I think I'm not quite making my point: there's simply no sense in talking about attributes on the scale of the Plank Length, or the electron missing a cross section. The fact of it is that we simply don't know what's going on in the electron and that's all speculation.
What we do know is that it, electromagnetically, has a magnetic dipole, a charge monopole, and - as best we can tell - no charge dipole. The electromagnetic properties are the shape in the only sense that anyone ever really uses the word shape. So its shape is round.
If you want a picture in your minds eye of what we know about the electron, with the understanding that this is just a picture and the theory is the authoritative description, then a ball of charge is, in my opinion, closer to our current theories than a mysterious point particle. You bring up the classical charge radius above: this is precisely the radius that electron-positron virtual pairs can be created, and in a meaningful sense is something like an electron radius. (Although note that they have set limits on the charge radius by comparing the measured magnetic g-factor with the QED calculation, this is the 10^-20something that wikipedia quotes, but this really measures something different - I think you need to be more specific than just saying size at this length scale).
I understand the complications due to the electrons being in molecules - if you haven't twigged yet, JonyEpsilon == J.J. Hudson == first author of paper under discussion - but it doesn't have any real bearing on what we're talking about.
I don't know why people are so convinced the electron is a point particle. A point particle is an idealisation, one that even theory essentially rejects these days (in as much as the bare electron is a theoretical fiction which can't, even in principle, be considered separately from the vacuum polarisation it induces).
I don't think it's particularly misleading to think of a ball of charge either - there's no evidence to suggest this isn't the case!
I stand by my comment, and the title of my paper: I don't see what else what terms like "shape" and "spherical" can mean in this context, if one restricts oneself, as one must as a physicist, to things that can be measured.
Yeah, it really is spherical in any sense that you can mean spherical.
It can't have any higher order multipole moments because it only has spin 1/2. (So the Wigner-Eckart theorem tells you that all matrix elements with operators greater than spin 1/2 are necessarily zero.)
Jony
We used the compton wavelength of the electron as the size scale for this analogy. You could argue that the 1/e radius of the electron/positron virtual particle cloud would be a better measure, and this is closer to the classical radius (off the top of my head, it's late here), which would give an accuracy measured in mm rather than microns.
The 10^-22 number comes from interpreting ion trap measurements of the electron's g-factor, comparing them to QED theory.
To some extent, the question of the electron's size depends on what you mean by size and how you might choose to measure it.
Jony
Good questions!
This is actually one of the central motivations for measuring this is. The standard model of particle physics predicts that the electron will be round. But most physicists think that the standard model isn't the full story. The interesting thing is most of the proposed extensions/replacements to the standard model predict that the electron will be somewhat distorted. To give a concrete example, supersymmetric theories, which are viewed by many as the most promising avenue for extending our theories of physics, usually predict a distorted electron.
Don't people have statutory rights with regards to purchased goods in the US? I'm pretty sure if they tried such a trick in the UK they'll get a kicking in court.
Wow. I guess I've been lucky then. I look after a large number of licences for a physics department and we never seem to have any problems. What sort of difficulties did you have?
Of all the commercial software I've used that's had "strong" copy protection (i.e. you'd need to use a cracked copy, not just find a serial number), I've found Wolfram Research's Mathematica to have the best system. It generates a unique ID for your computer, and then you need to go online/call to get a password that works with your licence number and unique ID. I think the secret to making this work smoothly, and Wolfram have got this right, is to make sure that it takes no more than a second, and that there's always someone on the end of the phone who doesn't make you feel like a criminal if anything goes wrong. They're also very tolerant towards generating new passwords if you change your hardware enough to change your ID.
The only other real "strong" option seems to be hardware dongles. I hate them! I don't have a parallel port anymore, or a floppy disk drive, and I hate carrying extra crap around if I want to use stuff on my laptop.
Re:iPhone Samsung S3C6400 vs Nokia N95 OMAP 2040 C
on
Apple iPhone Dissected
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· Score: 1
I don't see how iPhone with twice as fast CPU and five time more RAM can have more battery life than N95, and twice at that. Very tricky power management?
Well, not having GPS and 3G to suck the battery dry probably helps. I think the battery is bigger too.
While fiber optics may have various decorative purposes such a product that encourages direct physical contact with them is worrisome. Even if measures were taken in production to prevent glass dust, spikes, etc. from making it into the product consider that something like a tablecloth would become worn with use, breaking fibers and causing bits of glass to become embedded in the skin or, when shaken out, glass dust to become inhaled. Consider the sort of problems fiberglass insulation workers run into. The safest way to display one would probably be with a sealed frame, allowing you to visually enjoy it while maintaining a protective layer of plastic between the glass and your family.
Got to disagree with that. There are a few hold-outs that have thus far resisted metrification - basically anything that involves old, miserable people - like speed limits, temperature, clothing and body weight. And there were some big arguments about weighing fruit (I'm still amazed that people can get so worked up about units). But everything else is pretty much metric: the plumbing in your house, screws in your electrical system, paper sizes, temperature of your oven, power of your lightbulbs (ergs/s anyone?), anything to do with engineering or science. Everybody who's serious is using metric.
Double-meh, why are you using such a locked-down system?
Beacause, generally, it just works. Except it seems that sometimes it just doesn't, which is what I don't like about Oblivion (and PGR3 for that matter).
Hand in your geek badge at the door.
Don't worry, it's made of plastic. It's not dangerous.
I don't see how much difference the PCB can make though: it's just an electrical connection to the chips, right? Sure, you can keep the circuits short and use really high purity copper but that's about it isn't it?
