Now wait a sec, where is there a respectable scientist out there that insists that all life in the Universe is carbon-based? I don't see any hypotheses that say that. (at least no widely accepted ones!)
Here's an analogy for you: someone earlier said that we only find the really massive, quickly moving extrasolar planets because they are easiest to find. Likewise, the easiest life for us to find would be carbon-based life - we know what chemicals/molecules are required for carbon based life, we know what environments are required. The ONLY "life chemistry" (aka biochemistry) that we know is that of carbon-based lifeforms. In other words, we know the trademark signs of carbon-based life, so we know what to look for.
Example: we know that amino acids are required for (our sort of) carbon-based life. Therefore, we want to see how common these amino acids are in the universe, because we KNOW that amino acids are a trademark of life. So we go out and look for them. Simple as that. Notice here that no statement is being made about silicon-based or any other sort of life form.
We don't know what chemicals/molecules silicon-based life forms require, we don't know what they emit, and we don't know what sort of environments they thrive in - so how the hell are we going to detect their presence?
Statements like "life as we know it" are reasonable comments, because we can only comment on what we know, and we know carbon-based life. By the way, thanks for lumping all scientists into that insult.
I agree, the knowledge that humans have obtained is only a pebble on the cosmic beach of the universe. But to increase the size of that pebble, we have to begin to understand the other pebbles that are conceptually nearby. Silicon-based life is most definitely NOT conceptually nearby - we know nothing about it, and so all we have is speculation. Carbon-based life IS nearby, and so we're going to have to work with that before we can even think about silicon-based life. I think I've exhausted that analogy.
Moral of the story: all of our focus is on searching for carbon-based life because we know what to look for. But there's nothing saying that silicon-based life is impossible.
(Although as a side note, I have heard of studies that indicate that it would be more difficult to create sustainable life based on silicon because silicon compounds [we do agree that life requires chemical compounds, right?] are somewhat less chemically stable. But then again, that's just speculation right now.)
"The fact that these scientists would
go for an idea that contravenes ALL the rest of physics, with impossible infinities, "break downs" of the laws of physics (my ASS!)"
Nobody understands black holes. But this is for sure: at those types of fields, our physics DOES break down. Our physics has broken down before: Newtonian mechanics breaks down at high velocities, for example (hence relativity). Relativity breaks down at small distance scales (hence quantum mechanics). Now these theorists think they have a physics that DOES work at such fields, but they certainly are NOT using traditional physics. They are relying on this spacetime phase change, something that we definitely do not understand fully, just like a singularity. I'm not saying that this theory is wrong, but it is just as full of problems as black holes. Experimentation will tell which is correct (they are working on a mini-black-hole-maker, right?). Yeah, we don't have the physics to understand a singularity (I'm willing to bet it's not a true singularity, by the way) or infinity, but we also do not have the physics to understand a space-time phase change. What happens at an event horizon and below is all speculation right now. What we do know is that there is a point at which even quantum mechanics cannot hold a star up, at which point gravity inevitably wins. This is where we get stuck. GR predicts that singularity is the final state, but we definitely know that QM hates singularities. As far as I'm concerned, this implies that one or the other or both theories breaks down at that point, so I'm up for new theories. Maybe this one works, but I'm definitely not ready to toss out the black hole theory. This is just my take on it.
I know someone already said this, but photons HAVE NO MASS. NONE. The concept of linking mass with momentum comes from Newtonian mechanics, and does not always apply! As far back as the 1600's (Galileo), we figured out that gravitational acceleration was independent of mass. If we take the limit of this as mass goes to zero, we see that even something that is massless will be accelerated in a gravitational field. Think of it this way - we know (from relativity) that the percieved mass of an object increases as we see it speed up, to the point where it is infinitely massive at v=c=speed of light. If a photon had mass, the fact that it is moving at the speed of light implies that it would have infinite mass and therefore infinite energy. Of course this is unphysical, so light cannot be massive. That's just one explanation that is very thin on details and is overlooking a few things, but you get the idea.
The force cancellation is due to the degeneracy pressure. Think of it this way:
The neutrons cannot have identical quantum numbers, therefore they cannot have the same energies, therefore they "stack" their energies. Since each energy has a specific pressure associated with it, add up all these pressures of each individual fermion and you have the degeneracy pressure of the entire neutron star. I am an astrophysics major, and I just had a class devoted to black holes and neutron stars, in which I calculated this pressure. It works.
BH collapse occurs when even this degeneracy pressure cannot hold out any longer.
Yes, a single monochromatic photon cannot exist. But a good laser cavity can cut that inherent polychromaticity down to 1 part in 10^9. However, the inherent polychromaticity of photons isn't what makes the 6-8 micron range here.
Most research grade lasers (especially gas phase like Ar+, Kr+ and CO) emit in multiple wavelengths. I'm 20 feet away from one right now. It emits at 514nm, 488nm, and 457nm (it's an Ar+). However, what matters is if the photons of one specific wavelength are all in phase (coherent). If we do that, then we can also do something extremely simple, like send the resulting beam through a prism, and have thousands of laser beams, all coherent, and all of different wavelengths slightly separated in space. THAT is useful. The cool thing I see with this is that I could now make a laser beam that is 1mm tall, but, say 10cm long, and as I go along that 10cm, the wavelength is *nearly* continuously changing.
We do even better (or worse, depends on your perspective) than knowing hands down if energy is conserved - we declare it to be conserved, then create our physical laws around such a claim. This is one aspect of the "current scientific paradigm". It is so engrained in our thought that we have even predicted the existence of other particles as a result of it. Pauli, hanging on to the principle that energy is conserved, predicted the existence of a small, neutral, lightweight particle, the neutrino. It would take us 26 years after Pauli's prediction to verify the existence of the neutrino.
