By physical definition, "dark matter" refers to any baryonic or non-baryonic media that attributes to undetected gravitational masses surrounding galaxies and filling our Universe. So if there are a large number of isolated black holes that have not been detected, they may have some contribution to "dark matter" per se. It doesn't have to be BHs, either. It could well be Jupitar-size planets that are considered "dark matter" in this sense.
Each black hole is practically a point-like source, not good at blanketting to shield off the light from a bunch of stars all over the place. A thick smoke screen (like hydrogen) is better at doing that.
Besides, black holes may be bright in X-rays and other wavelengths. They should've been detected a long ago, if it were a full of BHs.
Since this guy was doing radio observations, he must have detected a weak radio signature for Hydrogen emission from this dwarf galaxy. A bulk of hydrogen gas (still dark matter) would look different from that of blackholes in radio.
Yep. But since I don't own a house (and expect many of slashdotters are renters), I lack in the common frame of reference...so sad...
Something as simple as how to lay down hot water pipe through the house can save some money here and there, too. I'm not really that much of a conservation freak, but I try to do my part when I can.
Here is one more thought: we now know that the universe is expanding faster. It means sooner or later the baryon density would decrease and we will run out of hydrogen, etc., as fuel. And in a long run proton would decay into ether. So yeah, the power won't be there then, but that's a long way to go.
Other than that, the power will be there, though the quantity is limited. So to conserve the usage is imperative for the continuous existence of the civilization.
The demand had better not grow exponentially, as the available energy resource is finite within our reach (or in the universe).
It's utopian thinking to assume that there will always be some power source available to meet the demand. Example? Blackout in NYC. Humans are going to learn this in a hard way unless we individuals start waking up and smell the coffee.
Besides, what I'm saying is not entirely unreasonable. Imagine a light bulb that consumes 60W of the electrical power. A cheap one will generate a lot of heat (IR). And unless you have IR vision, it ain't gonna make your room any brighter. On the other hand, design a light bulb that radiates mostly in the visual wavelength, while little is radiated away as heat. Now that will allow you to consume less energy but generating the same lumen as the cheap light bulb. Isn't that a profoundly wiser course of action for the civilization to take?
Both power providers and consumers need to work in harmony: (1) the power companies are to increase the efficiency in generating more power and (2) the consumers are to utilize the available energy in an efficient manner.
There isn't much I can do for (1). But I can do for (2) by replacing light bulbs with energy saving bulbs (ESBs, or compact fluorescent bulb that fits in an incadescent lamp), turn off the light where not needed, and turn the damned TV when/.ing. You can do a little to cut some energy expenses by following these actions. In reality I am not going to save over $20 a year. But when people start doing the same, it soon becomes a real money.
You dad can fill you in with more details, but here are my 2 cents for now:
(1) the orbital altitude of the ISS, I believe, is higher than that of the Hubble. The structural size of the ISS is much greater than the Hubble, hence the ISS experiences more drag through air (yes, some air is up there and it matters). And actually everytime a shuttle visits to the ISS, the shuttle pushes it up to a higher orbit with the shuttle's thruster.
(2) I wouldn't think even DoD is using a shuttle from now on. The recommendation, I believe, is to use the remaining shuttles for the ISS mission only. Besides, DoD would do better with using expendable rockets. Much less cargo restriction.
(3) The hubble's orbit is close to circle. Very close.
(4) logistically too improbable to visit two targets per mission with any shuttle. The limits are (a) fuel and (b) mission complexity that astronauts can comfortably handle.
(5) The limit on the crew's number on the ISS depends on the availability of seats in emergency escape vehicle. Right now it's Soyuz space capsule. Until some nation develops a reentry vehicle bigger in capacity, there will be no more than 3 people on board the ISS. This is why the ISS is bound to fail as a laboratory. To me the ISS is a lifeline for the Russian federation (how else you'd justifiably fund Russian scientists to continue their work and feed themselves? Otherwise they'll hit the black market. I'm just guessing).
It is not just at fault of the NASA as an organization. I'd dare say that the failure results from a lack of strong vision and support for fundamental science by a NASA director. It is becoming an institution for engineering, though its general objectives are being defined by the interest groups outside the government.
We need another NASA director like James Webb who had clear vision for the future of NASA and strong voice in the Capitol Hill.
