When astrophysicists say "dark matter" they don't just mean matter that isn't glowing, but matter that doesn't interact except by gravity. If DM were Plain Old Dim Matter (PODM) and evenly spread out, its drag would affect galactic dynamics like any gas. If it were clumped into compact objects (old white or brown dwarves, neutron stars, or black holes, i.e. MACHOs), we'd see more gravitational lensing events than we do. The clincher is that if any more ordinary matter had been present during the Big Bang, the nuclear reactions would have continued longer before freezing out (as the universe diluted itself by expanding), and we would have more of the heavier elements today.
The Economist is one of the most respected news magazines in the world.... all of their coverage, including policitcs and science, is superb.
I'd hardly call this article superb. By focusing on a problem with clusters and ignoring independent evidence for dark energy from supernovae, problems with MOND, and expectations from particle physics of at least some dark(ish) matter, it seemed to be saying "The very foundations of science are shaking, and you heard it here first!". I'd call that sensationalism. Of course, I'm being sensationalist too and exaggerating a bit.
On my own, I'd note that giving how flexible geometry can be, I can easily imagine someone constructing a geometry of the universe that doesn't need dark matter that turns out to be mathematically equivalent to a universe that does have dark matter.
Don't forget that although the geometry of the universe as a whole depends on Omega, and thus the amount of dark matter (DM), DM was originally postulated to explain the rotation curves of galaxies. Once formed, galaxies are small self-gravitating things that don't care much about the universe's global geometry.
As for the big picture, there are theories that replace DM with funky geometry, and an interesting one was recently featured in Scientific American. However, they should produce funky patterns in the cosmic microwave background (sort of like being in a hall of mirrors). Last I heard, funky geometry fans are starting to admit aren't there.
It's a neat idea, but it's throwing away the biggest advantage of amateurs - lots of telescopes that don't have to point in the same direction.
Other people have pointed out the problems with combining many small optical telescopes to get a deep image, but deep images tend to cover small fields. There's a lot of sky that goes unobserved every night, and moving or transient phenomena are easily missed. Why not coordinate your team to try to cover as much of the sky as possible? This could be great (depending on brightness and telescope size) for near Earth asteroids, optical SETI, (super)novae, optical counterparts to gamma ray bursters, and other things that go bump in the night. Plus the eyes and brains of amateurs are a distributed processing system for picking out the interesting stuff. I hope there's enough amateurs who are tired of taking yet another image of that nebula everyone else has taken images of, that this catches on.
The camera needs to put a trustable timestamp on the pictures, which I think necessitates onboard wireless networking. Besides being useful for evidence, it would people from gimping the original for an hour then trying to sneak in the new version.
I see the point of the people saying that pictures of pictures tend not to look exactly like the originals, but I think they're missing the fact that the image doctoring software could deliberately introduce reverse distortions in the printout that would produce an original-looking image when a picture was taken of it. Besides, the effects are less obvious and general than the time.
The team were refused time on a US telescope because many American astronomers believed the observations were technically impossible
A very common occurance. See below.
This is just sad. I sometimes think we'd be centuries ahead in science if theorists could lay aside their egos and realize that hardly any theory lasts forever in its entirety....
Maybe overdramatic
Way overdramatic, but the article sensationlistically led you on. For one thing, they were refused time on a particular U.S. telescope, not banned from using all U.S. telescopes, of which there are many.
Telescopes usually have more requests for observing time than there is available, so a committee is given the job of deciding who will get how much time. "We have doubts about the feasibility of your proposed observation" is a classic rejection. It usually means that the proposer is attempting to pull off something terribly exciting at the cutting edge of science, where things aren't easy. The committee realizes that, and presumably gets many such proposals, but figures that most of them won't work and will just waste telescope time. Their job is to guess, in a finite time with finite expertise in all the different subfields in astronomy in a batch of proposals, which ones have a shot....which means that subjectivity plays a big role and some telescopes are fairer than others. But it doesn't necessarily mean that the team was intentionally mistreated.
But is there a pager available for Sawfish which is as useful as FVWM's? Mine has the active window highlighted in a different color, and all of the windows have abbreviated (icon?) titles in a tiny but legible font. Far more useful than pictures.
since it's written (except for the lowest level stuff) in a LISPy language, you can
...actually understand and do new things. Sigh. There is a PERL interface to FVWM, but I haven't played with it much.
