There is an on-going research to forecast earthquakes via detecting ionospheric disturbances (can't find a good article now...it has to do with the detection of a very-remote FM radio signal that could only be detected when anomalous disturbance occurs in the ionosphere. An initial finding was done while amateur astronomers were monitoring FM radio signal for meteor detection). Maybe animals can detect minute changes in the terrestrial electro-magnetic field, I wonder?
I wondered about those fishes that died ashore after the tsunami...
The sound wave indeed propagates through water about 1400km/h, much greater than the propagation speed of tsunami wave at this time (~1000km/h). So the fishes most probably have "heard" the low freqency wave. I'm sure no fish can outswim the tsunami, but I'm a tiny bit surprised to see so many of them got stranged in land.
I know the physics of waves, but have little experience in ocean current under sea. Would tsunami wave actually whirl up and down so fast that deep ocean fishes get dredged up fast and get knocked out before dying ashore? Or do they simply get left behind waves and asphyxiate to death?
Hubble orbits at an altitude of about 550km. Its optical system is optimized to give the highest resultion at 280nm (which is useless for a spy satellite, but that's not the point), giving about 0.04 arcsecond resolution. At visible and near IR, the resolution degrades down to 0.06 -- 0.1 arcseconds. In more sensible term, the latter translates to about 25cm of spatial resolution from the orbital altitude.
Of course, atmosphere is very turbulent (like looking thru turbulent air generated by the wing of an airplane). To beat that, one needs to perform serious optical image reconstruction. NRO can probably do that well (astronomers learned the gut of it from them back in 1990s).
This is the kind of "kick in the butt" that NASA has been needed. Bravo to the SpaceShip team for the continuing development of their fleet.
I'm still waiting for it to grow and to become capable of reaching 500 km in altitude. If it can reach the altitude with a small payload launching capability, then a on-the-cheap space experiment becomes possible in future. I think that could change the way we think about space research.
Exploration and investment are the reasons for a mission like this.
The former -- exploration -- is what NASA and scientists will advertise in front. Why? Because we know so little about comets. Imagine, if the judgement day comes and we have to "shoot down" one of these in order to save the humanity, wouldn't you be rather comfortable to know what and how comets are really made of? We really do not know what happens to a comet when we toss a stick of dynamite into it, as its structural integrity is not well known.
The latter -- investment -- is the second and the foremost important reason. In order for a super-power nation to sustain its technological supremacy in this world, its government must invest its money for the advancement of engineering and science [*]. The investment to a NASA's mission like this may not seem as important as an investment toward curing cancer, etc., but such assessment is near-sighted. For example, building of a scientific instrument requires a miniaturization of electronic component (in order to reduce its size and weight). Each component is also certified to withstand harsh cosmic environment (sudden changes in temperature and severe bombardment by cosmic radiation). The skills learned through these R&D may eventually trickle down to the industry, and hence possibly leading to development of affordable high-tech components (e.g., IC chips in a decade ago). Basically the high cost of R&D may be paid by the government and the industry would benefit from such learned knowledge. It is not too surprising that a medical breakthrough on cancer may come from the spread of affordable technology obtained through space research.
[*] There was no time in history that a single nation had dominated the world without its technological advantage.
But at the bottom line, the choice is up to you and other constituents in the nation. You ask your representatives to choose either to feed the hungry right now or to invest on the future. I'm inclined to choose the latter.
You know how to spot Pleiades? A bunch of stars (like 7 of them) clustered around? If yes, wait til Jan 7 -- 9th, 2005 to look for it. The comet will pass by Pleiades around these dates.
The bottom line is that Russians need money to sustain their skill levels in space technology by retaining the old and training the new engineers and scientists. Or else these talents may end up in the darker side of the think-tank market.
I am in favor of paying them off for the lift. Heck, I'm surprised that we hadn't been so far.
So being "transparent" really doesn't mean much for sales point? It sounds like the key points are (1) the element can be made small (thin) and (2) cheap. I could be way off the mark, as I just skimmed the article out of curiousity on application.