Not at all! It's all about preserving signal integrity between the components. Remember, at these speeds you shouldn't really think of the signals as plain-old electrical currents flowing down the tracks. They're really high-frequency radio waves propagating down waveguides. Think of where 400MHz lies in the radio spectrum - it's well above fm radio (in the uk, at least) and that propagates pretty well as a wave:-)
The pcb's job is to guide these waves around, and this is trickier than you might think. You have to consider the effect of the dielectric circuit board (the fibre glass bit) and coupling between various tracks and layers in the board.
Jony
The judges' prize will be awarded to a team that produces reasonably competitive entries and, in the judges' opinion, has the most effective re-use of their first submission.
Slashdot Mirror
Jony
What we do know is that it, electromagnetically, has a magnetic dipole, a charge monopole, and - as best we can tell - no charge dipole. The electromagnetic properties are the shape in the only sense that anyone ever really uses the word shape. So its shape is round.
If you want a picture in your minds eye of what we know about the electron, with the understanding that this is just a picture and the theory is the authoritative description, then a ball of charge is, in my opinion, closer to our current theories than a mysterious point particle. You bring up the classical charge radius above: this is precisely the radius that electron-positron virtual pairs can be created, and in a meaningful sense is something like an electron radius. (Although note that they have set limits on the charge radius by comparing the measured magnetic g-factor with the QED calculation, this is the 10^-20something that wikipedia quotes, but this really measures something different - I think you need to be more specific than just saying size at this length scale).
I understand the complications due to the electrons being in molecules - if you haven't twigged yet, JonyEpsilon == J.J. Hudson == first author of paper under discussion - but it doesn't have any real bearing on what we're talking about.
Hope that makes sense :-)
I don't know why people are so convinced the electron is a point particle. A point particle is an idealisation, one that even theory essentially rejects these days (in as much as the bare electron is a theoretical fiction which can't, even in principle, be considered separately from the vacuum polarisation it induces). I don't think it's particularly misleading to think of a ball of charge either - there's no evidence to suggest this isn't the case! I stand by my comment, and the title of my paper: I don't see what else what terms like "shape" and "spherical" can mean in this context, if one restricts oneself, as one must as a physicist, to things that can be measured.
Oops, yes, exactly right. I shouldn't post before I've had my cornflakes.
Yeah, it really is spherical in any sense that you can mean spherical. It can't have any higher order multipole moments because it only has spin 1/2. (So the Wigner-Eckart theorem tells you that all matrix elements with operators greater than spin 1/2 are necessarily zero.) Jony
We used the compton wavelength of the electron as the size scale for this analogy. You could argue that the 1/e radius of the electron/positron virtual particle cloud would be a better measure, and this is closer to the classical radius (off the top of my head, it's late here), which would give an accuracy measured in mm rather than microns. The 10^-22 number comes from interpreting ion trap measurements of the electron's g-factor, comparing them to QED theory. To some extent, the question of the electron's size depends on what you mean by size and how you might choose to measure it. Jony
It took us ten years to build the experiment. We didn't average for ten years!
Good questions! This is actually one of the central motivations for measuring this is. The standard model of particle physics predicts that the electron will be round. But most physicists think that the standard model isn't the full story. The interesting thing is most of the proposed extensions/replacements to the standard model predict that the electron will be somewhat distorted. To give a concrete example, supersymmetric theories, which are viewed by many as the most promising avenue for extending our theories of physics, usually predict a distorted electron.
Don't people have statutory rights with regards to purchased goods in the US? I'm pretty sure if they tried such a trick in the UK they'll get a kicking in court.
Wow. I guess I've been lucky then. I look after a large number of licences for a physics department and we never seem to have any problems. What sort of difficulties did you have?
The only other real "strong" option seems to be hardware dongles. I hate them! I don't have a parallel port anymore, or a floppy disk drive, and I hate carrying extra crap around if I want to use stuff on my laptop.
Well, not having GPS and 3G to suck the battery dry probably helps. I think the battery is bigger too.
Won't somebody think of the children!!!
Got to disagree with that. There are a few hold-outs that have thus far resisted metrification - basically anything that involves old, miserable people - like speed limits, temperature, clothing and body weight. And there were some big arguments about weighing fruit (I'm still amazed that people can get so worked up about units). But everything else is pretty much metric: the plumbing in your house, screws in your electrical system, paper sizes, temperature of your oven, power of your lightbulbs (ergs/s anyone?), anything to do with engineering or science. Everybody who's serious is using metric.
If I've ever heard a compelling argument for an independent ICANN, this is it!
Beacause, generally, it just works. Except it seems that sometimes it just doesn't, which is what I don't like about Oblivion (and PGR3 for that matter).
Hand in your geek badge at the door.
Don't worry, it's made of plastic. It's not dangerous.
Jony
If only I could have typed some heiroglyphs into the console to reinstate the now missing dead dude at the bottom of the Mage's Guild well ...
Haven't downloaded the patch yet - still holding out hope that he'll reappear.
Jony
Not at all! It's all about preserving signal integrity between the components. Remember, at these speeds you shouldn't really think of the signals as plain-old electrical currents flowing down the tracks. They're really high-frequency radio waves propagating down waveguides. Think of where 400MHz lies in the radio spectrum - it's well above fm radio (in the uk, at least) and that propagates pretty well as a wave :-)
The pcb's job is to guide these waves around, and this is trickier than you might think. You have to consider the effect of the dielectric circuit board (the fibre glass bit) and coupling between various tracks and layers in the board.
Jony
Man, I'm like crying, that's so funny. It's the Bruce Lee bit that did it. I'll do my bit to popularize wooha, so to speak.
And here's me thinking trolling had gone out of fashion !
I'm sure I've seen one of those before somewhere ...
Not really, to be honest.
I think breech spelt that way means short trousers or buttocks. Which - call me childish - renders the sentence vaguely hilarious ...
Skeletal design ? I'm guessing the poster was schooled in Kansas :-)