What they're doing is a bit more straightforward. When you observe a point source with HST, the diffraction of the light off the supports and mirror give you a somewhat complicated not-really-symmetric pattern called the Point Spread Function (PSF). To detect a faint source right near a bright source, you need to subtract off the bright star, which means you need to know the PSF really really well so that you don't mistake some leftover light that's really from the primary as a companion.
What they're doing is observing the same field twice, once rotated slightly. The PSF doesn't depend on how the field is oriented, so faint spots that are rotated are real while ones that aren't rotated are due to instrumental effects. This means you can look at much fainter things and know if they're real or not.
To answer the original question, it will be harder the brighter the primary is... I don't know exactly what they're limits are, but it may be possible to push it to brighter stars. Working in the near-infrared, which they're doing, will help. But white dwarfs are pretty faint, so I'm not sure how much brighter a star you could get away with.
The blurb is slightly inaccurate... the follow-up observations aren't going to see if the object has moved around in its orbit (the distance between the primary and companion is larger than the orbit of Neptune, and the primary is a white dwarf so probably about 0.6 times the mass of the sun... from Kepler's laws, that means the period is 67% longer than Neptune's period, or about 275 years... so in 6 months it won't go very far!).
What they're going to look for is common proper motion... the white dwarf appears to move across the sky due to some combination of its motion in space and ours. If the candidate companion shows the same proper motion after 6 months, it is probably physically associated.
How exactly does letting me easily port my music library to the linux box that I want to listen to my music on screw over anyone??
It makes about as much sense as defending DVD region codes... "please, make it harder for me to use your product, that makes it much more likely that I'll buy it!"
And on that random segue... does anyone know what the official MPAA position is on what you're supposed to do when you move to a different continent, as I'll be doing later this year?
It is clumpy. The initial deviations from completely-smooth come from inflation. Some areas have very slightly higher density than average. Because gravity is attractive, areas with higher density attract matter from lower density regions, so the density increases further. Soon those tiny little fluctuations grow into large structures, with "halos" (roundish virialized clumps of dark matter in which galaxies form) are stretched along filaments and sheets that fill space.
The detailed distribution of matter within halos is a matter of some debate, but it's clumpy (even within any one halo) and falls off with radius with a slope (in log-log plots... ie log(density) vs log(radius)) that ranges from about -1 (there is considerable debate about this number... depending who you ask, you'll get answers ranging from 0, ie. a central constant-density core, to -1.5) in the center to -3 in the outer parts of the halo.
Because there is much more dark matter than baryonic (normal) matter, the baryons are also concentrated in the halos. That's where they cool and form galaxies.
There seems to be a common sense here that all of the evidence for dark matter could be equivalently explained by changing the force law.
However, that isn't true. One unique test of dark matter is that it is dynamical; it can move. And there are a bunch of tests that have started to be made that show evidence for dynamical dark matter:
- in order to explain rotation curves without dark matter, models like MOND require force laws that would make the derived "shape" of the dark matter halo spherical at large radius. You can test this by looking at the shapes of clusters using X-ray emitting gas (eg. Buote et al. 2002, ApJ, 577, 183; Lee & Suto 2003, ApJ, 585, 151; Lee & Suto 2004, ApJ, 601, 599) or the Sunyaev-Zeldovich effect (LS03,LS04). You can also look at the shapes of dark matter halos around galaxies using weak gravitational lensing (Hoekstra et al. 2004, ApJ, 606, 67). So far all of the tests indicate that dark matter halos are not spherical, but flattened exactly as predicted by cold dark matter.
- the bars in barred spiral galaxies should slow down and disperse quickly in a spherical static halo potential, like you'd get from modifying the force law, but they can be maintained for long periods of time if they can exchange angular momentum with the dark matter (Athanassoula 2002, ApJ, 569, L83; Valenzuela & Klypin 2003, MNRAS, 234, 459).
- there's a weak gravitational lensing observation of a group that is falling into a cluster, where the mass of the infalling group is offset from the light - the gas is moving slower because it's interacting with the cluster gas, while the dark matter has kept moving (Clowe et al. 2004, ApJ, 604, 596).
But then you'd have all the mass at the center, and the velocities would have a Keplerian fall off with radius (ie. like in the solar system, where most of the mass is in the sun). But rotation curves tell us that the matter is distributed in a much more extended way (the rotation curves don't fall off so fast, so as you go farther out there must be more and more mass inside your radius).
