Design or reuse protocols that push X over e-mail. Back in the day, services would essentially perform FTP or HTTP over e-mail. You don't need attachments -- uuencode data and use or create your own in-email attachment description. (This was done before attachment handling was standardized in mail clients.) E-mail size is not a problem, simply chop data up into less-than-1-MB pieces and rejoin them at the other end. (This is still done with newsgroups.) Set up your own server that is not limited to respond to your by-mail queries.
All of your problems have been solved in the past.:-)
If you'll read elsewhere, this measure isn't to try to stop anything. The I-95, which visitors have had to fill out for quite some time now, is simply being moved online.
I think my major problem is in understanding how something can have a rest mass when it never comes to rest.
It doesn't and can't have rest mass. But saying that the rest mass is undefined because it can't come to rest, knowing a priori that it can't come to rest, is unsatisfying. Various equations include rest mass; one should know that this is zero for a photon. (Unfortunately, particles with no rest mass are called "massless". Technically, something with no mass whatsoever has no energy, and as such is not a "thing" at all.)
There's actually a lot of significant to "unable to be at rest". Massive particles are constrained to have speeds less than c. This means that there exists some inertial reference frame where the particle has speeed zero (or, for that matter, any other arbitrarily-chosen velocity). Massless particles exist only at speed c. As such, in all inertial reference frames, their speed is still c. (This fact is really at the heart of relativistic mechanics.)
Does that make sense? You could give energy of composition its own letter, so that solving E=mc^2 for m doesn't draw people to the wrong conclusions.
Your understanding here of mass and energy seems correct. For mostly historical reasons, relativistic terminology isn't very good. Real physicists (tm) do separate correctly rest mass / rest energy and total energy. What terms you use can very depending on what sort of objects you're talking about.
Note that unfortunately, this ideal view of things where you have only "fundamental matter-energy" and various binding energies is inconvenient, as relativity doesn't (yet!) work very well for subatomic physics. (The other place relativity is really useful is at the astronomical scale, where such a treatment wouldn't be possible anyway. You have to abstract things like stars into "giant balls of mass" without knowing too much about their real internal composition.)
The big confusion is that laypeople view mass as an intrinsic property of an object and they understand (for a well-educated layperson) Newtonian mechanics. To a physicist, rest mass is an intrinsic property of an object, and mass is just energy (which is rest mass + energy from other sources). Despite being able to roughly interpret some relativistic principles, laypeople generally don't have much practice never mixing relativistic concepts with Newtonian concepts.
But yes, as I was telling my wife earlier today, someone should be punished for terminology in relativity. Mass and energy should be renamed weird, arcane terms that can't possibly be confused with other things.
Indeed. I'm misremembering electromagnetics a bit.:-) For one, wavenumber is generally written with a nu (although n is sometimes used), and it's really k-vec (wavevector) or nu*k-hat (wavenumber * wave direction).
I don't mean to imply that you're flat-out wrong, only that you're treading in dangerous territory with your understanding.
I should clarify that photons don't simply have "no rest mass". They have a rest mass, and it is exactly zero. (If I recall correctly, particles with zero rest mass are conveniently constrained to move at v=c, and particles with nonzero rest mass are always capable of moving at v=0 in some frame.)
Photons certainly do have mass, since they have energy, and the two are the same. In fact, if you had a perfect-mirror box, you could put five pounds of light in a box.
Most fundamental particles (quarks and leptons, for example) have some nonzero rest mass that appears to be a fundamental quantity. Everywhere else, "mass" is a euphemism for energy that isn't carefully-accounted for. The "rest mass" of a brick is made up of the fundamental rest masses of its constituent particles, plus lots of binding energy (between quarks, between nuclear particles, between electrons, et cetera). In the same way, we call kinetic energy, abstracted away in a statistical fashion, "heat". At a fine-grained level, there is no heat. Likewise, at a fine-grained level, there is only fundamental rest masses and energy. (And energy is the same as mass.)
