I take it you mean below, so any black hole above a certain size threshold won't decay until they eat all the background radiation in the universe. This size, presumeably, is above the lower limit for black hole creation in a supernova. Yes, I meant *below*. Thanks to all for correcting my error. I never remember to use "preview"....
Since we're doing an academic exercise here, let's imagine the situation from the point of view of something falling into the black hole. If this something was looking backwards (i.e. out at the Universe, and not towards its impending doom), it would see all incoming photons strongly blue-shifted. To someone watching it fall into the black hole, they'd see it becoming more and more red-shifted, and slowing down more and more, until it appears to freeze, infinitely red-shifted, on the surface of the event horizon. Thus, we'll never see it fall through the event horizon.
The person riding on the object would see the Universe more and more blue-shifted, until, due to the extreme time dilation, the Universe ends before they ever fall in. So, without Hawking Radiation, the black hole will outlive the Universe, and nothing will ever fall in. Weird, huh?
With Hawking Radiation, it's harder to predict what will happen. Will the infalling matter see a vicious blast of Hawking Radiation before ever crossing the event horizon? How can anything fall into a black hole if the black hole dissolves, and the Universe ends before it can cross the event horizon?
It is true that black holes will evaporate over time, but they will also gain mass from infalling matter.
But!
The temperature of a black hole can be defined by the rate at which Hawking photons are streaming away from it. In the case of a black hole of a few solar masses, this temperature will be in the nano-Kelvin (I think -- don't hurt me if I'm wrong by a few orders of magnitude). Now remember everything in the Universe is sitting in a bath of cold photons from the Big Bang (i.e. the microwave background). These photons have a temperature of ~4 Kelvin.
Therefore, black holes whose Hawking temperature is above the microwave background will be net *gaining* mass.
Which is all a long way of saying, no, this isn't a normal size black hole that has decayed over time. It must have been created at this mass (or smaller).
My main problem with all "Linux for Dummies" books is that, although they may be useful to begin with, they become almost entirely obsolete withing one or two major releases of the distro. The stuff that doesn't become obsolete is all stuff you can find in a shell scripting guide.
Forums, despite their low signal:noise, don't have this problem.
My recommendation would be to buy a good shell scripting book and read a few online tutorials on configuring whatever distro you have.
The only thing I've heard of is that there are talks of possibly turning PEP-II into a extremely low emittance synchrotron radiation source,a la PETRA Really?! I *work* there, and I've never heard anything like that!
Actually, this news, if true, reinforces my point. Light sources in general are in such demand, that there are plans to host up to four of them at one site (SSRL, LCLS, rumoured new Xray FEL, rumoured new PEPII based synchrotron)!
Are there really questions as to whether the LCLS will work (i.e., meet its stated design parameters), or do they center more around its actual utility? Remember that Xray FELs have never been built before, and there is every chance that SLAC could discover some new physics that means that making LCLS actually lase impossibly difficult. They've already had a few nasty surprises (look up the papers on how their OTRs are completely blinded by the coherent light), and there's nothing to say that there aren't a few more surprises lurking ahead. My bet is that it will work just fine, but the physicist in me urges caution.
As far as I can tell there isn't much of a point to building synchrotrons of an energy higher than 9-10 GeV. Even greater brightness isn't of much use anymore, at least in X-ray crystallography (according to the people I have talked to, IANAC(rystallographer)). Then why are LCLS aiming for 14 GeV, with upgrade plans to 30 (or even 50 is possible) GeV? Remember, the laser wavelength has an inverse relationship with the beam energy, so if you want to see smaller and smaller things, or you want to use shorter and shorter pulses, high energy is the only way to go.
IMHO I can imagine groups all over the place jumping to build an XFEL. They're just sitting watching LCLS's progress, and, once the first coherent photons come out of the switchyard, they'll start submitting proposals to their own funding bodies. Just my opinion though.
Having the use of the SLC linac certainly made life easier for LCLS, but XFEL is being built on completely virgin ground. If (and it's more of an "if" than a lot of people want to admit) LCLS works, then the demand for X-FELs will be *huge*. There are rumours of a second being planned at SLAC, and one in the UK. These machines are very very cool, and stunningly useful for many other fields of research. I'd bet they won't be able to build these machines fast enough to satisfy demand!