That the sensor has never detected something doesn't tell you that it's working or not working - or am I am missing something here?
Yes, you're missing something.:-)
The statement "the sensor has never detected something" is patently false. Figure 1 of the paper shows all of their detections - and there are lots of them! WIMPs aren't the only things that interact with Germanium.;-) However, once you exclude all of the events which are consistent with being cosmic-ray produced interactions with the shielding, you get Figure 4... all of the detections in the red region (which is where the WIMPs would show up) are gone.
So the detector works great and detects lots of things! But no WIMPs yet.
Challenge: Have a man really create something tangible with the five senses (seeing, hearing, touching, tasting, smelling) from absolutely nothing at all.
Oh come on, that's easy.
Though to be pedantic, it requires a man and a woman.;-)
Our estimate for the total information processing capability of any system in our Universe 8 implies an ultimate limit on the processing capability of any system in the future, independent of its physical manifestation and implies that Moore s Law cannot continue unabated for more than 600 years for any technological civilization.
Well... in 600 years of Moore's Law, you get 400 doublings of computing power. So you need 400 more bits in your key space than you think you do now.:-)
Has anyone gotten it to work under wine? I'd love to be able to use it under Linux, but since they don't seem to be forthcoming on a native client, at least it would be a way to let me give them money!;-)
But I was under the impression that, since the univserse is expanding faster than light and we cannot transfer data faster than light, then it would be impossible to obtain all the knowledge of the universe at once. Has this essay outlined anything other than what my single sentence did?
Quantitative analysis.:-)
Does this paper proove anything other than the fact that the universe cannot contain an exact replica of itself within itself?
Yes, because when you make a statement like that, you're pretending that the event horizon is always in the same place, while in fact it expands and eventually (in an accelerating universe) contracts again. Therefore, calculating the total amount of information that can be processed is complicated... but feasible.
Evil he may be, but he's not enough of an idiot to show a bias publicly when his company NEEDS him to have the appearance of evenhanded neutrality.
Let's look a little further down on that article on the Diebold website (you really should read it if you don't believe that he's publically partisan):
O'Dell said he will not stop supporting Bush's campaign.
The more I see about Diebold, the more I believe they really are idiots. I don't think they're malicious, just stupid. As you say, you'd have to be an idiot to publically take a partisan stand in an election as the CEO of a voting machine company... and yet, he did. He now realizes it was a mistake.
Riiiight.... I'm sure that's what he meant while talking at a Republican fund-raiser.;-)
He clearly wasn't saying "I'm going to rig the election for Bush"... it was probably a typical gung-ho "I'm going to do everything I can for Bush in the campaign and you should too" kind of speech. It's just quite frightening in this case because everything he could do for Bush is a lot more than what most other people can do when they say things like that...
I'm sure this has been mentioned before, but I don't know where to find original sources for this. Are there reputable sources that quote or describe the diebold ceo saying he would give the election to Bush?
In an invitation to a Republican fund-raiser at his suburban Columbus mansion, O'Dell said he was "committed to helping Ohio deliver its electoral votes for the president next year."
Yeah, but filling out the slip for "1/sqrt(2) |deposit> - i/sqrt(2) |withdrawal>" is a pain, and thanks to the epoch of inflation my balance is now much smaller than the rest of the universe... luckily, even in an income vacuum my balance randomly jumps up, but only for REEEEAAALLLLYY short lengths of time. I've been hawking radiation for a while but everyone says it's just a two slit operation.
Harry: Doesn't your job ever get you down? Prostitute: It sure beats waitressing. Harry: Every hooker I've ever talked to says it's better than waitressing. Waitressing must be the worst fucking job.
This reminds me of a thought I had of how the text could be made so good that it might fool even some of us...
(I'm kind of wary of mentioning it, in case the trojan writers haven't thought of it yet, but in the best open source tradition of "what you don't know can hurt you more"... )
Upon execution, Trojan reads through the user's Sent mail folder, picks some random emails (being sure to only send one to a given user, maybe even being clever and finding ones that include text suggesting that there is an attachment or that actually has an attachment), and forwards it again to the receipient with the preface "Sorry I forgot the attachment... try it this time."
I bet a lot of perfectly sane security-conscious people would fall for it.
there are very few stations that play entire albums. those that do often do it illegally. a station is only permitted to play (under the ASCAP or some other acronym's rules) three songs an hour from one artist and no more than two songs from the same album.