I attribute the complete absurdity of this article to a science writer who doesn't know anything about science. Or, it could have been an incompetent editor who screwed up the article.
Look again - the SFGate's science editor is the writer. And is the paper's main editor going to overrule the science editor on a science article? Don't think so. Hopefully this is just a temporary situation, like the editor filling in while the astronomy/physics reporter is on holiday or something.
Bah. mutt has had threading "visualization" that lets you see the sender, date, subject and/or whatever you want, and pattern limited views, for years. And it originated PGP/MIME.
Sure it's text based, but that's a darn good feature when you get porn spam with web bugs at work, or want to read/send email over ssh.
Not necessarily. Multiple antennas can be combined to form an interferometer, which can be electronically "pointed" anywhere above the horizon with quite good resolution.
This has been done since the early days, and will be done with LOFAR.
Canadian voters are a lot less loyal to a particular party.
I'm not sure that's true - probably it's the ridings that are less loyal, because they're less gerrymandered. If we define r as the ratio of a riding's perimeter to the circumference of a circle containing the same area, it would be interesting to compare the average r for various countries.
There does seem to be a tendency for Canadians to elect the provincial party they're least sick of, though.
How? Voronoi diagrams put the borders equidistant between points. If there were one voter per riding, the point could be the voter, but in a more realistic situation it's not clear what the points should be. Centroids of the voter distribution?
PanoTools has some impressive examples (using a spherical mirror to make a panorama inside a flower was brilliant!) but personally I had more success with xmerge. It's easy(ish) to use, but the transformation does not handle foreground objects perfectly. (I think PanoTools uses the same transformation, anyway.)
This is just a guess, but maybe the ideal way would be to use the different perspectives (and/or a stereoscopic adapter on the camera) to build a 3D model of the scene, and then render that onto the final picture.
Magnetic fields also create waves, but the waves form a kind of bubble, which stops growing after four feet, making them more secure than waves wafting endlessly in every direction, Cui said.
It's vague, but I think this means it it using the "near field" instead of the propagating field. A transmitting antenna emits two fields: a propagating electromagnetic wave (i.e. light) whose intensity drops off like 1/r^2, and a nonpropagating electromagnetic field that drops off like 1/r^4 (which is why it's called the near field). It can carry a lot of power, but since it doesn't go anywhere it is usually ignored.
The proposed system relies on the simultaneity of pulse arrival times to distinguish real pulses from noise photons. The poorer the synchronization, the poorer the signal to noise ratio.
Unfortunately the refractive index of the atmosphere is not uniform, and turbulence makes it vary fairly quickly and unpredictably. In other words, the same effect that makes stars twinkle should scatter the arrival times by an amount that I'm guessing is much more than a nanosecond. So distributed small telescopes are not quite the same as a single big telescope after all*.
The second problem is an old one for optical SETI, namely that dust in the plane of the Galaxy limits how far optical light (as opposed to radio) can travel. How much this matters is a matter of debate.
*Interferometers (try to) deal with this (and similar problems) by picking a known pointlike bright source (i.e. a quasar) and adjusting their relative phases to make that object look like a point. It's sort of like focusing a camera. The only way I can think of for distributed pulse detection to deal with random delays is to correlate the signals. That's a lot of CPU work, and more importantly requires the aliens to send a series of pulses so that the telescopes could detect multiple events. Even then, I haven't worked out what the signal to noise would be like.
Just to clarify, the SKA isn't built yet, and AFAIK a site has not yet been chosen. I know that at least the U.S/Mexico, Australia, and China would each like to have it in their backyard.
For comparison, 1 sq. km = apx. 100 million amateur telescopes. Doable? In a properly enthusiastic world, yes, but not (yet) with CCDs, because they're just too darn expensive. So how about 2.5 billion digital cameras/webcams pointing up?;-)
For a fairer comparison, the next rilly big optical telescopes are supposed to be about 25m in diameter, or about 62500 good amateur telescopes. Possibly doable, if the necessary detectors are cheap enough.
Hmmm...Pinky, your questions are so inane that one might almost think you were joking. Still, some deserve an answer.
> 1. What is the yield of this process technology?
Me. Seriously.
> 2. Does this yield go up as the process matures? > 3. Does Moore's Law apply to supernova production?
Aren't these practically the same question? The answer is no. Stars form when gas clouds collapse. Supernovae blow gas clouds apart - i.e. they tend to shut down star formation until the gas falls back. No star formation = no supernovae (at least of the type being discussed here).