It's true that accelerator science has been driven by HEP, but most accelerator physicists (like me) will admit that their market is changing, and our future customers will be biologists and chemists, not physicists.
I've never heard the story about XFEL being hampered by length. Do you mean the German one, or were you referring to LCLS?
If you think this stuff is cool, then LCLS and XFEL will blow you away when they come online. These are great times for accelerator physics, and great times for light sources (unless, of course, LHC destroys us all:S).
FYI: The news does not have sides. Politics does. But it has many more than the two sides you seem to think it has.
I know US news gives the impression that all news can only be cast in two lights -- liberal or conservative -- but that's a fallacy pushed to generate loyal viewers. If you were to read/watch the European press (particularly British, Irish, or Scandinavian) you might be pretty surprised. They comes across more as a stream of information, rather than the US press which comes across as pro/anti liberal/conservative ranting, even when the story has little to do with politics.
As an aside, I'm becoming increasingly irritated by the BBC website, as it seems to have stumbled across the American model for news -- a disappointing fraction of the news from that website now appears to be quite liberal in bias -- something which wasn't true ~5 years ago. Sad but true.
This is a perfect way to demonstrate to the perfect person why such invasions of privacy are bad, and of the unintended negative consequences of their plans. Sometimes people in power forget that the "solutions" they develop to certain problems may be worse than the problems themselves. All they see is that a certain issue will be fixed -- not that the fix raises even worse issues.
Sure, lots of stuff on/. that is compared to 1984 isn't like the book at all, but I thought, for once, that people were using the comparison correctly. As you said, it's entirely voluntary, but the thing that most people here (including me) are worrying about is that it may not continue to be voluntary -- especially once law enforcement realise how stunningly useful it could be.
Sooner or later someone will apply "think of the children" logic, and we'll all have one of these in our living rooms.
Yes, if the current and voltage scale in a way governed by Ohm's Law. However, since power is also equivalent to V^2/R, if you can build a chip that can operate at lower voltage AND the same current, then you win by the square of the voltage.
It's frightening that you think leaking information "about legal and non-controversial wire taps" is "borderline treason".
If this really is as boring as you think, then why would millions need to be spent to undo any damage, why would the US gov start legal action, and why would there need to be an internal investigation?
Whilst it's true that nutjub violence is often justified by religion and politics, this isn't the case for the IRA. Their particular brand of hate has only ever been justified by politics. I've never heard a "justification" for their violence based on Catholic dogma, and I lived in N.I. for the first 20 years of my life.
IRA violence is political, not religious. That they call themselves "Catholics" is neither here nor there. I bet, if you were to ask the nutjobs who planted that bomb, they would claim to have done it for political/nationalistic reasons. Not religious.
Yours is a good example of the evils of extremism, but a bad example of extremist religion.
It's not true that "nothing was accomplished". The thing I'm so happy about is that the system appears to be working again. For quite a few years now, we've had a legislative branch that simply agreed with whatever the President wanted, and didn't suggest anything that they knew he would veto. The system is supposed to provide balances against one branch achieving too much power, and that is the situation we lived in for the last few years. Finally, today, we see that the system can still work, and that the power of the executive can be limited -- even when said executive tries playing the terrorism card.
This is a *good* thing, and that is what has been accomplished today.
Slashdot Mirror
The person riding on the object would see the Universe more and more blue-shifted, until, due to the extreme time dilation, the Universe ends before they ever fall in. So, without Hawking Radiation, the black hole will outlive the Universe, and nothing will ever fall in. Weird, huh?
With Hawking Radiation, it's harder to predict what will happen. Will the infalling matter see a vicious blast of Hawking Radiation before ever crossing the event horizon? How can anything fall into a black hole if the black hole dissolves, and the Universe ends before it can cross the event horizon?
But!
The temperature of a black hole can be defined by the rate at which Hawking photons are streaming away from it. In the case of a black hole of a few solar masses, this temperature will be in the nano-Kelvin (I think -- don't hurt me if I'm wrong by a few orders of magnitude). Now remember everything in the Universe is sitting in a bath of cold photons from the Big Bang (i.e. the microwave background). These photons have a temperature of ~4 Kelvin.
Therefore, black holes whose Hawking temperature is above the microwave background will be net *gaining* mass.