Incidentally, a whole lot of the theories that have been experimentally verified (especially in thermodynamics) have made use of the conservation of energy. So if energy isn't conserved, then it is very very nearly conserved.
While I'm not saying that energy is undoubtedly conserved, we've done pretty well relying on it thus far. No huge problems have come about that force us to disagree with that assumption. Then again, we all thought mass was conserved until E=mc^2 came about...
As far as mini-black holes are concerned, I wouldn't worry...we can just make a bunch of mini-white holes, put the two together, and they'll cancel out, right?;)
I am surprised you can use a computer, yet you do not know how to spell surprised. Bitch.
Re:OK, now I'm disturbed...
on
Apollo 1
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· Score: 1
I'm really confused here. Guppy06 gets flamed for a serious, insightful post, then gets modded up to 2 for another post in which he says "THIS if flamebait" What the hell? Who is modding this?
I hope this post gets smacked as flamebait, because I sure as hell know it is.
2psi in general would be painful. I acknowledge that there are only 3psi of oxygen in normal atmosphere. But there is another 11.7psi that makes our atmosphere at a comfortable 14.7psi. 2psi of pressure as a whole, however, would not be a very comfortable environment to pull your helmet off in. Just a thought...
Regardless, that wasn't the point of my post. I'm just trying to say that the concentration seemed to be the real problem, not necessarily the pressure.
What are you talking about?! I'll say this at the risk of being shot down, because I don't know this for fact. The pressure in the cabin was supposed to be roughly 1ATM in the test (16.7psi is close enough - 2psi won't affect much of anything) AND in space. We have all seen pictures of the Apollo astronauts in the capsule with their helmets off, talking into microphones and waving to the camera in t-shirts. While this would be possible at 2psi, it would be quite painful. So my guess is that the cabin pressure is always supposed to stay near 1ATM (~14.7psi), whether on the ground or in space. It's also that way on today's shuttle. The problem (admitted by NASA in hindsight) was that all of that pressure was pure oxygen! On the ground, the air is only 21% oxygen. Thus, there was 5X as much oxygen in there as there naturally would have been. The increase in pressure due to the fire (pressure is proportional to temperature, remember) was enough to rupture the capsule (read: cause the capsule to split open), which means that it was definitely too much for a human being to try to open up a door against. (if say a 500 sq. in. door has even 10 psi more on one side than on the other, then it has 5000 pounds pushing against it.)
In any case, many scientists have studied the case, and found a primary cause of the fire was the large concentration of oxygen in the cabin. It has nothing to do with how much pressure was in the cabin - what's more important is the concentration of the oxygen. This is obvious when you look at the revisions NASA made to the training sessions - they didn't decrease the pressure in the cabin (except to maybe 14.7 psi), but instead just made the atmosphere have less oxygen in it. (and, of course, they made the door open out)
From the viewpoint of a person working in a research institution, what Yahoo is doing is not too innovative, nor is it any kind of a cheap money making scam. If (IF) Yahoo actually will be searching research databases, then it will be doing what other not-so-popular, non-internet-based search engines/databases have provided for a few decades. I'm talking about databases like SciFinder, Beilstein Crossfire, and Web of Science. These are databases that major institutions pay tens of thousands of dollars for each year so that they can have access to records of past research data from across the world. The only difference that I can see here is that Yahoo will be providing the service as a pay-per-search service, not a yearly fee like most other databases do.
In addition, this provides us nerds with the possibility of getting our very own copy of research classics, like
"You are dead wrong about 50ties and 60ties russian mentality"
Well, I get this idea of Russian space mentality from several (Russian) friends that followed Russia's space program during the 60's. In any case, I said that the mentality was "keep trying until one works." I didn't say that they had no direction, just that they had a different mentality while going in that direction. They could certainly have had it all planned out, but how they got there was different from the way that NASA would have done it.
Look at the numbers, the Soviets had far more failures in considerably more attempts, especially in the lunar lander department. I agree with you that this "not caring if you lose a craft" mentality is probably a result of not having to disclose failures to the public. But I think it's a mentality nonetheless, and it's one that the "states" did not have. Maybe it's just our definition of mentality that's different - it sounds like I'm calling "mentality" what you would call "technique".
In any case, I agree that only recently (until the early 90's) has NASA shown any real planning for the future.
Normally I'd laugh at that, but I do need to point out some technicalities. First, "crap" is a relative term. Yeah, if Dell tried to sell computers that worked as frequently (or infrequently) as NASA probes, it'd be out of business. Then again, Dell, Intel, AMD, Western Digital, et al all have the chance of trying their machinery out in real-life situations before putting it out on store shelves. How fortunate for them, but NASA doesn't have this luxury. Take a look at lunar missions starting in the early-to-mid sixties - see how many craft NASA shot up, and how many MORE Russia pumped up there. Then look at how many succeeded - you'll see a difference in approach right there. Russian mentality: keep trying, and if it drops out of the sky or flys by the moon or crashes, try it again! Just keep trying, and eventually you'll get one to work. NASA, on the other hand, has the opposite approach - make like the first shot is the only shot. Try to make sure it works as best as it can, then send it up. Maybe this is a result of a much more nosey press in America, or maybe its just the way Americans work.