So your five pounds of light in a box could suddenly become accounted away as box with a rest mass of five pounds (plus mass of empty box).
The danger is allowing any relativistic quantity to touch a non-relativistic equation or view of the world. It's sure to lead you to very wrong ideas. (See, for example, "zero mass is the same as infinite mass", elsewhere in this discussion.)
The problem is you're referring to mass as an intrinsic property. While rest mass is intrinsic, total mass isn't.
For all things, total mass is the relevant quantity, not rest mass -- so photons do, in theory, exert gravitational force.
Inertia, though, can only be thought of as some separate quantity in nonrelativistic mechanics -- which obviously doesn't apply to light. For any relativistic particle (particularly light, which has no rest mass and so cannot be treated at all with Newtonian mechanics), you need to use relativistic equations of motion.
However, rest mass is a different thing than "total mass". It's fairly similar to "heat" versus "kinetic energy" in that the rest mass for objects usually is hiding many different energies that we're not tallying individually (strong and electromagnetic binding energies, for example). The rest mass of an object is the mass it has with v=0. This is the same as rest energy, sure. It's not the same as total energy / mass.
Some physicists even refer to the quantity as mass-energy for clarity's sake. I prefer the convention that rest mass is always referred to as "mass", and total energy is referred to as "energy". Adding "rest" to "mass" and "relativistic" to "energy" doesn't hurt, though.
It's not a "hard rule" so much as a result of deeper theory that's confirmed by experiment.
Light does not have infinite mass. We do have the tools to measure its properties (momentum, energy, and rest mass).
The reason, by relativistic theory, that a particle with nonzero rest mass cannot move at the speed of light is that its energy is E = m_0 * c^2 / sqrt(1 - v^2/c^2). The energy diverges as v approaches c. (Note that this equation is undefined if v = c and m_0 = 0.) The kinetic energy, E - m_0 * c^2, must be supplied to the moving body. As available energy is finite, massive bodies are constrained to v c.
Massless bodies have energy determined solely by their momentum. (Without relativity, it's known that electromagnetic radiation carries momentum and energy.) Their energy is not divergent at v = c.
You're conflating two terms for mass. A photon does indeed have "mass". However, it does not have rest mass, which is what is usually meant by "mass", and is certainly what is meant when the photon is referred to as a "massless particle". (Since energy and mass are the same, it's rare in physics to see non-rest mass referred to as "mass" at all. It's energy -- or relativistic energy.)
No. The formulas for momentum and energy that are simply a product of mass and velocity are nonrelativistic equations, approximately correct for bodies with rest mass at "slow" speeds.
There are two quantities when discussing "mass". What we generally refer to as "mass", an intrinsic property of an object, is rest mass. Light has no rest mass (and never exists at rest). Objects with nonzero rest mass can have speeds between 0 (inclusive) and c (exclusive). Objects with zero rest mass have velocity c only.
The momentum carried by a photon with energy E is p = E / c.
It's sufficient to just call it an electromagnetic pulse. But, to be pedantic, your choices for terms are "electromagnetic field" and "electromotive force"; the term "EMF" generally refers to the latter.
It should do whatever the person configuring it tells it to do. But it's a bad feature because it has inconsistent behavior that's not clear to the user.
There's a certain usefulness to being familiar with what a science lab is like and the daily operations of scientific research, but that's not central to science fiction writing.
It is clear, though, that some science fiction writers have no understanding of scientific principles, and some certainly do. When science plays a visible role in a sci-fi story, particularly when the author is intending for the story to be not far from reality, the difference is really clear.
As far as I've seen, there are almost no science journalists that know a bit of science. As they say on the Internet, nearly all science news stories are full of fail.
It's not a legitimate feature because it's not at all part of the Internet mail standard. As such, it shouldn't be enabled if the Exchange server allows access over a protocol that doesn't accept this. It shouldn't be enabled at all, since it establishes different standards for internal and external e-mail, which are (presumably) bridged.