Which is all a long way of saying, no, this isn't a normal size black hole that has decayed over time. It must have been created at this mass (or smaller).
Forums, despite their low signal:noise, don't have this problem.
My recommendation would be to buy a good shell scripting book and read a few online tutorials on configuring whatever distro you have.
Actually, this news, if true, reinforces my point. Light sources in general are in such demand, that there are plans to host up to four of them at one site (SSRL, LCLS, rumoured new Xray FEL, rumoured new PEPII based synchrotron)!
Are there really questions as to whether the LCLS will work (i.e., meet its stated design parameters), or do they center more around its actual utility? Remember that Xray FELs have never been built before, and there is every chance that SLAC could discover some new physics that means that making LCLS actually lase impossibly difficult. They've already had a few nasty surprises (look up the papers on how their OTRs are completely blinded by the coherent light), and there's nothing to say that there aren't a few more surprises lurking ahead. My bet is that it will work just fine, but the physicist in me urges caution. As far as I can tell there isn't much of a point to building synchrotrons of an energy higher than 9-10 GeV. Even greater brightness isn't of much use anymore, at least in X-ray crystallography (according to the people I have talked to, IANAC(rystallographer)). Then why are LCLS aiming for 14 GeV, with upgrade plans to 30 (or even 50 is possible) GeV? Remember, the laser wavelength has an inverse relationship with the beam energy, so if you want to see smaller and smaller things, or you want to use shorter and shorter pulses, high energy is the only way to go.IMHO I can imagine groups all over the place jumping to build an XFEL. They're just sitting watching LCLS's progress, and, once the first coherent photons come out of the switchyard, they'll start submitting proposals to their own funding bodies. Just my opinion though.
It's true that accelerator science has been driven by HEP, but most accelerator physicists (like me) will admit that their market is changing, and our future customers will be biologists and chemists, not physicists.
I've never heard the story about XFEL being hampered by length. Do you mean the German one, or were you referring to LCLS?
If you think this stuff is cool, then LCLS and XFEL will blow you away when they come online. These are great times for accelerator physics, and great times for light sources (unless, of course, LHC destroys us all :S).
I know US news gives the impression that all news can only be cast in two lights -- liberal or conservative -- but that's a fallacy pushed to generate loyal viewers. If you were to read/watch the European press (particularly British, Irish, or Scandinavian) you might be pretty surprised. They comes across more as a stream of information, rather than the US press which comes across as pro/anti liberal/conservative ranting, even when the story has little to do with politics.
As an aside, I'm becoming increasingly irritated by the BBC website, as it seems to have stumbled across the American model for news -- a disappointing fraction of the news from that website now appears to be quite liberal in bias -- something which wasn't true ~5 years ago. Sad but true.
Bravo!
Mmmmm... Cake.
Sooner or later someone will apply "think of the children" logic, and we'll all have one of these in our living rooms.
Yes, if the current and voltage scale in a way governed by Ohm's Law. However, since power is also equivalent to V^2/R, if you can build a chip that can operate at lower voltage AND the same current, then you win by the square of the voltage.
It's frightening that you think leaking information "about legal and non-controversial wire taps" is "borderline treason". If this really is as boring as you think, then why would millions need to be spent to undo any damage, why would the US gov start legal action, and why would there need to be an internal investigation?
Whilst it's true that nutjub violence is often justified by religion and politics, this isn't the case for the IRA. Their particular brand of hate has only ever been justified by politics. I've never heard a "justification" for their violence based on Catholic dogma, and I lived in N.I. for the first 20 years of my life.
IRA violence is political, not religious. That they call themselves "Catholics" is neither here nor there. I bet, if you were to ask the nutjobs who planted that bomb, they would claim to have done it for political/nationalistic reasons. Not religious. Yours is a good example of the evils of extremism, but a bad example of extremist religion.
It's not true that "nothing was accomplished". The thing I'm so happy about is that the system appears to be working again. For quite a few years now, we've had a legislative branch that simply agreed with whatever the President wanted, and didn't suggest anything that they knew he would veto. The system is supposed to provide balances against one branch achieving too much power, and that is the situation we lived in for the last few years. Finally, today, we see that the system can still work, and that the power of the executive can be limited -- even when said executive tries playing the terrorism card. This is a *good* thing, and that is what has been accomplished today.