The spacecraft up there are the pinnacle of technological achievement. Go to http://nmp.jpl.nasa.gov/ds1/ , Deep Space 1's webpage and read about this amazing spacecraft if you don't believe me. Just to cut some people off right now - yes, the cpu's aboard these spacecraft are exceedingly slow (I'm talking PI or slower), but they are doing things longer and more continuously than any desktop here on Earth. Finally, if you want to see a spacecraft that has lasted longer than most of our cars, and acquired a lot more data, see Galileo's latest stat, as it's in its third extended mission and still going stronger than ever: http://www.jpl.nasa.gov/galileo/
I'm not quite sure what the big deal is. They said in the story that not only were they optimistic that it would be fixed, but that the lenses and optics are designed with heaters for this kind of thing. Shouldn't we be happy that finally one of those "just-in-case" prevention measures that NASA spends millions on finally might be the difference between a successful and, well, not-so-successful mission?
It sounds to me like a lot more information needs to come out before we start saying that the mission is even in danger...we do have 2+ more years.
JoeRobe
"the ice caps of Mars are believed to be frozen carbon dioxide"
No, the frozen caps are condsidered to be somewhat of a "slop" of dirt, CO2 ice (dry ice), and water ice. In addition, every summer, some of this water sublimes (we're below the triple point, for those chemists out there) and evaporates into the atmosphere. Mars isn't as completely dry as a lot of people think. The problem is that we haven't found water yet that is easily accessible. More can be found at
14x is a big deal. The 100-100000 solar mass black holes at the center of galaxies (which still isn't proven, but has a lot of data pointing towards it) are not stellar black holes. They would be called galactic black holes. Stellar black holes are byproducts of dead stars. The Chandra limit, 1.4 solar masses, is the minimum mass that is needed to make stellar remnants collapse. If it is over 2 or 3 solar masses, then it collapses all the way into a black hole. Now, that was figured out several decades ago, so of course that number might be slightly "off," but I seriously doubt that Chandra was off by a factor of 10. I'm curious where you get 10-100 solar masses from...
When a star with a mass of ~30 solar masses or higher dies, it supernovas, blowing off most of its mass. IF WHAT'S LEFT is greater than a couple of solar masses (and within the Schwarzschild radius), then it collapses into a black hole. I repeat: it MUST ONLY be more massive than a few (2 or 3 - it's under debate) solar masses! True, the original star must be greater than ~30 solar masses; but the mass of the black hole is far less than the mass of the original star. THIS is why a 14 solar mass black hole is so strange!
By the way, NO information regarding black holes is the subject of "worldwide consensus".
Just a comment: I'm reading some comments from people saying that this is the first time aerobraking has been used. This is not true. Mars Global Surveyor (http://mars.jpl.nasa.gov/mgs/) used aerobraking to do it's orbital insertion several years ago. This is said in the article, so I'm surprised that people are saying that's it's a new technique. In any case, MGS's aerobraking phase was extremely successful. There is of course this fear of the atmosphere suddenly thickening, but this wouldn't happen in a matter of seconds, it would take quite awhile, enough time for the spacecraft to respond.
The story says that the MGS had some problems with aerobraking. Yes, it had some problems, and they said it took longer than it should have, which it did, but the way that they did it was much safer than direct orbital insertion with conventional propulsion systems. The primary source of the problems was (and I know this from following its news DURING it's aerobraking phase) that they didn't want to hurt an already damaged solar panel, so they were being very conservative because if they lost that panel, the mission was over. They normally could have easily handled the inconsistencies, but that in combination with the solar panel problem made them reevaluate some things:
To make sure the panel would be alright, they needed the pressure on the panel to be less that 0.2 N/m^2. They could only do this by extending the aerobraking phase. The major reason for breaking it up into two phases was because there would be a solar conjunction in June, 1998 in which we would not be able to talk to MGS for awhile. Thus we got it out of aerobraking mode before we were going to lose communication. It began phase two so late because a major part of the mission was to map Mars, and to do this required the spacecraft to be in certain places at certain times. To achieve this, they needed to wait awhile before restarting aerobraking.
There was not a fear of "crashing" the spacecraft here - they wanted to keep that solar panel intact, so they lengthened the aerobraking phase, which made them rearrange the mission slightly. It really wasn't a big deal.
Also, "labor-intensive" is a bit of a stretch - the orbits at the beginning of the first aerobraking phase were on the order of a couple days, and only a fraction of that time was spent going through the atmosphere, which gave them a very large amount of time to figure out where the spacecraft was and where it was heading. The phase 2 aerobraking orbit (much easier than phase 1) to begin with was about 12 hours. It definitely wasn't a scramble. They also fail to mention that a lot of science was done both during and in between the aerobraking phases - it wasn't a wasted year.
Also, it seems to me that now that we have the information (density data, etc.) from the MGS aerobraking, the Odyssey aerobraking predictions will be much better. In addition, if the MGS predicted atmospheric densities and such were so far off for the MGS mission, and MGS still survived, then Odyssey will do fine. It's just a matter of being conservative.
Let's remember that the spacecraft doesn't just go flying into the atmosphere, it gets itself into a very large, very elliptical, "rough" orbit, after which it begins aerobraking to lower the orbit and slows itself down. I'm sure somewhere on the MGS website you can see how it lowered its orbit with each pass, making it more circular. It's really slow, and from what I've seen from MGS, quite safe procedure, assuming you're careful.
I don't know if this helps anyone out. But really, the aerobraking phase isn't all that dangerous, and using the MGS as an example of how difficult it is is definitely a mistake.