Of course, it is best if we have support from the greater audience, such as yourself. Remember, any superpower nation dies when it loses grips on the supremacy in technology and science.
If the satellite is smaller, one would attempt to position a satellite to maximize its drag force with magnetic torquers and IRW. It makes it easier, too, if the Sun is active (*). By dragging it, it slows its revolution rate, which leads to decay in orbital altitude. We've downed satellites this way a few times. But the HST is probably too large to do this safely.
CGRO was designed to be de-orbited at its end and had a thruster. I guess NASA really was planning to bring the Hubble down with the Columbia, since it has none of that.
(*) when the Sun is very active, it puffs up the scale height of the atmosphere. In turn it increases the particle density in the low earth orbit, which leads to a greater drag force.
Although modded down incorrectly by one, it served the intended purpose (the parent is modded +5). Thank you, Mods. I'm glad I have faith in the system.
All the key ingredients for the warming media (Fluorine based gas, according to the article) exists on Mars.
And yes, the warming agent will evaporate away in a long run. As Martian air warms it up, the rate of the evaporation would increase. This is easy to understand if you know Maxwellian distribution. If not, look it up. Basically each particles in the gas at a certain temperature doesn't all have the same kinetic energy (== mean speed); some particles have slower than the average speed, while others move much faster. And those particles that are moving faster -- especially faster than the escape velocity of Mars -- have a chance to escape (i.e., evaporate out).
But for those heavy molecular compound, the timescale of evaporation is long, and the article implies that the scale time is about 2 billion years.
It's not hard to derive these conclusions by reading the article. The Gurdian is generally better at it than any other news source in the U.S.
Considering this is a broad-band IR imaging, isn't it plausible that the bright spot in the south pole is not due to strong thermal continuum, but instead due to strong emission line features?
I wonder if Saturn is too bright for the Spitzer's spectrogrpah.
JWST is designed to achieve completely different kind of astrophysics that the HST is designed to do. (different waveband, imaging-centric mission, etc) The only thing that will be the same is that it will be operated by the Space Telescope Science Institute.
The HST and JWST is meant to be complementary. Neither does excel on what the other would do. That's why we fuss over it. And this has been said here once and again.
(1) The Hubble's mirror is designed to achieve its optimal spatial resolution at 280 nm, which is in the ultra-violet regime and not ideal for snapshot through atmosphere.
(2) It is a poor satellite for infrared picture. And its IR instrument on board is designed to capture faint objects, not the bright sources on earth (i.e., any object on earth may be too bright to see for the Hubble).
(3) the compensation for atmospheric disturbance is not readily available with the Hubble. That still needs to be done on the ground and that's the post-processing data cost that you will still have to bear (ain't cheap).
Remember, the Hubble is designed to take astrophysical data, not aereal photos on ground. One of these days people have to understand that engineers builds "stuff" to optimize the use for whatever it is intended for.
There has been an interesting resistence among rocket scientists to re-use some old technology to base a mission. I guess it has to do with no R&D funding being available and it is no longer attractive to the research lab rats type. NASA has not been very kind to that type of mission, either.
But in essence, we could build a mission based on scraps on the cheap side. Maybe the community will start thinking about the possibility.
PS. Multi-levels of redundancies in satellites already exist. Yet space instruments still fail.
The whole technology gone into the Hubble was based on 1970 and 80's cutting edge technology, pal...I still remember the day the Hubble's instrument used a photo-sensitive 1-dimensional, 512-element diode to sample data...
The true technological icons of the 90's are about to come in space.
You're wrong. If the investiment on military alone could sustain super-power status, then the evil empire CCCP would have been around and threating the mighty western civilization today.
Do you know what happened to the Soviets?
In my journal, I have described why a super-power nation needs to invest money into natural science and cutting edge technology to remain a super-power.
Slashdot Mirror
That could've been funny if i spelled "tough" right...oops, I meant to submit it as AC...oh screw that.
It's touch alright. It's makin' me its bitch.
By physical definition, "dark matter" refers to any baryonic or non-baryonic media that attributes to undetected gravitational masses surrounding galaxies and filling our Universe. So if there are a large number of isolated black holes that have not been detected, they may have some contribution to "dark matter" per se. It doesn't have to be BHs, either. It could well be Jupitar-size planets that are considered "dark matter" in this sense.