It's not often that we get a chance to examine the integrity of the remaining heat shield in these missions. Let it take a look and see what JPL guys can learn from it for future missions, eh?
Think a bit about where that "momentum" in the vaporized material originally come from. Then the conservation of momentum.
You are probably right about one thing: tensile strength of an asteroid is not certain. If it's pure iron, sure, blow it off the course. But nothing is that pure. Most probably admixture of chondrite and iron. That means it'll be like to cause fissures and to break it apart if not bomb it carefully (that's why I said we need to check geometrical anomaly).
That's one of the reasons that I do not think nuking is the prudent choice.
I have no idea what cobalt warheads are [but I know enough on how a hydrogen bomb works...]. Anyway I'm not saying that it cannot be done with nukes. Maybe we can send several probes to diagnose its composition (carbon rich or iron rich, or any ice?), then determine its rotational axis (if you misplace the bombs, it might just let it spin faster, you see?), and examine geometric anomaly to see where to place and detonate bombs in concert. It'll take some precision engineering to place everything, but we have done that with a NEO probe before. From engineering perspective, this can be done (not fail-safe, but...).
Whether it is the SMARTEST thing to do is up for debate. I'd be more interested in investing the use of a solar sail (Japan's ISAS/JAXA is the only institution that has done some engineering test on such sail, though).
First, my apology that I made an error in the previous post. The actual energy requied to move a 300m cube (with density of 3 g/cm3) laterally at 1km/s is about 4e16 joules (I shamefully admit that I forgot about SI unit).
Now let's fix up some bad concepts here. First, a detonation of a hydrogen bomb will provide impulse force, neither constant or gradual. Second, there is no mass in gamma ray (it's a photon). Alpha particles will be produced but it's insignificant compared to the asteriod, so we can omit them out of our consideration.
Now taking your number (thanks by the way), 1 mega ton TNT is about 4e15 joules. And like I said, a half of radiation just simply escapes away from the asteroid. Now suppose if the efficiency of radiative momenta is 100% (which is very unlikely, but let's assume that), then it would take 20 mega-ton TNTs at a minimum to give it a little push.
But again, the 100% efficiency is unlikely. Some photons will part its energy into heat, or re-radiated away. So for the safety factor, I'd feel confident if we are to deploy about 10x, or 200 mega-ton TNTs simultaneously.
It's not an impossible number, perhaps.
(ps. I ignore many physics here; the asteroid is bounded by the Sun's gravity and so its potential field must be taken into account as well..well, I will worry about that when NASA comes knocking my door for help).
Detonating a nuke in space isn't very effective when it comes to generating "pressure". At least 1/2 of the energy will be lost in form of radiation (a geometrical effect). Photons do carry momentum but I wonder how many nukes would it take to add a lateral velocity of 1 km/s (or more or less, it all depends on when we do it -- the earlier the better, like you say). For an cubic asteroid with 300 x 300 x 300m in size, it's roughly 5e7 Newtons of the force requied to add 1km/s velocity. Now that's a hell of the force.
I doubt that very much. If one just detonate it on the surface, it'd simply make a molten crater on the surface (remember, there is no blast wave as there is no air; the detonation of a thermonuclear device will generate a copiuos amount of radiation that photo-ionizes the surface of a rock). There has to be some penetrating mechanism to sink the nuke into the rock deeply and then detonate. But even then, there is no guarantee that it would break into smaller pieces (and even if you can do that, then you're creating a smaller pieces that falls all over the earth, like a shotgun blast, instead of a cannon blast).
I agree with your comment, Phirst. It's probably the most powerful SURVEY camera that I have seen. But I use grating/echelle spectrographs mostly, both on ground and space. So from *my* heavily biased perspective, the title of "most powerful" doesn't sound right.
I know it's just a matter of phrasing things. Like I said, this is a nifty instrument. I've always thought that detectors & instruments should define the quality and goodness of a telescope. You know, having an 8-m telescope with no working instrument just about do us no good...
I'm off to a party now. Happy holiday to you in Hawaii. And to all of you.
