pulse having 5uJ of energy (a factor of 1000 more). The amplifier does this by letting a "seed" pulse from the oscillator run several times through an amplifier medium (a laser crystal) until a maximum pulse energy is reached and the amplified pulse is released to the output. You cannot however amplify every of the 80MHz pulses this way, because the amplifier medium has to regenerate ("charge up") before it can amplify again - that's where the name "regenerative amplifier" comes from.
In some systems you can trade repetition rate for pulse energy, i.e. get more intense pulses by lowering
the repetition rate (giving the amlifying medium more time to regenerate and therby reaching higher "charge" levels), but only in a limited range.
With respect to gamma/X-ray shielding who depend on electron number, I don't think that large improvements in total weight of shielding can be made. The reason is of course that for charge neutrality reasons each electron has to be balanced by one proton in a core plus some amount of neutrons. It is only the amount of additional neutrons that can be varied by chosing different materials and as it happens to be the percentage of neutrons in nuclei increases with Z, with the extreme being the hydrogen 1H atom that has no proton at all. From this reasoning it would be best to use materials with high hydrogen amount (polymers for example) to reduce weight. But then volume is a concern too, esp. with polymers who have a low density (compared to high Z metals).
Neutrinos, however, (almost) do not interact, so they leave the star at c
Latest results indicate that neutrinos have mass and therefore they have to move below c. As the SN are lightyears away even a small deviation from c could be important. So the question remains: is this effect negligible compared to the time differences you mentioned ?