Each black hole is practically a point-like source, not good at blanketting to shield off the light from a bunch of stars all over the place. A thick smoke screen (like hydrogen) is better at doing that.
Besides, black holes may be bright in X-rays and other wavelengths. They should've been detected a long ago, if it were a full of BHs.
Since this guy was doing radio observations, he must have detected a weak radio signature for Hydrogen emission from this dwarf galaxy. A bulk of hydrogen gas (still dark matter) would look different from that of blackholes in radio.
...and God speed, Commander Eileen and her crew.
Thanks goodness for Atmosphere. It has protected us once again!
ps. It happened in August 1998. Back then it was SGR1900+14. Apparently a weaker event, but it knocked our socks off back then.
Don't need to mod me up there.
It's a silly article and I was replying in kind.
Bleh, this is nothing compared to Car Henge in Nebraska.
Screw astronomy. It's about used cars, man!
Yep. But since I don't own a house (and expect many of slashdotters are renters), I lack in the common frame of reference...so sad...
Something as simple as how to lay down hot water pipe through the house can save some money here and there, too. I'm not really that much of a conservation freak, but I try to do my part when I can.
Here is one more thought: we now know that the universe is expanding faster. It means sooner or later the baryon density would decrease and we will run out of hydrogen, etc., as fuel. And in a long run proton would decay into ether. So yeah, the power won't be there then, but that's a long way to go.
Other than that, the power will be there, though the quantity is limited. So to conserve the usage is imperative for the continuous existence of the civilization.
The demand had better not grow exponentially, as the available energy resource is finite within our reach (or in the universe).
It's utopian thinking to assume that there will always be some power source available to meet the demand. Example? Blackout in NYC. Humans are going to learn this in a hard way unless we individuals start waking up and smell the coffee.
Besides, what I'm saying is not entirely unreasonable. Imagine a light bulb that consumes 60W of the electrical power. A cheap one will generate a lot of heat (IR). And unless you have IR vision, it ain't gonna make your room any brighter. On the other hand, design a light bulb that radiates mostly in the visual wavelength, while little is radiated away as heat. Now that will allow you to consume less energy but generating the same lumen as the cheap light bulb. Isn't that a profoundly wiser course of action for the civilization to take?
Think about that one a bit.
Both power providers and consumers need to work in harmony: (1) the power companies are to increase the efficiency in generating more power and (2) the consumers are to utilize the available energy in an efficient manner.
/.ing. You can do a little to cut some energy expenses by following these actions. In reality I am not going to save over $20 a year. But when people start doing the same, it soon becomes a real money.
There isn't much I can do for (1). But I can do for (2) by replacing light bulbs with energy saving bulbs (ESBs, or compact fluorescent bulb that fits in an incadescent lamp), turn off the light where not needed, and turn the damned TV when
You dad can fill you in with more details, but here are my 2 cents for now:
(1) the orbital altitude of the ISS, I believe, is higher than that of the Hubble. The structural size of the ISS is much greater than the Hubble, hence the ISS experiences more drag through air (yes, some air is up there and it matters). And actually everytime a shuttle visits to the ISS, the shuttle pushes it up to a higher orbit with the shuttle's thruster.
(2) I wouldn't think even DoD is using a shuttle from now on. The recommendation, I believe, is to use the remaining shuttles for the ISS mission only. Besides, DoD would do better with using expendable rockets. Much less cargo restriction.
(3) The hubble's orbit is close to circle. Very close.
(4) logistically too improbable to visit two targets per mission with any shuttle. The limits are (a) fuel and (b) mission complexity that astronauts can comfortably handle.
(5) The limit on the crew's number on the ISS depends on the availability of seats in emergency escape vehicle. Right now it's Soyuz space capsule. Until some nation develops a reentry vehicle bigger in capacity, there will be no more than 3 people on board the ISS. This is why the ISS is bound to fail as a laboratory. To me the ISS is a lifeline for the Russian federation (how else you'd justifiably fund Russian scientists to continue their work and feed themselves? Otherwise they'll hit the black market. I'm just guessing).
Sounds like you father works at NASCOM/GSFC.