It probably is a galaxy, though not necessarily terrifically bright as you call it. It's located in the part where the intervening gas of the Orion nebula (and the Galaxy) is thinner and it doesn't take much brightness for us to see through the cloud. You'd be right that it's a dusty galaxy (though it is not so uncommon).
Not trying to take away anything from UKIRT (which is an awesome telescope from user's perspective), what do they mean by "most powerful" here? To me it means highest sensitivity to IR light or highest spatial resolution achievable with the combination of detector (which is the theme of this release) and its optical system (UKIRT). Apparently this instrument provides the largest field of view, which is cool indeed, but would that deserves "most powerful" title? It's a bit self-serving statement to me.
Again, I'm not making light of the instrument. Some people -- those who perform sky survey, etc. -- would find it "most powerful" indeed. But others like me (spectroscopists) would find that statement rather weak. Images are cool, but it can tell you very little about the physical condition of these objects.
My dad's explanation...
on
Ho, Ho, Ho
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· Score: 1
I still like my Dad's explanation on Santa much better:
"Son, there ain't no (expletive) Santa."
I must've been in kindergarden when I was told this. And it's no surprise that I picked up science as my career choice.
-h
ps. though I do not encourage anyone or myself for that matter to use my dad's answer. I'd prefer telling older kids that Santa Clause does exist in every one of the people who believes in him. The belief would magically turn the persons into Santa Clause on the night of Christmas Eve and bring you presents and happiness in your house....or some sentimental bullcrap like that.
Mars probably has a molten core (see Science article from 2003). But then it begs me another question: where has its magnetic field go?
If the dynamo theory is accurate, there could be a sign of the magnetic field. Has Mars Global Surveyer mapped it out yet (I'll google after this post...)?
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Man what you said sounds crazy enough that our prez may actually buy it! More budget for NASA, whooray!
Could it be ionospheric disturbance?
There is an on-going research to forecast earthquakes via detecting ionospheric disturbances (can't find a good article now...it has to do with the detection of a very-remote FM radio signal that could only be detected when anomalous disturbance occurs in the ionosphere. An initial finding was done while amateur astronomers were monitoring FM radio signal for meteor detection). Maybe animals can detect minute changes in the terrestrial electro-magnetic field, I wonder?
I wondered about those fishes that died ashore after the tsunami...
The sound wave indeed propagates through water about 1400km/h, much greater than the propagation speed of tsunami wave at this time (~1000km/h). So the fishes most probably have "heard" the low freqency wave. I'm sure no fish can outswim the tsunami, but I'm a tiny bit surprised to see so many of them got stranged in land.
I know the physics of waves, but have little experience in ocean current under sea. Would tsunami wave actually whirl up and down so fast that deep ocean fishes get dredged up fast and get knocked out before dying ashore? Or do they simply get left behind waves and asphyxiate to death?
Futher nit-picking here.
Hubble orbits at an altitude of about 550km. Its optical system is optimized to give the highest resultion at 280nm (which is useless for a spy satellite, but that's not the point), giving about 0.04 arcsecond resolution. At visible and near IR, the resolution degrades down to 0.06 -- 0.1 arcseconds. In more sensible term, the latter translates to about 25cm of spatial resolution from the orbital altitude.
Of course, atmosphere is very turbulent (like looking thru turbulent air generated by the wing of an airplane). To beat that, one needs to perform serious optical image reconstruction. NRO can probably do that well (astronomers learned the gut of it from them back in 1990s).
And that'll give "celibacy" a whole new meaning.
This is the kind of "kick in the butt" that NASA has been needed. Bravo to the SpaceShip team for the continuing development of their fleet.
I'm still waiting for it to grow and to become capable of reaching 500 km in altitude. If it can reach the altitude with a small payload launching capability, then a on-the-cheap space experiment becomes possible in future. I think that could change the way we think about space research.
I know the topic has nothing to do with lightning (but it is to do with kites). Oh and don't waste your karma points there...
What would Benjamin Franklin have to say about this?
Exploration and investment are the reasons for a mission like this.