It's easy to hit a planet with a spacecraft, it's far more difficult to make the orbit of the ISS coincide with the orbit of the incoming spacecraft, and that's assuming you even get the spacecraft into Earth orbit from Mars. Yes, if enough effort is put into it, it probably can happen, but how much easier and lower-risk is it to just toss a heat shield on it and drop it? We would need more fuel because of the added weight, yes; but we would also need more fuel to get into ISS orbit. In addition, I *assure* you that it's not as simple as just "tossing the spacecraft into the shuttle" and getting a free ride home. With the way our shuttle program works, there's no such thing as free - an astronaut sneezes in space and NASA forks out $X million dollars for some reason or another.
1) We simply cannot "catch" the spacecraft with the ISS. It's magnitudes cheaper to drop it into the ocean, and there's much less thought involved. Yeah we should use the ISS for something - this isn't one of them.
2) Let's say we get the Hubble into the same orbit as the ISS. When the ISS needs to do something to it, you're proposing moving the entire ISS (Hubble certianly can't do it) to the Hubble then grabbing it? The ISS isn't designed to be moved very much at all, it's designed to float. It doesn't have the fuel to move very far. While it may be a great place to fix satellites from, it's not a towtruck.
3) Satellites do not all have the same orbital altitude, and making a little "thing" (let's call it, oh, I don't know...CowboyNeal maybe) to go get them would require a lot of money and fuel. If we are going to get then in the first place, we're much better off letting the shuttle grab it and bring it in, like we have been doing. If we do any work on a satellite, we would probably need special replacement parts thatthe Shuttle would need to bring up anyways.
I don't mean to be picky here, but my math says that if 1 out of every 1,000,000,000 people going through is a terrorist, there will be 99,999 false alarms for every terrorist detected, not 9,999. Eh, what's an order of magnitude here or there, anyways...
This has been planned by the Planetary Society for quite awhile. One of their newsletters last year featured optical SETI, in which they went through the computing setup and everything. If you want to know more I suggets you check it out. One more thing: from what I've gathered about the project, it will most definitely not be in opposition to radio SETI, but just another approach. If I recall, one scientist described SETI as "trying to catch fish in a gutter with nothing more than a string...it probably won't work, but it's a start." Maybe optical SETI is just the next step as we work our way out of the cosmic gutter:)
So i read these posts about whether or not pluto is a planet. Then i read arguments about whether it is or not. Everyone had good points about it, but my vote is that it is still up for grabs. Pluto has a few characteristics that make it planet-like, ie: really interesting atmosphere. Then it has characteristics that make it not-planet-like, ie: it's small, has out-of-plane, highly elliptical orbit. I'd like to think it's a planet, just 'cause i'm so used to nine planets and all my memory devices for remembering their order will be missing the last word(kidding). One thing i am sure of, though: whether it is or not, a mission to pluto would definitely resolve the issue. Then i read these posts about why study pluto. In addition to resolving the planet issue, it also has a weird atmosphere that goes through cycles of condensation and vaporization, something we don't see very often. I'm thinking the main reason, though, is because we only have one planet left! After this we can say that we have visited all of our planets(or pseudo-planets). I also think it's a nice challenge for NASA to take on. That's quite a ride. But, alas, we may have to wait. If you want to read about challenging missions, check out http://nmp.jpl.nasa.gov/ds1/ where they had to rescue a blinded and spinning spacecraft before NASA decided to pull the plug. Or http://www.jpl.nasa.gov/galileo/ where the galileo spacecraft is on its 3rd extended mission, living WAY beyond its expectations, repeatedly leaving its controllers with the question "so what should we do with it now?"
I was on as an AC until I read this and was prompted to get on and make a quick comment (even though it's old and nobody will ever read it.) "Let me put it this way: is any chemist going to change how he works because the tau neutrino exists? No--his life is based on what happens near ROOM TEMPERATURE where any contributions of neutrino physics are either ZERO or taken into account by the effective fields that he uses (e.g. Maxwell's equations as an theory approximating QED)." Rarely are things people say simply, undoubtedly wrong. But this is one of those cases. I'm a chemist at U Pitt. (where Vittorio Paolone, one of the tau neutrino discoverers works!). My main project currently is high resolution UV molecular spectroscopy in the gas phase, where the temperature of the molecules is ~2K when crossed by the laser. This is chemistry at its most raw state, where molecules reveal their structure and interactions. At room temperature, this experiment is useless. There is another type of similar spectroscopy, microwave spec., where everything must be taken into account. This everything will probably include supernovae and GRB's when they are better understood, and currently neutrinos are thought to be very important in both SN's and GRB's. And so we see where molecules at extreme temperatures are in very valuable states, and where neutrinos may at some point be of importance to chemistry. True, the high school chemistry of mixing chemicals on Earth is rarely at extreme temperatures. But mixing chemicals is not chemistry. Understanding atoms and molecules is chemistry. And that is not necessarily done at room temperature, especially in interstellar gas clouds, where nature is doing the mixing. "EVERYTHING that any engineer might put into use is going to be made up of ordinary matter: i.e. protons, neutrons, electrons." Neutrinos, by their nature, are more "ordinary" and fundamental than protons, neutrons, or electrons(well, ok, maybe not electrons...). The understanding of neutrinos and other high energy subatomic particals can and will give insight into protons and neutrons and their interactions. On top of that, I think that anything that furthers our understanding of our origins and the matter that we're made of is worth the research. Let's also remember that many doubted the uses of Einstein's relativity when it became mainstream, but it is currently being *VERY* widely used in astronomy and practical matters like GPS. Just my thoughts. Enjoy! Rob
Slashdot Mirror
Now wait a sec, where is there a respectable scientist out there that insists that all life in the Universe is carbon-based? I don't see any hypotheses that say that. (at least no widely accepted ones!)