That really depends on the quality of the malware. There are some fairly low-level hacks that are difficult to interrupt via the Windows APIs. A downside of the APIs is that if you trust them too much, you'll discover that once a rootkit is in place, it's quite capable of circumventing nearly all API detection mechanisms.
If you have a clean system and a piece of malware, though, and the malware is fairly unsophisticated, figuring out what it's doing is pretty straighforward. (Most operating systems have these kind of hooks, too -- it's how you build device drivers and do low-level debugging.)
The point is to limit anonymous Internet access. Mobile phone communications are all tied to a particular mobile phone, which cannot be acquired anonymously in India (for appropriate definitions of "cannot").
The National Academies advise the government. As such, subjects of government spending are a major feature in this advice. However, they don't necessarily have access to information on military space endeavors, nor a voice in what its goals are. (At least, not in a public document.)
Of course, they could assess the importance of a private-industry space "program". That's a good topic for a separate report. It may even come up in this one, if private industry is viewed as a viable alternative for government-funded projects.
Good job not understanding the purpose of the report or the agency doing the reporting.
The people researching and publishing this are, essentially, people involved in the civil space industry. It's the National Academies Space Studies Board.
You are apparently readily confused with the language they use for these political reports. You interpret "Why do we have this program?" as if the speaker is implying that we should not.
What they are doing is looking at what function the space program performs, what it has accomplishes, what its goals are, what we can expect in terms of future accomplishments, et cetera. The purpose of this is not just to advise funding in general, but to provide a background for making decisions about setting future goals for the space program and determining how best to set about accomplishing those goals.
Slashdot Mirror
It was a snake, well before avians existed.
Before that, it was fish.
Eggs are created to be a large amount of nourishment in an enclosed package. The idea of eating them is probably as old as the existence of eggs.
Bad malware authors make it obvious that you're being scammed.
With good malware authors, you don't even know they're there, much less that you're being scanned. :-)
Hey, *someone's* got to apply all those malware techniques to a money-making venture.
You have unlimited access to e-mail?
Design or reuse protocols that push X over e-mail. Back in the day, services would essentially perform FTP or HTTP over e-mail. You don't need attachments -- uuencode data and use or create your own in-email attachment description. (This was done before attachment handling was standardized in mail clients.) E-mail size is not a problem, simply chop data up into less-than-1-MB pieces and rejoin them at the other end. (This is still done with newsgroups.) Set up your own server that is not limited to respond to your by-mail queries.
All of your problems have been solved in the past. :-)
If you'll read elsewhere, this measure isn't to try to stop anything. The I-95, which visitors have had to fill out for quite some time now, is simply being moved online.
I think my major problem is in understanding how something can have a rest mass when it never comes to rest.
It doesn't and can't have rest mass. But saying that the rest mass is undefined because it can't come to rest, knowing a priori that it can't come to rest, is unsatisfying. Various equations include rest mass; one should know that this is zero for a photon. (Unfortunately, particles with no rest mass are called "massless". Technically, something with no mass whatsoever has no energy, and as such is not a "thing" at all.)
There's actually a lot of significant to "unable to be at rest". Massive particles are constrained to have speeds less than c. This means that there exists some inertial reference frame where the particle has speeed zero (or, for that matter, any other arbitrarily-chosen velocity). Massless particles exist only at speed c. As such, in all inertial reference frames, their speed is still c. (This fact is really at the heart of relativistic mechanics.)
Does that make sense? You could give energy of composition its own letter, so that solving E=mc^2 for m doesn't draw people to the wrong conclusions.
Your understanding here of mass and energy seems correct. For mostly historical reasons, relativistic terminology isn't very good. Real physicists (tm) do separate correctly rest mass / rest energy and total energy. What terms you use can very depending on what sort of objects you're talking about.
Note that unfortunately, this ideal view of things where you have only "fundamental matter-energy" and various binding energies is inconvenient, as relativity doesn't (yet!) work very well for subatomic physics. (The other place relativity is really useful is at the astronomical scale, where such a treatment wouldn't be possible anyway. You have to abstract things like stars into "giant balls of mass" without knowing too much about their real internal composition.)