> 4. Can you get a refund/exchange on dud supernovas, or do they just provide firmware updates?
Sort of. If they're duds they don't hamper star formation very much.
> 5. Are supernovas legal for use in 4th of July celebrations in states that otherwise permit fireworks?
IANAL, but as far as I know they are not yet explicitly forbidden.
> 6. Does the EPA regulate supernovas, or do they fall under BATF?
Typical American (arrog+ignor)ance!:-P
> 7. Do you need a CCW permit to carry a concealed supernova?
Have you got a way to block the neutrinos? Please share.
> 8. Are supernova futures traded on the NASDAQ yet?
Look it up yourself.
> 9. Have the Democrats figured out a way to tax supernovas (since they fall in the highest out-go bracket)?
It's called the carbon tax up here.
> 10. Have the Republicans managed to regulate what supernovas can do in the privacy of their own interstellar gas clouds?
Apparently not. Surprise surprise.
> 11. Can the RIAA/MPAA use the DMCA to sue supernovas suspected of being P2P traders?
Again, IANAL, but seeing as how supernovae freely share of themselves, and provide the heavy elements necessary for hard drives and P2P traders (otherwise known as humans), the answer is probably yes.
This will probably just make you angrier, but worse than the fact that spammers don't care, is that pedophiles almost certainly purposely check out websites where children are likely to give out personal information like email addresses.
Certainly the 6 o'clock news shows like to point out a pedophile contacting a child over the internet (gasp!)* whenever they can.
* as in "Don't you dare think of using the evil internet, or letting anyone you know look at it, instead of watching the sacred television." But that's another rant...
Children shouldn't be giving out info to people they don't know, except to 911, etc. in an emergency. The trickle of sleazy spam (is there any other kind?) that gets thru spamassassin could actually help kids** understand why they should be careful.
**Well, the smart ones. The stupid ones will click thru on every offer. At least they'll waste the spammer's time.
In theory, CanCon should force Canadian radio stations to play some stuff that American radio *isn't* playing. Which has gotta be good, right? Unfortunately crap rises to the top in radio everywhere, and Canada has proven itself more than capable of producing its own crap. And I don't swallow Canadian radio stations blaming the crap on CanCon - they need local crap for their shopping mall promotions.
I think it's all a symptom of broadcasting with only a few stations available in any place. Specialty channels, whether by internet or satellite, have some hope, in that they should realize that they need to treat their audience right, or that audience will move on.
He had me going there for a second, but I think his assumption that virtual universes would outnumber real ones is incorrect.
First, an arbitrarily detailed simulation of a universe would require all of the resources of the host universe - so it might as well be a real universe, and there is no multiplication effect. Since we (and by we I mean I;-) have no evidence of this universe being a simulation, I assume that if it is a simulation it must be an arbitrarily detailed one.
Second, a simulated universe with limited detail would not spawn child universes. Oh, the inhabitants of the simulated universe might think they had started their own simulations, but back in the real universe the computer running the simulation they inhabit would have no reason to run the secondary simulations - it only needs to produce perceptions for the inhabitants of the first simulation. So again, there is no proliferation of virtual universes that would make it more likely for a conscious being to be in a simulation than in a real universe.
Note that I am not discounting the sort of simulation required for solipsism - it would come under the second sort of simulation.
Slashdot Mirror
(He did ask, after all...)
Like all large telescopes, Hubble uses a mirror, not a lens.
When astrophysicists say "dark matter" they don't just mean matter that isn't glowing, but matter that doesn't interact except by gravity. If DM were Plain Old Dim Matter (PODM) and evenly spread out, its drag would affect galactic dynamics like any gas. If it were clumped into compact objects (old white or brown dwarves, neutron stars, or black holes, i.e. MACHOs), we'd see more gravitational lensing events than we do. The clincher is that if any more ordinary matter had been present during the Big Bang, the nuclear reactions would have continued longer before freezing out (as the universe diluted itself by expanding), and we would have more of the heavier elements today.
I'd hardly call this article superb. By focusing on a problem with clusters and ignoring independent evidence for dark energy from supernovae, problems with MOND, and expectations from particle physics of at least some dark(ish) matter, it seemed to be saying "The very foundations of science are shaking, and you heard it here first!". I'd call that sensationalism. Of course, I'm being sensationalist too and exaggerating a bit.