Here's an analogy for you: someone earlier said that we only find the really massive, quickly moving extrasolar planets because they are easiest to find. Likewise, the easiest life for us to find would be carbon-based life - we know what chemicals/molecules are required for carbon based life, we know what environments are required. The ONLY "life chemistry" (aka biochemistry) that we know is that of carbon-based lifeforms. In other words, we know the trademark signs of carbon-based life, so we know what to look for.
Example: we know that amino acids are required for (our sort of) carbon-based life. Therefore, we want to see how common these amino acids are in the universe, because we KNOW that amino acids are a trademark of life. So we go out and look for them. Simple as that. Notice here that no statement is being made about silicon-based or any other sort of life form.
We don't know what chemicals/molecules silicon-based life forms require, we don't know what they emit, and we don't know what sort of environments they thrive in - so how the hell are we going to detect their presence?
Statements like "life as we know it" are reasonable comments, because we can only comment on what we know, and we know carbon-based life. By the way, thanks for lumping all scientists into that insult.
I agree, the knowledge that humans have obtained is only a pebble on the cosmic beach of the universe. But to increase the size of that pebble, we have to begin to understand the other pebbles that are conceptually nearby. Silicon-based life is most definitely NOT conceptually nearby - we know nothing about it, and so all we have is speculation. Carbon-based life IS nearby, and so we're going to have to work with that before we can even think about silicon-based life. I think I've exhausted that analogy.
Moral of the story: all of our focus is on searching for carbon-based life because we know what to look for. But there's nothing saying that silicon-based life is impossible.
(Although as a side note, I have heard of studies that indicate that it would be more difficult to create sustainable life based on silicon because silicon compounds [we do agree that life requires chemical compounds, right?] are somewhat less chemically stable. But then again, that's just speculation right now.)
"The fact that these scientists would
go for an idea that contravenes ALL the rest of physics, with impossible infinities, "break downs" of the laws of physics (my ASS!)"
Nobody understands black holes. But this is for sure: at those types of fields, our physics DOES break down. Our physics has broken down before: Newtonian mechanics breaks down at high velocities, for example (hence relativity). Relativity breaks down at small distance scales (hence quantum mechanics). Now these theorists think they have a physics that DOES work at such fields, but they certainly are NOT using traditional physics. They are relying on this spacetime phase change, something that we definitely do not understand fully, just like a singularity. I'm not saying that this theory is wrong, but it is just as full of problems as black holes. Experimentation will tell which is correct (they are working on a mini-black-hole-maker, right?).
Yeah, we don't have the physics to understand a singularity (I'm willing to bet it's not a true singularity, by the way) or infinity, but we also do not have the physics to understand a space-time phase change. What happens at an event horizon and below is all speculation right now. What we do know is that there is a point at which even quantum mechanics cannot hold a star up, at which point gravity inevitably wins. This is where we get stuck. GR predicts that singularity is the final state, but we definitely know that QM hates singularities. As far as I'm concerned, this implies that one or the other or both theories breaks down at that point, so I'm up for new theories. Maybe this one works, but I'm definitely not ready to toss out the black hole theory. This is just my take on it.
joerobe
I know someone already said this, but photons HAVE NO MASS. NONE. The concept of linking mass with momentum comes from Newtonian mechanics, and does not always apply! As far back as the 1600's (Galileo), we figured out that gravitational acceleration was independent of mass. If we take the limit of this as mass goes to zero, we see that even something that is massless will be accelerated in a gravitational field. Think of it this way - we know (from relativity) that the percieved mass of an object increases as we see it speed up, to the point where it is infinitely massive at v=c=speed of light. If a photon had mass, the fact that it is moving at the speed of light implies that it would have infinite mass and therefore infinite energy. Of course this is unphysical, so light cannot be massive. That's just one explanation that is very thin on details and is overlooking a few things, but you get the idea.
joerobe
The force cancellation is due to the degeneracy pressure. Think of it this way:
The neutrons cannot have identical quantum numbers, therefore they cannot have the same energies, therefore they "stack" their energies. Since each energy has a specific pressure associated with it, add up all these pressures of each individual fermion and you have the degeneracy pressure of the entire neutron star. I am an astrophysics major, and I just had a class devoted to black holes and neutron stars, in which I calculated this pressure. It works.
BH collapse occurs when even this degeneracy pressure cannot hold out any longer.
joerobe
Yes, a single monochromatic photon cannot exist. But a good laser cavity can cut that inherent polychromaticity down to 1 part in 10^9. However, the inherent polychromaticity of photons isn't what makes the 6-8 micron range here.
Most research grade lasers (especially gas phase like Ar+, Kr+ and CO) emit in multiple wavelengths. I'm 20 feet away from one right now. It emits at 514nm, 488nm, and 457nm (it's an Ar+). However, what matters is if the photons of one specific wavelength are all in phase (coherent). If we do that, then we can also do something extremely simple, like send the resulting beam through a prism, and have thousands of laser beams, all coherent, and all of different wavelengths slightly separated in space. THAT is useful. The cool thing I see with this is that I could now make a laser beam that is 1mm tall, but, say 10cm long, and as I go along that 10cm, the wavelength is *nearly* continuously changing.
JoeRobe
Incidentally, I'm a physicist and a philosopher:)
;)
We do even better (or worse, depends on your perspective) than knowing hands down if energy is conserved - we declare it to be conserved, then create our physical laws around such a claim. This is one aspect of the "current scientific paradigm". It is so engrained in our thought that we have even predicted the existence of other particles as a result of it. Pauli, hanging on to the principle that energy is conserved, predicted the existence of a small, neutral, lightweight particle, the neutrino. It would take us 26 years after Pauli's prediction to verify the existence of the neutrino.
