This is definitely very cool, but "reveals" is a strong word. They've demonstrated that it's a plausible explanation for the puzzling distribution of stars in this cluster, but there are still other explanations that have not been ruled out.
What's puzzling about the cluster is that the stars appear well-mixed -- the high mass stars follow the same distribution as the lower mass stars. That's weird because globular clusters should undergo mass segregation, where the high mass stars slowly congregate towards the center while the lower-mass stars migrate towards the outside (interestingly, this is because self-gravitating systems have negative heat capacity, which is a concept that tends to freak out non-astronomers). And we indeed see that most clusters are mass-segregated.
So why do black holes help? They form from the most massive stars, which died early, and they end up being significantly more massive than the lower-mass stars that are left. So if there are lots of black holes, then the effect of mass segregation is to make the *black holes* congregate towards the center. In other words, mass segregation is still happening, but it's operating on black holes (which we can't see, so we don't notice its effect) instead of stars (which we can see).
There are other ways you can explain this, though. If there's a massive-enough intermediate-mass black hole at the cluster center, that makes the process of mass segregation take longer, so it might not have had time to make any significant change. A sufficiently large fraction of binary stars within the cluster could have a similar effect (i.e. make the mass segregation timescale much longer). Or, more speculatively, you could posit that there was some dynamical event that happened to the cluster since its formation that mixed the stars, so mass segregation has not had as long to operate as we assume. So their explanation is a plausible interesting one that they have demonstrated can indeed cause the desired effect, which is really cool! But these other options also need to be investigated.
Another exception is Israel -- the only country on that list that's at all hostile to Israel is Pakistan, but Israel's nuclear weapons program predates Pakistan's.
...and this is why I don't like the balloon analogy -- people point to the way in which the analogy is completely unlike the analogous system, and then assume that there is a comparable property in reality.
Think of the universe as the dolly zoom in the movie Vertigo. No matter where Jimmy Stewart is, as he climbs up the tower, when he looks down you see the bottom of the tower stretching away from him. There is no real center point -- it's not like the center of expansion suddenly moves up the tower with him. And it's not as if the bottom of the tower is expanding into the ground below. It's just that the space between him and the bottom appears to stretch away.
Actually, let me rephrase that -- it's not counter-intuitive at all that amplitude goes as 1/r, but what's odd is that with gravitational waves, you directly detect the wave amplitude, so detectability falls off as 1/r. For most waves, you detect the wave intensity, which goes as amplitude squared and therefore 1/r^2.
The Earth-Moon system is bound, so not useful to measure the Hubble constant. By definition, a bound system is one in which gravity has overcome cosmological expansion.
I spend a large fraction of my time deep in the National Radio Quiet Zone. WiFi is illegal. The assumption that you will always be able to do wireless is faulty.
For some reason that I don't understand, ethernet adapters die at a ridiculous rate. I've been through 7 in 3.5 years, and everyone I know who uses them has similar stories. I've tried a variety of brands, with no difference in the results.
They show differences, but they don't show what the typical bottle-to-bottle dispersion is in the concentrations for Earth-aged bottles, without which there's no way to judge whether the difference is significant.
I agree, but the problem with arguing against conspiracy theory is that "a vast conspiracy is hiding all the truth so no one can find it" is inherently unfalsifiable, which makes scientific argument (i.e. presenting evidence that falsifies the proposition) pretty useless.
Yeah, we have 2 of these in our family, and they're fine. I do find that mine loses connectivity faster than other phones at low signal, but I mainly use it as an emergency phone (I still don't get the point of cell phone culture, never mind smartphone culture) so I don't really mind.
The authors of this work didn't invent the word -- that's been one of the standard descriptions of this process for decades, and I'm not sure who first came up with it. I think it evolved from "suffocation", which does make more sense (it runs out of gas).
This is in contrast to other dramatic ways of making a galaxy "red and dead" like "harassment", "tidal strippping", and "cannibalism", during which the galaxy undergoes "violent relaxation" (the single best technical term in all of astrophysics).
The academic job market is so tight right now that there's not much danger of hiring unqualified people -- there are many more highly qualified job-seekers than there are jobs available.