The big confusion is that laypeople view mass as an intrinsic property of an object and they understand (for a well-educated layperson) Newtonian mechanics. To a physicist, rest mass is an intrinsic property of an object, and mass is just energy (which is rest mass + energy from other sources). Despite being able to roughly interpret some relativistic principles, laypeople generally don't have much practice never mixing relativistic concepts with Newtonian concepts.
But yes, as I was telling my wife earlier today, someone should be punished for terminology in relativity. Mass and energy should be renamed weird, arcane terms that can't possibly be confused with other things.
Indeed. I'm misremembering electromagnetics a bit. :-) For one, wavenumber is generally written with a nu (although n is sometimes used), and it's really k-vec (wavevector) or nu*k-hat (wavenumber * wave direction).
I don't mean to imply that you're flat-out wrong, only that you're treading in dangerous territory with your understanding.
I should clarify that photons don't simply have "no rest mass". They have a rest mass, and it is exactly zero. (If I recall correctly, particles with zero rest mass are conveniently constrained to move at v=c, and particles with nonzero rest mass are always capable of moving at v=0 in some frame.)
Photons certainly do have mass, since they have energy, and the two are the same. In fact, if you had a perfect-mirror box, you could put five pounds of light in a box.
Most fundamental particles (quarks and leptons, for example) have some nonzero rest mass that appears to be a fundamental quantity. Everywhere else, "mass" is a euphemism for energy that isn't carefully-accounted for. The "rest mass" of a brick is made up of the fundamental rest masses of its constituent particles, plus lots of binding energy (between quarks, between nuclear particles, between electrons, et cetera). In the same way, we call kinetic energy, abstracted away in a statistical fashion, "heat". At a fine-grained level, there is no heat. Likewise, at a fine-grained level, there is only fundamental rest masses and energy. (And energy is the same as mass.)
So your five pounds of light in a box could suddenly become accounted away as box with a rest mass of five pounds (plus mass of empty box).
The danger is allowing any relativistic quantity to touch a non-relativistic equation or view of the world. It's sure to lead you to very wrong ideas. (See, for example, "zero mass is the same as infinite mass", elsewhere in this discussion.)
As it turns out, your stunning revelation is actually readily answered by a fairly small amount of education in physics.
Hint: you are referring to two different quantities using the same term, "mass".
Wavenumber (n), wavevector (k), and Planck's constant (h).
E = nhk = hf = hbar*omega
The problem is you're referring to mass as an intrinsic property. While rest mass is intrinsic, total mass isn't.
For all things, total mass is the relevant quantity, not rest mass -- so photons do, in theory, exert gravitational force.
Inertia, though, can only be thought of as some separate quantity in nonrelativistic mechanics -- which obviously doesn't apply to light. For any relativistic particle (particularly light, which has no rest mass and so cannot be treated at all with Newtonian mechanics), you need to use relativistic equations of motion.
No, energy and mass are exactly the same thing.
However, rest mass is a different thing than "total mass". It's fairly similar to "heat" versus "kinetic energy" in that the rest mass for objects usually is hiding many different energies that we're not tallying individually (strong and electromagnetic binding energies, for example). The rest mass of an object is the mass it has with v=0. This is the same as rest energy, sure. It's not the same as total energy / mass.
Some physicists even refer to the quantity as mass-energy for clarity's sake. I prefer the convention that rest mass is always referred to as "mass", and total energy is referred to as "energy". Adding "rest" to "mass" and "relativistic" to "energy" doesn't hurt, though.
It's not a "hard rule" so much as a result of deeper theory that's confirmed by experiment.
Light does not have infinite mass. We do have the tools to measure its properties (momentum, energy, and rest mass).