Incidentally, a whole lot of the theories that have been experimentally verified (especially in thermodynamics) have made use of the conservation of energy. So if energy isn't conserved, then it is very very nearly conserved.
While I'm not saying that energy is undoubtedly conserved, we've done pretty well relying on it thus far. No huge problems have come about that force us to disagree with that assumption. Then again, we all thought mass was conserved until E=mc^2 came about...
As far as mini-black holes are concerned, I wouldn't worry...we can just make a bunch of mini-white holes, put the two together, and they'll cancel out, right?
JoeRobe.
I am surprised you can use a computer, yet you do not know how to spell surprised. Bitch.
I'm really confused here. Guppy06 gets flamed for a serious, insightful post, then gets modded up to 2 for another post in which he says "THIS if flamebait" What the hell? Who is modding this?
I hope this post gets smacked as flamebait, because I sure as hell know it is.
2psi in general would be painful. I acknowledge that there are only 3psi of oxygen in normal atmosphere. But there is another 11.7psi that makes our atmosphere at a comfortable 14.7psi. 2psi of pressure as a whole, however, would not be a very comfortable environment to pull your helmet off in. Just a thought...
Regardless, that wasn't the point of my post. I'm just trying to say that the concentration seemed to be the real problem, not necessarily the pressure.
What are you talking about?! I'll say this at the risk of being shot down, because I don't know this for fact. The pressure in the cabin was supposed to be roughly 1ATM in the test (16.7psi is close enough - 2psi won't affect much of anything) AND in space. We have all seen pictures of the Apollo astronauts in the capsule with their helmets off, talking into microphones and waving to the camera in t-shirts. While this would be possible at 2psi, it would be quite painful. So my guess is that the cabin pressure is always supposed to stay near 1ATM (~14.7psi), whether on the ground or in space. It's also that way on today's shuttle. The problem (admitted by NASA in hindsight) was that all of that pressure was pure oxygen! On the ground, the air is only 21% oxygen. Thus, there was 5X as much oxygen in there as there naturally would have been. The increase in pressure due to the fire (pressure is proportional to temperature, remember) was enough to rupture the capsule (read: cause the capsule to split open), which means that it was definitely too much for a human being to try to open up a door against. (if say a 500 sq. in. door has even 10 psi more on one side than on the other, then it has 5000 pounds pushing against it.)
In any case, many scientists have studied the case, and found a primary cause of the fire was the large concentration of oxygen in the cabin. It has nothing to do with how much pressure was in the cabin - what's more important is the concentration of the oxygen. This is obvious when you look at the revisions NASA made to the training sessions - they didn't decrease the pressure in the cabin (except to maybe 14.7 psi), but instead just made the atmosphere have less oxygen in it. (and, of course, they made the door open out)
From the viewpoint of a person working in a research institution, what Yahoo is doing is not too innovative, nor is it any kind of a cheap money making scam. If (IF) Yahoo actually will be searching research databases, then it will be doing what other not-so-popular, non-internet-based search engines/databases have provided for a few decades. I'm talking about databases like SciFinder, Beilstein Crossfire, and Web of Science. These are databases that major institutions pay tens of thousands of dollars for each year so that they can have access to records of past research data from across the world. The only difference that I can see here is that Yahoo will be providing the service as a pay-per-search service, not a yearly fee like most other databases do.
In addition, this provides us nerds with the possibility of getting our very own copy of research classics, like
Nature, 2 April 1953, VOL 171,737 1953
:?)
"You are dead wrong about 50ties and 60ties russian mentality"
Well, I get this idea of Russian space mentality from several (Russian) friends that followed Russia's space program during the 60's. In any case, I said that the mentality was "keep trying until one works." I didn't say that they had no direction, just that they had a different mentality while going in that direction. They could certainly have had it all planned out, but how they got there was different from the way that NASA would have done it.
Look at the numbers, the Soviets had far more failures in considerably more attempts, especially in the lunar lander department. I agree with you that this "not caring if you lose a craft" mentality is probably a result of not having to disclose failures to the public. But I think it's a mentality nonetheless, and it's one that the "states" did not have. Maybe it's just our definition of mentality that's different - it sounds like I'm calling "mentality" what you would call "technique".
In any case, I agree that only recently (until the early 90's) has NASA shown any real planning for the future.
Normally I'd laugh at that, but I do need to point out some technicalities. First, "crap" is a relative term. Yeah, if Dell tried to sell computers that worked as frequently (or infrequently) as NASA probes, it'd be out of business. Then again, Dell, Intel, AMD, Western Digital, et al all have the chance of trying their machinery out in real-life situations before putting it out on store shelves. How fortunate for them, but NASA doesn't have this luxury. Take a look at lunar missions starting in the early-to-mid sixties - see how many craft NASA shot up, and how many MORE Russia pumped up there. Then look at how many succeeded - you'll see a difference in approach right there. Russian mentality: keep trying, and if it drops out of the sky or flys by the moon or crashes, try it again! Just keep trying, and eventually you'll get one to work. NASA, on the other hand, has the opposite approach - make like the first shot is the only shot. Try to make sure it works as best as it can, then send it up. Maybe this is a result of a much more nosey press in America, or maybe its just the way Americans work.