The energy density in the universe from light is much less than the energy density from baryonic matter, which is in itself much less than the total matter energy density of the universe (which is why we infer the existence of non-baryonic, or "dark", matter).
The best piece of code I ever wrote in my life was nearly 100x faster than the next best algorithm ever written to do that problem. That took the expected run time down from a few days to an hour.
It was not a particularly well-commented piece of code. If it were, it would have been even better.
It was not a particularly obvious algorithm for solving the problem. If it were more obvious why one would choose to do it this way, it would have been even better.
If the primary concern is runtime (because it normally takes days to run), and you literally make it orders of magnitude faster, that's good code. It could be better if it were also better commented and easier to maintain, but those aren't *always* the primary concern (yes, sometimes they are. That's the point -- criteria differ!)
That was what was first assumed. There's only one minor problem.
The amount of zero point energy is *120 orders of magnitude* larger than the measured magnitude of dark energy. And dark energy has about 3x the energy density of dark matter.
So, despite the fact that it looks like zero point energy, there's something else going on.
There are actually many proposed extensions to the standard model that predict dark matter particles that would be classified as WIMPs, and there are some others where the interaction is not through the weak force but through a "hidden sector" force. Some of the possible parameter space of some those hidden sector models predict a cross-section that they would have been able to detect in this experiment. So this is indeed a useful result -- it does rule out some possibilities. But they're not necessarily the possibilities that most people would be betting on anyway, so the headline is overhyped.
Are you worried that creationists will try to subvert BAHFest by pointing to it as "Look, even the evolutionists think it's a joke that they can use to explain anything they want"?
Slashdot Mirror
This is definitely very cool, but "reveals" is a strong word. They've demonstrated that it's a plausible explanation for the puzzling distribution of stars in this cluster, but there are still other explanations that have not been ruled out.
What's puzzling about the cluster is that the stars appear well-mixed -- the high mass stars follow the same distribution as the lower mass stars. That's weird because globular clusters should undergo mass segregation, where the high mass stars slowly congregate towards the center while the lower-mass stars migrate towards the outside (interestingly, this is because self-gravitating systems have negative heat capacity, which is a concept that tends to freak out non-astronomers). And we indeed see that most clusters are mass-segregated.
So why do black holes help? They form from the most massive stars, which died early, and they end up being significantly more massive than the lower-mass stars that are left. So if there are lots of black holes, then the effect of mass segregation is to make the *black holes* congregate towards the center. In other words, mass segregation is still happening, but it's operating on black holes (which we can't see, so we don't notice its effect) instead of stars (which we can see).
There are other ways you can explain this, though. If there's a massive-enough intermediate-mass black hole at the cluster center, that makes the process of mass segregation take longer, so it might not have had time to make any significant change. A sufficiently large fraction of binary stars within the cluster could have a similar effect (i.e. make the mass segregation timescale much longer). Or, more speculatively, you could posit that there was some dynamical event that happened to the cluster since its formation that mixed the stars, so mass segregation has not had as long to operate as we assume. So their explanation is a plausible interesting one that they have demonstrated can indeed cause the desired effect, which is really cool! But these other options also need to be investigated.
Another exception is Israel -- the only country on that list that's at all hostile to Israel is Pakistan, but Israel's nuclear weapons program predates Pakistan's.
...and this is why I don't like the balloon analogy -- people point to the way in which the analogy is completely unlike the analogous system, and then assume that there is a comparable property in reality.
Think of the universe as the dolly zoom in the movie Vertigo. No matter where Jimmy Stewart is, as he climbs up the tower, when he looks down you see the bottom of the tower stretching away from him. There is no real center point -- it's not like the center of expansion suddenly moves up the tower with him. And it's not as if the bottom of the tower is expanding into the ground below. It's just that the space between him and the bottom appears to stretch away.
Actually, let me rephrase that -- it's not counter-intuitive at all that amplitude goes as 1/r, but what's odd is that with gravitational waves, you directly detect the wave amplitude, so detectability falls off as 1/r. For most waves, you detect the wave intensity, which goes as amplitude squared and therefore 1/r^2.