Is that true over-the-air too? I got the impression that was a streaming-online-only rule (at least, the station I used to DJ for never mentioned it until we began streaming, and still had shows that broked this rule - such as a weekly 3-hour long Grateful Dead show - but just didn't stream them).
Slashdot Mirror
Gaack... too early in the morning... that should of course read:
"I don't know exactly what *their* limits are"
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No, you're thinking about nulling interferometry, which is also very cool. :-)
What they're doing is a bit more straightforward. When you observe a point source with HST, the diffraction of the light off the supports and mirror give you a somewhat complicated not-really-symmetric pattern called the Point Spread Function (PSF). To detect a faint source right near a bright source, you need to subtract off the bright star, which means you need to know the PSF really really well so that you don't mistake some leftover light that's really from the primary as a companion.
What they're doing is observing the same field twice, once rotated slightly. The PSF doesn't depend on how the field is oriented, so faint spots that are rotated are real while ones that aren't rotated are due to instrumental effects. This means you can look at much fainter things and know if they're real or not.
To answer the original question, it will be harder the brighter the primary is... I don't know exactly what they're limits are, but it may be possible to push it to brighter stars. Working in the near-infrared, which they're doing, will help. But white dwarfs are pretty faint, so I'm not sure how much brighter a star you could get away with.
[TMB]
The blurb is slightly inaccurate... the follow-up observations aren't going to see if the object has moved around in its orbit (the distance between the primary and companion is larger than the orbit of Neptune, and the primary is a white dwarf so probably about 0.6 times the mass of the sun... from Kepler's laws, that means the period is 67% longer than Neptune's period, or about 275 years... so in 6 months it won't go very far!).
What they're going to look for is common proper motion... the white dwarf appears to move across the sky due to some combination of its motion in space and ours. If the candidate companion shows the same proper motion after 6 months, it is probably physically associated.
[TMB]
How exactly does letting me easily port my music library to the linux box that I want to listen to my music on screw over anyone??
It makes about as much sense as defending DVD region codes... "please, make it harder for me to use your product, that makes it much more likely that I'll buy it!"
And on that random segue... does anyone know what the official MPAA position is on what you're supposed to do when you move to a different continent, as I'll be doing later this year?
[TMB]
It is clumpy. The initial deviations from completely-smooth come from inflation. Some areas have very slightly higher density than average. Because gravity is attractive, areas with higher density attract matter from lower density regions, so the density increases further. Soon those tiny little fluctuations grow into large structures, with "halos" (roundish virialized clumps of dark matter in which galaxies form) are stretched along filaments and sheets that fill space.
Take a look at some of the Virgo consortium pictures and movies for an idea of what this looks like.
The detailed distribution of matter within halos is a matter of some debate, but it's clumpy (even within any one halo) and falls off with radius with a slope (in log-log plots... ie log(density) vs log(radius)) that ranges from about -1 (there is considerable debate about this number... depending who you ask, you'll get answers ranging from 0, ie. a central constant-density core, to -1.5) in the center to -3 in the outer parts of the halo.
Because there is much more dark matter than baryonic (normal) matter, the baryons are also concentrated in the halos. That's where they cool and form galaxies.
[TMB]
There seems to be a common sense here that all of the evidence for dark matter could be equivalently explained by changing the force law.
However, that isn't true. One unique test of dark matter is that it is dynamical; it can move. And there are a bunch of tests that have started to be made that show evidence for dynamical dark matter:
- in order to explain rotation curves without dark matter, models like MOND require force laws that would make the derived "shape" of the dark matter halo spherical at large radius. You can test this by looking at the shapes of clusters using X-ray emitting gas (eg. Buote et al. 2002, ApJ, 577, 183; Lee & Suto 2003, ApJ, 585, 151; Lee & Suto 2004, ApJ, 601, 599) or the Sunyaev-Zeldovich effect (LS03,LS04). You can also look at the shapes of dark matter halos around galaxies using weak gravitational lensing (Hoekstra et al. 2004, ApJ, 606, 67). So far all of the tests indicate that dark matter halos are not spherical, but flattened exactly as predicted by cold dark matter.
- the bars in barred spiral galaxies should slow down and disperse quickly in a spherical static halo potential, like you'd get from modifying the force law, but they can be maintained for long periods of time if they can exchange angular momentum with the dark matter (Athanassoula 2002, ApJ, 569, L83; Valenzuela & Klypin 2003, MNRAS, 234, 459).