The spacecraft up there are the pinnacle of technological achievement. Go to http://nmp.jpl.nasa.gov/ds1/ , Deep Space 1's webpage and read about this amazing spacecraft if you don't believe me. Just to cut some people off right now - yes, the cpu's aboard these spacecraft are exceedingly slow (I'm talking PI or slower), but they are doing things longer and more continuously than any desktop here on Earth. Finally, if you want to see a spacecraft that has lasted longer than most of our cars, and acquired a lot more data, see Galileo's latest stat, as it's in its third extended mission and still going stronger than ever: http://www.jpl.nasa.gov/galileo/
Just my thoughts,
JoeRobe
I'm not quite sure what the big deal is. They said in the story that not only were they optimistic that it would be fixed, but that the lenses and optics are designed with heaters for this kind of thing. Shouldn't we be happy that finally one of those "just-in-case" prevention measures that NASA spends millions on finally might be the difference between a successful and, well, not-so-successful mission?
It sounds to me like a lot more information needs to come out before we start saying that the mission is even in danger...we do have 2+ more years.
JoeRobe
"the ice caps of Mars are believed to be frozen carbon dioxide"
No, the frozen caps are condsidered to be somewhat of a "slop" of dirt, CO2 ice (dry ice), and water ice. In addition, every summer, some of this water sublimes (we're below the triple point, for those chemists out there) and evaporates into the atmosphere. Mars isn't as completely dry as a lot of people think. The problem is that we haven't found water yet that is easily accessible. More can be found at
More can be found at the Mars Global Surveyor Homepage
14x is a big deal. The 100-100000 solar mass black holes at the center of galaxies (which still isn't proven, but has a lot of data pointing towards it) are not stellar black holes. They would be called galactic black holes. Stellar black holes are byproducts of dead stars. The Chandra limit, 1.4 solar masses, is the minimum mass that is needed to make stellar remnants collapse. If it is over 2 or 3 solar masses, then it collapses all the way into a black hole. Now, that was figured out several decades ago, so of course that number might be slightly "off," but I seriously doubt that Chandra was off by a factor of 10. I'm curious where you get 10-100 solar masses from...
When a star with a mass of ~30 solar masses or higher dies, it supernovas, blowing off most of its mass. IF WHAT'S LEFT is greater than a couple of solar masses (and within the Schwarzschild radius), then it collapses into a black hole. I repeat: it MUST ONLY be more massive than a few (2 or 3 - it's under debate) solar masses! True, the original star must be greater than ~30 solar masses; but the mass of the black hole is far less than the mass of the original star. THIS is why a 14 solar mass black hole is so strange!
By the way, NO information regarding black holes is the subject of "worldwide consensus".
Just a comment: I'm reading some comments from people saying that this is the first time aerobraking has been used. This is not true. Mars Global Surveyor (http://mars.jpl.nasa.gov/mgs/) used aerobraking to do it's orbital insertion several years ago. This is said in the article, so I'm surprised that people are saying that's it's a new technique. In any case, MGS's aerobraking phase was extremely successful. There is of course this fear of the atmosphere suddenly thickening, but this wouldn't happen in a matter of seconds, it would take quite awhile, enough time for the spacecraft to respond.
The story says that the MGS had some problems with aerobraking. Yes, it had some problems, and they said it took longer than it should have, which it did, but the way that they did it was much safer than direct orbital insertion with conventional propulsion systems. The primary source of the problems was (and I know this from following its news DURING it's aerobraking phase) that they didn't want to hurt an already damaged solar panel, so they were being very conservative because if they lost that panel, the mission was over. They normally could have easily handled the inconsistencies, but that in combination with the solar panel problem made them reevaluate some things:
To make sure the panel would be alright, they needed the pressure on the panel to be less that 0.2 N/m^2. They could only do this by extending the aerobraking phase. The major reason for breaking it up into two phases was because there would be a solar conjunction in June, 1998 in which we would not be able to talk to MGS for awhile. Thus we got it out of aerobraking mode before we were going to lose communication. It began phase two so late because a major part of the mission was to map Mars, and to do this required the spacecraft to be in certain places at certain times. To achieve this, they needed to wait awhile before restarting aerobraking.
There was not a fear of "crashing" the spacecraft here - they wanted to keep that solar panel intact, so they lengthened the aerobraking phase, which made them rearrange the mission slightly. It really wasn't a big deal.
Also, "labor-intensive" is a bit of a stretch - the orbits at the beginning of the first aerobraking phase were on the order of a couple days, and only a fraction of that time was spent going through the atmosphere, which gave them a very large amount of time to figure out where the spacecraft was and where it was heading. The phase 2 aerobraking orbit (much easier than phase 1) to begin with was about 12 hours. It definitely wasn't a scramble. They also fail to mention that a lot of science was done both during and in between the aerobraking phases - it wasn't a wasted year.
Also, it seems to me that now that we have the information (density data, etc.) from the MGS aerobraking, the Odyssey aerobraking predictions will be much better. In addition, if the MGS predicted atmospheric densities and such were so far off for the MGS mission, and MGS still survived, then Odyssey will do fine. It's just a matter of being conservative.
Let's remember that the spacecraft doesn't just go flying into the atmosphere, it gets itself into a very large, very elliptical, "rough" orbit, after which it begins aerobraking to lower the orbit and slows itself down. I'm sure somewhere on the MGS website you can see how it lowered its orbit with each pass, making it more circular. It's really slow, and from what I've seen from MGS, quite safe procedure, assuming you're careful.
I don't know if this helps anyone out. But really, the aerobraking phase isn't all that dangerous, and using the MGS as an example of how difficult it is is definitely a mistake.