It is not just at fault of the NASA as an organization. I'd dare say that the failure results from a lack of strong vision and support for fundamental science by a NASA director. It is becoming an institution for engineering, though its general objectives are being defined by the interest groups outside the government.
We need another NASA director like James Webb who had clear vision for the future of NASA and strong voice in the Capitol Hill.
Of course, it is best if we have support from the greater audience, such as yourself. Remember, any superpower nation dies when it loses grips on the supremacy in technology and science.
Thanks.
If the satellite is smaller, one would attempt to position a satellite to maximize its drag force with magnetic torquers and IRW. It makes it easier, too, if the Sun is active (*). By dragging it, it slows its revolution rate, which leads to decay in orbital altitude. We've downed satellites this way a few times. But the HST is probably too large to do this safely.
CGRO was designed to be de-orbited at its end and had a thruster. I guess NASA really was planning to bring the Hubble down with the Columbia, since it has none of that.
(*) when the Sun is very active, it puffs up the scale height of the atmosphere. In turn it increases the particle density in the low earth orbit, which leads to a greater drag force.
Although modded down incorrectly by one, it served the intended purpose (the parent is modded +5). Thank you, Mods. I'm glad I have faith in the system.
This is a good comment. Much better than the parent's overrated comment.
Crazy and pointless, maybe ,but not stupid.
All the key ingredients for the warming media (Fluorine based gas, according to the article) exists on Mars.
And yes, the warming agent will evaporate away in a long run. As Martian air warms it up, the rate of the evaporation would increase. This is easy to understand if you know Maxwellian distribution. If not, look it up. Basically each particles in the gas at a certain temperature doesn't all have the same kinetic energy (== mean speed); some particles have slower than the average speed, while others move much faster. And those particles that are moving faster -- especially faster than the escape velocity of Mars -- have a chance to escape (i.e., evaporate out).
But for those heavy molecular compound, the timescale of evaporation is long, and the article implies that the scale time is about 2 billion years.
It's not hard to derive these conclusions by reading the article. The Gurdian is generally better at it than any other news source in the U.S.
Considering this is a broad-band IR imaging, isn't it plausible that the bright spot in the south pole is not due to strong thermal continuum, but instead due to strong emission line features?
I wonder if Saturn is too bright for the Spitzer's spectrogrpah.
JWST is designed to achieve completely different kind of astrophysics that the HST is designed to do. (different waveband, imaging-centric mission, etc) The only thing that will be the same is that it will be operated by the Space Telescope Science Institute.
The HST and JWST is meant to be complementary. Neither does excel on what the other would do. That's why we fuss over it. And this has been said here once and again.
(1) The Hubble's mirror is designed to achieve its optimal spatial resolution at 280 nm, which is in the ultra-violet regime and not ideal for snapshot through atmosphere.
(2) It is a poor satellite for infrared picture. And its IR instrument on board is designed to capture faint objects, not the bright sources on earth (i.e., any object on earth may be too bright to see for the Hubble).
(3) the compensation for atmospheric disturbance is not readily available with the Hubble. That still needs to be done on the ground and that's the post-processing data cost that you will still have to bear (ain't cheap).
Remember, the Hubble is designed to take astrophysical data, not aereal photos on ground. One of these days people have to understand that engineers builds "stuff" to optimize the use for whatever it is intended for.
There has been an interesting resistence among rocket scientists to re-use some old technology to base a mission. I guess it has to do with no R&D funding being available and it is no longer attractive to the research lab rats type. NASA has not been very kind to that type of mission, either.
But in essence, we could build a mission based on scraps on the cheap side. Maybe the community will start thinking about the possibility.
PS. Multi-levels of redundancies in satellites already exist. Yet space instruments still fail.
The whole technology gone into the Hubble was based on 1970 and 80's cutting edge technology, pal...I still remember the day the Hubble's instrument used a photo-sensitive 1-dimensional, 512-element diode to sample data...
The true technological icons of the 90's are about to come in space.
Though you're just a troll, I'll bite.
You're wrong. If the investiment on military alone could sustain super-power status, then the evil empire CCCP would have been around and threating the mighty western civilization today.
Do you know what happened to the Soviets?
In my journal, I have described why a super-power nation needs to invest money into natural science and cutting edge technology to remain a super-power.