- there's a weak gravitational lensing observation of a group that is falling into a cluster, where the mass of the infalling group is offset from the light - the gas is moving slower because it's interacting with the cluster gas, while the dark matter has kept moving (Clowe et al. 2004, ApJ, 604, 596).
[TMB]
But then you'd have all the mass at the center, and the velocities would have a Keplerian fall off with radius (ie. like in the solar system, where most of the mass is in the sun). But rotation curves tell us that the matter is distributed in a much more extended way (the rotation curves don't fall off so fast, so as you go farther out there must be more and more mass inside your radius).
[TMB]
Yes, you're missing something. :-)
The statement "the sensor has never detected something" is patently false. Figure 1 of the paper shows all of their detections - and there are lots of them! WIMPs aren't the only things that interact with Germanium. ;-) However, once you exclude all of the events which are consistent with being cosmic-ray produced interactions with the shielding, you get Figure 4... all of the detections in the red region (which is where the WIMPs would show up) are gone.
So the detector works great and detects lots of things! But no WIMPs yet.
[TMB]
Oh come on, that's easy.
Though to be pedantic, it requires a man and a woman. ;-)
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Oops.... heheh... I didn't even notice that typo, so I assumed you meant the only other number in the post. :-)
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Cool, thanks for the info. :-)
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(final paragraph, before the acknowledgements)
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Well... in 600 years of Moore's Law, you get 400 doublings of computing power. So you need 400 more bits in your key space than you think you do now. :-)
[TMB]
You can define its duration in time. That's finite.
Has anyone gotten it to work under wine? I'd love to be able to use it under Linux, but since they don't seem to be forthcoming on a native client, at least it would be a way to let me give them money! ;-)
[TMB]
Quantitative analysis. :-)
Yes, because when you make a statement like that, you're pretending that the event horizon is always in the same place, while in fact it expands and eventually (in an accelerating universe) contracts again. Therefore, calculating the total amount of information that can be processed is complicated... but feasible.
[TMB]
Heheh... well, with all of those terabytes of audio, do you ever just put the entire database on shuffle? :-)=
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Let's look a little further down on that article on the Diebold website (you really should read it if you don't believe that he's publically partisan):
The more I see about Diebold, the more I believe they really are idiots. I don't think they're malicious, just stupid. As you say, you'd have to be an idiot to publically take a partisan stand in an election as the CEO of a voting machine company... and yet, he did. He now realizes it was a mistake.
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I think 640kb ought to be enough for anybody!
-BillG.
Riiiight.... I'm sure that's what he meant while talking at a Republican fund-raiser. ;-)
He clearly wasn't saying "I'm going to rig the election for Bush"... it was probably a typical gung-ho "I'm going to do everything I can for Bush in the campaign and you should too" kind of speech. It's just quite frightening in this case because everything he could do for Bush is a lot more than what most other people can do when they say things like that...
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How about on Diebold's own website ? :-) From the article:
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Yeah, but filling out the slip for "1/sqrt(2) |deposit> - i/sqrt(2) |withdrawal>" is a pain, and thanks to the epoch of inflation my balance is now much smaller than the rest of the universe... luckily, even in an income vacuum my balance randomly jumps up, but only for REEEEAAALLLLYY short lengths of time. I've been hawking radiation for a while but everyone says it's just a two slit operation.
Okay, I'm done now.
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(from Deconstructing Harry)
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This reminds me of a thought I had of how the text could be made so good that it might fool even some of us...
(I'm kind of wary of mentioning it, in case the trojan writers haven't thought of it yet, but in the best open source tradition of "what you don't know can hurt you more"... )
Upon execution, Trojan reads through the user's Sent mail folder, picks some random emails (being sure to only send one to a given user, maybe even being clever and finding ones that include text suggesting that there is an attachment or that actually has an attachment), and forwards it again to the receipient with the preface "Sorry I forgot the attachment... try it this time."
I bet a lot of perfectly sane security-conscious people would fall for it.
[TMB]
Is that true over-the-air too? I got the impression that was a streaming-online-only rule (at least, the station I used to DJ for never mentioned it until we began streaming, and still had shows that broked this rule - such as a weekly 3-hour long Grateful Dead show - but just didn't stream them).
[TMB]