JoeRobe
It's easy to hit a planet with a spacecraft, it's far more difficult to make the orbit of the ISS coincide with the orbit of the incoming spacecraft, and that's assuming you even get the spacecraft into Earth orbit from Mars. Yes, if enough effort is put into it, it probably can happen, but how much easier and lower-risk is it to just toss a heat shield on it and drop it? We would need more fuel because of the added weight, yes; but we would also need more fuel to get into ISS orbit. In addition, I *assure* you that it's not as simple as just "tossing the spacecraft into the shuttle" and getting a free ride home. With the way our shuttle program works, there's no such thing as free - an astronaut sneezes in space and NASA forks out $X million dollars for some reason or another.
1) We simply cannot "catch" the spacecraft with the ISS. It's magnitudes cheaper to drop it into the ocean, and there's much less thought involved. Yeah we should use the ISS for something - this isn't one of them.
2) Let's say we get the Hubble into the same orbit as the ISS. When the ISS needs to do something to it, you're proposing moving the entire ISS (Hubble certianly can't do it) to the Hubble then grabbing it? The ISS isn't designed to be moved very much at all, it's designed to float. It doesn't have the fuel to move very far. While it may be a great place to fix satellites from, it's not a towtruck.
3) Satellites do not all have the same orbital altitude, and making a little "thing" (let's call it, oh, I don't know...CowboyNeal maybe) to go get them would require a lot of money and fuel. If we are going to get then in the first place, we're much better off letting the shuttle grab it and bring it in, like we have been doing. If we do any work on a satellite, we would probably need special replacement parts thatthe Shuttle would need to bring up anyways.
Just my thoughts,
JoeRobe
I don't mean to be picky here, but my math says that if 1 out of every 1,000,000,000 people going through is a terrorist, there will be 99,999 false alarms for every terrorist detected, not 9,999. Eh, what's an order of magnitude here or there, anyways...
This has been planned by the Planetary Society for quite awhile. One of their newsletters last year featured optical SETI, in which they went through the computing setup and everything. If you want to know more I suggets you check it out. One more thing: from what I've gathered about the project, it will most definitely not be in opposition to radio SETI, but just another approach. If I recall, one scientist described SETI as "trying to catch fish in a gutter with nothing more than a string...it probably won't work, but it's a start." Maybe optical SETI is just the next step as we work our way out of the cosmic gutter:)
So i read these posts about whether or not pluto is a planet. Then i read arguments about whether it is or not. Everyone had good points about it, but my vote is that it is still up for grabs. Pluto has a few characteristics that make it planet-like, ie: really interesting atmosphere. Then it has characteristics that make it not-planet-like, ie: it's small, has out-of-plane, highly elliptical orbit. I'd like to think it's a planet, just 'cause i'm so used to nine planets and all my memory devices for remembering their order will be missing the last word(kidding). One thing i am sure of, though: whether it is or not, a mission to pluto would definitely resolve the issue. Then i read these posts about why study pluto. In addition to resolving the planet issue, it also has a weird atmosphere that goes through cycles of condensation and vaporization, something we don't see very often. I'm thinking the main reason, though, is because we only have one planet left! After this we can say that we have visited all of our planets(or pseudo-planets). I also think it's a nice challenge for NASA to take on. That's quite a ride. But, alas, we may have to wait. If you want to read about challenging missions, check out http://nmp.jpl.nasa.gov/ds1/ where they had to rescue a blinded and spinning spacecraft before NASA decided to pull the plug. Or http://www.jpl.nasa.gov/galileo/ where the galileo spacecraft is on its 3rd extended mission, living WAY beyond its expectations, repeatedly leaving its controllers with the question "so what should we do with it now?"
I was on as an AC until I read this and was prompted to get on and make a quick comment (even though it's old and nobody will ever read it.) "Let me put it this way: is any chemist going to change how he works because the tau neutrino exists? No--his life is based on what happens near ROOM TEMPERATURE where any contributions of neutrino physics are either ZERO or taken into account by the effective fields that he uses (e.g. Maxwell's equations as an theory approximating QED)." Rarely are things people say simply, undoubtedly wrong. But this is one of those cases. I'm a chemist at U Pitt. (where Vittorio Paolone, one of the tau neutrino discoverers works!). My main project currently is high resolution UV molecular spectroscopy in the gas phase, where the temperature of the molecules is ~2K when crossed by the laser. This is chemistry at its most raw state, where molecules reveal their structure and interactions. At room temperature, this experiment is useless. There is another type of similar spectroscopy, microwave spec., where everything must be taken into account. This everything will probably include supernovae and GRB's when they are better understood, and currently neutrinos are thought to be very important in both SN's and GRB's. And so we see where molecules at extreme temperatures are in very valuable states, and where neutrinos may at some point be of importance to chemistry. True, the high school chemistry of mixing chemicals on Earth is rarely at extreme temperatures. But mixing chemicals is not chemistry. Understanding atoms and molecules is chemistry. And that is not necessarily done at room temperature, especially in interstellar gas clouds, where nature is doing the mixing. "EVERYTHING that any engineer might put into use is going to be made up of ordinary matter: i.e. protons, neutrons, electrons." Neutrinos, by their nature, are more "ordinary" and fundamental than protons, neutrons, or electrons(well, ok, maybe not electrons...). The understanding of neutrinos and other high energy subatomic particals can and will give insight into protons and neutrons and their interactions. On top of that, I think that anything that furthers our understanding of our origins and the matter that we're made of is worth the research. Let's also remember that many doubted the uses of Einstein's relativity when it became mainstream, but it is currently being *VERY* widely used in astronomy and practical matters like GPS. Just my thoughts. Enjoy! Rob