The former -- exploration -- is what NASA and scientists will advertise in front. Why? Because we know so little about comets. Imagine, if the judgement day comes and we have to "shoot down" one of these in order to save the humanity, wouldn't you be rather comfortable to know what and how comets are really made of? We really do not know what happens to a comet when we toss a stick of dynamite into it, as its structural integrity is not well known.
The latter -- investment -- is the second and the foremost important reason. In order for a super-power nation to sustain its technological supremacy in this world, its government must invest its money for the advancement of engineering and science [*]. The investment to a NASA's mission like this may not seem as important as an investment toward curing cancer, etc., but such assessment is near-sighted. For example, building of a scientific instrument requires a miniaturization of electronic component (in order to reduce its size and weight). Each component is also certified to withstand harsh cosmic environment (sudden changes in temperature and severe bombardment by cosmic radiation). The skills learned through these R&D may eventually trickle down to the industry, and hence possibly leading to development of affordable high-tech components (e.g., IC chips in a decade ago). Basically the high cost of R&D may be paid by the government and the industry would benefit from such learned knowledge. It is not too surprising that a medical breakthrough on cancer may come from the spread of affordable technology obtained through space research.
[*] There was no time in history that a single nation had dominated the world without its technological advantage.
But at the bottom line, the choice is up to you and other constituents in the nation. You ask your representatives to choose either to feed the hungry right now or to invest on the future. I'm inclined to choose the latter.
Yes it is. Makes you feel better?
You know how to spot Pleiades? A bunch of stars (like 7 of them) clustered around? If yes, wait til Jan 7 -- 9th, 2005 to look for it. The comet will pass by Pleiades around these dates.
The bottom line is that Russians need money to sustain their skill levels in space technology by retaining the old and training the new engineers and scientists. Or else these talents may end up in the darker side of the think-tank market.
I am in favor of paying them off for the lift. Heck, I'm surprised that we hadn't been so far.
So being "transparent" really doesn't mean much for sales point? It sounds like the key points are (1) the element can be made small (thin) and (2) cheap. I could be way off the mark, as I just skimmed the article out of curiousity on application.
Perfect for a throw-away phone and such?
Considering possible contamination risks, I do not believe that the rovers carry any liquid coolant.
It's not often that we get a chance to examine the integrity of the remaining heat shield in these missions. Let it take a look and see what JPL guys can learn from it for future missions, eh?
Think a bit about where that "momentum" in the vaporized material originally come from. Then the conservation of momentum.
You are probably right about one thing: tensile strength of an asteroid is not certain. If it's pure iron, sure, blow it off the course. But nothing is that pure. Most probably admixture of chondrite and iron. That means it'll be like to cause fissures and to break it apart if not bomb it carefully (that's why I said we need to check geometrical anomaly).
That's one of the reasons that I do not think nuking is the prudent choice.
I have no idea what cobalt warheads are [but I know enough on how a hydrogen bomb works...]. Anyway I'm not saying that it cannot be done with nukes. Maybe we can send several probes to diagnose its composition (carbon rich or iron rich, or any ice?), then determine its rotational axis (if you misplace the bombs, it might just let it spin faster, you see?), and examine geometric anomaly to see where to place and detonate bombs in concert. It'll take some precision engineering to place everything, but we have done that with a NEO probe before. From engineering perspective, this can be done (not fail-safe, but...).
Whether it is the SMARTEST thing to do is up for debate. I'd be more interested in investing the use of a solar sail (Japan's ISAS/JAXA is the only institution that has done some engineering test on such sail, though).
First, my apology that I made an error in the previous post. The actual energy requied to move a 300m cube (with density of 3 g/cm3) laterally at 1km/s is about 4e16 joules (I shamefully admit that I forgot about SI unit).
Now let's fix up some bad concepts here. First, a detonation of a hydrogen bomb will provide impulse force, neither constant or gradual. Second, there is no mass in gamma ray (it's a photon). Alpha particles will be produced but it's insignificant compared to the asteriod, so we can omit them out of our consideration.