As for the big picture, there are theories that replace DM with funky geometry, and an interesting one was recently featured in Scientific American. However, they should produce funky patterns in the cosmic microwave background (sort of like being in a hall of mirrors). Last I heard, funky geometry fans are starting to admit aren't there.
Other people have pointed out the problems with combining many small optical telescopes to get a deep image, but deep images tend to cover small fields. There's a lot of sky that goes unobserved every night, and moving or transient phenomena are easily missed. Why not coordinate your team to try to cover as much of the sky as possible? This could be great (depending on brightness and telescope size) for near Earth asteroids, optical SETI, (super)novae, optical counterparts to gamma ray bursters, and other things that go bump in the night. Plus the eyes and brains of amateurs are a distributed processing system for picking out the interesting stuff. I hope there's enough amateurs who are tired of taking yet another image of that nebula everyone else has taken images of, that this catches on.
I see the point of the people saying that pictures of pictures tend not to look exactly like the originals, but I think they're missing the fact that the image doctoring software could deliberately introduce reverse distortions in the printout that would produce an original-looking image when a picture was taken of it. Besides, the effects are less obvious and general than the time.
A very common occurance. See below.
Way overdramatic, but the article sensationlistically led you on. For one thing, they were refused time on a particular U.S. telescope, not banned from using all U.S. telescopes, of which there are many.Telescopes usually have more requests for observing time than there is available, so a committee is given the job of deciding who will get how much time. "We have doubts about the feasibility of your proposed observation" is a classic rejection. It usually means that the proposer is attempting to pull off something terribly exciting at the cutting edge of science, where things aren't easy. The committee realizes that, and presumably gets many such proposals, but figures that most of them won't work and will just waste telescope time. Their job is to guess, in a finite time with finite expertise in all the different subfields in astronomy in a batch of proposals, which ones have a shot. ...which means that subjectivity plays a big role and some telescopes are fairer than others. But it doesn't necessarily mean that the team was intentionally mistreated.
But is there a pager available for Sawfish which is as useful as FVWM's? Mine has the active window highlighted in a different color, and all of the windows have abbreviated (icon?) titles in a tiny but legible font. Far more useful than pictures.
Look again - the SFGate's science editor is the writer. And is the paper's main editor going to overrule the science editor on a science article? Don't think so. Hopefully this is just a temporary situation, like the editor filling in while the astronomy/physics reporter is on holiday or something.
Dare I ask why /.'s editor didn't catch this?
You started off well, but wouldn't the eagle (try to) eat the rat?
Sure it's text based, but that's a darn good feature when you get porn spam with web bugs at work, or want to read/send email over ssh.
This has been done since the early days, and will be done with LOFAR.
I'm not sure that's true - probably it's the ridings that are less loyal, because they're less gerrymandered. If we define r as the ratio of a riding's perimeter to the circumference of a circle containing the same area, it would be interesting to compare the average r for various countries.
There does seem to be a tendency for Canadians to elect the provincial party they're least sick of, though.
How? Voronoi diagrams put the borders equidistant between points. If there were one voter per riding, the point could be the voter, but in a more realistic situation it's not clear what the points should be. Centroids of the voter distribution?
This is just a guess, but maybe the ideal way would be to use the different perspectives (and/or a stereoscopic adapter on the camera) to build a 3D model of the scene, and then render that onto the final picture.
It's vague, but I think this means it it using the "near field" instead of the propagating field. A transmitting antenna emits two fields: a propagating electromagnetic wave (i.e. light) whose intensity drops off like 1/r^2, and a nonpropagating electromagnetic field that drops off like 1/r^4 (which is why it's called the near field). It can carry a lot of power, but since it doesn't go anywhere it is usually ignored.
Unfortunately the refractive index of the atmosphere is not uniform, and turbulence makes it vary fairly quickly and unpredictably. In other words, the same effect that makes stars twinkle should scatter the arrival times by an amount that I'm guessing is much more than a nanosecond. So distributed small telescopes are not quite the same as a single big telescope after all*.
The second problem is an old one for optical SETI, namely that dust in the plane of the Galaxy limits how far optical light (as opposed to radio) can travel. How much this matters is a matter of debate.
*Interferometers (try to) deal with this (and similar problems) by picking a known pointlike bright source (i.e. a quasar) and adjusting their relative phases to make that object look like a point. It's sort of like focusing a camera. The only way I can think of for distributed pulse detection to deal with random delays is to correlate the signals. That's a lot of CPU work, and more importantly requires the aliens to send a series of pulses so that the telescopes could detect multiple events. Even then, I haven't worked out what the signal to noise would be like.