Counter-intuitively, the strain amplitude goes as the inverse of the distance, not the inverse square!
The Earth-Moon system is bound, so not useful to measure the Hubble constant. By definition, a bound system is one in which gravity has overcome cosmological expansion.
These are all true, but I find the reasons people are giving for grocery stores completely miss the point:
No two tomatoes are the same.
I can't tell you which tomato I want without picking it up, looking at it, and feeling it.
[TMB]
And every US state has official road maps for free at the first visitor's center after you cross the state line.
http://www.urbandictionary.com...
I spend a large fraction of my time deep in the National Radio Quiet Zone. WiFi is illegal. The assumption that you will always be able to do wireless is faulty.
For some reason that I don't understand, ethernet adapters die at a ridiculous rate. I've been through 7 in 3.5 years, and everyone I know who uses them has similar stories. I've tried a variety of brands, with no difference in the results.
Discerning Australians drink beer from New Zealand because it's a hell of a lot better.
They show differences, but they don't show what the typical bottle-to-bottle dispersion is in the concentrations for Earth-aged bottles, without which there's no way to judge whether the difference is significant.
[TMB]
I agree, but the problem with arguing against conspiracy theory is that "a vast conspiracy is hiding all the truth so no one can find it" is inherently unfalsifiable, which makes scientific argument (i.e. presenting evidence that falsifies the proposition) pretty useless.
[TMB]
You beat me to this comment... Rocky's Boots was awesome, and a great intro to programming for a kid.
Based on the summary, I'm forced to conclude that it is safe to tampering from male hackers, but that female hackers can safely modify the results!
Yeah, we have 2 of these in our family, and they're fine. I do find that mine loses connectivity faster than other phones at low signal, but I mainly use it as an emergency phone (I still don't get the point of cell phone culture, never mind smartphone culture) so I don't really mind.
The authors of this work didn't invent the word -- that's been one of the standard descriptions of this process for decades, and I'm not sure who first came up with it. I think it evolved from "suffocation", which does make more sense (it runs out of gas).
This is in contrast to other dramatic ways of making a galaxy "red and dead" like "harassment", "tidal strippping", and "cannibalism", during which the galaxy undergoes "violent relaxation" (the single best technical term in all of astrophysics).
[TMB]
How about green card? I know that I can't work directly for the federal government, but I'm curious about other constraints.
The academic job market is so tight right now that there's not much danger of hiring unqualified people -- there are many more highly qualified job-seekers than there are jobs available.
The energy density in the universe from light is much less than the energy density from baryonic matter, which is in itself much less than the total matter energy density of the universe (which is why we infer the existence of non-baryonic, or "dark", matter).
The best piece of code I ever wrote in my life was nearly 100x faster than the next best algorithm ever written to do that problem. That took the expected run time down from a few days to an hour.
It was not a particularly well-commented piece of code. If it were, it would have been even better.
It was not a particularly obvious algorithm for solving the problem. If it were more obvious why one would choose to do it this way, it would have been even better.
If the primary concern is runtime (because it normally takes days to run), and you literally make it orders of magnitude faster, that's good code. It could be better if it were also better commented and easier to maintain, but those aren't *always* the primary concern (yes, sometimes they are. That's the point -- criteria differ!)
[TMB]
That was what was first assumed. There's only one minor problem.
The amount of zero point energy is *120 orders of magnitude* larger than the measured magnitude of dark energy. And dark energy has about 3x the energy density of dark matter.
So, despite the fact that it looks like zero point energy, there's something else going on.
[TMB]
Yes.
There are actually many proposed extensions to the standard model that predict dark matter particles that would be classified as WIMPs, and there are some others where the interaction is not through the weak force but through a "hidden sector" force. Some of the possible parameter space of some those hidden sector models predict a cross-section that they would have been able to detect in this experiment. So this is indeed a useful result -- it does rule out some possibilities. But they're not necessarily the possibilities that most people would be betting on anyway, so the headline is overhyped.
[TMB]
Are you worried that creationists will try to subvert BAHFest by pointing to it as "Look, even the evolutionists think it's a joke that they can use to explain anything they want"?