The reason, by relativistic theory, that a particle with nonzero rest mass cannot move at the speed of light is that its energy is E = m_0 * c^2 / sqrt(1 - v^2/c^2). The energy diverges as v approaches c. (Note that this equation is undefined if v = c and m_0 = 0.) The kinetic energy, E - m_0 * c^2, must be supplied to the moving body. As available energy is finite, massive bodies are constrained to v c.
Massless bodies have energy determined solely by their momentum. (Without relativity, it's known that electromagnetic radiation carries momentum and energy.) Their energy is not divergent at v = c.
You're conflating two terms for mass. A photon does indeed have "mass". However, it does not have rest mass, which is what is usually meant by "mass", and is certainly what is meant when the photon is referred to as a "massless particle". (Since energy and mass are the same, it's rare in physics to see non-rest mass referred to as "mass" at all. It's energy -- or relativistic energy.)
No. The formulas for momentum and energy that are simply a product of mass and velocity are nonrelativistic equations, approximately correct for bodies with rest mass at "slow" speeds.
There are two quantities when discussing "mass". What we generally refer to as "mass", an intrinsic property of an object, is rest mass. Light has no rest mass (and never exists at rest). Objects with nonzero rest mass can have speeds between 0 (inclusive) and c (exclusive). Objects with zero rest mass have velocity c only.
The momentum carried by a photon with energy E is p = E / c.
It's sufficient to just call it an electromagnetic pulse. But, to be pedantic, your choices for terms are "electromagnetic field" and "electromotive force"; the term "EMF" generally refers to the latter.
You don't know this either. You've just been told by people who want to disagree with the media and organizations like the U.N.
It should do whatever the person configuring it tells it to do. But it's a bad feature because it has inconsistent behavior that's not clear to the user.
There's a certain usefulness to being familiar with what a science lab is like and the daily operations of scientific research, but that's not central to science fiction writing.
It is clear, though, that some science fiction writers have no understanding of scientific principles, and some certainly do. When science plays a visible role in a sci-fi story, particularly when the author is intending for the story to be not far from reality, the difference is really clear.
As far as I've seen, there are almost no science journalists that know a bit of science. As they say on the Internet, nearly all science news stories are full of fail.
It's not a legitimate feature because it's not at all part of the Internet mail standard. As such, it shouldn't be enabled if the Exchange server allows access over a protocol that doesn't accept this. It shouldn't be enabled at all, since it establishes different standards for internal and external e-mail, which are (presumably) bridged.
That really depends on the quality of the malware. There are some fairly low-level hacks that are difficult to interrupt via the Windows APIs. A downside of the APIs is that if you trust them too much, you'll discover that once a rootkit is in place, it's quite capable of circumventing nearly all API detection mechanisms.
If you have a clean system and a piece of malware, though, and the malware is fairly unsophisticated, figuring out what it's doing is pretty straighforward. (Most operating systems have these kind of hooks, too -- it's how you build device drivers and do low-level debugging.)
You can secure both wired and wireless connections very well. It's just not convenient or cost-effective.
The point is to limit anonymous Internet access. Mobile phone communications are all tied to a particular mobile phone, which cannot be acquired anonymously in India (for appropriate definitions of "cannot").
The National Academies advise the government. As such, subjects of government spending are a major feature in this advice. However, they don't necessarily have access to information on military space endeavors, nor a voice in what its goals are. (At least, not in a public document.)
Of course, they could assess the importance of a private-industry space "program". That's a good topic for a separate report. It may even come up in this one, if private industry is viewed as a viable alternative for government-funded projects.
Good job not understanding the purpose of the report or the agency doing the reporting.
The people researching and publishing this are, essentially, people involved in the civil space industry. It's the National Academies Space Studies Board.
You are apparently readily confused with the language they use for these political reports. You interpret "Why do we have this program?" as if the speaker is implying that we should not.
What they are doing is looking at what function the space program performs, what it has accomplishes, what its goals are, what we can expect in terms of future accomplishments, et cetera. The purpose of this is not just to advise funding in general, but to provide a background for making decisions about setting future goals for the space program and determining how best to set about accomplishing those goals.