One telescope looking thru the window and 9999 looking at the walls of the house?! Your request for telescope time is denied!
Just to clarify, the SKA isn't built yet, and AFAIK a site has not yet been chosen. I know that at least the U.S/Mexico, Australia, and China would each like to have it in their backyard.
For comparison, 1 sq. km = apx. 100 million amateur telescopes. Doable? In a properly enthusiastic world, yes, but not (yet) with CCDs, because they're just too darn expensive. So how about 2.5 billion digital cameras/webcams pointing up? ;-)
For a fairer comparison, the next rilly big optical telescopes are supposed to be about 25m in diameter, or about 62500 good amateur telescopes. Possibly doable, if the necessary detectors are cheap enough.
Well...we knew (in increasing order of controversy ;-) that
- the star formation rate was higher in the past (the Butcher-Oemler effect)
- galaxy mergers encourage star formation
- galaxy mergers were more common in the past
- the Arp atlas has a whack of ultraluminous, star forming, merging galaxies that are worth checking in on every now and then.
But still, every 2 years is really exciting. We can literally watch a massive cluster of stars go boom in a human lifetime!Hmmm...Pinky, your questions are so inane that one might almost think you were joking. Still, some deserve an answer.
:-P
> 1. What is the yield of this process technology?
Me. Seriously.
> 2. Does this yield go up as the process matures?
> 3. Does Moore's Law apply to supernova production?
Aren't these practically the same question? The answer is no. Stars form when gas clouds collapse. Supernovae blow gas clouds apart - i.e. they tend to shut down star formation until the gas falls back. No star formation = no supernovae (at least of the type being discussed here).
> 4. Can you get a refund/exchange on dud supernovas, or do they just provide firmware updates?
Sort of. If they're duds they don't hamper star formation very much.
> 5. Are supernovas legal for use in 4th of July celebrations in states that otherwise permit fireworks?
IANAL, but as far as I know they are not yet explicitly forbidden.
> 6. Does the EPA regulate supernovas, or do they fall under BATF?
Typical American (arrog+ignor)ance!
> 7. Do you need a CCW permit to carry a concealed supernova?
Have you got a way to block the neutrinos? Please share.
> 8. Are supernova futures traded on the NASDAQ yet?
Look it up yourself.
> 9. Have the Democrats figured out a way to tax supernovas (since they fall in the highest out-go bracket)?
It's called the carbon tax up here.
> 10. Have the Republicans managed to regulate what supernovas can do in the privacy of their own interstellar gas clouds?
Apparently not. Surprise surprise.
> 11. Can the RIAA/MPAA use the DMCA to sue supernovas suspected of being P2P traders?
Again, IANAL, but seeing as how supernovae freely share of themselves, and provide the heavy elements necessary for hard drives and P2P traders (otherwise known as humans), the answer is probably yes.
Certainly the 6 o'clock news shows like to point out a pedophile contacting a child over the internet (gasp!)* whenever they can.
* as in "Don't you dare think of using the evil internet, or letting anyone you know look at it, instead of watching the sacred television." But that's another rant...
Children shouldn't be giving out info to people they don't know, except to 911, etc. in an emergency. The trickle of sleazy spam (is there any other kind?) that gets thru spamassassin could actually help kids** understand why they should be careful.
**Well, the smart ones. The stupid ones will click thru on every offer. At least they'll waste the spammer's time.
I think it's all a symptom of broadcasting with only a few stations available in any place. Specialty channels, whether by internet or satellite, have some hope, in that they should realize that they need to treat their audience right, or that audience will move on.
First, an arbitrarily detailed simulation of a universe would require all of the resources of the host universe - so it might as well be a real universe, and there is no multiplication effect. Since we (and by we I mean I ;-) have no evidence of this universe being a simulation, I assume that if it is a simulation it must be an arbitrarily detailed one.
Second, a simulated universe with limited detail would not spawn child universes. Oh, the inhabitants of the simulated universe might think they had started their own simulations, but back in the real universe the computer running the simulation they inhabit would have no reason to run the secondary simulations - it only needs to produce perceptions for the inhabitants of the first simulation. So again, there is no proliferation of virtual universes that would make it more likely for a conscious being to be in a simulation than in a real universe.
Note that I am not discounting the sort of simulation required for solipsism - it would come under the second sort of simulation.