Now taking your number (thanks by the way), 1 mega ton TNT is about 4e15 joules. And like I said, a half of radiation just simply escapes away from the asteroid. Now suppose if the efficiency of radiative momenta is 100% (which is very unlikely, but let's assume that), then it would take 20 mega-ton TNTs at a minimum to give it a little push.
But again, the 100% efficiency is unlikely. Some photons will part its energy into heat, or re-radiated away. So for the safety factor, I'd feel confident if we are to deploy about 10x, or 200 mega-ton TNTs simultaneously.
It's not an impossible number, perhaps.
(ps. I ignore many physics here; the asteroid is bounded by the Sun's gravity and so its potential field must be taken into account as well..well, I will worry about that when NASA comes knocking my door for help).
I am thinking of the actual number.
Detonating a nuke in space isn't very effective when it comes to generating "pressure". At least 1/2 of the energy will be lost in form of radiation (a geometrical effect). Photons do carry momentum but I wonder how many nukes would it take to add a lateral velocity of 1 km/s (or more or less, it all depends on when we do it -- the earlier the better, like you say). For an cubic asteroid with 300 x 300 x 300m in size, it's roughly 5e7 Newtons of the force requied to add 1km/s velocity. Now that's a hell of the force.
Can it be broken into pieces by nuking it?
I doubt that very much. If one just detonate it on the surface, it'd simply make a molten crater on the surface (remember, there is no blast wave as there is no air; the detonation of a thermonuclear device will generate a copiuos amount of radiation that photo-ionizes the surface of a rock). There has to be some penetrating mechanism to sink the nuke into the rock deeply and then detonate. But even then, there is no guarantee that it would break into smaller pieces (and even if you can do that, then you're creating a smaller pieces that falls all over the earth, like a shotgun blast, instead of a cannon blast).
I agree with your comment, Phirst. It's probably the most powerful SURVEY camera that I have seen.
But I use grating/echelle spectrographs mostly, both on ground and space. So from *my* heavily biased perspective, the title of "most powerful" doesn't sound right.
I know it's just a matter of phrasing things. Like I said, this is a nifty instrument. I've always thought that detectors & instruments should define the quality and goodness of a telescope. You know, having an 8-m telescope with no working instrument just about do us no good...
I'm off to a party now. Happy holiday to you in Hawaii. And to all of you.
-h
You've got good eyes spotting it.
It probably is a galaxy, though not necessarily terrifically bright as you call it. It's located in the part where the intervening gas of the Orion nebula (and the Galaxy) is thinner and it doesn't take much brightness for us to see through the cloud. You'd be right that it's a dusty galaxy (though it is not so uncommon).
Cheers,
-h
Not trying to take away anything from UKIRT (which is an awesome telescope from user's perspective), what do they mean by "most powerful" here? To me it means highest sensitivity to IR light or highest spatial resolution achievable with the combination of detector (which is the theme of this release) and its optical system (UKIRT). Apparently this instrument provides the largest field of view, which is cool indeed, but would that deserves "most powerful" title? It's a bit self-serving statement to me.
Again, I'm not making light of the instrument. Some people -- those who perform sky survey, etc. -- would find it "most powerful" indeed. But others like me (spectroscopists) would find that statement rather weak. Images are cool, but it can tell you very little about the physical condition of these objects.
I still like my Dad's explanation on Santa much better:
"Son, there ain't no (expletive) Santa."
I must've been in kindergarden when I was told this. And it's no surprise that I picked up science as my career choice.
-h
ps. though I do not encourage anyone or myself for that matter to use my dad's answer. I'd prefer telling older kids that Santa Clause does exist in every one of the people who believes in him. The belief would magically turn the persons into Santa Clause on the night of Christmas Eve and bring you presents and happiness in your house....or some sentimental bullcrap like that.
Mars probably has a molten core (see Science article from 2003). But then it begs me another question: where has its magnetic field go?
If the dynamo theory is accurate, there could be a sign of the magnetic field. Has Mars Global Surveyer mapped it out yet (I'll google after this post...)?